Polymerization method for preparing a lignin-derived functional polyester

Abstract

In general, the present invention relates to a method to prepare a thermoplastic functional polyester, and in particular provides a ring-opening co-polymerization method of epoxide monomers and cyclic anhydride monomers, wherein at least part of the epoxide monomers are lignin-derived glycidyl ether monomers. The present invention further relates to the polymer obtained by the method, in particular a thermoplastic lignin-derived functional polyester, and the use of the polymer in the preparation of further polymers, such as polyurethanes.

Description

[0001] POLYMERIZATION METHOD FOR PREPARING A LIGNIN-DERIVED FUNCTIONAL POLYESTER

[0002] FIELD OF THE INVENTION

[0003] In general, the present invention relates to a method for preparing a thermoplastic functional polyester, and in particular provides a ring-opening co-polymerization method of epoxide monomers and cyclic anhydride monomers, wherein at least part of the epoxide monomers are lignin-derived glycidyl ether monomers. The present invention further relates to the polymer obtained by the method, in particular a thermoplastic lignin-derived functional polyester, and the use of the polymer in the preparation of further polymers, such as polyurethanes.

[0004] BACKGROUND TO THE INVENTION

[0005] Polyesters are widely used and versatile polymers having a number of advantages in terms of their general biocompatibility, their benign and facile end-of-life (EOL) hydrolytic degradation potential and their potential to have its monomers sourced from renewable feedstocks.

[0006] The traditional and most common method for their synthesis is via step-growth, selfcondensation polymerization of diols and diacids. There are however limitations with this method, including the requirement of precise stoichiometry and relatively demanding conditions to access useful, high molecular weight polymers. Another disadvantage is the lack of control in the overall reaction and the broader molecular weight distributions generally obtained.

[0007] To allow for better control, ring opening polymerization (ROP) of cyclic esters has been reported, via a chain-growth mechanism. Ring-opening polymerization of cyclic esters like lactide and E- caprolactone provides aliphatic polyesters. These aliphatic polyesters are however inherently non-aromatic and less rigid. As a result, they can display unsuitable and inferior thermal properties, such as low glass-transition temperatures, which limits their use in further applications and suitability in replacing fossil-based polymers with higher glass-transition temperatures. In addition, the main drawback holding this area from progressing further is the lack of available cyclic monomers that can be polymerized, whereas novel substrates can be challenging to synthesize.

[0008] Ring-opening co-polymerization (ROCOP) is a versatile tool for preparing a wide range of polyester co-polymers from epoxides and cyclic anhydrides. Typically, this polymerization is achieved by employing a binary catalytic system with both Lewis acid catalyst and nucleophilic co-catalyst components. In the past, the ring-opening co-polymerization of epoxides and cyclic anhydrides has been successfully achieved with a range of metal initiators based on elements such as aluminum(lll), chromium(lll), cobalt(lll), magnesium(ll), zinc(ll) and iron(lll). In the majority of cases, homogeneous binary catalytic systems have been employed with the metal behaving as a Lewis acid catalyst and an anionic, nucleophilic, Lewis basic co-catalyst, such as bis(triphenylphosphoranylidene)iminium chloride (PPNCI) or 4-(dimethylamino)pyridine (DMAP), to cooperatively aid the ring opening of the substrates. A downside of using metal catalysts, in ring opening polymerizations, is that purification and removal of residual metal species from the polymer can be challenging, and therefore less attractive to industry in specific cases.

[0009] A particular downside of the current state-of-the-art regarding ring-opening co-polymerization (ROCOP), and limitation to its commercialization, is to employ heavily purified reagents, such as heavily distilled epoxides, recrystallized or sublimed cyclic anhydrides and even a recrystallized or sublimed catalyst and co-catalyst, and rigorously conduct the reactions under inert and anhydrous conditions (high air-sensitivity) in attempts to remove contaminants, such as diols residing from the epoxides, diacids residing from the anhydrides, and residual moisture, which tend to lower the molecular weight of the final polymer.

[0010] Recently, North et al. (Journal of Polymer Science 2022, 61 , 4, 31 1 -322) disclosed a ROCOP procedure using Coates’ chromium(lll)-salen-chloride complex, the analogous aluminium(lll) complex, or a dicyclohexylurea organic compound as the catalyst and PPNCI as the co-catalyst.

[0011] KR101880390B1 discloses a method of epoxidizing a methanol soluble fraction of a Kraft lignin, and reacting the derived epoxy resin with phthalic anhydride to provide a thermoset biopolyester, which was further cured at elevated temperatures.

[0012] It is an object of the present invention to provide a novel ring-opening co-polymerization method that overcomes or improves one or more of the disadvantages of the prior art, or at least offers one or more useful alternatives. It is a further object of the present invention to provide novel thermoplastic functional polyesters that overcome or improve one or more of the disadvantages of the prior art, or at least offer one or more useful alternatives.

[0013] SUMMARY OF THE INVENTION

[0014] According to a first aspect, the present invention provides a method for preparing a thermoplastic functional polyester, the method comprising heating a mixture comprising epoxide monomers and cyclic anhydride monomers; wherein at least part of the epoxide monomers are lignin-derived glycidyl ether monomers represented by formula (I) wherein

[0015] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and

[0016] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci-ealkyl; wherein at least a part of the lignin-derived glycidyl ether monomers comprise hydroxy groups; and wherein the average epoxide functionality of the epoxide monomers, being the product of the epoxide content, calculated from the epoxide equivalent weight determined according to ASTM D 1652-97 (1997), and the number average molecular weight determined by GPC, is at most 2.0, preferably from 0.5 to 1 .5, more preferably from 0.6 to 1 .4, even more preferably from 0.7 to 1 .3, yet even more preferably from 0.8 to 1 .2, most preferably from 0.9 to 1 .1 .

[0017] It was found that polymerization occurs, in particular ring-opening polymerization, more in particular ring-opening co-polymerization (ROCOP), when a mixture of epoxide monomers, in particular glycidyl ether monomers, and cyclic anhydride monomers is heated, when at least part of the epoxide monomers comprise hydroxy groups. Advantageously, polymerization occurs in the method as defined herein, in the absence of external initiators or catalysts typically used for ring-opening polymerization, thereby avoiding contamination of said initiators or catalysts of, or the need for their removal from, the resulting polymers. Without willing to be bound by any theory, it may well be that the hydroxy groups are capable of initiating and / or propagating and / or accelerating the polymerization reaction, which could be considered ‘self-initiation’, ‘selfpromotion’ or ‘self-catalysis’.

[0018] It was also found that thermoplastic polyesters may be provided by the method as defined herein, as the average epoxide functionality of the epoxide monomers of at most 2.0 largely avoids crosslinking of the polymer. In contrast, it was found that an epoxidized methanol soluble Kraft lignin, similar to the one reported in KR101880390B1 , has an average epoxide functionality of more than 4.0. Heating said epoxidized methanol soluble Kraft lignin with a cyclic anhydride, provides a thermoset material, which is undesirable for the envisaged applications of the thermoplastic functional polyesters as defined herein.

[0019] It was further found that the method as defined herein, may allow to leave the hydroxy groups, in particular the aliphatic hydroxy groups, comprised in the epoxide monomers, unreacted. It was also found that the hydroxy groups, in particular the aliphatic hydroxy groups of the epoxide monomers, may react in the method as defined herein. In the latter case, the hydroxy groups resulting from opening of the oxirane ring of the epoxide monomers may remain unreacted. The presence of unreacted hydroxy groups in the polymer resulting from the method as defined herein, may allow the use of the polymer, in particular the functional polyester, in the preparation of further polymers, such as polyurethanes, polycarbonates, and polyesters.

[0020] A further advantage of the method as described herein, is that the reaction takes place under more industrially relevant and robust conditions. It appeared that the reaction proceeds without the need for inert conditions, such as an atmosphere of nitrogen (N2) or argon (Ar), commonly employed for this purpose, or the use of a glovebox. It further appeared that extensive purification of the reactants was not needed to allow the polymerization reaction to occur. It was further found that the reaction may be performed without the use of a solvent.

[0021] The method as described herein, advantageously allows to tailor the thermomechanical properties of the resulting polymer, in particular the thermoplastic functional polyester. The structure of the functional polyester may be tailored by the choice of (a combination of) cyclic anhydride monomers. The structure of the functional polyester may be tailored by the choice of (a combination) epoxide monomers. The amount of hydroxy group comprising epoxy monomers, relative to the total mixture comprising the epoxide monomers and the cyclic anhydride monomers, may lead to different first structural units, and therefore to a different structure of the functional polyester. The structure of the functional polyester may be tailored by the reaction conditions, such as the presence of an external catalyst, in particular an organocatalyst. The structure of the functional polyester may also be tailored by a combination of one or more of the options, such as the choice of cyclic anhydride monomers, the choice epoxide monomers, and the reaction conditions, mentioned above.

[0022] Control of the thermomechanical properties of the functional polyesters furthermore advantageously allows to tailor the properties of any further polymers based on said functional polyesters, such as polyurethanes.

[0023] In an embodiment, the present invention provides the method as defined herein, wherein the lignin-derived glycidyl ether monomers are selected from coumaryl alcohol glycidyl ether monomers, dihydrocoumaryl alcohol glycidyl ether monomers, 4-propylphenol glycidyl ether monomers, coniferyl alcohol glycidyl ether monomers, dihydroconiferyl alcohol glycidyl ether monomers, propylguaiacol glycidyl ether monomers, sinapyl alcohol glycidyl ether monomers, dihydrosinapyl alcohol glycidyl ether monomers, propylsyringol glycidyl ether monomers, or any combination thereof.

[0024] In an embodiment, the present invention provides the method as defined herein, wherein the lignin-derived glycidyl ether monomers comprising hydroxy groups are represented by formula (I) wherein

[0025] Ri and Rr are each independently selected from -H, and -OMe; and

[0026] R2 is selected from -Ci ealkyl-OH, and -Cz ealkenyl-OH; preferably from -Cs ealkyl-OH, and -C3- ealkenyl-OH; more preferably from -(CHz^CHzOH, and -CHCHCH2OH.

[0027] In an embodiment, the present invention provides the method as defined herein, wherein the OH-content of the mixture comprising the epoxide monomers and the cyclic anhydride monomers, is at least 0.005 mmol / g.

[0028] In a further embodiment, the present invention provides the method as defined herein, wherein the OH-content of the mixture comprising the epoxide monomers and the cyclic anhydride monomers, is at least 0.050 mmol / g, preferably at least 0.100 mmol / g, more preferably at least 0.250 mmol / g, even more preferably at least 0.500 mmol / g, yet even more preferably from 1 .0 to 10.0 mmol / g, yet even more preferably from 2.0 to 8.0 mmol / g.

[0029] In a further embodiment, the present invention provides the method as defined herein, wherein the number average molecular weight of the epoxide monomers, determined by GPC, is at most 3000 g / mol, preferably at most 2500 g / mol, more preferably at most 2000 g / mol, even more preferably at most 1500 g / mol, yet even more preferably from 300 to 1000 g / mol. In a further embodiment, the present invention provides the method as defined herein, wherein the mixture further comprises a catalyst, preferably an organocatalyst, more preferably bis(triphenylphosphoranylidene)iminium chloride (PPNCI).

[0030] In a further embodiment, the present invention provides the method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers is heated at a temperature of at least 50 °C, preferably at most 150 °C, more preferably from 60 to 140 °C.

[0031] In a further embodiment, the present invention provides the method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers is heated in an atmosphere which comprises 10 % of oxygen or more, preferably air.

[0032] In a further embodiment, the present invention provides the method as defined herein, wherein the cyclic anhydride monomers are represented by formula (II) wherein

[0033] R3 and FU are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0034] According to a further aspect, the present invention provides a polymer, in particular a thermoplastic functional polyester, obtainable by the method as defined herein.

[0035] According to yet a further aspect, the present invention provides a polymer, in particular a thermoplastic functional polyester, comprising first structural units derived from glycidyl ether monomers, and second structural units derived from cyclic anhydride monomers; wherein at least 10 wt.% of the first structural units are derived from lignin-derived glycidyl ether monomers, preferably at least 20 wt.%, more preferably at least 40 wt.%, even more preferably from 50 to 100 wt.%; and wherein at least a part of the first structural units derived from lignin- derived glycidyl ether monomers comprise hydroxy groups. Because lignin-derived products or mixtures typically contain both aromatic (phenolic) and aliphatic hydroxy groups, it was advantageously found that these lignin-derived products or mixtures may be used to prepare the corresponding lignin-derived glycidyl ethers, and subsequently use the lignin-derived glycidyl ethers to prepare the thermoplastic functional polymer as described herein.

