Polyurethanes, BIO-oil and biochar from lignin valorization

Abstract

A polyurethane is formed with cross-linked polyols and lignin degradation products (bio-oil) produced by depolymerizing lignin. The lignin is mixed with a solvent comprising a short-chain alcohol such as isopropanol and a short chain carboxylic acid and heating the mixture to between about 100° C to about 300° C in a microwave vessel. The lignin degradation products have a number-average molecular weight of between about 600 to about 1500 g / mol, an average molecular weight of about 1200 to about 2900 g / mol, with a poly dispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g. The polyols and bio-oil are polymerized with a polyfunctional isocyanate.

Description

POLYURETHANES, BIO-OIL AND BIOCHAR FROM LIGNIN VALORIZATION FIELD OF THE INVENTION

[0001] This invention relates to methods and systems for producing valuable products from lignin, including bio-oils, biochar, and polyurethanes. BACKGROUND

[0002] There is an increasingly urgent need to develop sustainable alternatives to fossil fuels.1,2Lignin is a potentially sustainable feedstock candidate for replacing fossil fuels. However, its complex chemical structure has relegated lignin to a low-value byproduct, primarily generated in paper and pulp mills, where most of it is currently burned to produce heat and electricity, with less than 2% used to synthesize value- added products.3,4The direct use of lignin as a macromolecule has been extensively studied, and it is considered more economically viable and desirable; however, due to its complex molecular structure, which limits hydroxyl group accessibility, resulting in low or uneven reactivity.5Depolymerizing lignin structure into low-molecular-weight compounds offers a practical method to enhance its reactivity and reduce heterogeneity compared to native lignin. While many techniques aim to obtain higher yields of monomeric compounds from lignin,6the amorphous and cross-linked nature of lignin makes its complete depolymerization challenging. As a result, substantial amounts of aromatic oligomers are inevitably produced alongside monomers.7Regardless of the depolymerization technique employed, a substantial amount of oligomers is inevitably generated as byproducts in considerable yields.8,9

[0003] Harnessing the potential to valorize oligomers from lignin depolymerization presents a promising opportunity to replace petroleum-derived precursors in bio-based polymer production.10,11Polyurethanes (PU) are versatile polymers formed through the reaction of polyols with polyfunctional isocyanate, forming a carbamate functional group known as the urethane group. PU can be formulated as rigid or flexible foams, coatings, elastomers, adhesives, and materials for biomedical applications.13,14Its remarkable versatility makes it ideal for various applications and paves the way for an exciting future.13

[0004] While native lignin has been explored as a renewable alternative to non-renewable polyols in PU synthesis, its high molecular weight and poor reactivity often result in brittleness, compromising the final product's mechanical properties and overall performance.12,15In contrast, lignin-derived oligomers offer improved compatibility, lower polydispersity, reduced steric hindrance, and more accessible functional 1WSLEGAL\055326\00537\41739072v5groups, making them promising candidates for PU formulations.11,16Building on this approach, previous studies have shown that lignin-derived materials with lower molecular weight have better dispersity while maintaining good mechanical properties. For example, Li et al.17demonstrated that PU from lignin with lower molecular weight lignin resulting in a greater tensile strength than higher molecular weight lignin. Huang et al.18explored the use of lignin with a reduced molecular weight of 900 g / mol as a partial replacement for petroleum-based polyol in the formulation of polyurethane elastomers. Huang et al.19demonstrated that lignin with a molecular weight of 2121 g / mol could be effectively incorporated into the PU matrix, resulting in excellent mechanical properties, including a tensile strength of 73 MPa, albeit with a relatively low lignin content of 5.4 wt.%.

[0005] Diverse studies have focused on lignin depolymerization primarily to obtain the fraction that contains oligomers, monomers and dimers, with effort to reduce or eliminate the formation of solid residues. However, the repolymerization of lignin-derived intermediates into biochar is a complex process that remains difficult to control, and the solid residues present an underutilized opportunity for valorization.

[0006] There remains a need in the art for alternative methods of valorizing lignin, including the production of bio-oil, biochar, and alternative methods of producing polyurethanes from lignin. SUMMARY OF THE INVENTION

[0007] In one aspect, disclosed is a polyurethane comprising cross-linked polyols and lignin degradation products (bio-oil) produced by depolymerizing lignin by mixing the lignin with a solvent comprising a short-chain alcohol and a short chain carboxylic acid, and heating the mixture to between about 100° C to about 300° C.

[0008] In some embodiments, the bio-oil has a number-average molecular weight of between about 600 to about 1500 g / mol, an average molecular weight of about 1200 to about 2900 g / mol, with a polydispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g. Preferably, the polyols comprise aromatic polyester polyols. Preferably, the blend of polyols and bio-oil comprises about 1% to about 60% by wt bio-oil, and more preferably the blend comprises between about 10% to about 20 wt% bio-oil.

[0009] In another aspect, disclosed is a method of producing a polyurethane, comprising the steps of 2WSLEGAL\055326\00537\41739072v5(a) depolymerizing lignin by mixing the lignin with a solvent comprising a short-chain alcohol and a short chain carboxylic acid, and heating the mixture to between about 100° C to about 300° C to produce bio-oil, and (b) polymerizing a blend of bio-oil and polyol with a polyfunctional isocyanate.

[0010] In some embodiments, the blend comprises between about 1% to about 60% by wt bio-oil, and preferably the blend comprises between about 10% to about 20 wt% bio-oil.

[0011] In some embodiments, the bio-oil comprises oligomeric lignin degradation compounds, and having an number-average molecular weight of about 600 to about 1500 g / mol and an average molecular weight of about 1200 to about 2900 g / mol, with a polydispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g.

[0012] In some embodiments, the isocyanate comprises 4, 4’-Methylenebis (phenyl isocyanate) (MDI) and / or the polyol comprises aromatic polyester polyols.

[0013] In some embodiments, the bio-oil is first dissolved in a solvent, such as dimethylformamide, in a ratio of about 1:10 by weight.

[0014] In some embodiments, the heating step comprises irradiating the mixture with microwaves, and the mixture is heated to between about 100° C to about 200° C; or the heating step comprising heating the mixture in a sealed reactor, such as a PARR reactor, and the mixture is heated to about 200° to about 300° C.

[0015] In some embodiments, the, wherein the short chain alcohol comprises methanol, ethanol, propanol, isopropanol or butanol; and / or the short chain carboxylic acid comprises formic acid, acetic acid, or propanoic acid. Preferably the short chain alcohol comprises isopropanol and the short chain carboxylic acid comprises formic acid.

[0016] In some embodiments, the ratio of lignin to formic acid is between about 0.0033 g to about 0.67 g per 1.0 ml of formic acid, and preferably between about 0.053 g to about 0.33 g per 1.0 ml of formic acid.

[0017] In some embodiments, the reaction time of step (a) is between about 5 min and 120 min.

[0018] In some embodiments, the process is performed without a catalyst. 3WSLEGAL\055326\00537\41739072v5

[0019] The compositions or methods described herein include any variant or alternative comprising any combination of features or steps, or omitting any feature or step, whether or not explicitly described in such fashion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1. Relative molecular mass distribution curves of a) KL before depolymerization and BO obtained after depolymerization, and b) polyol PS-3524.

[0021] Figure 2. FTIR spectra of Kraft lignin (KL) before depolymerization and the bio-oil (BO) obtained after depolymerization.

[0022] Fig. 3. Effect of lignin dosages on the bio-oil yield (A) and average molecular weight of bio-oil (B). Reaction conditions: T=140 °C, and t=30 min using microwave.

[0023] Fig.4. Effect of reaction temperature on depolymerization yield (A) and molecular weight of bio- oils (B). Reaction conditions: lignin concentration: 0.5 g, and t=30 minutes. The means that do not share a letter are significantly different.

[0024] Fig.5. Effect of reaction time on depolymerization yield (A) and molecular weight of bio-oils (B). Reaction conditions: lignin concentration: 0.5 g, and T=140 °C.

[0025] Fig.6. Flowchart of solvent sequential extraction of obtained bio-oil

[0026] Fig.7 Molecular weight of bio-oil and its fractions after liquid-liquid extraction.

[0027] Figure 8. Schematic of one embodiment of a polyurethane synthesis process using a BO produced by depolymerizing lignin as described herein.

[0028] Figure 9. (a) synthesis route of PBDM network; (b) crosslinked structure and hydrogen bonds interactions.

[0029] Figure 10. (a) FTIR spectra of PBDMs. (b) DTG and (c) DSC curves of PBDMs with different levels of bio-oil substitution.

[0030] Figure 11. Thermomechanical and mechanical properties of the PBDMs. (a) Storage modulus, E', and (b) loss modulus, E'', at varying bio-oil content. analysis for the PBDMs. (c) Representative engineering stress–strain curves of the PBDMs. (d) Ashby plot comparing ultimate 4WSLEGAL\055326\00537\41739072v5tensile strength and elongation at break of our PBDMs with some commercial polyurethanes (D1, D2, P1, and E1) and previously reported lignin-based polyurethanes using high content of lignin; from references: code 1-515, 647, 748, 849, 950, and 1051(e) the tensile fractured surfaces of PBDM20 and PBDM50.

[0031] Figure 12A. Representative engineering stress–strain curves of PBDM0, PBDM10, and PBDM30. Figure 12B. Tan delta curves of the PBDM samples at varying BO content.

[0032] Figure 13. (a) Before and after swelling of PBDM sheets in DMF, (b) gel content, and (c) histogram of crosslink density and swelling rate for PBDM sheets.

[0033] Figure 14. (a) Digital photos showing the PBDM sheets' capacity to deform and keep the temporary shape at room temperature and then recover after five cycles at 100 °C. (b) Diagram for the angle of the temporary shape and the recovered shape. Modified from55. Rr and Rf of the PBDM samples at (c) 100°C and (d) 110°C. (e) Demonstration of shape manipulation via shape memory effect. (The weight used was 500 g). (f) Shape memory aids in self-healing for closing the gap in the material, and a schematic diagram shows the shape memory effect healing the gap.

