A tetrahydrofuran-α-amino acid multiblock copolymer, its preparation method and application

Abstract

This invention discloses a tetrahydrofuran-α-amino acid multiblock copolymer, the structure of which is shown below: where R1 and R2 are each independently selected from one or more of hydrogen, C1-C12 saturated and aliphatic hydrocarbon groups, C1-C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1-C6 carboxylalkyl groups with protected carboxyl groups, and C1-C6 aminoalkyl groups with protected amino groups; m is selected from 1-400, n is selected from 1-5000, and x is selected from 1-10. This invention also discloses its synthesis method, comprising two-stage polymerization of α-amino acid-N-carboxylic anhydride monomers and tetrahydrofuran monomers catalyzed by trifluoromethanesulfonate compounds. This multiblock copolymer possesses high strength, good toughness, good elasticity, good processability, and biodegradability, making it a high-quality substitute for petroleum-based thermoplastic elastomers and possessing significant commercial application value.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis technology, specifically to a tetrahydrofuran-α-amino acid multiblock copolymer, its preparation method, and its application. Background Technology

[0002] Thermoplastic elastomers combine the elasticity of rubber with excellent processability, making them widely used in industries such as home appliances and sporting goods. However, most mainstream thermoplastic elastomers are currently derived from petrochemicals, highlighting the urgent need to develop bio-based thermoplastic elastomer materials to reduce dependence on fossil fuels. Alpha-amino acids, the building blocks of proteins, are inexpensive and readily available, making them ideal for constructing novel bio-based thermoplastic elastomer materials.

[0003] The construction of thermoplastic elastomer materials relies on a chemical structure of alternating hard and soft segments. Poly-α-amino acids are highly rigid and polar, and possess advanced structures (such as β-sheets), making them suitable as hard segments. They can be combined with polytetrahydrofuran soft segments to construct polytetrahydrofuran-poly-α-amino acid multiblock polymers.

[0004] The common method for synthesizing poly-α-amino acids is the ring-opening polymerization of α-amino acids with N-carboxylic anhydrides (NCA) (J. Am. Chem. Soc., 2024, 146(35): 24189-24208), which follows the nucleophilic or anionic ring-opening polymerization mechanism. Tetrahydrofuran, however, can only be polymerized using cationic ring-opening polymerization (Macromolecules, 2023, 56(18):7389-7395). Due to the incompatibility of the active centers of the anions and cations, the one-pot, single-feed synthesis of this multi-block polymer is very difficult. Currently reported polymerization methods require multiple steps, namely, first synthesizing poly-α-amino acids via NCA polymerization, and then coupling them with polytetrahydrofuran using diisocyanate (Adv. Mater., 2019, 31(48): 1904311). Considering the economic viability of applications, developing novel one-pot, single-feed polymerization methods is crucial.

[0005] The two-stage polymerization method was first proposed in 2014 (Macromolecules, 2014, 47(7): 2219-2225). In two-stage polymerization, cationic ring-opening polymerization and anionic ring-opening polymerization occur at both ends of the polymeric active chain, respectively, followed by spontaneous coupling between the active ends of the chains to generate multi-block polymers in one pot. However, this polymerization method is currently only applicable to oxoheterocyclic monomers, and there are no reports on amino acid monomers. The ring-opening polymerization mechanisms of lactone monomers and NCA monomers are very different, and there are no reports on the random polymerization of the two. In particular, there is a significant difference in the active centers of cyclic esters and other oxoheterocyclic monomers and NCA monomers in two-stage polymerization. The former has an oxygen active end while the latter has a nitrogen active end. This difference makes NCA monomers unsuitable for the reported two-stage polymerization catalyzed by rare earth trifluoromethanesulfonic acid. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a tetrahydrofuran-α-amino acid multiblock copolymer with controllable molecular weight and adjustable copolymer composition. More importantly, this multiblock copolymer does not use an external coupling agent; the polytetrahydrofuran and poly-α-amino acid are directly linked to the amine group via ester bonds. This multiblock copolymer exhibits high strength, good toughness, good elasticity, good processability, and biodegradability, possessing significant application value.