[0036] As mentioned hereinbefore, the (aliphatic) hydroxy groups of the lignin-derived glycidyl ethers may react in the polymerization reaction, leading to different first structural units. The hydroxy groups of the lignin-derived glycidyl ethers may lead to improved (thermomechanical) properties of the polymer prepared therefrom, such as a thermoplastic functional polyester. The resulting hydroxy groups of the thermoplastic lignin-derived functional polyesters as defined herein, may be used to prepare further polymers by reaction of the hydroxy groups with other functional groups, such as isocyanates, thereby providing polyurethanes.

[0037] A further advantage of using lignin-derived glycidyl ether monomers, in particular lignin hydrogenolysis oil derived glycidyl ether monomers and / or mixtures of lignin-derived glycidyl ether monomers comprising dihydroconiferyl alcohol glycidyl ether monomers, is that a thermoplastic functional polyester (polyol) may be obtained with a high biobased content. Consequently, any further polymers based on said functional polyester (polyol) may also be obtained with a high biobased content.

[0038] In an embodiment, the present invention provides the polymer as defined herein, wherein the polymer is an alternating copolymer.

[0039] In a further embodiment, the present invention provides the polymer as defined herein, wherein at least part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (Illa) or (I lib) wherein

[0040] Ri and R are each independently selected from -H, and -O-Ci-ealkyl; and

[0041] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci-ealkyl.

[0042] In a further embodiment, the present invention provides the polymer as defined herein, wherein at least part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (IVa) or (IVb)

[0043] (Ha) (Hb) wherein

[0044] Ri and Rr are each independently selected from -H, and -O-Ci-ealkyl; and X is selected from -Ci ealkyl, and -Cz ealkenyl.

[0045] In a further embodiment, the present invention provides the polymer as defined herein, wherein a first part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (Illa) or (I Hb) wherein

[0046] Ri and Rr are each independently selected from -H, and -O-Ci-ealkyl; and R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci-ealkyl; and a second part of the first structural units derived from lignin-derived glycidyl ether monomers, are represented by formula (IVa) or (IVb) wherein

[0047] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and X is selected from -Ci ealkyl, and -Cz ealkenyl.

[0048] In a further embodiment, the present invention provides the polymer as defined herein, wherein the second structural units derived from cyclic anhydride monomers are represented by formula wherein

[0049] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0050] In a further embodiment, the present invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VII) wherein

[0051] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl;

[0052] R2 is selected from -H, -Ci ealkyl, and -Czealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci ealkyl; and

[0053] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0054] In a further embodiment, the present invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VIII) wherein

[0055] R1 and Rr are each independently selected from -H, and -O-Ci ealkyl;

[0056] X is selected from -Ci ealkyl, and -C2-ealkenyl; and

[0057] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0058] According to yet a further aspect, the present invention provides a use of the polymer as defined herein, as a polyol in the preparation of a further polymer.

[0059] In an embodiment, the present invention provides the use as defined herein, wherein the further polymer is selected from polyurethanes, polyesters, polycarbonates, or any combination thereof.

[0060] BRIEF DESCRIPTION OF THE DRAWINGS

[0061] With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

[0062] Figure 1 (also shown as FIG. 1 ) shows stacked1H NMR spectra of the crude MPA / DCAGE ROCOP reaction mixture according to Example 2a (Ex. 2a), as well as its starting materials MPA and DCAGE.

[0063] Figure 2 (also shown as FIG. 2) shows stacked1H NMR spectra of the crude MPA / LHO-GE ROCOP reaction mixture according to Example 2c (Ex. 2c), as well as its starting materials MPA and LHO-GE.

[0064] Figure 3 (also shown as FIG. 3) shows stacked1H NMR spectra of the crude PA / DCAGE ROCOP reaction mixture according to Example 3b (Ex. 3b), as well as its starting materials PA and DCAGE.

[0065] Figure 4 (also shown as FIG. 4) shows stacked1H NMR spectra of the crude PA / LHO-GE ROCOP reaction mixture according to Example 4b (Ex. 4b), as well as its starting materials PA and LHO-GE.

[0066] Figure 5 (also shown as FIG. 5) shows stacked1H NMR spectra of the crude SA / DCAGE ROCOP reaction mixture according to Example 5d (Ex. 5d), as well as its starting materials SA and DCAGE. Figure 6 (also shown as FIG. 6) shows stacked1H NMR spectra of the crude SA / LHO-GE ROCOP reaction mixture according to Example 6e (Ex. 6e), as well as its starting materials SA and LHO-GE.

[0067] Figure 7 (also shown as FIG. 7) shows stacked1H NMR spectra of the crude MPA / SA / DCAGE ROCOP reaction mixture according to Example 8a (Ex. 8a), as well as its starting materials MPA, SA and DCAGE.

[0068] Figure 8 (also shown as FIG. 8) shows stacked1H NMR spectra of the crude MPA / SA / LHO-GE ROCOP reaction mixture according to Example 8b (Ex. 8b), as well as its starting materials MPA, SA and LHO-GE.

[0069] Figure 9a (also shown as FIG. 9a) shows a31P {1H} NMR spectrum of the phosph itylated crude reaction mixture according to Example 9f (Ex. 9f), wherein PA was spiked with 25% [DCAGE], without PPNCI organic catalyst.

[0070] Figure 9b (also shown as FIG. 9a) shows a31P {1H} NMR spectrum of the phosph itylated crude reaction mixture according to Example 9e (Ex. 9e), wherein PA was spiked with 10% [DCAGE], without PPNCI organic catalyst.

[0071] Figure 9c (also shown as FIG. 9a) shows a31P {1H} NMR spectrum of the phosph itylated crude reaction mixture according to Example 9d (Ex. 9d), wherein PA was spiked with 5% [DCAGE], without PPNCI organic catalyst.

[0072] Figure 10a (also shown as FIG. 10a) shows stacked31P {1H} NMR spectra of poly(PA-co- DCAGE) polyester samples according to Example 3b (Ex. 3b), and Example 3h (Ex. 3h), as well as its starting materials DCA, and DCAGE.

[0073] Figure 10b (also shown as FIG. 10a) shows stacked31P {1H} NMR spectra of poly(PA-co- DCAGE) polyester samples according to Example 3b (Ex. 3b), and Example 3h (Ex. 3h), as well as its starting materials DCA, and DCAGE, focused in on the aliphatic OH region.

[0074] Figure 11a (also shown as FIG. 1 1 a) shows stacked31P {1H} NMR spectra of poly(PA-co- LHOGE) polyester samples according to Example 4a (Ex. 4a), and Example 4c (Ex. 4c), as well as its starting materials LHO, and LHOGE.

[0075] Figure 11b (also shown as FIG. 1 1 b) shows stacked31P {1H} NMR spectra of poly(PA-co- LHOGE) polyester samples according to Example 4a (Ex. 4a), and Example 4c (Ex. 4c), as well as its starting materials LHO, and LHOGE, focused in on the aliphatic OH region. DETAILED DESCRIPTION OF THE INVENTION

[0076] The present invention will now be further described. In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0077] When describing the compounds of the present invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise:

[0078] The term "alkyl" by itself or as part of another substituent refers to a fully saturated hydrocarbon of formula CxHzx+i wherein x is a number greater than or equal to 1 . Generally, alkyl groups of this invention comprise from 1 to 20 carbon atoms. Alkyl groups may be linear or branched and may be substituted as indicated herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, Ci-4alkyl means an alkyl of one to four carbon atoms. Examples of alkyl groups are methyl, ethyl, n-propyl, i-propyl, butyl, and its isomers (e.g. n-butyl, i-butyl and t- butyl); pentyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomers, nonyl and its isomers; decyl and its isomers, undecyl and its isomers, dodecyl and its isomers, tridecyl and its isomers, tetradecyl and its isomers, pentadecyl and its isomers, hexadecyl and its isomers, heptadecyl and its isomers, octadecyl and its isomers, nonadecyl and its isomers, eicosanyl and its isomers. The term "optionally substituted alkyl" refers to an alkyl group optionally substituted with one or more substituents (for example 1 to 4 substituents, for example 1 , 2, 3, or 4 substituents) at any available point of attachment. Non-limiting examples of such substituents include esters, carboxylic acids, alkyl moieties, alkene moieties, alkyne moieties, and the like.

[0079] The term "alkenyl" or “alkene”, as used herein, unless otherwise indicated, means straight-chain, cyclic, or branched-chain hydrocarbon radicals containing at least one carbon-carbon double bond. Examples of alkenyl radicals include ethenyl, E- and Z-propenyl, isopropenyl, E- and Z- butenyl, E- and Z-isobutenyl, E- and Z-pentenyl, E- and Z-hexenyl, E,E-, E,Z-, Z,E-, Z,Z- hexadienyl, be it in the terminal or internal positions, and the like. Generally alkenyl or alkene moieties of the present invention comprise from 2 to 20 C atoms. An optionally substituted alkenyl refers to an alkenyl having optionally one or more substituents (for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl.

[0080] The term “cycloalkyl” by itself or as part of another substituent is a cyclic alkyl group, that is to say, a monovalent, saturated, or unsaturated hydrocarbyl group having a cyclic structure. Cycloalkyl includes all saturated or partially saturated (containing 1 or 2 double bonds) hydrocarbon groups containing 1 to 3 rings, including monocyclic, bicyclic, or polycyclic alkyl groups. Cycloalkyl groups may comprise 3 or more carbon atoms in the ring and generally, according to this invention comprise from 3 to 15 atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, adamantanyl and cyclodecyl. An “optionally substituted cycloalkyl” refers to a cycloalkyl having optionally one or more substituents (for example 1 to 3 substituents, for example 1 , 2, 3 or 4 substituents), selected from those defined above for substituted alkyl.

[0081] The term "alkynyl", as used herein, unless otherwise indicated, means straight-chain or branched-chain hydrocarbon radicals containing at least one carbon-carbon triple bond. Examples of alkynyl radicals include ethynyl, propynyl, butynyl, pentynyl, hexynyl, hexadiynyl, be it in the terminal or internal positions, and the like. An optionally substituted alkynyl refers to an alkynyl having optionally one or more substituents (for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl.

[0082] Where alkyl groups as defined are divalent, i.e., with two single bonds for attachment to two other groups, they are termed "alkylene" groups. Non-limiting examples of alkylene groups includes methylene, ethylene, methylmethylene, trimethylene, propylene, tetramethylene, ethylethylene, 1 ,2-dimethylethylene, pentamethylene and hexamethylene. Similarly, where alkenyl groups as defined above and alkynyl groups as defined above, respectively, are divalent radicals having single bonds for attachment to two other groups, they are termed "alkenylene" and "alkynylene" respectively.

[0083] In the context of the present invention, the alkyl, alkenyl and alkynyl moieties as defined herein may also further comprise one or more heteroatoms, such as selected from N, S or O, in that for example a carbon atom in an alkyl, alkene or alkyne chain is replaced by a heteroatom. When two or more C atoms are replaced by heteroatoms, the heteroatoms may be adjacent or separated, as long as it results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation. An example of a stable combination of two adjacent heteroatoms is a disulfide (-S- S-) group. Where a carbon atom in an alkyl, alkenyl or alkynyl chain is replaced by an N atom, the N atom may be N or NH depending on the number of bonds connected to said C atom.

[0084] The term "heterocycle" as used herein by itself or as part of another group refers to a nonaromatic, fully saturated or partially unsaturated cyclic group (for example, 3 to 13 membered monocyclic, 7 to 17 membered bicyclic, or 10 to 20 membered tricyclic ring systems, or containing a total of 3 to 10 ring atoms) which have at least one heteroatom in at least one carbon atom-containing ring. Each ring of the heterocyclic group containing a heteroatom may have 1 , 2, 3 or 4 heteroatoms selected from nitrogen atoms, oxygen atoms and / or sulfur atoms, where the nitrogen and sulfur heteroatoms may optionally be oxidized and the nitrogen heteroatoms may optionally be quaternized. The heterocyclic group may be attached at any heteroatom or carbon atom of the ring or ring system, where valence allows. The rings of multiring heterocycles may be fused, bridged and / or joined through one or more spiro atoms. An optionally substituted heterocyclyl refers to a heterocyclyl having optionally one or more substituents (for example 1 to 4 substituents, or for example 1 , 2, 3 or 4), selected from those defined above for substituted alkyl. Non-limiting examples of a heterocycle comprise: piperidinyl, piperazinyl, azepanyl, morpholinyl.