[0034] Figure 15. (a) Process to solubilize the PBDMs in DMF for the recycling process, (b) schematic of the specimen for the lap shear strength test, and (c) shear strength of adhesives for PBDM10 and PBDM20 after the recycling process. The dashed line at 0.7 MPa in (c) indicates the minimum industrial requirement for the adhesion strength61. (d) Radical Scavenging Activity of PBDM samples.

[0035] Fig.16. (a) Removal rate percentage, (b) adsorption capacity of Pb2+, Cd2+, and Li+at different adsorption contact times, and (c) removal rate comparison at low pH and natural pH for 24 h contact time. All samples were at an initial metal concentration of 50 mg / L for each metal, using 1g / L of adsorbent dose for Pb2+and Cd2+and 10 g / L for Li+.

[0036] Fig.17. Removal rate (a) and adsorption capacity (b) of Pb2+, Cd2+, and Li+at different initial metal concentrations for 24 h adsorption time.

[0037] Fig.18. Adsorption isotherms of Pb2+, Cd2+, and Li+at room temperature during 24 h. The Ce data fitted into Langmuir (q Langmuir) and Freundlich (q Freundlich) models were plotted along with the experimental data (q measured) 5WSLEGAL\055326\00537\41739072v5DETAILED DESCRIPTION

[0038] As used herein, "lignin" means a class of organic polymers that forms a structural component in support tissues of most plants. Lignin’s three-dimensional structure is composed of aromatic alcohols (monolignols) which depolymerizes to aromatic compounds. "Kraft lignin" or "KL" means lignin which has been separated from cellulose by a Kraft process.

[0039] As used herein, "bio-oil" means a composition comprising monomeric, dimeric, trimeric, and / or oligomeric compounds obtained from depolymerization of lignin.

[0040] As used herein, the term "short-chain" in reference to carboxylic acids or alkyl alcohols means compounds with 6 or fewer carbon atoms.

[0041] As used herein, "polyurethane" is a polymer comprising organic units joined by carbamate or urethane linkages. Polyurethanes are formed by the reaction between a diisocyanate with organic compounds such as glycols or polyols. In preferred embodiments, the polyurethane is the result of reacting a diisocyanate with a blend of conventional polyols and a bio-oil produced in accordance with the lignin depolymerization methods described herein.

[0042] In one aspect, described herein is a polyurethane and a process of producing a polyurethane from the depolymerization products of lignin. In some embodiments, the lignin is a kraft lignin (KL) which is heated in a solvent comprising an alcohol, a short-chain carboxylic acid to produce bio-oil and bio-char. In some embodiments, the alcohol comprises a short chain alkyl alcohol, such as butanol, isopropanol, propanol, ethanol, or methanol; the organic acid comprises a short chain carboxylic acid such as formic acid, acetic acid or propanoic acid; and the optional metal catalyst comprises a polymer-supported nickel catalyst.

[0043] Embodiments of the invention described herein are related to the effect of heating, and microwave heating in particular, and hydrogen donor solvents, such as formic acid and isopropanol, on the depolymerization of Kraft lignin. In some embodiments, the process occurs with a lignin dosage of between about 0.01 to about 0.1 g / ml of solvent, a reaction temperature between about 100° to about 200 °C, and a reaction time of between about 5 to about 120 min. Reaction temperature and lignin concentration were found to have a more significant impact on the lignin fragmentation than reaction time. The bio-oils obtained upon depolymerization were analyzed by GPC, FTIR, TGA, and elemental analysis 6WSLEGAL\055326\00537\41739072v5techniques. The highest bio-oil yield of 55% was obtained upon depolymerization of 0.5g lignin (5.5 ml of solvent) at 120 °C for 30 min.

[0044] In some embodiments, the obtained bio-oil treated with a solvent sequential extraction method to produce relatively more homogenous fractions of the bio-oil. Preferably, the bio-oil is dissolved in ethyl acetate, then the soluble fractions were extracted with DCM / toluene, and then hexane. Four different fractions were obtained and analyzed by GPC. The first fraction consisted of compounds with a number- average molecular weight (Mn) range of 1300 to 700 g / mol, followed by a second fraction with a Mn range of 700 to 500 g / mol obtained from the precipitated compounds after using DCM / toluene. The hexane insoluble fraction had an Mn range of 500 to 300 g / mol, and the hexane soluble fraction had 300 to 200 g / mol.

[0045] Bio-oil yield can be increased using a catalyst, for example, a nickel catalyst. In preferred embodiment, the nickel catalyst may comprise polyhedral oligomeric silsesquioxane supported catalyst (POSS-Ni) or reduced graphene oxide supported catalyst (RGO-Ni). The results showed a notable improvement in bio-oil yield reaching 61.82% with POSS-Ni when employing 0.1g lignin (in 5.5 ml of solvent) at 140 °C for 30 min. RGO-Ni required achieves a 63.73 % yield when utilizing 0.5 g lignin (in 5.5 ml of solvent) at 140 °C, however with a longer reaction time of 120 min.

[0046] In some embodiments, the reaction may take place in a high-pressure reactor vessel such as a PARR reactor at 250 °C for 4 h, in which two POSS catalysts were tested in comparison with Ni-RGO; using this method, 71% of bio-oil was obtained using Ni-RGO with a molecular weight of Mn= 245 g / mol and Mw=572 g / mol.

[0047] In one aspect, described herein is a bio-oil comprising oligomeric lignin degradation compounds, and having a number-average molecular weight Mn of about 600 to about 1500 g / mol and an average molecular weight Mw of about 1200 to about 2900 g / mol, with a polydispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g. Preferably, the bio-oil has a Mn of between about 700 to 800 g / mol and a Mw of between about 1300 to 1600 g / mol, with a total hydroxyl value of between about 300 to about 310 mg of KOH / g.

[0048] In another aspect, described herein are polyurethane (PU) materials produced by polymerizing a blend comprising conventional polyols and the bio-oil produced by depolymerizing lignin using the 7WSLEGAL\055326\00537\41739072v5methods described herein. The resulting PU can have higher tensile strength than conventional petroleum- based PU, as well as improved thermal stability, anti-oxidant, and shape memory properties. Further, when processed with a solvent, the PU can form an excellent adhesive material. In preferred embodiments, the method comprises controlling the lignin-derived bio-oil molecular weight, which enhances its incorporation into the PU network by improving compatibility and dispersion. This modification facilitates increased replacement ratios of conventional polyols while preserving or improving mechanical performance.

[0049] In another aspect, described herein are methods of producing biochar as a resulting product from the lignin depolymerization that increases lignin valorization. The biochar is a fraction of the solid residues left after reactions. Preferably, the solid residues are washed with a solvent such as THF to remove any remaining unreacted lignin. The biochar may be used as an adsorbent material to remove heavy metals such as Cadmium, Lead and Lithium.

[0050] In one aspect, described herein is a process of producing a polyurethane comprising bio-oil compounds which replace at least a portion of conventional polyols. The bio-oil compounds result from a depolymerization process of lignin, such as kraft lignin (KL), under microwave heating in a solvent comprising an alcohol, a short-chain carboxylic acid and optionally, a metal catalyst, to produce bio-oil. In preferred embodiments, the alcohol comprises a short chain alkyl alcohol, such as butanol, isopropanol, propanol, ethanol, or methanol; the organic acid comprises a short-chain carboxylic acid such as formic acid, acetic acid or propanoic acid; and the optional metal catalyst comprises a polymer-supported nickel catalyst.

[0051] For example, polyurethane films may be produced by a vacuum casting method, blending a commercial polyester polyol with bio-oil and reacting it with aromatic diisocyanate. Notably, the formulations proceed without any added catalyst. The catalyst-free route contrasts with conventional PU synthesis that largely depends on a suitable catalyst, such as dibutyltin dilaurate. However, health concerns, regulations, and high costs are prompting research to avoid organotin compounds as catalysts.20,21Embodiments described herein provide PU synthesis without organotin catalysts while successfully incorporating depolymerized lignin. Depolymerization of lignin to bio-oil 8WSLEGAL\055326\00537\41739072v5

[0052] In one aspect, described is a process which depolymerizes lignin, such as kraft lignin (KL), by microwave heating in a solvent comprising an alcohol and a short-chain carboxylic acid to produce bio- oil and bio-char. In some embodiments, the alcohol comprises a short chain alkyl alcohol, such as butanol, isopropanol, propanol, ethanol, or methanol; the organic acid comprises a simple carboxylic acid such as formic acid, acetic acid or propanoic acid.

[0053] The solvent acts as hydrogen donors to depolymerize the lignin. In some embodiments, the process occurs with a lignin dosage of between about 0.01 to about 0.1 g / ml of solvent, with a reaction temperature between about 100° to about 200 °C, and a reaction time of between about 5 to about 120 min. Preferably, the solvent comprises the alcohol and the acid in about a 1:1 to about a 5:1 ratio by volume, and more preferably about 8:3. Reaction temperature and lignin concentration were found to have a more significant impact on the lignin fragmentation than reaction time. The bio-oils obtained upon depolymerization were analyzed by GPC, FTIR, TGA, and elemental analysis techniques. The highest bio-oil yield of 55% was obtained upon depolymerization of 0.5 g lignin per ml of solvent (8:3 ratio), at 120 °C for 30 min.

[0054] In some embodiments, the obtained bio-oil is treated with at least one solvent extraction step, and preferably a multi-step sequential extraction, to produce more homogenous fractions of the bio-oil. Preferably, the bio-oil is first dissolved in ethyl acetate, then the soluble fractions are extracted with DCM / toluene, and then hexane. The four different fractions comprised a first fraction of compounds with a number-average molecular weight (Mn) range of 1300 to 700 g / mol, followed by a second fraction with a Mn range of 700 to 500 g / mol obtained from the precipitated compounds after using DCM / toluene. The hexane insoluble fraction had an Mn range of 500 to 300 g / mol, and the hexane soluble fraction had 300 to 200 g / mol. .