[0007] A tetrahydrofuran-α-amino acid multiblock copolymer has the following structure: , R1 and R2 are each independently selected from one or more of hydrogen, C1~C12 saturated and aliphatic hydrocarbon groups, C1~C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1~C6 carboxylalkyl groups with protected carboxyl groups, and C1~C6 aminoalkyl groups with protected amino groups. m is selected from 1 to 400, n is selected from 1 to 5000, and x is selected from 1 to 10.

[0008] Preferably, the number-average molecular weight of the tetrahydrofuran-α-amino acid multiblock copolymer is 1~300 kg / mol, and the PDI is <5.

[0009] In the prior art, due to the inability to solve the problem of coexistence of anionic and cationic active centers during polymerization, it is impossible to achieve one-pot, single-feed block copolymerization of amino acid monomers and tetrahydrofuran monomers, making it difficult to obtain polytetrahydrofuran-poly-α-amino acid multiblock polymers. However, in this application, through catalyst optimization, two-stage polymerization of amino acid monomers and tetrahydrofuran was successfully achieved, and tetrahydrofuran and α-amino acid multiblock copolymers were prepared in one pot and one step.

[0010] The present invention also provides a method for preparing the above-mentioned tetrahydrofuran and α-amino acid multiblock copolymer, comprising the following steps: two-stage polymerization of α-amino acid-N-carboxylic anhydride monomer and tetrahydrofuran monomer under the catalysis of trifluoromethanesulfonate compound.

[0011] Preferably, the structure of the trifluoromethanesulfonate compound is shown in any one of formulas (I) to (III):

[0012] Equation (Ⅰ);

[0013] Equation (II);

[0014] Formula (Ⅲ); R4 to R10 are each independently selected from hydrogen, saturated aliphatic hydrocarbon groups of C1 to C12, and unsaturated aliphatic hydrocarbon groups of C1 to C12.

[0015] The synthetic method disclosed in this invention uses trifluoromethanesulfonate compounds as catalysts to achieve the binary polymerization of α-amino acid-N-carboxylic anhydride monomers with tetrahydrofuran. In this method, the cationic ring-opening polymerization of tetrahydrofuran and the anionic polymerization of α-amino acid-N-carboxylic anhydride monomers occur separately at the two ends of the polymeric active chain, followed by spontaneous coupling between the active anionic and anionic ends of the chains, generating a tetrahydrofuran-α-amino acid multiblock copolymer. This avoids multi-step reactions and provides a convenient synthetic method for the synthesis of this polymer.

[0016] Preferably, the trifluoromethanesulfonate compound is one or more selected from trimethylsilyltrifluoromethanesulfonate, tert-butyldimethylsilyltrifluoromethanesulfonate, di-tert-butylsilylbis(trifluoromethanesulfonic acid), dibutylboron trifluoromethanesulfonate, and dicyclohexyl(trifluoromethanesulfonyloxy)borane.

[0017] Preferably, the structure of the α-amino acid-N-carboxylic anhydride monomer is as follows: , R1 and R2 are each independently selected from one or more of hydrogen, C1~C12 saturated and aliphatic hydrocarbon groups, C1~C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1~C6 carboxylalkyl groups with protected carboxyl groups, and C1~C6 aminoalkyl groups with protected amino groups.

[0018] The method of this invention is universally applicable to a variety of α-amino acid-N-carboxylic anhydride monomers. Studies have found that various inert substituents such as alkyl, aromatic, ether, thioether, amide, and ester groups on α-amino acid-NCA monomers have almost no effect on the ring-opening polymerization performance of the five-membered ring in the monomer structure. Therefore, α-amino acid-NCA monomers with different substituents are all suitable for the polymerization reaction system of this invention.