[0085] The term “aryl" as used herein refers to a polyunsaturated, aromatic hydrocarbyl group having a single ring (i.e. phenyl) or multiple aromatic rings fused together (e.g. naphthalene or anthracene) or linked covalently, typically containing 6 to 10 atoms; wherein at least one ring is aromatic. The aromatic ring may optionally include one to three additional rings (either cycloalkyl, heterocyclyl, or heteroaryl) fused thereto. Aryl is also intended to include the partially hydrogenated derivatives of the carbocyclic systems enumerated herein. Non-limiting examples of aryl comprise phenyl, napthyl, and the like. The aryl group or heterocycle as defined herein can optionally be substituted by one or more substituents (for example 1 to 5 substituents, for example 1 , 2, 3, 4 or 5) at any available point of attachment. Non-limiting examples of such substituents are selected from halogen, hydroxy, oxo, nitro, amino, hydrazine, aminocarbonyl, azido, cyano, alkyl, cycloalkyl, alkenyl, alkynyl, cycloalkylalkyl, alkylamino, alkoxy, -SO2-NH2, aryl, heteroaryl, aralkyl, haloalkyl, haloalkoxy, alkoxycarbonyl, alkylaminocarbonyl, heteroarylalkyl, alkylsulfonamide, heterocyclyl, alkylcarbonylaminoalkyl, aryloxy, alkylcarbonyl, acyl, arylcarbonyl, aminocarbonyl, alkylsulfoxide, -SC F , alkylthio, carboxyl, and the like, wherein Rxis alkyl or cycloalkyl.

[0086] The term “heteroaryl” as used herein by itself or as part of another group refers but is not limited to 5 to 12 carbon-atom aromatic rings or ring systems containing 1 to 3 rings which are fused together or linked covalently, typically containing 5 to 8 atoms; at least one of which is aromatic in which one or more carbon atoms in one or more of these rings can be replaced by oxygen, nitrogen or sulfur atoms where the nitrogen and sulfur heteroatoms may optionally be oxidized and the nitrogen heteroatoms may optionally be quaternized. Such rings may be fused to an aryl, cycloalkyl, heteroaryl or heterocyclyl ring. Non-limiting examples of such heteroaryl, include: piridinyl, oxazolyl, thiazolyl, and the like. An “optionally substituted heteroaryl” refers to a heteroaryl having optionally one or more substituents (for example 1 to 4 substituents, for example 1 , 2, 3 or 4), selected from those defined above for substituted aryl.

[0087] The term “oxo” as used herein refers to the group =0.

[0088] The term “alkoxy" or “alkyloxy” as used herein refers to a radical having the Formula -ORy wherein Ry is alkyl, as defined above. Non-limiting examples of suitable alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxy. Where the oxygen atom in an alkoxy group is substituted with sulfur, the resultant radical is referred to as thioalkoxy. Generally, the alkyl groups comprised in the alkoxy groups of this invention comprise from 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms. The alkyl groups may be linear or branched and may be substituted as indicated herein. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, -O-Ci-4alkyl means an alkoxy group comprising an alkyl group of one to four carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, and tert-butoxy.

[0089] The term "carboxy" or “carboxyl” or “hydroxycarbonyl” by itself or as part of another substituent refers to the group -CO2H.

[0090] The term “ester” or "alkoxycarbonyl" by itself or as part of another substituent refers to a carboxy group linked to an alkyl radical i.e. to form -C(O)ORy, wherein Ryis alkyl, as defined above.

[0091] The term “alkylcarbonyloxy” by itself or as part of another substituent refers to a -O-C(O)RZwherein Rzis alkyl, as defined above.

[0092] Whenever the term “substituted” is used in the present invention, it is meant to indicate that one or more hydrogens on the atom indicated in the expression using “substituted” is replaced with a selection from the indicated group, provided that the indicated atom’s normal valency is not exceeded, and that the substitution results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation. Where groups may be optionally substituted, such groups may be substituted once or more, and preferably once, twice or thrice. Substituents may be selected from, for example, the group comprising halogen, hydroxy, oxo, nitro, amido, carboxy, amino, cyano, haloalkoxy, and haloalkyl.

[0093] As used herein the terms such as “alkyl, aryl, or cycloalkyl, each being optionally substituted with” or “alkyl, aryl, or cycloalkyl, optionally substituted with” refers to optionally substituted alkyl, optionally substituted aryl and optionally substituted cycloalkyl.

[0094] The compounds of the present invention can be prepared according to the reaction schemes provided in the examples hereinafter, but those skilled in the art will appreciate that these are only illustrative for the invention and that the compounds of this invention can be prepared by any of several standard synthetic processes commonly used by those skilled in the art of organic chemistry. According to a first aspect, the present invention provides a method for the ring-opening copolymerization of epoxide monomers and cyclic anhydride monomers, the method comprising heating a mixture comprising the epoxide monomers and the cyclic anhydride monomers; wherein at least part of the epoxide monomers comprise hydroxy groups.

[0095] In the context of current invention, the terms “method for preparing a thermoplastic functional polyester as defined herein” and “ring-opening co-polymerization method as defined herein” are synonymously used to refer to the method of the invention as defined herein.

[0096] In the context of the current invention, the term “epoxide monomer(s)” is used for (a) chemical compound(s) comprising an oxirane moiety.

[0097] In the context of the current invention, the term “at least part of” refers to a definite, non-zero, portion of the item it refers to. The term “at least part of” may therefore refer to about 1 %, 2 %, 3 %, 5 %, 10 %, 20 %, 25 %, 30 %, 40 %, 50 %, 60 %, 70 %, 75 %, 80 %, or substantially all, such as about 90 %, 95 %, 99 %, and even about 100 %, of the item it refers to.

[0098] It was further found that glycidyl ethers may be particularly suited to be used in the copolymerization method as described herein. In useful embodiments of the invention, the epoxide monomers comprise glycidyl ether monomers. For instance, at least 10 wt.% of the epoxide monomers are glycidyl ether monomers, such as 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%; or the majority of the epoxide monomers are glycidyl ether monomers, such as 60 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 90 wt.%; or substantially all the epoxide monomers are glycidyl ether monomers, such as 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, 99 wt.%, or even 100 wt.%. In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are glycidyl ether monomers.

[0099] In the context of the current invention, the terms “glycidyl ether(s)” or “glycidyl ether monomer(s)” are synonymously used for (a) chemical compound(s) comprising a glycidyl ether moiety. Scheme 1 provides a representation of a glycidyl ether moiety, with the point of attachment to the ether O atom.

[0100] Scheme 1. Glycidyl ether moiety

[0101] In the context of the current invention, the terms “cyclic anhydride(s)” or “cyclic anhydride monomer(s)” are synonymously used for (a) chemical cyclic compound(s) comprising an acid anhydride moiety. Scheme 2 provides a representation of a cyclic anhydride.

[0102] Scheme 2. Cyclic anhydride

[0103] In the context of the current invention, the terms “initiator(s)”, “promoter(s)”, and “catalyst(s)” are synonymously used for (a) compound(s), other than the reactants or reaction products, capable of initiating and / or propagating and / or accelerating the polymerization reaction, in particular the ring-opening co-polymerization, as disclosed herein.

[0104] The hydroxy groups on the epoxide monomers may be present at any part or point of connection on the epoxide monomers. It is however preferred that the hydroxy groups are connected to an aliphatic part of the glycidyl ether monomers, i.e. aliphatic hydroxy groups. The aliphatic hydroxy groups (in the side chain of the epoxide monomers) are of particular interest, as they may allow for post-functionalization and / or further polymerization of the copolymer obtained from the method as disclosed herein.

[0105] An epoxide monomer, in particular a glycidyl ether monomer, comprising hydroxy groups, contains at least 1 hydroxy group, but it may also contain 2 or more hydroxy groups, such as 3, 4, or 5 hydroxy groups, or more. Preferably, epoxide monomers, in particular glycidyl ether monomers, comprising hydroxy groups contain 1 or 2 hydroxy groups. In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprising hydroxy groups contain at least 1 aliphatic hydroxy group. In a further particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprising hydroxy groups essentially consist of epoxide monomers comprising at least 1 aliphatic hydroxy group. In an even further embodiment, the present invention provides the ringopening co-polymerization method as defined herein, wherein the epoxide monomers comprising hydroxy groups essentially consist of glycidyl ether monomers comprising at least 1 aliphatic hydroxy group.

[0106] It was surprisingly found that even a small amount of hydroxy group comprising epoxy monomers in the reaction mixture is sufficient to initiate and / or catalyze and / or promote the polymerization reaction, in particular the ring-opening co-polymerization reaction. Even in a reaction mixture with only 0.1 wt.% of hydroxy group comprising epoxy monomers, relative to the total mixture comprising the epoxide monomers and the cyclic anhydride monomers, ringopening co-polymerization reaction occurs when the mixture is heated.

[0107] While the wt.% of hydroxy group comprising epoxy monomers, relative to the total mixture comprising the epoxide monomers and the cyclic anhydride monomers, can be calculated for known mixtures of discrete compounds, it may prove challenging to calculate it for unknown mixtures. It is therefore preferred to refer to the hydroxy-content (‘OH-content’) as a measure for the amount of hydroxy group comprising epoxy monomers, relative to the total mixture comprising the epoxide monomers and the cyclic anhydride monomers. The OH-content refers to the molar equivalents of hydroxy groups, expressed in mmol / g. The OH-content may be calculated theoretically if applicable, or it may be determined experimentally by quantitative31P NMR spectroscopy according to the experimental protocol reported by van de Pas (Holzforschung 2014, 68, 151 -155) using endo-A / -hydroxy-5-norbornene-2,3-dicarboximide as the internal standard. In the experimental determination of the OH-content it is furthermore feasible to distinguish between aliphatic, aromatic (phenolic), and carboxylic OH groups. As shown in the experimental section, the theoretical and experimental determination of the OH- content of known mixtures of epoxide monomers are in good agreement. Unless stated otherwise, when referring to the OH-content, it refers to the theoretical OH-content.

[0108] It appeared that polymerization still occurs when a mixture of epoxide monomers and cyclic anhydride monomers is heated, wherein the OH-content of the mixture of epoxide monomers and cyclic anhydride monomers is about 0.003 mmol / g. In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the OH-content of the mixture of epoxide monomers and cyclic anhydride monomers is at least 0.005 mmol / g.

[0109] It further appeared that the rate of polymerization may be improved when the amount of epoxide monomers comprising hydroxy groups is increased, relative to the total amount of epoxide monomers in the reaction mixture, which typically corresponds to a higher OH-content of the mixture of epoxide monomers and cyclic anhydride monomers. The OH-content may be at least 0.010 mmol / g, such as, but not limited to, 0.025 mmol / g, 0.050 mmol / g, 0.075 mmol / g, 0.100 mmol / g, 0.200 mmol / g, 0.300 mmol / g, 0.400 mmol / g, 0.500 mmol / g, 0.600 mmol / g, 0.700 mmol / g, 0.800 mmol / g, 0.900 mmol / g, 1 .0 mmol / g, 1 .5 mmol / g, 2.0 mmol / g, 2.5 mmol / g, 3.0 mmol / g, 3.5 mmol / g, 4.0 mmol / g, 4.5 mmol / g, 5.0 mmol / g, 6.0 mmol / g, 7.0 mmol / g, 8.0 mmol / g, 9.0 mmol / g, or even 10.0 mmol / g or more. In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the OH-content of the total amount of epoxide monomers in the reaction mixture is at least 0.050 mmol / g, preferably at least 0.100 mmol / g, more preferably at least 0.250 mmol / g, even more preferably at least 0.500 mmol / g, yet even more preferably from about 1 .0 to 10.0 mmol / g, yet even more preferably from about 2.0 to 8.0 mmol / g.

[0110] It was further found that aryl glycidyl ethers, also referred to as aryl glycidyl ether monomers, may be particularly suited to be used in the co-polymerization method as described herein. In useful embodiments of the invention, the epoxide monomers comprise aryl glycidyl ethers. For instance, at least 10 wt.% of the epoxide monomers are aryl glycidyl ethers, such as 20 wt.%, 30 wt.%, 40 wt.%, 50 wt.%; or the majority of the epoxide monomers are aryl glycidyl ethers, such as 60 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 90 wt.%; or substantially all the epoxide monomers are glycidyl ethers, such as 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, 99 wt.%, or even 100 wt.%. In a particular embodiment, the present invention provides the ring-opening copolymerization method as defined herein, wherein substantially all the epoxide monomers are aryl glycidyl ether monomers. In a more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are aryl glycidyl ether monomers, and wherein at least part of the aryl glycidyl ether monomers comprise hydroxy groups.

[0111] Aryl glycidyl ethers may be commercially available or may be prepared according to procedures known to the skilled person. An aryl glycidyl ether may for instance be prepared from the corresponding aryl alcohol, also known as a phenol, by reaction with epichlorohydrin and subsequent formation of the oxirane or epoxide ring by treatment with a base. Scheme 3 provides an exemplary preparation method for aryl glycidyl ethers, represented by the formation of phenyl glycidyl ether from phenol.