[0055] In a preferred embodiment, kraft lignin is depolymerized under microwave heating under mild reaction conditions (e.g.140 °C for 30 min) using isopropanol and formic acid, without a metal catalyst. A complete characterization of the resulting bio-oil has been published (Lopez Camas et al.2025), however, the GPC and FTIR results reveal that the molecular weight of bio-oil significantly decreased from that of the KL, as shown in Figure 1. Initially, KL had an Mw of 10177 g / mol and an Mn of 2923.8 g / mol with a polydispersity of 3.5. In contrast, the Mw and Mn of bio-oil were reduced to 1477 g / mol and 733 g / mol, respectively, with a polydispersity of 2. 9WSLEGAL\055326\00537\41739072v5

[0056] Figure 2 presents the comparison of the FTIR spectra of KL and bio-oil. Both samples exhibited a broad band in the 3400 to 3460 cm⁻¹ range, attributed to hydroxyl groups in phenolic and aliphatic structures, and peaks at 2938 and 2842 cm-1related to -C-H stretching in aromatic methoxy groups, in methyl and methylene groups. A notable change after depolymerization is the intensified band at 1710- 1715 cm-1in the bio-oil, indicating increased unconjugated carbonyl groups (-C=O).33,34Effect of lignin loading on bio-oil yield.

[0057] In some embodiments, the lignin dose is between about 0.01 g to about 0.1 g per ml of solvent (which is preferably 8:3 isopropanol:formic acid, by volume). The lignin dose can preferably be about 0.018 g / ml.

[0058] Experiments were conducted with varying amounts of lignin (0.1 g to 0.75 g per 5.5 ml of solvent) at a temperature of 140 °C for 30 minutes. It was found that a lower lignin loading of 0.1 g yielded a higher bio-oil output of 52.5% (Fig. 3). Although this increase was not significantly higher than that obtained from the 0.5 g and 0.75 g loads. A key observation was made regarding the number-average molecular weight (Mn) and weight-average molecular weight (Mw) values obtained; those achieved using 0.1 g of lignin were notably lower (Mn=377 g / mol and Mw=1008 g / mol) compared to higher lignin loadings. In contrast, using 0.75 g of lignin drastically increased Mn to 902.5 g / mol and Mw= 1746 g / mol. These results show that the ratio of lignin compared to solvents plays a significant role in the depolymerization of KL into lower molecular weight compounds.

[0059] The results showed that increasing the lignin dosage in the microwave vessel from low to higher dosages while keeping the temperature and reaction time constant led to no significant difference in the bio-oil and solid residue yield. However, there was a significant difference in the molecular weight of compounds obtained from a low loading of 0.1 g compared to the higher loading levels of 0.5 g and 0.75 g. Contrary to the literature suggesting that lower lignin dosages can help achieve higher bio-oil yields, this was not observed in our case because the lignin:formic acid ratio is another important factor that plays a role in depolymerization. Formic acid helps in the fragmentation, but higher lignin-to-formic acid ratios can hinder its fragmentation.

[0060] Increasing lignin dosage in the reaction mixture results in a higher demand for hydrogen to cleave the lignin linkages. Formic acid (FA) and isopropanol, which are the in-situ hydrogen source, were kept 10WSLEGAL\055326\00537\41739072v5constant in all experiments, resulting in a lower hydrogen-to-lignin ratio. This led to slower bond cleavage and less efficient fragmentation due to reduced hydrogen availability. It is believed that hydrogen generated in the reaction suppresses the repolymerization of the reactive intermediate compounds. However, if the FA concentration is elevated, it can make the reaction more acidic, leading to an opposite effect and creating repolymerization of the reactive intermediates, resulting in a bio-oil with higher molecular weight and a decrease in bio-oil yield.

[0061] Thus, a preferred range of lignin to acid may be between about 0.05 g to about 1.0 g per 1.5 ml of formic acid, and more preferably 0.08 g to about 0.5 g per 1.5 ml of formic acid.

[0062] Using lower lignin loading may lead to the production of a compound with a lower molecular weight and a higher yield of the desired product, higher loads may provide superior resource efficiency (greater output with lower yield). In preferred embodiments, lignin at 0.5 g per 1.5 ml of FA is an efficient choice. Effect of the reaction temperature on bio-oil yield.

[0063] Depolymerization reactions can take place in the temperature range of 100° to 200°C for 30 min using 0.5 g lignin. Fig. 4 illustrates the relationship between temperature and molecular weight of the bio-oil. Yield increases as the temperature rose from 100 to 120 °C, where it reached its maximum value of 55.3%. However, as the temperature continued to increase, yield decreases, a slightly lower bio-oil yield was obtained at 140 °C (47.6% bio-oil yield) with a lower molecular weight than that obtained at 120 °C.

[0064] While the bio-oil yield decreased from 55.3% to 31.6% from 120°C to 200°C, the solid residues (SR) increased from 46.41% to 69.25%. The increase in SR indicates that the recondensation of lignin fragments is promoted at higher reaction temperatures. Without restriction to a theory, the microwave heating reactions may generate different radicals or unstable fragments that are not saturated with the hydrogen in situ obtained from the medium reaction, and these fragments may react with the lignin structure, creating a repolymerization and char formation. The conversion between the SR and bio-oil showed values of 100 %. This suggests that the temperature was insufficient to form gas products. Although the conversion value of some samples was slightly higher than 100%, this could indicate that Isopropanol reacted with lignin through an alkylation reaction. Alkyl groups could have been introduced 11WSLEGAL\055326\00537\41739072v5to the lignin structure, and the alkylation could have increased the yield and molecular weight (48). Regarding Mn and Mw of the bio-oil (Fig.4-B), at 100 °C, the Mw and Mn values of bio-oil were found to be 1269 g / mol and 678 g / mol, respectively; however, until 160 °C, the molecular weight value (Mn= 595 g / mol) decreased and then it started to increase until it reached to value of Mn= 1585 g / mol at 200 °C. When the formic acid-to-lignin ratio is low, reactions tend to be more effective at lower temperatures. This may be because FA acts as a hydrogen donor and reacts with lignin through formylation-elimination- hydrogenolysis. This mechanism leads to the depolymerization and stabilization of the lignin fragments under the synergistic effect of FA with the solvent used, i.e., isopropanol. The beneficial impact of FA in lignin depolymerization can be triggered by temperature; the higher temperature can enhance the repolymerization reactions; thus, its increase may result in lower yield and higher molecular weight compounds due to a competition between repolymerization and depolymerization. Higher temperatures led to repolymerization due to decreased lignin solubility in the solvent system, resulting in the condensation of intermediate fragments. Effect of reaction time on bio-oil yield

[0065] The reaction time may range from about 5 to about 120 minutes, for example while maintaining a temperature of 140°C and 0.5 g lignin per 5.5 ml of solvent (1.5 ml formic acid). The impact of the reaction time on bio-oil yield (Fig. 5A) is less significant compared to the effect of reaction temperature. The highest yield was 52.7% for 5 min reaction time. The yield decreased when reaction time increased; the lowest yield obtained was 42% in a reaction held for 120 minutes. Although the bio-oil yield varied, no significant difference was found among the samples. This suggests that the impact of fragmenting lignin structure is more influenced by the reaction temperature and solvents alone rather than the reaction time. Additionally, it demonstrates that obtaining lignin bio-oil does not necessarily require prolonged reaction times. Furthermore, extended times reduced the conversion rate, which could be an indication that part of the products were converted into gas due to activation of intermediate species by subsequent cracking and gasification.

[0066] Regarding the average molecular weight of the bio-oils obtained at different reaction times is illustrated in Fig. 5B, the Mw value reduced sharply from 13229 g / mol of initial lignin to 2986 g / mol during the initial 5 min of reaction, then continually reduced until reaching its lowest value of Mw=1477 g / mol and Mn=756.6 g / mol after maintaining the reaction for 30 min. After this point, the Mw started to 12WSLEGAL\055326\00537\41739072v5increase. According to the findings, it appears that the yield of bio-oil obtained at 5 minutes was considerably higher than other bio-oils obtained at longer reaction times. However, this bio-oil was primarily composed of high molecular weight fragments, as the Mw and Mn values indicated. These results indicated that the solvent isopropanol and formic acid released H2, facilitating lignin's depolymerization. However, it was consumed quickly in the reaction; extended reaction times were not favourable for the fragmentation of Kraft lignin. Total conversion may be reduced due to an increase in the CO / CO2formation from 30 to 120 min (Kristianto et al. (45)). Bio-oil fractionation

[0067] The resulting bio-oil is a complex mixture of various compound groups. Each group can be upgraded to achieve desired chemical transformations. Additionally, the presence of oligomers in bio-oil poses a significant challenge to its utilization. In preferred embodiments, fractionation techniques may be employed to separate the lower molecular weight compounds from oligomers. One such technique is solvent fractionation, which leverages the partial solubility of high-molecular-weight compounds in different solvents. Given the heterogeneity of lignin oligomer chains, dissolution in different solvents can help reduce their molecular weight and polydispersity. This approach improves the overall quality of bio- oils and facilitates their more efficient and versatile application.