[0019] More preferably, the α-amino acid-N-carboxylic anhydride monomer is one or more of the following: sarcosine-NCA, N-substituted glycine-NCA, ε-benzyloxycarbonyllysine-NCA, ε-trifluoroacetyllysine-NCA, γ-methylglutamate-NCA, γ-ethylglutamate-NCA, γ-benzylglutamate-NCA, β-benzylaspartate-NCA, phenylalanine-NCA, valine-NCA, leucine-NCA, isoleucine-NCA, methionine-NCA, and tert-butylserine-NCA.

[0020] In this invention, the structure of the α-amino acid-N-carboxylic anhydride monomer is as follows: .

[0021] More preferably, the structure of the N-substituted glycine-NCA is as follows: , R3 is selected from C2~C12 saturated aliphatic hydrocarbon groups, C2~C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1~C6 carboxyl alkyl groups with protected carboxyl groups, and C1~C6 amine alkyl groups with protected amino groups.

[0022] Preferably, the molar ratio of the α-amino acid-N-carboxylic anhydride monomer to the tetrahydrofuran monomer is 1:0.01~500.

[0023] Preferably, the molar ratio of the trifluoromethanesulfonate compound to the total monomers of α-amino acid-N-carboxylic anhydride monomer and tetrahydrofuran monomer is 1:10~2000.

[0024] Preferably, the two-element polymerization temperature is 10~100 ℃ and the time is 1~192 h.

[0025] The present invention also provides the application of the above-mentioned tetrahydrofuran-α-amino acid multiblock copolymer in the preparation of thermoplastic elastomers.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: Limited by the incompatible polymerization mechanism between amino acid monomers and tetrahydrofuran, existing technologies cannot achieve copolymerization of amino acid monomers and tetrahydrofuran monomers in a single-pot, single-feed process, let alone directly synthesize tetrahydrofuran-α-amino acid multiblock copolymers. This invention, for the first time, achieves two-stage polymerization of amino acid monomers and tetrahydrofuran monomers, synthesizing tetrahydrofuran-α-amino acid multiblock copolymers in a single-pot, single-feed process. The molecular weight of this multiblock copolymer is controllable, and its composition is adjustable. No external coupling agent is used; polytetrahydrofuran and poly-α-amino acids are directly linked to amine groups via ester bonds. It exhibits high strength, good toughness, good elasticity, good processability, and biodegradability, showing broad application prospects in biomedical and sporting goods industries. In particular, the tetrahydrofuran-sarcosine-NCA multiblock copolymer exhibits superior tensile properties compared to commercially available thermoplastic elastomers, making it a superior alternative to common petroleum-based thermoplastic elastomers.

[0027] This invention discloses a method for synthesizing tetrahydrofuran and α-amino acid multiblock copolymers, which can be successfully catalyzed using simple trifluoromethanesulfonate compounds. This polymerization method is simple to operate, highly versatile, and applicable to most amino acids. The α-amino acids are derived from biomass, and tetrahydrofuran is a petroleum product, both being inexpensive and readily available, making it suitable for large-scale industrial production. Attached Figure Description

[0028] Figure 1 The image shows the 1H NMR spectrum of the tetrahydrofuran-sarcosine-NCA multiblock copolymer prepared in Example 1.

[0029] Figure 2 The image shows the 1H NMR spectrum of the tetrahydrofuran and N-benzylglycine-NCA multiblock copolymer prepared in Example 2.

[0030] Figure 3 The image shows the 1H NMR spectrum of the tetrahydrofuran copolymer prepared in Example 3 with sarcosine-NCA and alanine-NCA.

[0031] Figure 4 The stretching curves are for the tetrahydrofuran-sarcosine-NCA multiblock copolymer prepared in Example 1, where the three curves correspond to test data repeated three times.

[0032] Figure 5 The 1H NMR spectrum of the tetrahydrofuran-sarcosine-NCA multiblock copolymer prepared in Example 4. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0034] In this invention, the molecular weight and molecular weight distribution of the multiblock copolymer were determined by gel permeation chromatography (SEC, Waters 1515) (containing 3 mg / L potassium trifluoroacetate in hexafluoroisopropanol, 40 °C, flow rate of 0.8 mL / min). The proton nuclear magnetic resonance spectrum in this invention (NMR) 1 The H NMR was measured on a Bruker Avance DMX 400 instrument, using deuterated chloroform as solvent and tetramethylsilane as internal standard.