[0112] Scheme 3. Aryl glycidyl ether preparation

[0113] Examples of aryl glycidyl ethers, thereby referring to their corresponding aryl alcohols if applicable, are phenyl glycidyl ether, guaiacol glycidyl ether, eugenol glycidyl ether, vanillyl alcohol glycidyl ether, coniferyl alcohol glycidyl ether, dihydroconiferyl alcohol glycidyl ether, sinapyl alcohol glycidyl ether, dihydrosinapyl alcohol glycidyl ether, coumaryl alcohol glycidyl ether, dihydrocoumaryl alcohol glycidyl ether, and their alkylated analogs, such as ethylguaiacol glycidyl ether, propylsyringol glycidyl ether, and the like.

[0114] It is well-known that lignocellulosic biomass is a promising natural source of chemical compounds comprising three main components, namely cellulose, hemicellulose and lignin, with lignin being the most abundant source of biobased phenolics. Lignin is a complex polydisperse biopolymer mainly composed of three main monolignols, p-coumaryl alcohol (H units), sinapyl alcohol (S units) and coniferyl alcohol (G units). Their respective content in the lignocellulosic biomass depends on the plant source. For example, gymnosperms contain almost exclusively G units, angiosperms contain a mixture of G and S units, while H units are more abundant in grasses and softwood. p-Coumaryl alcohol Coniferyl alcohol Sinapyl alcohol

[0115] Depending on the process used to separate the lignin from the (hemi-)cellulose, different types of lignin are obtained as a byproduct. Lignosulfonates for instance are byproducts of the sulfite pulping process and consist of aromatic and aliphatic phenolic groups, and carboxylic acid groups like other types of lignin, but it additionally contains aliphatic sulfonic acid salts. Lignosulfonates are water-soluble anionic polymers that can be very polydisperse in terms of molecular mass. Other pulping processes, such as the Kraft process which make use of a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (NazS), lead to a black liquor containing lignin. This black liquor may be further processed into sulfonated lignin, but it may also be further refined by selective solvent extraction with a suitable solvent. This extraction may lead to fractions with lower dispersity.

[0116] In the context of the current invention, the term ‘lignin-derived’ refers to any product or mixture of products resulting from the pre-treatment, modification, functionalization, depolymerization, conversion, degradation, hydrolysis, extraction and / or dissolution of lignin, lignin-containing mixtures or lignocellulosic biomass. Typical, yet non-limiting, examples of lignocellulosic biomass are softwood, hardwood, crops, trees, bushes, grasses, agricultural residues and waste wood. Typical, yet non-limiting, lignin-containing mixtures are mixtures resulting from various (pulping) processes, such as kraft lignin, black liquor, lignosulfonates, organosolv lignins, hydrolysed lignin, soda lignin, steam exploded lignin, lignin hydrogenolysis oil. The term ‘lignin- derived’ may also refer to synthetically produced products or mixtures from (reduced) monolignols, such as propylguiacol, a propylguiacol dimer, dihydroconiferyl alcohol, and the like. The term ‘lignin-derived’ may also refer to products or mixtures of (reduced) monolignols obtained from other natural sources, such as eugenol extracted from clove.

[0117] Because lignin-derived products or mixtures typically contain both aromatic (phenolic) and aliphatic hydroxy groups, it was found that these lignin-derived products or mixtures may be particularly suited to prepare the corresponding aryl glycidyl ethers, and subsequently use the aryl glycidyl ethers in the method as described herein. In useful embodiments of the invention, the epoxide monomers comprise lignin-derived glycidyl ether monomers.

[0118] In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprise lignin-derived glycidyl ether monomers. In a more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprise lignin- derived glycidyl ether monomers, and wherein at least a part of the lignin-derived glycidyl ether monomers comprise hydroxy groups. In an even more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprise lignin-derived glycidyl ether monomers, and wherein at least a part of the lignin-derived glycidyl ether monomers comprise at least 1 aliphatic hydroxy group.

[0119] In a specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin-derived glycidyl ether monomers. In a more specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin-derived glycidyl ether monomers, and wherein at least a part of the lignin- derived glycidyl ether monomers comprise hydroxy groups. In an even more specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin-derived glycidyl ether monomers, and wherein at least a part of the lignin-derived glycidyl ether monomers comprise at least 1 aliphatic hydroxy group.

[0120] In the context of the current invention, the terms “(a) lignin-derived glycidyl ether(s)” “(a) lignin- derived aryl glycidyl ether(s)”, “(a) lignin-derived aryl glycidyl ether monomer(s)”, and “(a) lignin- derived glycidyl ether monomer(s)” therefore refers to any compound or mixture of compounds resulting from conversion of at least part of the phenolic hydroxy groups of the lignin-derived (mixture of) compounds into the corresponding glycidyl ether groups.

[0121] It further appeared that aryl glycidyl ethers obtained from a lignin hydrogenolysis oil may be particularly suited to be used to be used in the co-polymerization method as described herein, as such aryl glycidyl ethers obtained from a lignin hydrogenolysis oil will comprise hydroxy groups, and in particular aliphatic hydroxy groups.

[0122] The term ‘lignin hydrogenolysis oil’ (‘LHO’) is a known term in the art, and refers to a mixture of lignin monomers, dimers, and oligomers obtained from the metal-catalyzed hydrogenolysis of lignin, lignin-containing mixtures or lignocellulosic biomass, such as described by Torr et al. (Bioresource Technology 102(16) :7608-1 1 ). Lignin hydrogenolysis oil is sometimes also referred to as ‘depolymerised lignin oil’, ‘lignin oil from lignin-first biorefining’, or ‘lignin oil from reductive catalytic fractionation of lignocellulosic biomass’. Depending on the reaction conditions, this process produces reduced monolignols and dimeric and oligomeric structures, also known as lignin oils. The main small molecular weight compounds, such as reduced monolignols, commonly found in depolymerized lignins are propylguaiacol (PG), propylsyringol (PS), dihydroconiferyl alcohol (DCA) and dihydrosinapyl alcohol (DSA). The ratio between G and S may be tuned by the choice of feedstock, while the ratio between alcohol and propyl derivatives may be tuned by the choice of catalyst. A lignin hydrogenolysis oil may therefore be characterized by its major constituents, such as dihydroconiferyl alcohol.

[0123] Dihydroooniferyl alcohol (DCA) Dihydrosinapyl alcohol (DSA)

[0124] Propylguaiacol (PG) Propylsyringol (PS)

[0125] The presence of hydroxy groups in the aliphatic side-chains, i.e. aliphatic OH-groups, allows the co-polymerization to occur and may also accelerate the reaction. Aliphatic OH-groups remaining after the polymerization reaction and / or aliphatic groups resulting from opening of the oxirane ring of the glycidyl ether monomers, may be suitable for post-modification and / or further polymerization.

[0126] In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprise lignin hydrogenolysis oil derived glycidyl ether monomers. In a more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the epoxide monomers comprise lignin hydrogenolysis oil derived glycidyl ether monomers, and wherein a part of the lignin hydrogenolysis oil derived glycidyl ether monomers comprise hydroxy groups. In an even more particular embodiment, the present invention provides the ring-opening copolymerization method as defined herein, wherein the epoxide monomers comprise lignin hydrogenolysis oil derived glycidyl ether monomers, and wherein a part of the lignin hydrogenolysis oil derived glycidyl ether monomers comprise at least 1 aliphatic hydroxy group.

[0127] In a specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin hydrogenolysis oil derived glycidyl ether monomers. In a more specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin hydrogenolysis oil derived glycidyl ether monomers, and wherein a part of the lignin hydrogenolysis oil derived glycidyl ether monomers comprise hydroxy groups. In an even more specific embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein substantially all the epoxide monomers are lignin hydrogenolysis oil derived glycidyl ether monomers, and wherein a part of the lignin hydrogenolysis oil derived glycidyl ether monomers comprise at least 1 aliphatic hydroxy group.

[0128] The advantage of using lignin-derived glycidyl ether monomers, such as lignin hydrogenolysis oil derived glycidyl ether monomers and / or a mixture of lignin-derived glycidyl ether monomers comprising dihydroconiferyl alcohol glycidyl ether monomers, is that a functional polyester polyol may be obtained with a high biobased content, and any polymers based on said polyol.

[0129] In a further particular embodiment, the present invention provides the ring-opening copolymerization method as defined herein, wherein the lignin-derived glycidyl ether monomers, in particular the lignin hydrogenolysis oil derived glycidyl ether monomers, are represented by formula (I) wherein

[0130] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and

[0131] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci-ealkyl.

[0132] In embodiments, the present invention provides the method as defined herein, wherein the lignin-derived glycidyl ether monomers comprising hydroxy groups are represented by formula (I) wherein

[0133] Ri and Rr are each independently selected from -H, and -O-Ci-ealkyl; and

[0134] R2 is selected from -Ci-ealkyl-OH, and -Cz ealkenyl-OH; preferably from -Cs ealkyl-OH, and -C3- ealkenyl-OH; more preferably from -(CHz^CHzOH, and -CHCHCH2OH.

[0135] In embodiments of the invention, R1 and Rr are each independently selected from -H, and - OMe. In embodiments of the invention, R2 is selected from -Cs-ealkyl , and -Cs-ealkenyl, wherein each of said -Cs-ealkyl, and -Cs-ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci-ealkyl. In useful embodiments of the invention, R1 and Rr are each independently selected from -H, and -OMe; and R2 is selected from -Cs- ealkyl, and -Cs-ealkenyl, wherein each of said -Cs-ealkyl, and -Cs-ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci-ealkyl. In preferred embodiments of the invention, R1 and Rr are each independently selected from -H, and -OMe; and R2 is selected from -(CH2)2CH3, -CH2CHCH2, -(CH2)2CH2OH, and - CHCHCH2OH.

[0136] In useful embodiments of the invention, the epoxide monomers comprise a mixture of lignin- derived glycidyl ether monomers comprising dihydroconiferyl alcohol glycidyl ether monomers.

[0137] In other useful embodiments of the invention, the epoxide monomers are a mixture of lignin- derived glycidyl ether monomers comprising dihydroconiferyl alcohol glycidyl ether monomers.

[0138] When the epoxide monomers are a mixture, such as a mixture of lignin-derived glycidyl ether monomers, the number average molecular weight (Mn) of the mixture can be determined, for instance by GPC. While the method as defined herein is not limited to a particular number average molecular weight, it was found that a mixture of lignin-derived glycidyl ether monomers with a lower Mn, such as a glycidylated lignin hydrogenolysis oil (LHO-GE), may be advantageous. Indeed, a glycidylated lignin hydrogenolysis oil (LHO-GE) is a viscous oil, and it was shown to react with cyclic anhydrides in the absence of a solvent. It was further found that other mixtures of lignin-derived glycidyl ether monomers may also benefit from a lower Mn, as this may increase the solubility in a solvent and / or may increase the reactivity in the polymerization method as defined herein. In embodiments, the present invention provides the method as defined herein, wherein the number average molecular weight of the epoxide monomers, determined by GPC, is at most 3000 g / mol, preferably from 200 to 2500 g / mol, more preferably from 300 to 2000 g / mol, even more preferably from 400 to 1500 g / mol, yet even more preferably from 500 to 1000 g / mol.

[0139] As mentioned hereinbefore, it was found to be beneficial that the average epoxide functionality of the epoxide monomers is at most 2.0, as this avoids extensive crosslinking, and provides a thermoplastic polymer instead of a thermoset polymer /

[0140] In the context of the present invention, the term “average epoxide functionality of the epoxide monomers” or “ / ”, as reported by Quinstaat et al. (Industrial Crops & Products 194 (2023) 1 16305) is calculated by the following formula: f = EPC x Mn / 1000 wherein EPC represents the epoxide content (expressed in mmol / g) of the mixture of epoxide monomers, calculated from the epoxide equivalent weight determined according to ASTM D 1652-97 (1997), and Mnrepresents the number average molecular weight of the mixtures of epoxide monomers (expressed in g / mol), determined by GPC.

[0141] In embodiments, the present invention provides the method as defined herein, wherein the average epoxide functionality of the epoxide monomers is at most 2.0, preferably from 0.5 to 1 .5, more preferably from 0.6 to 1 .4, even more preferably from 0.7 to 1 .3, yet even more preferably from 0.8 to 1 .2, most preferably from 0.9 to 1 .1 .

[0142] The temperature of the polymerization reaction may be selected to allow the polymerization reaction to occur at a suitable rate. The temperature of the polymerization reaction may be selected to allow one or more of the reagents to be melted to allow for better mixing of the reagents, such as by stirring or agitation. In useful embodiments of the invention, the mixture comprising the glycidyl ether monomers and the cyclic anhydride monomers is heated to a temperature of at least 50°C, such as 50 °C, 60 °C, 70 °C, 75 °C, 80 °C, 90 °C, preferably of at most 150 °C, such as 150 °C, 140 °C, 130 °C, 125 °C, 120 °C, 1 10 °C, 100 °C. It was further found that when one or more of the reagents is a solid, it may be beneficial to add a solvent to the mixture before subjecting the mixture to heating. In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the mixture comprising the glycidyl ether monomers and the cyclic anhydride monomers further comprises a solvent.