[0068] Various fractions with lower molecular weights are obtained from the bio-oil through solvent sequential extraction. One embodiment is schematically illustrated in Fig.6, where the average molecular weight decreases as each step of solvent fractionation is carried out. The Mn and Mw ranges were chosen based on the minimum and maximum values obtained from various bio-oil fractions (Fig. 7). The molecular weight distribution indicates that the fractionation of the bio-oil by solvent extraction helps to reduce and narrow the molecular weight, indicating that the molecular weight of the compounds predominantly influences the fractionation. The GPC chromatograms of each fraction revealed that the molecular weight and polydispersity remained consistent across all samples, regardless of the initial reaction temperature. Specifically, the molecular weight and polydispersity of the bio-oil fractions consistently fell within the ranges shown in Table 1. This uniformity suggests that the solvent sequential extraction method is highly effective in separating bio-oil into fractions with known properties, independent of the initial reaction conditions used. This fractionation method can also be applied to different BOs obtained from different depolymerization methods. It ensures predictable and reproducible 13WSLEGAL\055326\00537\41739072v5properties of the bio-oil fractions. The fraction with higher Mn and Mw was obtained after adding ethyl acetate to the bio-oil; however, from GPC chromatograms, small molecular weight molecules also precipitated together with the larger molecular weight compounds, resulting in a fraction with high polydispersity. The EAcI fraction has the highest molecular weight (Mn: 1100-700 g / mol) compared to the other fractions. Adding ethyl acetate to the sample separates the lighter compounds in the bio-oil mixture; the precipitated fraction is mostly enriched with higher average molecular weight compounds. The soluble portion (EAcS) was dried and then mixed with DCM and toluene, resulting in the precipitation of the DCTI fraction, containing compounds with Mn values of 700 to 500 g / mol. The soluble fraction was mixed with hexane, precipitating a third fraction, hexane insoluble (HI), containing compounds with Mn values of 500 to 300 g / mol. Lastly, the hexane soluble fraction (HS) contained compounds with 200 to 300 g / mol Mn values. In contrast to EAcI, the later fractions obtained showed a narrower polydispersity. Table 1. Average molecular weights, polydispersity and hydroxyl number for bio-oil and fractions. Total OH Mn Mw PDI Fraction groups± EAcI 1300-700 2400-1100 1.8 389.7 ± 4.8 EAcS 500-600 730-900 1.5 390.2 ± 0.3 DCTI 700-500 1000-750 1.4 - HI 500-300 500-350 1.1 - HS 300-200 300-200 1.1 -

[0069] The total hydroxyl value is another important aspect to consider when using lignin-based products to synthesize value-added materials such as polymers. The bio-oil and the fraction EAcI were analyzed for the total hydroxyl content, showing values between 300 to 400 mg KOH / g, as shown in Table 1. The total hydroxyl groups present in the bio-oil and EAcI fraction produced by the process described herein satisfy the value needed to make it an excellent raw material for biobased polyols, which can be used in the production of polyurethane foams, epoxy resins, phenolic resins, adhesives, foams, and other products. 14WSLEGAL\055326\00537\41739072v5Production of Polyurethane (PU)

[0070] The produced bio-oil as described herein can be used at least as a partial substitute for conventional petroleum-based polyols suitable for polyurethane production. In some embodiments, the polyol / bio-oil blend can comprise from about 5 wt% up to about 60 wt% of bio-oil. The bio-oil, polyols and a multifunctional isocyanate are mixed and reacted in conventional fashion in the desired proportions. In some embodiments, the polyol may be a commercially available polyol, preferably an aromatic polyester polyol, such as Stepanpol PS-3524™. In preferred embodiments, the isocyanate comprises an aromatic diisocyanate, such as methylene diphenyl diisocyanate (MDI).

[0071] The content of polyol, bio-oil, and MDI can be calculated using the following equation12: ^NCO^ ^NCO^^ Eq. 1 ൌୈ୍^OH^^OH^ୗ^ ^ ^OHୠ୧୭ି୭୧୪^where, the NCO^ୈ୍is the molar content of isocyanate groups (-NCO) for MDI, OH^ୗand, OHୠ୧୭ି୭୧୪denotes the molar content of the total hydroxyl groups in the polyol and the bio-oil, respectively. The [NCO] / [OH] ratio is preferably maintained at 1.5 for all the formulations. In a typical synthesis, the bio- oil is mixed with a suitable solvent, such as a polar aprotic solvent such as dimethylformamide (DMF). Preferably for formulations which contain 20 wt.% or higher, a consistent 1:10 ratio of bio-oil to DMF is 15WSLEGAL\055326\00537\41739072v5employed. However, to avoid a rapid gelling process that hinders the effective elimination of bubbles during the subsequent synthesis stages, the same amount of DMF was applied in the formulations of 0 and 10 wt.% bio-oil as in the 20 wt.% bio-oil formulation. The lower DMF content in these formulations would have otherwise accelerated the gelling process too quickly.

[0072] In some embodiments, a PU synthesis process is shown schematically in Figure 8. In general, the PU synthesis process is substantially conventional, except that at least a portion of the polyols are substituted with a bio-oil as described herein. For example, a bio-oil-solvent mixture is sealed and stirred for about 10 min until the bio-oil was completely dissolved. Subsequently, the bio-oil-solvent solution is mixed with the polyols (PS) and stirred to ensure the complete dissolution of the PS in the bio-oil-solvent mixture. Then, the isocyanate (e.g. MDI) is heated to melt the MDI flakes. Once the PS and bio-oil-solvent are entirely dissolved in a uniform homogenous solution, it is added to the melted MDI in an aluminum pan and stirred, for example with a metal spatula for 1 to 5 min (Table 2) at 50 °C on a hot plate.

[0073] The mixture may then be poured into a mold and cured, preferably during or after a vacuum step to remove bubbles. For example, the mixture may be poured into an aluminum mold previously sprayed with a dry film release agent (Sprayon™). The pan is then immediately placed in a vacuum oven set to 100 °C with a vacuum pressure of 0.087 MPa for a duration which may be determined by the bio-oil content, as specified in Table 3. This step is preferred to remove the bubbles generated during the reaction and from the solvent, ensuring a more uniform final product.

[0074] After the vacuum, the sample is transferred to an air-circulated oven and cured, for example at 80°C for 8 h. The PU sheets were carefully peeled off and placed between two stainless steel plates to obtain materials with a flat surface. Preferably, the PU may be further cured in a secondary curing stage, for example at 120 °C for 24 h to complete the synthesis.

[0075] In some specific examples, various PUs can be prepared in accordance with the parameters specified in Table 3. Each sample is referred to as PBDM followed by the number indicating the percentage of bio-oil that replaced the commercial polyol. Thus, the control sample with no bio-oil was labeled as PBDM0; and the bio-oil percentage followed the rest. For synthesizing the control sample, PBDM0, the methodology was identical to that described above except for omitting the step involving 16WSLEGAL\055326\00537\41739072v5the dissolution of bio-oil in DMF. In its place, DMF was directly added to PS, which helped decrease the viscosity and facilitate the reaction with MDI. Table 3. Formulation parameters for the synthesis of PBDM with different bio-oil substitution content. Formulations are sufficient to fill a 96 mm diameter aluminum mold with an [NCO] / [OH] ratio of 1.5. Sample PS bio-oil MDI DMF PS / bio-oil Agitation Vacuum time time mmol g mmol g mmol G ml wt.% min min PBDM0 28.1 4.5 0 0.0 42.1 5.3 9 100 / 0 1 2.5 PBDM10 25.2 4.1 2.4 0.5 41.5 5.2 9 90 / 10 1 2.5 PBDM20 22.4 3.6 4.9 0.9 41.0 5.1 9 80 / 20 1 2.5 PBDM30 19.6 3.2 7.3 1.4 40.4 5.1 14 70 / 30 2 2.75 PBDM40 16.8 2.7 9.8 1.8 39.9 5.0 18 60 / 40 2 3 PBDM50 14.0 2.3 12.2 2.3 39.3 4.9 23 50 / 50 4 4 PBDM60 11.2 1.8 14.6 2.7 38.8 4.9 27 40 / 60 5 4.5

[0076] In preferred embodiments, a sufficient amount of solvent to dissolve the bio-oil is desirable to produce homogeneous films with enhanced mechanical properties. For example, a ratio of 1:10 for bio- oil to DMF is preferred for formulations containing 20 to 60 wt.% of bio-oil.

[0077] A reduced solvent-to-bio-oil ratio can lead to rapid curing and bubble entrapment due to CO2 and solvent release. This is not preferred as the resulting PU materials can exhibit pinholes, bubbles, cracks, agglomeration of bio-oil, and poor mechanical properties. Preferably, the PU is formed with a vacuum- assisted film formation process to eliminate or reduce bubble entrapment. This approach effectively removed excess DMF before curing and prevented gas entrapment. The vacuum time was essential for achieving smooth surfaces, while subsequent curing at 80 and 120 °C facilitated further DMF evaporation from the PU matrix.

[0078] Preferably, the PU synthesis process is catalyst free, which simplifies the reaction, reducing steps and minimizing unwanted byproducts. One embodiment of a reaction process and mechanism are illustrated in Figure 9. Since PS is more reactive than bio-oil in this formulation, it is possible that a 17WSLEGAL\055326\00537\41739072v5portion of the hydroxyl groups in bio-oil did not react with MDI. These unreacted -OH groups may have formed hydrogen bonds with the -C=O groups of the urethane linkages,35as illustrated in Figure 9b.