[0035] All the α-amino acid-NCA monomers used in this invention can be prepared by referring to the synthesis process in the prior art (Nat.Commun., 2021, 12 (1), 5810), and the preparation process will not be described in detail.

[0036] All other raw materials not mentioned in this invention are commercially available.

[0037] Example 1 400 mg of sarcosine-NCA (3.48 mmol) was dissolved in 5.00 g (69.6 mmol) of tetrahydrofuran, and then 31 mg of trimethylsilyltrifluoromethanesulfonate (0.14 mmol) was added. After shaking and mixing, the mixture was reacted in an oil bath at 60 °C for five days. The polymerization product was dissolved in chloroform, precipitated in n-hexane, filtered, and dried under vacuum to constant weight to obtain a tetrahydrofuran-α-amino acid multiblock copolymer with a yield of 51%.

[0038] The multiblock copolymer (SEC) was tested and found to have a number-average molecular weight of 76.3 kg / mol, a tetrahydrofuran to sarcosine residue ratio of 8.1:1, and a polydispersity index (PDI) of 2.69. The multiblock copolymer's... 1 H NMR spectrum (CDCl3) as follows Figure 1 As shown, the signals are clearly assigned and the structure is clearly characterized, indicating that the obtained product is a multi-block copolymer of tetrahydrofuran and sarcosine-NCA. This multi-block polymer exhibits excellent tensile properties, with a tensile strength of 39.3 MPa, an elongation at break of 1245%, and a tensile toughness of 234 MJ / m. 3 ,like Figure 4 As shown.

[0039] Example 2 The synthesis process is basically the same as in Example 1, except that N-benzylglycine-NCA and tetrahydrofuran are copolymerized. The molar ratio of N-benzylglycine-NCA, tetrahydrofuran and catalyst is 25:1000:1.

[0040] The multiblock copolymer SEC was tested and found to have a number-average molecular weight of 68.9 kg / mol, a tetrahydrofuran to N-benzylglycine residue ratio of 10.3:1, and a polydispersity index (PDI) of 1.70. The multiblock copolymer's... 1 H NMR spectrum (CDCl3) as follows Figure 2 As shown, each signal is clearly assigned and the structure is clearly characterized, indicating that the obtained product is a multiblock copolymer of tetrahydrofuran and N-benzylglycine-NCA.

[0041] Example 3 The synthesis process is basically the same as in Example 1, except that sarcosine-NCA, alanine-NCA, and tetrahydrofuran are copolymerized. The molar ratio of tetrahydrofuran, sarcosine-NCA, alanine-NCA, and catalyst is 500:20:5:1.

[0042] The multiblock copolymer (SEC) was tested and found to have a number-average molecular weight of 51.8 kg / mol, a tetrahydrofuran to sarcosine residue to alanine residue ratio of 24:3.2:1, and a polydispersity index (PDI) of 2.33. The multiblock copolymer's... 1 H NMR spectrum (CDCl3) as follows Figure 3 As shown, each signal is clearly assigned and the structure is clearly characterized, indicating that the obtained product is a multi-block copolymer of tetrahydrofuran with sarcosine-NCA and alanine-NCA.

[0043] Example 4 The synthesis process was basically the same as in Example 1, except that dibutyl boron trifluoromethanesulfonate was used as a catalyst. The molar ratio of sarcosine-NCA, tetrahydrofuran, and catalyst was 8:160:1.

[0044] The multiblock copolymer (SEC) was tested and found to have a number-average molecular weight of 20.5 kg / mol, a tetrahydrofuran to sarcosine residue ratio of 14.6:1, and a polydispersity index (PDI) of 2.55. The multiblock copolymer's... 1 H NMR spectrum (CDCl3) as follows Figure 5 As shown, each signal is clearly assigned and the structure is clearly characterized, indicating that the obtained product is a multiblock copolymer of tetrahydrofuran and sarcosine-NCA.