[0143] As mentioned hereinbefore, it is an advantage of the ring-opening co-polymerization method as defined herein, that the reaction mixture does not have to be flushed with an inert atmosphere, such as nitrogen (N2) or argon (Ar). In useful embodiments of the invention, the mixture comprising the epoxide monomers and the cyclic anhydride monomers is heated in an atmosphere which comprises 10 % of oxygen or more, such as 15 % of oxygen or more, or even 20 % of oxygen or more. In a particular embodiment, the present invention provides the ringopening co-polymerization method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers is heated in an atmosphere substantially composed of air.

[0144] It was also found that specific cyclic anhydrides may be particularly suited to be used in the copolymerization method as described herein. In useful embodiments of the invention, the cyclic anhydrides are monocyclic or bicyclic saturated or unsaturated cyclic anhydrides. Examples of cyclic anhydrides that may be used in the method of invention are succinic anhydride, maleic anhydride, itaconic anhydride, citraconic anhydride, phthalic anhydride, 2-methylphthalic anhydride, and 3-methylphthalic anhydride.

[0145] In a particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the cyclic anhydride monomers are represented by formula (H) wherein

[0146] R3 and FU are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0147] The advantage of a cyclic anhydride such as 3-methylphthalic anhydride, is that it can be obtained from biomass, and therefore may (further) enhance the biobased content of the resulting functional polyester polyol, and any polymers based on said polyol. Although the ring-opening co-polymerization method as described herein proceeds without an external catalyst or initiator, it appeared that addition of an external catalyst or initiator may have a beneficial effect on the polymerization rate and / or on to avoid homo-polymerization of the epoxide monomers. It was specifically found that an organocatalyst may lead to an acceleration of the polymerization rate. In a particular embodiment, the present invention provides the ringopening co-polymerization method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers further comprises a catalyst. In a more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers further comprises an organocatalyst. In an even more particular embodiment, the present invention provides the ring-opening co-polymerization method as defined herein, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers further comprises an organocatalyst selected from bis(triphenylphosphoranylidene)iminium chloride (PPNCI), 4-(dimethylamino)pyridine (DMAP), or any combination thereof.

[0148] To provide for a substantially alternating co-polymer, it is preferred that the epoxide monomers and the cyclic anhydride monomers in the mixture are present in a stoichiometric ratio, in other words a 1 :1 molar ratio. It should however be appreciated that the invention is not limited to 1 :1 mixtures of epoxide monomers and cyclic anhydride monomers, nor will such a 1 :1 mixture per se lead to a substantially alternating copolymer.

[0149] The epoxide monomers, wherein at least part of the epoxide monomers comprise one or more hydroxy groups, may be fully composed of one specific type of epoxide monomer, such as dihydroconiferyl glycidyl ether. The epoxide monomers may also be composed of different type of epoxide monomers, such as a mixture of lignin-derived glycidyl ethers or lignin hydrogenolysis oil derived glycidyl ethers.

[0150] The cyclic anhydride monomers may be composed of one specific type of cyclic anhydride monomers, such as 3-methylphthalic anhydride, phthalic anhydride, or succinic anhydride, leading to a so-called copolymer. The cyclic anhydride can also be composed of a mixture of two or more specific types of cyclic anhydride monomers, such as a mixture of 3-methylphthalic anhydride, and succinic anhydride, leading to a so-called terpolymer.

[0151] According to a further aspect, the present invention provides a polymer obtainable by the ringopening co-polymerization method as defined herein, wherein the polymer comprises hydroxy groups. It was found that a polymer obtained by the ring-opening co-polymerization of epoxide monomers and cyclic anhydride monomers, wherein at least part of the epoxide monomers comprise hydroxy groups, may show interesting properties as a building block for other polymers. Due to the presence of hydroxy groups in the polymer, it may for instance be used as a polyol for the preparation of polyurethanes, polycarbonates, and other polymers employing polyols.

[0152] The ring-opening co-polymerization method as defined herein typically leads to an alternating copolymer of first structural units derived from glycidyl ether monomers and second structural units derived from cyclic anhydride monomers, wherein the number of first and second structural units is substantially equal. In a particular embodiment of the invention, the present invention provides the polymer obtainable by the ring-opening co-polymerization method as defined herein, wherein the polymer is a substantially alternating copolymer. In another particular embodiment, the present invention provides the polymer as defined herein, wherein the ratio of first and second structural units is about 1 , such as from 0.8 to 1 .2, preferably from 0.9 to 1 .1 , even more preferably from 0.95 to 1 .05.

[0153] In the context of the current invention, the terms “(a) first structural unit(s) derived from (a) epoxide(s)” or “(a) first structural unit(s) derived from (a) epoxide monomer(s)” are synonymously used for (a) chemically defined compound(s) comprising a glycidyl ether moiety after ring-opening of the oxirane ring of the epoxide monomer.

[0154] Similarly, the terms “(a) first structural unit(s) derived from (a) glycidyl ether(s)” or “(a) first structural unit(s) derived from (a) glycidyl ether monomer(s)” are synonymously used for (a) chemically defined compound(s) comprising a glycidyl ether moiety after ring-opening of the oxirane ring of the glycidyl ether monomer.

[0155] Ring-opening of the oxirane ring may have occurred by a nucleophilic attack on either one of the carbon atoms of the oxirane ring, leading to two different isomers. For sake of simplicity, when referring to either one of said ring-opening isomers, it is deemed to include both isomers.

[0156] After ring-opening, the hydroxy group resulting from the ring-opening of the oxirane ring may have reacted further in the polymerization reaction, leading to a first structural unit connected via the oxygen atom of said hydroxy group. Alternatively or complementary, and if present, any other hydroxy group, in particular aliphatic hydroxy group, comprised in the epoxide monomer may have reacted further in the polymerization reaction, leading to a first structural unit connected via the oxygen atom of said other hydroxy group. In other words, the polymer as defined herein may contain only first structural units connected via the oxygen atom of the hydroxy group resulting from the ring-opening of the oxirane ring, it may contain only first structural units connected via the oxygen atom of any other hydroxy groups present in the epoxide monomers, or it may contain a combination of both types of first structural units.

[0157] Scheme 4 provides a representation of both isomers of first structural units derived from epoxide monomers, connected via the oxygen atom of the hydroxy group resulting from the ring-opening of the oxirane ring, wherein R represents any substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl group, or any combination of two or more thereof.

[0158] Scheme 4. Representation of a first structural unit derived from an epoxide monomer

[0159] Scheme 5 provides a representation of both isomers of first structural units derived from epoxide monomers, connected via the oxygen atom of any other hydroxy group comprised in the epoxide monomer, wherein R represents any substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl group, or any combination of two or more thereof.

[0160] Scheme 5. Representation of a first structural unit derived from a glycidyl ether monomer

[0161] In the context of the current invention, the terms “(a) second structural unit(s) derived from (a) cyclic anhydride(s)” or “(a) second structural unit(s) derived from (a) cyclic anhydride monomer(s)” are synonymously used for (a) chemically defined compound(s) comprising a cyclic anhydride moiety after ring-opening of the cyclic anhydride.

[0162] It should however be appreciated that the invention is not limited to a polymer wherein the number of first and second structural units is substantially equal, as deviation of this parameter may occur during the polymerization reaction. For instance, homo-polymerization of two or more epoxide monomers may lead to a fragment, in particular an oligo- or polyether fragment, which leads to deviation of the number of first and second structural units in the polymer as defined herein. In a particular embodiment, the present invention provides the polymer as defined herein, wherein the polymer is an alternating copolymer of the first and second structural units. In a further particular embodiment, the present invention provides the polymer as defined herein, wherein the ratio of first and second structural units is substantially 1 , such as from 0.8 to 1 .2, preferably from 0.9 to 1 .1 , even more preferably from 0.95 to 1 .05.

[0163] In the context of the current invention, regardless of the ratio of first and second structural units, the terms “(a) functional polyester(s)”, “(a) functional polyesters polyol(s)” or “(a) polyesters polyol(s)” are synonymously used for the polymer as defined herein.

[0164] When two or more types of second structural units are present in the functional polyester, resulting from two more types of cyclic anhydride monomers, the functional polyester as described herein may be referred to as a terpolymer. The terpolymer may be a random terpolymer, a block terpolymer, or a combination thereof. Random or block terpolymers may be the result of the relative reactivities of each type of cyclic anhydride monomer, of their concentration in the reaction mixture at any given time, and / or of the sequence of adding reagents to the reaction mixture.

[0165] In a specific embodiment, the present invention provides the polymer as defined herein, wherein at least part of the first structural units derived from glycidyl ether monomers, in particular from lignin-derived glycidyl ether monomers, are represented by formula (Illa) or (I lib) wherein Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and

[0166] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci-ealkyl.

[0167] In a more specific embodiment, the present invention accordingly provides the polymer as defined herein, wherein at least part of the first structural units derived from glycidyl ether monomers, in particular from lignin-derived glycidyl ether monomers, are represented by formula (Illa’), (Illa”), (lllb’) or (lllb”) wherein R1 and Rr are each independently selected from -H, and -O-Ci-ealkyl.

[0168] In a further specific embodiment, the present invention accordingly provides the polymer as defined herein, wherein the first structural units derived from glycidyl ether monomers, in particular from glycidyl ether monomers comprising an hydroxy group, more in particular from lignin-derived glycidyl ether monomers comprising an hydroxy group, are represented by formula (IVa) or (IVb) wherein

[0169] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and X is selected from -Ci ealkyl, and -Cz ealkenyl. In useful embodiments of the invention, X is selected from -Cs-ealkyl, and -Cs ealkenyl. In preferred embodiments of the invention, X is selected from -(CHz)3-, and -CH=CHCH2-.

[0170] In a further specific embodiment, the present invention accordingly provides the polymer as defined herein, wherein the first structural units derived from glycidyl ether monomers, in particular from glycidyl ether monomers comprising an hydroxy group, more in particular from lignin-derived glycidyl ether monomers comprising an hydroxy group, are represented by formula (IVa’), (IVa”), (IVb’) or (IVb”) wherein

[0171] Ri and Rr are each independently selected from -H, and -O-Ci-ealkyl.

[0172] It further appeared that when said glycidyl ether monomers, in particular lignin-derived glycidyl ether monomers, which are used to prepare the polymer as defined herein, comprise one or more aliphatic hydroxy groups, it may also lead to a polymer comprising two different first structural units derived from glycidyl ether monomers, in particular from lignin-derived glycidyl ether monomers. A first part of the first structural units may be connected via the oxygen atom of the hydroxy group resulting from opening of the oxirane ring of the glycidyl ether monomers, while a second part of the first structural units may be connected via the oxygen atom of the one or more other aliphatic hydroxy groups present in the glycidyl ether monomers, in particular in the lignin-derived glycidyl ether monomers.

[0173] When the glycidyl ether monomers used to prepare the polymer as defined herein, comprises an aliphatic hydroxy group, and a first structural unit is connected via the oxygen atom of the hydroxy group resulting from opening of the oxirane ring of the glycidyl ether monomer, such as represented by formula (Illa), (Illa’), (Illa”), (II lb), (I I lb’) or (I lib”) , then the aliphatic hydroxy group of the first structural unit may be present as a primary aliphatic hydroxy group.

[0174] When the glycidyl ether monomers used to prepare the polymer as defined herein, comprise an aliphatic hydroxy group, and a first structural unit is connected via the oxygen atom of the aliphatic hydroxy group, such as represented by formula (IVa), (I Va’), (IVa”), (I Vb), (I Vb’) or (IVb”), then the hydroxy group resulting from opening of the oxirane ring of the glycidyl ether monomer may be present as a secondary aliphatic hydroxy group.

[0175] In a further specific embodiment, the present invention provides the polymer as defined herein, wherein a first part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (Illa) or (II lb) wherein

[0176] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and

[0177] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci ealkyl; and a second part of the first structural units derived from lignin-derived glycidyl ether monomers, are represented by formula (IVa) or (IVb)

[0178] (IVa) (IVb) wherein

[0179] R1 and Rr are each independently selected from -H, and -O-Ci ealkyl; and

[0180] X is selected from -Ci ealkyl, and -C2-ealkenyl.