[0079] In preferred embodiments, the polyols comprise polyester polyols such as Stepanpol PS-3524™. The polyester polyols have shown better compatibility with kraft lignin than polyether polyols.36Effective dispersion of the bio-oil within the polyol may enable greater substitution levels and improve overall material homogeneity. Without restriction to a theory, the bio-oil exhibits good dispersion in the polyester polyol, likely due to the influence of the ester and ether linkages in the bio-oil.37

[0080] The resulting PBDMs were characterized by FTIR, as shown in Figure 10a. The different PBDM samples exhibited characteristic absorption peaks corresponding to urethane -N-H stretching vibration (3310-3340 cm-1), -C=O stretching vibration (1716 cm-1), -N-O stretching vibration (970-990 cm-1), and the peak at 1220 cm-1that is attributed to the -C=O linked to -N-H.5,38All these peaks indicate that the bio-oil and PS were covalently linked to the isocyanate, forming urethane bonds, confirming that the polymerization was successfully achieved. The characteristic peak corresponding to hydroxyl groups was also replaced by a narrower peak located at 3280 cm-1in all the PBDMs, which is attributed to the - N-H groups. The asymmetric stretching vibration band of the isocyanate groups (-N=C=O) is expected to appear at 2256 cm-1in the spectra. Still, the peak was absent for all the PBDMs, confirming that MDI had fully reacted in the polymerization synthesis.18The ratio of [NCO] / [OH] used was 1.5; thus, a fraction of the -NCO groups was expected to remain unreacted. However, a peak was also observed at 1641 cm-1, corresponding to urea moieties. This indicates that the excess of isocyanate groups reacted with amines moieties (formed by the reaction of isocyanate with moisture) to form the urea -C=O functional group.39The absence of this band in the neat polyurethane sample suggests that the isocyanate groups have fully and completely reacted with the hydroxyl groups from the PS to create urethane bonds. Incorporating 1.5 equivalents of [NCO] / [OH] offsets the effects of secondary reactions, thereby facilitating the formation of urethane linkages crucial for maintaining the desirable properties of polyurethane films.

[0081] The thermogravimetric analysis of PU produced as described herein is presented in Figures 10b. The thermal degradation profile can be divided into four main regions. The first, from 100 to 200 °C, is associated with lower molecular compounds in the samples, such as moisture and unreacted polyols / isocyanates. The second region, between 200 and 300 °C, corresponds to degradation of the soft 18WSLEGAL\055326\00537\41739072v5segments in the polyurethane matrix. The 300 to 450 °C range is attributed to the decomposition of hard segments of the polyurethane matrix, including aromatics and urethane bonds (-HN-CO-O-), which causes the release of gases such as CO and CO2as well as amines and aldehydes. Lastly, the stage between 450 and 550 °C is characteristic of the breakdown of C-C chemical bonds.27,40Table 4. Thermal properties data of the PBDM films determined by DSC, DMA, and TGA. Sample Tg(°C) T5%a(°C) Tmaxb(°C) Residues (%) Tg(°C) (DSC) (DMA) PBDM0 60 230.9 293 20.7 61 PBDM20 55 249.1 333 27.9 64 PBDM40 44 212.8 345 27.2 53 PBDM60 43 219.8 350 25.7 51 aT5%is set as the initial degradation temperature at 95% residual mass. b Tmaxis the temperature at the maximum degradation rate.

[0082] The summary of the thermal properties in Table 4 shows that the T5% increased for the sample PBDM20, then decreased as the bio-oil content increased due to the thermal instability of bio-oil, which has a lower T5%value of 179 °C; however, all the samples remained >200 °C. On the other hand, the maximum weight loss temperature (Tmax) of PBDM films increased gradually with bio-oil content. The highest Tmax for PBDM60 was 350 °C, 57 °C higher than the neat PU. Similarly, the residues at 600 °C were higher when bio-oil was part of the formulation. The highest residue observed for the PBDM20 film was 27.9 %, compared to 20.7 % for the neat PU film. This result confirms that replacing the PS polyol with bio-oil can enhance the thermal stability of the PUs.

[0083] The improved thermal behavior of the PBDM material can be attributed to the intrinsic properties of lignin, as the bio-oil used is derived from it. Softwood Kraft lignin typically shows a weight loss under 300 °C, corresponding to phenylpropane side chain unit degradation. This process occurs at elevated temperatures, eliminating compounds such as formic acid, formaldehyde, carbon dioxide, sulfur dioxide, and water.41The chemical structure of bio-oil contains aromatic compounds that form more char residues at higher temperatures, which delays further weight loss and increases Tmax. 19WSLEGAL\055326\00537\41739072v5Considering residue values is crucial for determining the optimal application of materials. In the event of a fire, a higher residue content at elevated temperatures reduces the emission of harmful gases and limits heat transfer from the fire to the condensed phase.26

[0084] DSC characterization for PU analysis provides information about possible phase transitions or an incomplete curing process. The miscibility of formulations indicates a thorough mixing at the molecular level, leading to a uniform phase. Observing the material’s single glass transition temperature (Tg) suggests complete miscibility. When two Tgvalues match those of the neat components, it suggests complete immiscibility. On the other hand, a shift in either of the Tg values indicates partial miscibility of the components.42,43Figure 10c presents the analysis of the Tgof the PBDM films using DSC, with the results summarized in Table 2. All PBDMs from 0 to 60 wt.% exhibit a single Tg; however, the Tgis noticeably shifted to lower values when the bio-oil content was 40 wt.% or higher; this change indicates that adding more bio-oil content affects intermolecular interactions. In this study, the bio-oil used had an Mw of 1477 g / mol and a polydispersity of 2. The broader weight distribution may have partially disrupted the regular structure of PBDMs, resulting in lower Tg values. Additionally, the samples with higher bio-oil content exhibited reduced cross-linking density. This suggests that the bio-oil mixture has created steric hindrance, which can prevent the complete reaction, decreased the crosslinking density, and stopped the formation of a tightly packed and well-structured polymer network, resulting in increased polymer chain mobility. Finally, the absence of any melting or cold crystallization peak confirms the development of a fully crosslinked structure and the lack of any crystal structure within the material. Dynamic mechanical analysis (DMA)

[0085] DMA was employed to investigate the thermomechanical properties of the PBDMs. The storage modulus (E'), which is the ability of a material to store energy as a function of temperature,44is displayed in Figure 11a. E' increases with increased bio-oil content in the formulation. For instance, the E' value for PBDM0 at 20 °C was ~1749 MPa, while for PBDM20, the value was about 40 % higher. The highest E' was recorded for PBDM60, about 92 % higher than that of PBMD0. This substantial increase is attributed to the stiffening effect of the rigid bio-oil chemical backbone within the soft PU matrix.45Bio-oil in the formulation enhances the stiffness but interferes with crosslinking density and chain packing, lowering the Tg. On the other hand, for all PBDMs, the E' gradually decreased until 20WSLEGAL\055326\00537\41739072v5reaching the transition zone (the temperature range where the material transitions from a glassy state to a rubbery plateau), where a rapid decrease of two orders of magnitude in E' was observed.

[0086] The loss modulus (E'') represents the energy dissipation resulting from the internal friction associated with the movement of polymer chains.46In this study, the Tg values of the materials were also determined from the peak of the E'' versus temperature curves (Figure 11b) and compared with those obtained from the DSC curves (Table 2). As expected, the Tgvalues obtained from both techniques exhibited slight variations due to differences in their methodologies. Initially, the Tgincreased by 3 °C for PBDM20, then decreased for higher bio-oil content. Although PBDM60 had the highest E', it exhibited the lowest Tg, indicating that bio-oil may not have entirely reacted at higher concentrations. Excess bio-oil may have functioned as particles agglomerating with weak interfacial interaction with the PU matrix.18Conversely, the increase in Tg for PBDM20 could be due to better dispersion of bio-oil, improved interfacial interaction with the PU matrix, and a higher crosslinking density.44As shown in Figure 12, the height and area initially increased with rising bio-oil content but later declined significantly as the material became more brittle and less effective at dissipating energy. PBDM60 showed a broader peak between 40 and 100 °C, indicating the presence of microphase separation structures. Mechanical properties of PU

[0087] Uniaxial tensile tests were performed on PBDM dogbone specimens to evaluate their mechanical properties. Representative stress–strain curves for different samples are provided in Figure 11c. At least three specimens were tested for each material, and the average values (with standard deviation) of ultimate tensile strength, elongation at break, and Young’s modulus are summarized in Table 5. The stress–strain curves demonstrate that the presence of bio-oil significantly influences the mechanical behavior of the materials. PBDM0, the control sample, exhibited ductile behavior, with an ultimate tensile strength of 41.8 MPa and an elongation at break of 26.8%. When 20 wt.% of bio-oil was incorporated into the PBDM structure, the fracture behavior shifted from ductile to semi-ductile. This resulted in a remarkable ~66% increase in ultimate tensile strength while maintaining good elongation at break. The well-balanced strength and toughness observed in PBDM20 may be attributed to a higher cross-linking degree and an abundance of hydrogen bonds. Under external load, the intra- and inter- molecular hydrogen bonds absorbed substantial energy before breaking, improving strength.5221WSLEGAL\055326\00537\41739072v5Interestingly, when the bio-oil content exceeded 20 wt.%, the material can exhibit brittle fracture with reduced ultimate tensile strength and elongation at break. As the bio-oil content increased to 40% or more, it behaved more like non-homogenously dispersed particles within the PU matrix rather than actively participating in urethane bond formation, which resulted in a lower crosslinking density. Possibly, these particles also agglomerated and acted as stress concentration points or crack initiation zones. On the other hand, since a bio-oil to solvent ratio (i.e., DMF) of 1:10 was maintained for all the samples, an increase in bio-oil content likely resulted in a higher viscosity of the formulation, which may have led to the rod-climbing effect, interfering with uniform mixing and the reaction of the bio-oil with isocyanate and polyol, affecting the properties of the material.18Thus higher levels of bio-oil may require increase in solvent to reduce viscosity of the blend. Table 5: Mechanical properties of polyurethane with different percentage levels of bio-oil. Ultimate tensile strength Elongation at break Young’s modulus Samples (MPa) (%) (GPa) PBDM0 41.8 ± 0.9 26.8 ± 8.8 1.6 ± 0.1 PBDM10 44.8 ± 3.2 29.6 ± 8.4 1.7 ± 0.2 PBDM20 69.1 ± 4.3 10.4 ± 0.9 2.0 ± 0.1 PBDM30 58.3 ± 3.1 12.0 ± 4.4 1.8 ± 0.1 PBDM40 46.2 ± 1.7 9.5 ± 1.9 1.9 ± 0.3 PBDM50 33.8 ± 3.7 2.7 ± 0.5 1.5 ± 0.6

[0088] The tensile fractured surfaces of PBDM20 and PBDM50 are shown in Figure 11e as representative examples. The nature of the stress–strain curve indicated that PBDM20 fractured in a semi-ductile manner. This is further confirmed by the fractured surface analysis, which shows evidence of shear yielding and uneven, rough surfaces. In contrast, PBDM50 exhibits a relatively smooth fractured surface with few ridges and valleys, indicating a brittle fracture, consistent with its stress– strain curve.