[0045] Comparative Example 1 The synthesis process was basically the same as in Example 1, except that lutetium trifluoromethanesulfonate catalyst was used. The molar ratio of sarcosine-NCA, tetrahydrofuran, and catalyst was 25:500:1.

[0046] Tests showed that Comparative Example 1 could not produce any copolymer products.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tetrahydrofuran-α-amino acid multiblock copolymer, characterized in that, The structure of the multiblock copolymer is shown below: ， R1 and R2 are each independently selected from one or more of hydrogen, C1~C12 saturated and aliphatic hydrocarbon groups, C1~C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1~C6 carboxylalkyl groups with protected carboxyl groups, and C1~C6 aminoalkyl groups with protected amino groups. m is selected from 1 to 400, n is selected from 1 to 5000, and x is selected from 1 to 10.

2. The tetrahydrofuran and α-amino acid multiblock copolymer according to claim 1, characterized in that, The number-average molecular weight of the tetrahydrofuran-α-amino acid multiblock copolymer is 1~300 kg / mol, and the PDI is <5.

3. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 1 or 2, characterized in that, Includes the following steps: The α-amino acid-N-carboxylic anhydride monomer and the tetrahydrofuran monomer undergo two-stage polymerization catalyzed by trifluoromethanesulfonate compounds.

4. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 3, characterized in that, The structures of the trifluoromethanesulfonate compounds are shown in any of formulas (I) to (III): Equation (Ⅰ); Equation (II); Formula (Ⅲ); Among them, R4~R 10 Each is independently selected from hydrogen, saturated aliphatic hydrocarbon groups of C1~C12 and unsaturated aliphatic hydrocarbon groups of C1~C12.

5. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 4, characterized in that, The trifluoromethanesulfonate compounds are one or more selected from trimethylsilyltrifluoromethanesulfonate, tert-butyldimethylsilyltrifluoromethanesulfonate, di-tert-butylsilylbis(trifluoromethanesulfonic acid), dibutylboron trifluoromethanesulfonate, and dicyclohexyl(trifluoromethanesulfonyloxy)borane.

6. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 3, characterized in that, The structure of the α-amino acid-N-carboxylic anhydride monomer is shown below: ， R1 and R2 are each independently selected from one or more of hydrogen, C1~C12 saturated and aliphatic hydrocarbon groups, C1~C12 unsaturated aliphatic hydrocarbon groups, aromatic hydrocarbon groups, ether groups, thioether groups, C1~C6 carboxylalkyl groups with protected carboxyl groups, and C1~C6 aminoalkyl groups with protected amino groups.

7. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 6, characterized in that, The α-amino acid-N-carboxylic anhydride monomer is one or more of the following: sarcosine-NCA, N-substituted glycine-NCA, ε-benzyloxycarbonyl lysine-NCA, ε-trifluoroacetyl lysine-NCA, γ-methylglutamate-NCA, γ-ethylglutamate-NCA, γ-benzylglutamate-NCA, β-benzyl aspartate-NCA, phenylalanine-NCA, valine-NCA, leucine-NCA, isoleucine-NCA, methionine-NCA, and tert-butylserine-NCA.

8. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 3, characterized in that, The molar ratio of the α-amino acid-N-carboxylic anhydride monomer to the tetrahydrofuran monomer is 1:0.01~500.

9. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 3, characterized in that, The molar ratio of the trifluoromethanesulfonate compound to the total monomers of α-amino acid-N-carboxylic anhydride monomer and tetrahydrofuran monomer is 1:10~2000.

10. The method for preparing the tetrahydrofuran-α-amino acid multiblock copolymer according to claim 3, characterized in that, The two-element polymerization is carried out at a temperature of 10~100 ℃ for a time of 1~192 h.

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