[0181] In a further specific embodiment, the present invention provides the polymer as defined herein, wherein the second structural units derived from cyclic anhydride monomers are represented by formula (V) wherein

[0182] Rs and FU are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0183] In a more particular embodiment of the invention, the presentation invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VI) wherein

[0184] Ar is an aryl group, said aryl group being optionally substituted with 1 or more substituents selected from -Ci ealkyl, -Cz ealkenyl, -Cz ealkynyl, -OH, and -O-Ci-ealkyl; wherein each of said - Ci ealkyl , -Cz ealkenyl, and -Cz ealkynyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci-ealkyl; and

[0185] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0186] In a more particular embodiment of the invention, the presentation invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VII) wherein

[0187] Ri and Rr are each independently selected from -H, and -O-Ci ealkyl;

[0188] R2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci ealkyl; and

[0189] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0190] In a further particular embodiment, the present invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VIII) wherein

[0191] R1 and Rr are each independently selected from -H, and -O-Ci ealkyl;

[0192] X is selected from -Ci ealkyl, and -C2-ealkenyl; and

[0193] R3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

[0194] In a more particular embodiment, the present invention provides the polymer as defined herein, wherein the polymer comprises repetitive units represented by formula (VII), and repetitive units represented by formula (VIII), wherein Ri , Rr, R2, R3, R4, and X are as defined in any one of the embodiments described herein.

[0195] It was also found that the molecular weight (number average molecular weight, Mn) of the polymer as defined herein may influence its thermomechanical properties and / or the properties of any further polymers based on the functional polyesters as described herein. In useful embodiments of the invention, the number average molecular weight (Mn) of the polymer ranges from 500 to 8000 g / mol, preferably from 1000 to 5000 g / mol.

[0196] According to yet a further aspect, the present invention provides a use of the polymer as defined herein in the preparation of further polymers. As mentioned hereinbefore, the polymer as defined herein, comprising hydroxy groups, may be used as a polyol in the preparation of further polymers, such as polyurethanes, polyesters, polycarbonates. In a particular embodiment, the present invention provides the use of the polymer obtainable by the ring-opening copolymerization as defined herein in the preparation of further polymers. In a more particular embodiment, the present invention provides the use of the polymer obtainable by the ringopening co-polymerization as defined herein in the preparation of polyurethanes, polyesters, and polycarbonates.

[0197] The compounds of the present invention can be prepared according to the reaction schemes provided in the examples hereinafter, but those skilled in the art will appreciate that these are only illustrative for the invention and that the compounds of this invention can be prepared by any of several standard synthetic processes commonly used by those skilled in the art of organic chemistry.

[0198] EXAMPLES

[0199] Materials

[0200] All the chemicals were commercially obtained from Merck (Sigma-Aldrich) or VWR and used as received unless stated otherwise. Reagents were used as received, unless stated otherwise. 3- Methylphthalic anhydride was commercially obtained from ThermoFisher Scientific®. Phthalic anhydride (PA), 3-methylphthalic anhydride (MPA), and succinic anhydride (SA) were dried in a vacuum oven overnight and stored in a desiccator before use, unless stated otherwise. Dihydroconiferyl alcohol glycidyl ether (DCAGE) and lignin hydrogenolysis oil glycidyl ether (LHO-GE), were prepared following reported protocols (Quinsaat et al., Biomacromolecules 2022, 23, 4562-4573).

[0201] A lignin hydrogenolysis oil (LHO) was prepared as reported previously (Feghali et al., Biomacromolecules 2020, 21 , 1548-1559) as a dark amber colored oil, with a phenolic hydroxy content of 4.71 mmol / g. The LHO was epoxidized as reported previously (Quinsaat et al., Biomacromolecules 2022, 23, 4562-4573) in a two-step approach by reaction with epichlorohydrin, and subsequently with NaOH, providing a lignin hydrogenolysis oil glycidyl ether (LHO-GE). The number average molecular weight (Mn) of the LHO-GE, determined by GPC, is 346 Da.

[0202] 31P {1H} NMR spectroscopy revealed 96% of the phenolic OH groups were epoxidized (phenolic hydroxy content of 0.20 mmol / g), while the aliphatic OH groups were undisturbed, at the reaction conditions employed, to allow access to a desired functional epoxide substrate for polymer synthesis. The phenolic epoxide content present in the LHO-GE (4.51 mmol epoxide / g) was determined from the difference between the LHO and the LHO-GE. The epoxide equivalent weight (EEW) and epoxide content of the LHO-GE samples were determined in triplicate by potentiometric titration following ASTM Standard D 1652-97 (1997) scaled down to analyze 30- 40 mg samples, and was found to be 2.97 mmol / g. The average epoxide functionality ( / epoxide) of the LHO-GE, being the product of the number average molecular weight (Mn) and the epoxide content, is therefore 1 .0.

[0203] A methanol soluble fraction of Kraft lignin (MSKL) was prepared a reported previously (Jung et al. Journal of Wood Chemistry and Technology 2017, 37 (6), 433-442) on a Kraft lignin with a number average molecular weight (Mn) of 1090 Da, and a weight average molecular weight (Mw) of 3850 Da, determined by GPC. The methanol soluble fraction was found to have an Mnof 1 130 Da, and an Mwof 2300 Da. The MSKL was epoxidized in the same way as the LHO, to provide methanol soluble Kraft lignin glycidyl ether (MSKL-GE). The epoxide content of the MSKL-GE was found to be 2.93 mmol / g, leading to an average epoxide functionality ( / epoxide) of 4.7.

[0204] Analysis

[0205] Total lignin content was determined in duplicate as the sum of Klason lignin (acid insoluble) and acid-soluble lignin following methods used in previous work (Green Chem. 2012, 14, 1447).1H,13C {1H}, HSQC and31P {1H} NMR spectra were obtained using a AVIII 400 MHz spectrometer equipped with a Prodigy 5 mm broadband probe (Bruker, Switzerland).

[0206] NMR spectroscopy was recorded on a Bruker AVIII 400 MHz or benchtop Magritek Spinsolve 80 MHz Ultra series Phosphor instrument and referenced to residual solvent signals such as CHCI3. Hydroxy content was determined using phosphitylation and quantitative31P {1H} NMR spectroscopy, using chromium acetylacetone, endo-N-hydroxy-5-norbornene-2,3- dicarboximide, pyridine, deuterated chloroform (CDC ) and 2-chloro-4,4,5,5-tetramethyl- 1 ,3,2-dioxaphospholane, as reported by Pas et al. (Holzforschung 2014, 68, 151 ), Gracia- Vittoria et al. (Ind Crops Prod 2022, 176, 1 14405), Granata et al. (J Agric Food Chem 1995, 43 (6), 1538-1544), and Meng et al. (Nat Protoc 2019, 14 (9), 2627-2647).

[0207] Fourier-transform infrared spectroscopy (FT-IR) was performed using a Thermo Fischer Nicolet iS10 or Bruker Tensor 27 spectrometer and was measured using attenuated total reflectance mode (ATR-FTIR) under standard atmospheric conditions on a diamond crystal with a spectral range of 400-4000 cm1. The scan resolution was 4 cm1with 32 scans per sample and the spectra was baseline corrected.

[0208] LC-MS was performed on a Thermo Orbitrap Q Exactive coupled with a dionex UPLC-MS. A reversed phase LC measurement was performed using an Acquity BEH C18 100 x 2.1 mm 1 .7 pm column with 10 mMH4Ac as buffer A and CH3CN as buffer B. With gradient: t= 0 min: 2% B, t= 2 min: 2% B, t= 10 min 100% B, t = 12 min 100% B, t= 12.1 min: 2% B, t= 15 min: 2% B. The column temperature was 60 °C and 5 pl was injected. Measurements were performed using ESI in positive and negative ion mode.

[0209] Gel permeation chromatography (GPC) was performed on a Shimadzu system using a combination of three Styragel columns (guard-HRE4-HRE4 or guard-HR0.5-HR1 ) connected to a refractive index (Rl) and UV detector. The instrument was calibrated with polystyrene (PS) internal standards (162-204000 g.mol-1for the HRE4-HRE4 columns or 162-12980 g.mol-1for the HR0.5-HR1 columns) and eluted with THF solvent. The molecular weight (Mn) and dispersity (D) values were obtained from the Rl detector.

[0210] Differential Scanning Calorimetry (DSC) analyses were recorded on a TA Instruments Discovery DSC 250 or Discovery DSC with the samples placed in Tzero pans with Tzero hermetic lids perforated to allow for a nitrogen atmosphere upon measurement. The sample was cooled to - 60 °C at 10 °C / min, equilibrated and held at this temperature for 2 minutes, heated to 150 °C at 10 °C / min (1 st heating cycle), held at this temperature for 2 minutes, cooled to -60 °C at 10 °C / min, equilibrated and held at this temperature for 2 minutes and heated to 150 °C at 10 °C / min (2nd heating cycle). The Tgvalues were determined from the 2ndheating cycle.

[0211] Dynamic mechanical thermal analysis (DMTA) was conducted using a RSA-G2 TA instrument in tensile mode and rectangular geometry. The ramp rate was 2.0 °C / min with a frequency of 1 .0 Hz. Liquid nitrogen cooling was employed in cases to allow for a -20 °C start temperature if required. Each material sample was measured at least three times to get an average value and the standard deviation error for the Tg. The DMTA was also employed for the tensile strength testing via measuring the stress-strain curves at 23 °C and 50% humidity at a rate of 0.002-0.1 mm / s depending on the brittleness or flexibility of the film sample. Each sample was measured 4-5 times to get average values and the standard deviation error, for the ultimate tensile strength, Young’s modulus and elongation at break. Samples were cut with the help of a ISO 527-2 I ISO 37-4 metal cutter or die (PIONEER Die-tecs®) with sample dimensions of ca. 12 mm length x 2 mm width.

[0212] General procedure A

[0213] Cyclic anhydride monomer(s) and epoxide monomer(s) were weighed into a 20 mL vial, and a magnetic stirring bar was added. The vial was capped, and the mixture was heated at 1 10 °C under stirring. The mixture was heated during a desired reaction time, or until the stirring stopped due to an increase in viscosity. After the vial was removed from heating, an aliquot of the crude mixture was taken and analysed via1H NMR spectroscopy to determine the conversion, based on the cyclic anhydride monomer(s).

[0214] To purify and isolate the polymer, dichloromethane was added to form a concentrated solution, followed by acidified methanol (2 M) to precipitate a copolymer solid. This was isolated via centrifugation (RPM = 3500, 15 minutes). The polymer solid would collect at the bottom of the centrifuge tube, the solvent could be decanted and discarded away, and the polymer redissolved in dichloromethane to transfer all product to another vial. The solvents were removed in vacuo on a rotary evaporator and dried in a vacuum oven at 35 °C overnight.

[0215] Example 1

[0216] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial MPA (0.4054 g, 2.5 mmol), synthesized DCAGE (0.5957 g, 2.5 mmol) or synthesized LHO-GE (1 .0417 g, 2.5 mmol [epoxide]), with and without [PPNCI] catalyst (1 .0 mol%, 0.025 mmol).

[0217] Example 2

[0218] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial MPA (1 .1350 g, 7.0 mmol), synthesized DCAGE (1 .6680 g, 7.0 mmol) or synthesized LHO-GE ((2.9167 g, 7.0 mmol [epoxide]), with and without [PPNCI] catalyst (1 .0 mol%, 0.070 mmol).

[0219] Table 1 provides an overview of the copolymers prepared according to example 1 and 2, and Table 2 provides the analysis data of those copolymers. Table 1. Reaction mixtures and conversion according to Example 1 and 2

[0220] Time

[0221] Entry Epoxide [MPA]:[epoxide]:[PPNCI] Conv. (%)

[0222] (min)

[0223] Ex. 1 a DCAGE

[0100] :

[0100] :[0] 5 84% MPA

[0224] Ex. 1 b DCAGE

[0100] :

[0100] :

[0001] 5 82% MPA

[0225] Ex. 1 c LHO-GE

[0100] :

[0100] :[0] 35 71 % MPA

[0226] Ex. 2a DCAGE

[0100] :

[0100] :[0] 10 85% MPA

[0227] Ex. 2b DCAGE

[0100] :

[0100] :

[0001] 10 84% MPA

[0228] Ex. 2c LHO-GE

[0100] :

[0100] :[0] 45 73% MPA

[0229] Table 2. Analysis data of copolymers prepared according to Example 1 and 2

[0230] MnTotal OH value

[0231] Entry Epoxide Da f T (°C)

[0232] (Da) (mmol / g)

[0233] Ex. 1 a DCAGE 2400 1 .65 2.96 7.1 41 .3

[0234] Ex. 1 b DCAGE 2500 1 .59 3.05 7.6 40.6

[0235] Ex. 1 c LHO-GE 3000 1 .99 3.1 1 9.3 56.2

[0236] Ex. 2a DCAGE 2900 1 .68 3.01 8.7 42.6

[0237] Ex. 2b DCAGE 2800 1 .61 2.98 8.3 41 .3

[0238] Ex. 2c LHO-GE 3100 2.36 3.61 1 1 .2 53.7

[0239] It was observed that the polymerization reaction proceeded rapidly, with an increase in viscosity after only 5 min for Examples 1 a and 1 b, and after 10 min for larger-scale Examples 2a and 2b, when DCAGE was used as the epoxide monomer. The reaction was slower when LHO-GE was used as the epoxide monomer(s), as can be seen from Examples 1 c and 2c. The presence of an external catalyst only seemed to have a minimal effect on the reaction, and the resulting copolymers.