[0089] PBDM60, although it appears uniform, is quite brittle. PBDM60 with increased thickness appeared more suitable for mechanical analysis; however, the sample failed to hold securely in the tensile grips, leading to inconsistent and unreliable results. As such, the mechanical properties of 22WSLEGAL\055326\00537\41739072v5PBDM50 are given in Figure 11c and Table 5. Also, given these limitations, bio-oil incorporation was restricted to 60 wt.%, which is believed to be the maximum viable replacement for the commercial polyol. For a better understanding of the ductile-to-brittle transition, PBDM10 and PBDM30 specimens were also prepared and tested, and the results are shown in Figure 12A and Tables 5 and 6. Table 6: Shape recovery temperature and its correlation with the Tg to achieve a sshape recovery over 90% within 5 min. Sample Optimal shape recovery Rr(%) temperatures (°C) PBDM0 110 (Tg+ 50) 94.7 ± 2.4 PBDM10 110 (Tg+ 50) 94.1 ± 2.7 PBDM20 110 (Tg+ 55) 92.0 ± 2.1 PBDM30 110 (Tg+ 56) 94.4 ± 2.7 PBDM40 110 (Tg+ 66) 96.1 ± 1.5 PBDM50 110 (Tg+ 70) 96.1 ± 1.5 PBDM60 110 (Tg+ 67) 90.0 ± 3.2

[0090] Figure 11d compares the ultimate tensile strength and elongation at break of PBDMs alongside several commercial polyurethane materials. The graph denotes specific materials as follows: Desmovit® D1 corresponds to DPR3922, D2 to DPR3914; and Ecomass® E1 to 4703ZB92. PTM&W Industries, Inc., coded as P1 for the material coded as PT7988. Besides the comparison with the commercial PU, the graphs show the comparison with other previously reported works on lignin-based polyurethanes. All these materials exhibit distinct mechanical behaviors based on their formulation. Different formulations can lead to materials with higher elongation at break or improved tensile strength; the resulting mechanical properties are highly related to the type of polyol used and the lignin-based materials.26

[0091] The PU formed as described herein achieved significantly higher ultimate tensile strength than other material using high lignin content. The resulting mechanical properties of the PBDMs can make our material suitable for various applications, such as in the automotive industry, tools, industrial components, furniture, and sports materials. Additionally, it exhibits properties comparable to some commercially available polyurethanes. 23WSLEGAL\055326\00537\41739072v5Swelling behavior

[0092] Swelling behavior, crosslink density, and gel content are critical parameters for evaluating polyurethane materials' structural integrity, network formation, and solvent resistance. Swelling behavior indicates how well the polymer network can absorb solvent, which is inversely related to the crosslink density (CD), a measure of the extent of network connectivity. Figure 13c shows the relationship between crosslink density and swelling behavior of all PBDM samples after one week of swelling in DMF. The PBDM samples show a CD between 0.6 and 1 mmol / cm3, PBDM20 being the highest CD value. Bio-oil addition of up to 20 wt.% helped to form crosslinked structures, indicating that bio-oil effectively contributes to network formation by reacting with MDI. The PBDM30 to PBDM60 showed decreased CD. This decrease can be attributed to phase separation, steric hindrance, and possible bio-oil agglomeration, which can disrupt the network uniformity. The samples with 50 and 60 wt.% showed the highest reduction of CD. Both samples also showed that more bio-oil was leached out from the PU network, as visible in Figure 13a. Wadekar et al.26reported using Kraft lignin with polypropylene glycol, resulting in a CD of around 1 mmol / cm3using 20 wt.% of lignin substitution and an NCO / OH ratio of 1.5. Another factor influencing CD is the molecular weight of the polyol. In a preferred embodiment, the PS has a molecular weight of 385 g / mol. Polyols with shorter chain lengths can be more challenging to incorporate into the PU network due to the increased distance from the reacted MDI with bio-oil. This distance effect arises from the steric hindrance of bio-oil with an increased chain length, making the reaction less efficient when the bio-oil content is further increased.53As a result, the PU network may exhibit brittleness or insufficient mechanical strength due to reduced crosslinking, as was observed for the samples PBDM50 and PBDM60.

[0093] Conversely, bio-oil with a higher molecular weight than PS may introduce some chain entanglements, hindering the accessibility of reactive -OH groups and trapping them with the long chains of bio-oil. Consequently, the excess of free isocyanate that fails to react with -OH groups may instead react with existing urethane groups.53This is one of the primary reasons that makes lignin with a higher molecular weight more challenging to incorporate into a PU network with higher percentages without losing mechanical properties and structural characteristics.

[0094] On the other hand, gel fraction significantly influences the final properties of PUs, as it directly indicates the level of cross-linking.54A high gel fraction and a reduced swelling rate indicate a higher 24WSLEGAL\055326\00537\41739072v5degree of CD, as shown in Figure 13b and c, the gel fractions of different PBDM sheets up to 40 wt.% bio-oil was higher than 80%, indicating good CD. For PBDM50 and PBDM60, the gel content was slightly reduced, which explains the decrease in the mechanical properties of these samples. Although there was a reduction in the gel content and CD after bio-oil content was increased, the samples still showed some degree of crosslinking, proving that the reactions of bio-oil, PS, and MDI proceeded adequately despite the absence of a catalyst. Adsorption of metals using lignin-based biochar.

[0095] Biochar derived from lignin depolymerization can be an effective adsorbent for heavy metals. The inventors have demonstrated that biochar can adsorb lead, with high removal rates of 85.69% and 62.64% at initial concentrations of 1 mg / L and 20 mg / L, respectively, using a 100 mg char dosage. The evaluation showed that reducing the char dosage had a positive impact on metal adsorption. Specifically, a dosage of 10 mg resulted in a higher removal rate for Cd and Pb, while 100 mg still yielded better results for Li. Furthermore, the study assessed the impact of contact time on adsorption. It was found that a 24-hour contact time resulted in the highest removal rates for all three metals.

[0096] The biochar obtained from lignin depolymerization at low temperatures consists of multiple layers, with the outermost layer an incomplete depolymerized lignin fragment. This shows a brown colour in the resulting solid residue left after the depolymerization reaction. However, after washing this solid residue at least 3 times, the outer layer of lignin dissolves, leaving the interlayer of black char. This phenomenon does not tend to occur in chars obtained from lignin depolymerization at temperatures above 240 °C (54).

[0097] Biochar is an effective adsorbent to removing metals such as Lead (Pb), Cadmium (Cd) and / or Lithium (Li) from water. Pb and Cd are toxic, and the recovery of Li is mostly motivated by the desire to recover lithium from aquatic sources.

[0098] Figure 16 shows the comparison of the removal rate percentage while maintaining a pH of 3 throughout the entire 24 hours of contact time, tested against the natural pH behavior of the biochar, demonstrating that pH 3 was not adequate for the metal adsorption. At a pH of 3, the functional groups were not the main adsorption site for the metals because the biochar was heavily protonated. In this acidic environment, positively charged ions, plus the presence of the inorganic compounds in the biochar, were 25WSLEGAL\055326\00537\41739072v5competing with the metal ions for the limited permanent negatively charged sites in the biochar. This resulted in a low removal rate even after 24 h.

[0099] When pH was higher than 8, Cd2+began to precipitate, and the species in the aqueous solution started forming such as Cd(CO3)2, CdOH+ and Cd(OH)2(aq) became dominant species, and for Pb2+, at pH higher than 7, PbCO3 and PbOH+were the predominant species. Figure 17 shows the removal rate (a) and adsorption capacity (b) of Pb2+, Cd2+, and Li+at different initial metal concentrations for 24 h adsorption time.

[0100] Langmuir and Freundlich's isotherm models were employed to describe the adsorption equilibrium results of the biochar for the metals studied. The fitting curves and parameters of the two models for each metal are displayed in Fig. 18a-d. As seen in Fig. 18c-d, Li+exhibited the best fitting reliability of the adsorption results for both models. In contrast, the adsorption of Pb2+fitted better with the Langmuir model, and Cd2+with the Freundlich model. The Langmuir model assumes a monolayer adsorption on a surface that has a limited number of uniform sites available. The Freundlich model characterizes the adsorption on heterogeneous surfaces and multilayer adsorption. The factor "1 / n" indicates the favorability of adsorption, with a generally accepted range of 0 to 1 signifying easy adsorption. EXAMPLES

[0101] The following examples are provided to illustrate embodiments of the invention and are not intended to limit the claimed invention in any way. Example 1 - Materials

[0102] Amallin™ LPH Kraft Lignin (KL) was purchased from West Fraser Mills Ltd. ACS Reagent grade isopropanol (99.5%), formic acid (FA, 88%), acetone (99.5%), dichloromethane (DCM, 99.5%), hexane (95%) and HPLC grade tetrahydrofuran (THF) and toluene (99.8%), were purchased from Fisher Chemical, and ACS reagent grade ethyl acetate (EAc, 99.5%) was purchased from Sigma Aldrich Ltd. All chemicals were used as received. Example 2 - Depolymerization of Kraft lignin under microwave irradiation 26WSLEGAL\055326\00537\41739072v5

[0103] A Kraft lignin depolymerization reaction was conducted using a CEM-Discover microwave synthesizer (120V, Matthews, USA). A 10 mL vessel containing a magnetic stir bar was filled with a desired amount of Kraft lignin (0.1, 0.5 or 0.75 g), 4 mL of isopropanol, and 1.5 ml of formic acid. The vessel was then closed and placed in the MW reactor with adjusted maximum pressure and power of 250 psi and 250 W, respectively. While stirring continuously, the reaction mixture was heated to the desired temperature (100 to 200 °C) and kept for the desired reaction time (5 to 120 min). The start time of each reaction was considered from the moment of reaching the desired temperature. Once the reaction time was completed, the sample was cooled to room temperature for further separation. Example 3 - Product Separation

[0104] The reaction products comprised a mixture of liquid and solid, and was washed with isopropanol and separated by filtration with a pre-weighed Whatman No.5 filter paper. The vessel was washed with acetone several times until any leftover solid residue or matter adhered to the glass was left, followed by filtration in the same filter paper. The filter cake containing solid residues was dried for 12 h at 105 °C. The filtrate evaporated at room temperature overnight, followed by drying at 105 °C for 3 h in an oven to eliminate moisture. The experiments were conducted in triplicate for each reaction condition, and the results were presented using mean values. The solid residues (SR) and the bio-oil (bio-oil) yield were calculated using equations 1 and 2. The solid residues were dissolved in THF, stirred for 24 h, and filtrated to separate the THF-soluble fraction, which is the unreacted lignin (UL) and the THF-insoluble fraction, which is a carbon-rich solid material, referred to as char in this work. The yield for both fractions was calculated using Equations 3 and 4. Yield of bio-oilൌ mass of bio-oilmass of dry ligninൈ100% (Eq. 1)Yield of SRൌ mass of SRmass of dry ligninൈ100%Yield of ULൌ mass of ULmass of dry ligninൈ100%Yield of charൌ mass of Charmass of dry ligninൈ100% (Eq. 4)

[0105] The biomass was further purified through sequential solvent extraction; the ratio of bio-oil to solvent was maintained at 1 g to 10 ml for each solvent used. First, the bio-oil was dissolved in ethyl 27WSLEGAL\055326\00537\41739072v5acetate under stirring for 30 min; the precipitated fraction was separated by filtration and labelled as ethyl acetate insoluble (EAcI). Afterward, the soluble phase was concentrated by a rotary evaporator at 60 °C. The resulting dry organic phase labelled as ethyl acetate soluble fraction (EAcS), was then dissolved in dichloromethane (DCM) and toluene, keeping a ratio of DCM: toluene of 2 ml:8 ml based on a previous study by Zijlstra (37). Initially, it is dissolved in DCM by sonication for 20 min and 30 min of stirring. Then, toluene was added to the mixture, and the same process of sonication and stirring was repeated. The precipitated fraction was filtrated with a Whatman No.5 filter paper. The dichloromethane-toluene soluble fraction was labelled as DCTS, while the solid fraction left on the filter paper was called dichloromethane- toluene insoluble fraction (DCTI). The DCTS was then evaporated until only 5 ml of solvent remained. Then, 5 ml of hexane was added to purify the bio-oil further, and the formed precipitate was separated by filtration and identified as the hexane insoluble fraction (HI); the filtrate was called hexane soluble fraction (HS). Example 4 - Fourier-transformed infrared spectroscopy (FTIR)

[0106] Fourier-transformed infrared spectroscopy (FTIR) was used to analyze the functional groups of kraft lignin, solid residues, depolymerized products, and the fractions obtained after solvent sequential extraction. FTIR spectra were conducted on a Bruker Alpha FTIR spectrometer (Bruker optics, Esslingen, Germany) equipped with a single bounced diamond ATR crystal, with a resolution of 4 cm-1over the range of 400 to 4000 cm-1using 24 scans for each sample and averaged using the OPUS software (Bruker version 6.5). Before applying and collecting the sample spectrum, the background spectrum of the clean ATR crystal was recorded. The baseline correction was done using Omnic Software (version 8), while peak normalization and data analysis were done using OriginPro 2021 software. Example 5 - Gel permeation chromatography (GPC)

[0107] GPC was used to determine the number average molecular mass (Mn), weight average molecular mass (Mw) of the bio-oil, and initial KL. Samples were dissolved in THF and filtered through a PTFE syringe filter (pore size: 0.2 µm). The GPC instrument consisted of an Agilent 1200 series pump and autosampler, an Agilent 1200 series Evaporative Light Scattering Detector (ELSD), and a Phenogel™ 5 µm 500A column. THF was the eluent with a 0.5 mL / min flow rate. Polystyrene standards were used for calibration. Acetylation was required to properly dissolve KL in THF before depolymerization to analyze KL in THF, following the method reported by McClelland and collaborators. Briefly, 100 mg of KL was 28WSLEGAL\055326\00537\41739072v5dissolved in 3 mL pyridine. Then, 3 mL of acetic anhydride was added, and this mixture was heated at 80 °C for three hours. The solution was added dropwise to ice water (500 mL), then centrifuged to separate the water. Water was added again to wash the pyridine properly; this process was repeated three times. The acetylated lignin was dried in a vacuum oven at 60 °C for 24 h. Catalytic depolymerization using PARR reactor

[0108] The process of catalytic depolymerization of Kraft lignin was carried out in a 50 mL PARR reactor. The reactor was filled with 2.7 g of Kraft lignin, 22 mL of isopropanol, 4 mL of formic acid, and the catalyst (4 wt.% or 8 wt.% of lignin weight). Prior to heating, the reactor was purged with nitrogen (60 PSI). The reaction mixture was heated to 250 °C for 4 hours, starting the timing upon reaching the desired temperature. After completing the reaction time, the sample was cooled with an ice bath, and a gas sample was taken before opening the reactor. The depolymerization product was filtered, and the reactor was rinsed with acetone for further product separation by filtration. The resulting liquid was identified as bio-oil, while the lignin left on the filter paper was termed solid residue. The bio-oil was dried at 60 °C for 24 hours, and the solid residue at 105 °C for 24 hours. Example 6- Biochar preparation

[0109] Biochar was obtained through a series of steps. First, a lignin depolymerization reaction was initiated as described in Example 2. After the reaction, the solid residues were separated from the liquid product using a Whatman 5 filter paper. These residues were left to dry at room temperature overnight and dried at 100 °C for 24 h to eliminate adsorbed moisture. The dried solid residue was thoroughly purified with THF and deionized water to separate the unreacted lignin and eliminate soluble impurities. First, 1 g of solid residues were mixed with 20 mL of THF and stirred for 3 h. The resulting mixture was filtered, and the precipitate fraction was washed twice with THF, stirring for 6 h per wash. The solid residue remaining in the filter paper, referred to as the lignin char, was left at room temperature to allow the solvent to evaporate. Then, it was washed twice with deionized water, separated by centrifugation, and dried at 100 °C for 24 h. A rotary grinding machine further processed it to obtain a fine powder. Example 7 - Removal of metals by biochar obtained from lignin depolymerization.

[0110] Biochar performance was characterized with adsorption isotherms, pH effect, initial metal concentration, and adsorbent dose studies as they directly quantify and optimize adsorption behavior. 29WSLEGAL\055326\00537\41739072v5Other characterization techniques such as FTIR and XPS provide insight into chemical interactions and surface composition, while SEM and EDS reveal structural and elemental features.

[0111] To study the adsorption of metals, synthetic water was prepared with nano-pure water (18.2 MU cm; Barnstead, Thermo ScientificTM) with the different metals and at different concentrations. The experiments were carried out in 15 mL centrifuge tubes, containing 10 mL of metal solution at different initial solution concentrations (1, 10, 20, 50, and 100 mg / L) for each metal, at a specific adsorbent dose ( 0.5, 1, 5 and 10 g / L), pH (3 and natural pH) and at different contact time (0.5, 1, 2, 4, 8, 16, and 24 hours) to evaluate the various parameters of initial metal concentration, adsorbent dosage, pH and contact time respectively. The tubes were left to stir at room temperature using a rotary mixer and the metal solutions pH was adjusted using 0.1 M HCl and 0.1 M NaOH solutions. After the stirring time was completed, the samples were filtered, and metal concentrations were analyzed by an inductively coupled plasma-optical emission spectrometer (ICP-OES;Thermo iCAP6300 Duo, N. America, Thermo Fisher Corp.).

[0112] The removal rate percentage (R, %) of metals and the adsorption capacity (qe, mg / g) of the adsorbent were calculated using Equation 1 and 2, respectively.Where C0 is the initial concentration of metal ions before adsorption (mg / L), Ceq is the equilibrium concentration of metal ion solution after adsorption test (mg / L), qe corresponds to the amount of solute adsorbed per unit weight of adsorbent (mg / g), V is the volume of equilibrating solution containing metals (L), ms is the mass of the adsorbent, char (g).

[0113] Adsorption isotherms were evaluated to determine the distribution of adsorbate molecules between the synthetic water and the biochar

[0018] . The adsorption isotherms were constructed by assessing the adsorption experiments by varying the initial concentration of the adsorbate while maintaining a fixed dosage of biochar at room temperature for 24 h, with stirring. The resulting data were analyzed using standard adsorption models, specifically the Langmuir and Freundlich isotherms, to describe the adsorption mechanism. The Langmuir model assumes that adsorption occurs at specific, homogeneous sites, forming a monolayer of atoms. In contrast, the Freundlich model accounts for multilayer adsorption 30WSLEGAL\055326\00537\41739072v5in heterogeneous systems

[0018] . The isotherms for Langmuir model were calculated based on Eq.3 and Eq 4; and Freundlich isotherms were calculated by Eq.5 and Eq.6 [19,20].1 ^^^^^^ ^^(linear form) Eq.5 ^ൌ ^^^^^^ ^^^^^^ ^^ி ^^^ൈ^^^^^^ ^^^^^^ ^^^^(non-linear form) Eq.6Where qecorresponds to the amount of solute adsorbed per unit weight of adsorbent (mg / g), Ceqis the equilibrium concentration of metal ion solution after adsorption test (mg / L), qmax is the monolayer adsorption capacity (mg / g), KL is the adsorption constant related to Langmuir model, KF is the relative adsorption capacity of the adsorbent for Freundlinch model and the term 1 / n is the intensity of adsorption factor, which typically ranges between 0 and 1.