[0240] Example 3

[0241] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial PA (0.3703 g, 2.5 mmol), synthesized DCAGE (0.5957 g, 2.5 mmol), with and without [PPNCI] catalyst (0.2-1 .0 mol%, 0.005-0.025 mmol). Example 3f was also prepared according to General procedure A, but at a larger scale, by using grounded and vacuum oven dried, commercial PA (3.1 1 10 g, 21 .0 mmol), synthesized DCAGE (5.0046 g, 21 .0 mmol), and [PPNCI] catalyst (1 .0 mol%, 0.21 mmol). Example 4

[0242] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial PA (0.1871 g, 1 .25 mmol), synthesized LHO-GE (0.4209 g, 1 .25 mmol [epoxide]), with and without [PPNCI] catalyst (0.2-1 .0 mol%, 0.005-0.0125 mmol). Example 4f was also prepared according to General procedure A, but at a larger scale, by using grounded and vacuum oven dried, commercial PA (1 .0084 g, 6.808 mmol), LHO-GE (2.837 g, 6.808 mmol [epoxide]), and [PPNCI] catalyst (1 .0 mol%, 0.06808 mmol).

[0243] Table 3 provides an overview of the copolymers prepared according to example 5 and 6, and Table 4 provides the analysis data of those copolymers.

[0244] Table 3. Reaction mixtures and conversion according to Example 3 and 4

[0245] Time

[0246] Entry Epoxide [PA]:[epoxide]:[PPNCI] Conv. (%)

[0247] (min)

[0248] Ex. 3a DCAGE

[0100] :

[0100] :[0] 10 97 % PA

[0249] Ex. 3b DCAGE

[0100] :

[0100] :

[0001] 5 87 % PA

[0250] Ex. 3c DCAGE

[0250] :

[0250] :

[0001] 5 92 % PA

[0251] Ex. 3d DCAGE

[0500] :

[0500] :

[0001] 6 88 % PA

[0252] Ex. 3e DCAGE

[0500] :

[0500] :

[0001] 10 >99 % PA

[0253] Ex. 3f DCAGE

[0100] :

[0100] :

[0001] 1 1 98 % PA

[0254] Ex. 4a LHO-GE

[0250] :

[0250] :[0] 15 38 % PA

[0255] Ex. 4b LHO-GE

[0100] :

[0100] :

[0001] 15 78 % PA

[0256] Ex. 4c LHO-GE

[0250] :

[0250] :

[0001] 15 63 % PA

[0257] Ex. 4d LHO-GE

[0250] :

[0250] :

[0001] 20 83 % PA

[0258] Ex. 4e LHO-GE

[0500] :

[0500] :

[0001] 30 79 % PA

[0259] Ex. 4f LHO-GE

[0100] :

[0100] :

[0001] 20 88 % PA Table 4. Analysis data of copolymers prepared according to Example 5 and 6

[0260] MnTotal OH value

[0261] Entry Epoxide Da f T I°Q\

[0262] (Da) (mmol / g)

[0263] Ex. 3a DCAGE 1950 1 .95 n.d n.d n.d

[0264] Ex. 3b DCAGE 2800 1 .51 3.22 9.0 31 .2

[0265] Ex. 3c DCAGE 2650 1 .79 3.07 8.1 33.0

[0266] Ex. 3d DCAGE 2650 1 .78 3.1 1 8.2 37.9

[0267] Ex. 3e DCAGE 2800 1 .78 3.13 8.8 37.0

[0268] Ex. 3f DCAGE 1950 1 .58 2.33 4.8 29.5

[0269] Ex. 4a LHO-GE 2000 1 .92 3.13 6.3 58.6

[0270] Ex. 4b LHO-GE 2750 1 .92 2.90 7.8 58.1

[0271] Ex. 4c LHO-GE 2600 1 .90 3.21 8.3 59.5

[0272] Ex. 4d LHO-GE 2800 1 .93 3.01 8.4 59.3

[0273] Ex. 4e LHO-GE 2950 1 .94 3.03 8.9 61 .3

[0274] Ex. 4f LHO-GE 2450 1 .93 3.31 8.1 57.4

[0275] It was observed that the presence of an organocatalyst may result in a copolymer with a higher molecular weight and / or a lower dispersity and / or faster reaction kinetics of the polymerization reaction.

[0276] Example 5

[0277] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial SA (0.2502 g, 2.5 mmol), synthesized DCAGE (0.5957 g, 2.5 mmol), with and without [PPNCI] catalyst (0.2-1 .0 mol%, 0.005-0.025 mmol).

[0278] Example 5d was also prepared according to General procedure A, but at a larger scale, by using grounded and vacuum oven-dried commercial SA (2.0998 g, 21 .0 mmol), DCAGE (5.000 g, 21 .0 mmol), and [PPNCI] catalyst (1 .0 mol%, 0.21 mmol).

[0279] Instead of being sealed after weighing all reagents (Example 5a), the vials of Examples 5b-5d were flushed with nitrogen before sealing.

[0280] Example 6

[0281] Copolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial SA (0.1251 g, 1 .25 mmol), synthesized LHO-GE (0.4209 g, 1 .25 mmol [epoxide]), with and without [PPNCI] catalyst (0.2-1 .0 mol%, 0.005-0.0125 mmol).

[0282] Example 6e was also prepared according to General procedure A, but at a larger scale, by using grounded and vacuum oven dried commercial SA (0.6813 g, 6.808 mmol), LHO-GE (2.837 g, 6.808 mmol [epoxide]), and [PPNCI] catalyst (1 .0 mol%, 0.06808 mmol).

[0283] Instead of being sealed after weighing all reagents (Example 6a), the vials of Examples 6b-6e were flushed with nitrogen before sealing. Table 5 provides an overview of the copolymers prepared according to example 5 and 6, and Table 6 provides the analysis data of those copolymers.

[0284] Table 5. Reaction mixtures and conversion according to Example 3 and 4

[0285] Time

[0286] Entry Epoxide [SA]:[epoxide]:[PPNCI] Conv. (%)

[0287] (min)

[0288] Ex. 5a DCAGE

[0100] :

[0100] :

[0001] 15 >99 % SA

[0289] Ex. 5b DCAGE

[0100] :

[0100] :

[0001] 15 >99 % SA

[0290] Ex. 5c DCAGE

[0500] :

[0500] :

[0001] 15 >99 % SA

[0291] Ex. 5d DCAGE

[0100] :

[0100] :

[0001] 15 >99 % SA

[0292] Ex. 6a LHO-GE

[0100] :

[0100] :

[0001] 15 96 % SA

[0293] Ex. 6b LHO-GE

[0100] :

[0100] :[0] 30 94 % SA

[0294] Ex. 6c LHO-GE

[0100] :

[0100] :

[0001] 15 98 % SA

[0295] Ex. 6d LHO-GE

[0500] :

[0500] :

[0001] 30 96 % SA

[0296] Ex. 6e LHO-GE

[0100] :

[0100] :

[0001] 20 >99 % SA Table 6. Analysis data of copolymers prepared according to Example 5 and 6

[0297] MnTotal OH value

[0298] Entry Epoxide Da f T (°C)

[0299] (Da) (mmol / g)

[0300] Ex. 5a DCAGE 2790 1 .83 2.81 7.8 n.d.

[0301] Ex. 5b DCAGE 2350 1 .75 2.56 6.0 -1 .4

[0302] Ex. 5c DCAGE 2450 1 .78 2.57 6.3 -2.2

[0303] Ex. 5d DCAGE 1 100 2.01 3.1 1 3.4 -12.1 Ex. 6a LHO-GE 6550 3.91 2.25* 14.7* n.d.

[0304] Ex. 6b LHO-GE 3250 2.39 2.55 8.3 25.8

[0305] Ex. 6c LHO-GE 3550 2.1 1 3.46 12.3 1 1 .4

[0306] Ex. 6d LHO-GE 4200 1 .97 3.05 12.8 21 .8

[0307] Ex. 6e LHO-GE 2750 1 .83 3.10 8.5 32.6

[0308] * polymer sample did not fully dissolve during analysis

[0309] It was observed that the presence of an organocatalyst may result in a copolymer with a higher molecular weight and / or a lower dispersity and / or faster reaction kinetics of the polymerization reaction. It was further observed that flushing the vial only seemed to have a minor influence on the polymerization reaction, further showing the robustness of the method as described herein.

[0310] Example 7

[0311] Terpolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial MPA (0.2027 g, 1 .25 mmol), grounded and vacuum oven-dried commercial SA (0.1251 g, 1 .25 mmol), synthesized DCAGE (0.5957 g, 2.5 mmol) or synthesized LHO-GE (1 .0417 g, 2.5 mmol [epoxide]), without [PPNCI] catalyst.

[0312] Example 8

[0313] Terpolymers were prepared according to General procedure A based on grounded and vacuum oven-dried commercial MPA (0.5675 g, 3.5 mmol), grounded and vacuum oven-dried commercial SA (0.3502 g, 3.5 mmol), synthesized DCAGE 1 .6680 g, 7.0 mmol) or synthesized LHO-GE (2.886 g, 7.0 mmol [epoxide]), without [PPNCI] catalyst.

[0314] Table 7 provides an overview of the terpolymers prepared according to example 7 and 8, and Table 8 provides the analysis data of those terpolymers.

[0315] Table 7. Reaction mixtures and conversion according to Example 7 and 8

[0316] Time

[0317] Entry Epoxide [MPA]:[SA]:[epoxide] Conv. (%)

[0318] (min)

[0319] 87% MPA /

[0320] Ex. 7a DCAGE

[0050] :

[0050] :

[0100] 10

[0321] >99% SA

[0322] 70% MPA /

[0323] Ex. 7b LHO-GE

[0050] :

[0050] :

[0100] 45

[0324] >99% SA 91 % MPA /

[0325] Ex. 8a DCAGE

[0050] :

[0050] :

[0100] 15

[0326] >99% SA

[0327] 75% MPA /

[0328] Ex. 8b LHO-GE

[0050] :

[0050] :

[0100] 45

[0329] >99% SA

[0330] Table 8. Analysis data of terpolymers prepared according to Example 7 and 8

[0331] MnTotal OH value

[0332] Entry Epoxide Da f T (°C)

[0333] (Da) (mmol / g)

[0334] Ex. 7a DCAGE 2400 1 .80 2.61 6.3 19.8

[0335] Ex. 7b LHO-GE 3500 2.74 2.86 10.0 45.2

[0336] Ex. 8a DCAGE 2100 1 .87 2.73 5.7 16.1

[0337] Ex. 8b LHO-GE 2600 2.95 3.59 9.3 32.3

[0338] No evidence of remaining SA was observed, which may result from a higher reactivity of SA monomers compared to MPA monomers.

[0339] Example 9

[0340] To determine the influence of the amount of epoxide monomers comprising hydroxy groups, General procedure A was applied to different ratios of commercial PGE spiked with DCAGE. For this purpose, grounded and vacuum oven dried, commercial PA (0.3703 g, 2.5 mmol), commercial PGE and synthesized DCAGE (overall 2.5 mmol), with no [PPNCI] added, was reacted according to General procedure A.

[0341] Table 9 provides an overview and the analysis data of the copolymers prepared according to example 9. The experimental OH-content ([OH] (rnrnol / g)experimentai) was determined via phosphitylation and quantitative31P {1H} NMR spectroscopy. This was achieved by taking an aliquot of the crude ROCOP product mixture as soon as the reaction was complete. The value was calculated by subtracting the integral of the observed carboxylic acid OH resonance signals from the integral of the aliphatic OH resonance signals. Table 9. Overview and analysis date of copolymers prepared according to example 9

[0342] Example 10

[0343] Polyurethane film materials were prepared from the copolymers or terpolymers as described herein (as polyols) in combination with an isocyanate. Scheme 6 provides a representation of this reaction.

[0344] 1 ) Dissolution, 40 C poly(PA / SA / MPA-co / ter- DCAGE / LHO-GE) polyol 2) HDI, 40 °C

[0345] +

[0346] Sn(ll) initiator

[0347] +

[0348] THF

[0349] Scheme 6. Representation of the formation of a urethane bond from a co / terpolymer and an isocyanate For each reaction, the functional polyester was dissolved in tetrahydrofuran together with Sn(ll) octanoate (Sn(Oct)2) (0.8 mol% OH). While stirring the solution at 40 °C, hexamethylene diisocyanate (HDI, 1 .05 equivalents) was added. After stirring for 90 °C at 40 °C, the resulting crude mixture was degassed for one minute in vacuo, poured into a mold and left in the fume hood to further crosslink, and slowly remove the solvent overnight. To ensure complete removal of the solvent, the film was placed in a 105 °C oven and then followed by treatment in a vacuum oven at 85 °C overnight. Fourier transform-infra red (FT-IR) spectroscopy of the thin film, compared to the HDI and the functional polyester reagents, demonstrated that all the NCO groups had reacted with the OH groups via the disappearance of the NCO stretch in the PU product

[0350] Table 10 provides an overview of the PU film materials prepared according to example 10, and

[0351] Table 10. Reaction mixtures according to Example 10

[0352] Entry Polyester polyol Example [NCO] [OH]:[NCO]

[0353] Ex. 10a Poly(PA-co-DCAGE) Ex. 3b HDI 1 :1 .05

[0354] Ex. 10b Poly(PA-co-LHO-GE) Ex. 4f HDI 1 :1 .05

[0355] Ex. 10c Poly(SA-co-DCAGE) Ex. 5d HDI 1 :1 .05

[0356] Ex. 10d Poly(SA-co-LHO-GE) Ex. 6e HDI 1 :1 .05

[0357] Ex. 10e Poly(MPA-co-DCAGE) Ex. 2a HDI 1 :1 .05

[0358] Ex. 10f Poly(MPA-co-LHO-GE) Ex. 2c HDI 1 :1 .05

[0359] Ex. 10g Poly(MPA-co-SA-co-DCAGE) Ex. 8a HDI 1 :1 .05

[0360] Ex. 10h Poly(MPA-co-SA-co-LHO-GE) Ex. 8b HDI 1 :1 .05

[0361] Based on visual inspection, it was observed that PU films made from SA-based copolymers were more flexible compared to those from PA-based copolymers, which were more brittle. A similar observation was made when comparing MPA-based copolymer PU films with MPA / SA- based terpolymer PU films. PU materials were screened and studied using DSC, dynamic mechanical thermal analysis (DMTA) and measured for their tensile strength via their stressstrain curves. Table 1 1 provides the analysis data of those materials. Table 11. Analysis data PU films prepared according to Example 10

[0362] . T- ,O. YoungAs modulus Ultimate tensile Elongat ..ion at . . brea .k

[0363] Entry Tg.tana (°C)a

[0364] (MPa) strength (MPa) (%)

[0365] Ex. 10a 73.8 ± 0.61 1450 ± 51 40.0 ± 5.8 5.40 ± 0.99

[0366] Ex. 10b 66.9 ± 1 .4 1469 ± 266 5.59 ± 1 .1 0.436 ± 0.12

[0367] Ex. 10c 10.1 ± 0.80 37.6 ± 2.7 2.15 ± 0.17 30.8 ± 3.2

[0368] Ex. 10d 62.5 ± 1 .6 1294 ± 95 28.3 ± 3.3 42.7 ± 12

[0369] Ex. 10e 57.3 ± 1 .3 1492 ± 197 32.7 ± 6.2 8.27 ± 2.2

[0370] Ex. 10f 77.5 ± 1 .1 2022 ± 47 39.9 ± 0.81 3.88 ± 0.86 Ex. 10g 37.2 ± 0.95 169 ± 28 9.25 ± 0.96 162 ± 14

[0371] Ex. 10h 63.9 ± 1 .5 526 ± 86 13.0 ± 1 .7 49.5 ± 9.4

[0372] It was finally observed that the thermomechanical properties of the PU film materials may among others be tailored by the choice of (a combination of) cyclic anhydride monomers, the choice of epoxide monomers and / or the molecular weight of the functional polyester polyol.

[0373] Comparative example A

[0374] Phenyl glycidyl ether (PGE) was used an epoxide monomer, i.e. an epoxide monomer that does not comprise hydroxy groups. For this purpose, grounded and vacuum oven dried, commercial PA (0.3703 g, 2.5 mmol), and commercial PGE (0.339 mL, 2.5 mmol) were weighed into a 20 mL vial, a magnetic stirring bar was added, and the vial was capped. The resulting mixture was magnetically stirred under air at 1 10 °C for 2 h, whereas no conversion of PA was observed.

[0375] Comparative example B

[0376] Phenyl glycidyl ether (PGE) was used an epoxide monomer, in combination with an organocatalyst. For this purpose, grounded and vacuum oven dried, commercial PA (0.3703 g, 2.5 mmol), commercial PGE (0.339 mL, 2.5 mmol), and [PPNCI] (0.2 mol%, 0.005 mmol) were weighed into a 20 mL vial, a magnetic stirring bar was added, and the vial was capped. The resulting mixture was magnetically stirred at 1 10 °C for 2 h, showing a PA conversion of 77 %.

[0377] Comparative example C

[0378] General procedure A was used based on grounded and vacuum oven-dried commercial PA (0.1871 g, 1 .25 mmol), synthesized MSKL-GE (0.4270 g, 1 .25 mmol [epoxide]), with and without [PPNCI] catalyst (0.4 mol%, 0.005 mmol). The reaction mixture was stirred for 15 min.

[0379] As MSKL-GE is a solid, in contrast to LHO-GE being a viscous oil, MSKL-GE did not mix effectively with the PA during the neat reaction. As a result, the crude product was observed to be mostly unreacted starting reagents implying minimal reactivity, with and without catalyst, which was confirmed with1H NMR spectroscopy.

[0380] Comparative example D

[0381] General procedure A was used based on grounded and vacuum oven-dried commercial PA (0.1871 g, 1 .25 mmol), synthesized MSKL-GE (0.4270 g, 1 .25 mmol [epoxide]), with and without [PPNCI] catalyst (0.4 mol%, 0.005 mmol), and DMF (2 mL), under a nitrogen atmosphere. The reaction mixture was stirred for 24 h.

[0382] It was observed that all the reactants dissolved in the solvent, providing a dark red solution. However, insoluble solid product was observed to form on the walls of the vial (precipitating out of the dark red solution) over the course of the reaction. Without willing to be bound to theory, the precipitate is believed to be a crosslinked, thermoset material, resulting from the high average epoxide functionality of MSKL-GE.

[0383] Comparative example E

[0384] Comparative example D was repeated with the addition of 1 .25 mmol of pyridine. Also in this case, insoluble solid product was observed to form on the walls of the vial.

Claims

CLAIMS1 . A method for preparing a thermoplastic functional polyester, the method comprising heating a mixture comprising epoxide monomers and cyclic anhydride monomers; wherein at least part of the epoxide monomers are lignin-derived glycidyl ether monomers represented by formula (I)whereinRi and Rr are each independently selected from -H, and -O-Ci ealkyl; andR2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci ealkyl; wherein at least a part of the lignin-derived glycidyl ether monomers comprise hydroxy groups; and wherein the average epoxide functionality of the epoxide monomers, being the product of the epoxide content, calculated from the epoxide equivalent weight determined according to ASTM D 1652-97 (1997), and the number average molecular weight determined by GPC, is at most 2.0, preferably from 0.5 to 1 .5, more preferably from 0.6 to 1 .4, even more preferably from 0.7 to 1 .3, yet even more preferably from 0.8 to 1 .2, most preferably from 0.9 to 1 .1 .

2. The method as claimed in claim 1 , wherein the lignin-derived glycidyl ether monomers are selected from coumaryl alcohol glycidyl ether monomers, dihydrocoumaryl alcohol glycidyl ether monomers, 4-propylphenol glycidyl ether monomers, coniferyl alcohol glycidyl ether monomers, dihydroconiferyl alcohol glycidyl ether monomers, propylguaiacol glycidyl ether monomers, sinapyl alcohol glycidyl ether monomers, dihydrosinapyl alcohol glycidyl ether monomers, propylsyringol glycidyl ether monomers, or any combination thereof.

3. The method as claimed in claim 1 or 2, wherein the lignin-derived glycidyl ether monomers comprising hydroxy groups are represented by formula (I)whereinRi and Rr are each independently selected from -H, and -OMe; andR2 is selected from -Ci ealkyl-OH, and -Cz ealkenyl-OH; preferably from -Cs ealkyl-OH, and -C3- ealkenyl-OH; more preferably from -(CHz^CHzOH, and -CHCHCH2OH.

4. The method as claimed in any one of claims 1 to 3, wherein the OH-content of the mixture comprising the epoxide monomers and the cyclic anhydride monomers, is at least 0.005 mol / g, preferably at least 0.050 mmol / g, more preferably at least 0.100 mmol / g, even more preferably at least 0.250 mmol / g, yet even more preferably at least 0.500 mmol / g, yet even more preferably from 1 .0 to 10.0 mmol / g, yet even more preferably from 2.0 to 8.0 mmol / g.

5. The method as claimed in any one of claims 1 to 4, wherein the number average molecular weight of the epoxide monomers, determined by GPC, is at most 3000 g / mol, preferably at most 2500 g / mol, more preferably at most 2000 g / mol, even more preferably at most 1500 g / mol, yet even more preferably from 300 to 1000 g / mol.

6. The method as claimed in any one of claims 1 to 5, wherein the mixture further comprises a catalyst, preferably an organocatalyst, more preferably bis(triphenylphosphoranylidene)iminium chloride (PPNCI).

7. The method as claimed in any one of claims 1 to 6, wherein the mixture comprising the epoxide monomers and the cyclic anhydride monomers is heated at a temperature of at least 50 °C, preferably at most 150 °C, more preferably from 60 to 140 °C.

8. The method as claimed in any one of claims 1 to 6, wherein the cyclic anhydride monomers are represented by formula (II)whereinR3 and FU are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

9. A polymer, in particular a thermoplastic functional polyester, comprising first structural units derived from glycidyl ether monomers, and second structural units derived from cyclic anhydride monomers; wherein at least 10 wt.% of the first structural units are derived from lignin-derived glycidyl ether monomers, preferably at least 20 wt.%, more preferably at least 40 wt.%, even more preferably from 50 to 100 wt.%; and wherein at least a part of the first structural units derived from lignin-derived glycidyl ether monomers comprise hydroxy groups.

10. Polymer as claimed in claim 9, wherein the polymer is a substantially alternating copolymer of the first and the second structural units.1 1 . Polymer as claimed in claim 9 or 10, wherein at least part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (Illa) or (II lb)whereinR1 and Rr are each independently selected from -H, and -O-Ci-ealkyl; andR2 is selected from -H, -Ci ealkyl, and -C2-ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci-ealkyl.

12. Polymer as claimed in claim 9 or 10, wherein at least part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (IVa) or (IVb)whereinR1 and Rr are each independently selected from -H, and -O-Ci-ealkyl; and X is selected from -Ci ealkyl, and -C2-ealkenyl.

13. Polymer as claimed in claim 9 or 10, wherein a first part of the first structural units derived from lignin-derived glycidyl ether monomers are represented by formula (Illa) or (I lib)whereinRi and Rr are each independently selected from -H, and -O-Ci-ealkyl; andR2 is selected from -H, -Ci ealkyl, and -Cz ealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from -OH, and -O-Ci-ealkyl; anda second part of the first structural units derived from lignin-derived glycidyl ether monomers, are represented by formula (IVa) or (IVb)(IVa) (IVb) wherein Ri and Rr are each independently selected from -H, and -O-Ci ealkyl; and X is selected from -Ci ealkyl, and -Cz ealkenyl.

14. Polymer as claimed in any one of claims 9 to 13, wherein the second structural units derived from cyclic anhydride monomers are represented by formula (V)whereinR3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

15. Polymer as claimed in any one of claims 9 to 14, wherein the polymer comprises repetitive units represented by formula (VII)whereinRi and Rr are each independently selected from -H, and -O-Ci ealkyl;R2 is selected from -H, -Ci ealkyl, and -Czealkenyl, wherein each of said -Ci ealkyl, and -C2- ealkenyl is independently and optionally substituted with from 1 to 3 substituents selected from - OH, and -O-Ci ealkyl; andR3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated or unsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

16. Polymer as claimed in any one of claims 9 to 15, wherein the polymer comprises repetitive units represented by formula (VIII)whereinR1 and Rr are each independently selected from -H, and -O-Ci ealkyl;X is selected from -Ci ealkyl, and -C2-ealkenyl; andR3 and R4 are each independently selected from -H, -Ci ealkyl, and -Ci ealkenyl, or R3 and R4 together with the carbon atoms to which they are attached form a 6-membered saturated orunsaturated cycle, wherein said cycle is independently and optionally substituted with from 1 to 3 substituents selected from -Ci ealkyl, and -Ci ealkenyl.

17. Use of the polymer as claimed in any one of claims 9 to 16 as a polyol in the preparation of a further polymer.

18. Use as claimed in claim 17, wherein the further polymer is selected from polyurethanes, polyesters, polycarbonates, or any combination thereof.

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