[0114] The initial pH value of the biochar before the metal adsorption test showed a value in the acidic range of 2.8-3.5, which indicates biochars have many phenolic and carboxyl groups, and also a lower degree of carbonization due to the low temperature used in the depolymerization reaction, these factors reduce the pH of biochar. The pH level plays a role in the adsorption process because it affects the surface charge of the adsorbent, as well as complexation. Example 8 - Characterization of lignin char

[0115] The changes in the lignin char before and after the adsorption of Pb, Cd and Li were characterized as follows. Fourier-transformed infrared spectroscopy (FTIR) was used to analyze the functional groups of lignin char before and after Pb, Cd and Li adsorption. FTIR spectra were conducted on a Bruker Alpha FTIR spectrometer (Bruker optics, Esslingen, Germany) equipped with a single bounced diamond ATR crystal, with a resolution of 4 cm-1over the range of 400 to 4000 cm-1using 24 scans for each sample and averaged using the OPUS software (Bruker version 6.5). Before applying and collecting the sample spectrum, the background spectrum of the clean ATR crystal was recorded. The baseline correction was done using Omnic Software (version 8), while data analysis was done using OriginPro 2021 software. 31WSLEGAL\055326\00537\41739072v5

[0116] The morphology of samples was characterized by scanning electron microscopy (SEM); the images were taken with Zeiss Sigma 300 VP-FESEM operating at 15 kV with a resolution of 10 nm equipped with Bruker energy dispersive X-ray spectroscopy (EDS) system with a dual silicon drift detectors each with an area of 60 mm2and a resolution of 123 eV. Before analysis, the samples were prepared by dispersing powder onto the adhesive surface of stubs, then coated with conductive carbon using Leica EM SCD005.

[0117] Thermogravimetric analysis (TGA) was performed to evaluate the thermal degradation of samples before and after adsorption. A thermogravimetric analyzer (TGA Q50, TA Instruments) was used to test ~10mg of the dry sample was placed in a platinum crucible under nitrogen flow. The heating rate remained constant at 10°C min-1from 25 to 800 °C. Example 9 - Production of Polyurethane from bio-oil

[0118] Bio-oil obtained from Kraft lignin (KL) depolymerization was produced and characterized as described above. The bio-oil had an average molecular weight (Mw) of 1477 g / mol, a number-average molecular weight (Mn) of 733 g / mol, a total hydroxyl value of 303.97 mg of KOH / g, and an ash content of 0.29 %. The bio-oil was dried at 60°C under vacuum for 24 h before each procedure.

[0119] Stepanpol PS-3524 (PS) is an aromatic polyester polyol manufactured by Stepan company. Its hydroxyl functionality is 2.4, a total hydroxyl value of 350 mg KOH / g, a viscosity of 6000 – 9000 cP at 25°C, and a moisture content of ≤0.15 wt.%. Table 7: Properties of the bio-oil and PS Sample Mn Mw PDI Total Hydroxyl content Hydroxyl - (g / mol) (g / mol) (mg of KOH / g) functionality bio-oil 733 1477 2.0 304 8.9 PS - 385 - 350 2.4 Characterizations of Polyurethane

[0120] Fourier-Transformed Infrared Spectroscopy (FTIR): Fourier-transformed infrared spectroscopy (FTIR) was used to analyze the functional groups of the polyurethane films obtained. FTIR spectroscopy was performed using a Bruker Alpha FTIR spectrometer (Bruker optics, Esslingen, Germany) equipped with a single bounced diamond ATR crystal, with a resolution of 4 cm-1over the range 32WSLEGAL\055326\00537\41739072v5of 400 to 4000 cm-1using 24 scans for each sample and averaged using the OPUS software (Bruker version 6.5). Before applying and collecting the sample spectrum, the background spectrum of the clean ATR crystal was recorded. The baseline correction was done using Omnic Software (version 8).

[0121] Differential Scanning Calorimetry (DSC): DSC experiments were performed using a Discovery DSC Q100 (TA instruments). Approximately 5 to 10 mg of samples were placed and constrained in aluminum sample pans. The thermograms were recorded while heating from -40 to 120°C at 5°C / min. The glass transition temperature (Tg) was determined from the reversing heat flow signal as the midpoint at half the height of the step transition.

[0122] Mechanical analysis: The tensile tests were performed using a Shimadzu AGS-X Universal Tensile Machine with a 1000 N static cell by ASTM D638.24A predetermined value for the crosshead speed of 5 mm / min. Dog bone-shaped tensile test samples were prepared for each material, and at least three samples were evaluated. The average was taken as the report’s value. The tensile strength was calculated using Equation 2, where ^^ (MPa or N / mm2) is the tensile strength; P (N) is the force applied to the sample; A is the specimen's initial cross-sectional area before testing. Strain is the change in length per unit of the original length of the material before testing.25It can be calculated using Equation 3. Where ^^^is the initial specimen length, and L is the length after a force has been applied. These data were used to plot stress-strain curves. P σൌEq.2 A Strain 100Eq.3

[0123] Dynamic mechanical analysis (DMA): The DMA experiments were performed on a TA instrument, a Q800 dynamic mechanical analyzer employing a film tension geometry using rectangular films under nitrogen flow at 1 Hz of an oscillatory frequency and amplitude of 10 µm. The sample's length, width, and thickness were measured, and the film was analyzed from -20 to 100 °C, with a heating rate of 3 °C / min. The tan ^^ / loss tangent, loss modulus (E’’), and storage modulus (E’) were calculated in terms of temperature.

[0124] Scanning electron microscopy (SEM): The morphologies of the PBDM films were characterized by using scanning electron microscopy (SEM) by capturing cross-sectional and surface 33WSLEGAL\055326\00537\41739072v5images. The images were taken with Zeiss Sigma 300 VP-FESEM operating at 15 kV with a resolution of 10 nm. The surface of the films and a section of the tensile fractured surface film were cut from the film mounted on the adhesive surface of stubs and coated with conductive carbon using Leica EM SCD005.

[0125] Swelling behavior: The crosslinking density (CD) of polyurethane was estimated using the method previously reported by Wadekar et al.,26which is followed in this study. Briefly, the films were cut to a dry weight ranging from 0.20 to 0.25 g and placed into vials. Subsequently, 20 mL of analytically pure DMF was added, and the vials were securely closed. They were left at room temperature for one week to achieve equilibrium swelling. After this period, the swollen films were removed from the DMF and carefully blotted with lint-free tissue to eliminate any excess DMF before weighing. The crosslinking density in mol cm-3was calculated using the following equation: ϑୡ െ2^ϑ ^ Xϑଶ ^ ln^1 െ ϑ^^Eq.4 ൌ V^ V^^2ϑ^ / ଷ െ ϑ^Where, ^^^is the effective number of crosslinking chains, ^^^is the dry polymer film volume, ^^^is the DMF molar volume (76.87 mL mol-1), X is the polyurethane-DMF interaction parameter (0.40), ^^ is thevolume fraction of polyurethane in the total swollen film (ϑ ൌ V^ / V), V refers to the volume atequilibrium swollen mass (cm3). The density of the films was determined using AccuPyc II 1340 gas pycnometer. Using the values obtained from this analysis, the swelling rate was determined by Equation 5: Swelling rateWhere ^^^is the weight of the film is after removing the excess of the DMF solvent from the surface, ^^^is the weight of the dry sample before adding the DMF. After recording the weight of the samples, they were placed in a vacuum oven at 60 °C for 24 h, and the samples were weighed again; this value corresponded to ^^ଶ.27The gel content of the samples was calculated via Equation 6: Gel content Eq. 6

[0126] DPPH activity: Antioxidant activity of the bio-oil loaded in the polyurethane films was assessed based on DPPH free radical scavenging capacity, which was determined according to a method published by T. He et al.28The films were cut into small pieces into 1 g sample, immersed in 20 mL methanol, and 34WSLEGAL\055326\00537\41739072v5stirred for 24 h at room temperature. The supernatant (2 mL) was filtered through a PTFE syringe filter (pore size: 0.2 µm) and mixed with 2 mL of DPPH in methanol (50 mgL-1); the mixture was kept at room temperature in the dark for 1 h. The mixtures were analyzed using a microtiter plate and UV-vis spectrometer (UV-) at 517 nm. Methanol was used as the blank, and DPPH-methanol solution was set as the control. Equation 7 was used to calculate the DPPH radical scavenging activity (RSA).

[0127] Thermal-induced shape memory performance: To investigate shape memory property, the PBDM sheets were placed in an oven at 110 °C for a minimum of 5 min. Afterward, they were deformed into a temporary shape and fixed in an ice bath for 5 seconds. Then, the sample with the temporary shape was placed back in the oven, allowing it to recover its original shape gradually. The process was recorded to demonstrate the samples' excellent thermally triggered shape memory effect.

[0128] The fold-deploy shape memory method was applied to quantitatively measure PBDM's shape memory ability.29The samples were cut in a rectangular shape (30 mm x 10 mm x 1.3 mm) and placed in the oven at 100 °C for a minimum of 5 min. Then, right away, the samples were folded into a temporary “U” shape and then fixed in an ice water bath for 5 s. The bending angle was recorded as θ^. Finally, the temporary “U” shape samples were placed back in the oven at 100 °C for 5 min. The recovery process was recorded, and the final angle of the recovered shape was measured and recorded as ^^ଶ. This process was repeated 5 times, and the average value of θ^and θଶwere used in Equations 8 and 9 to calculate the shape fixation rate ^R^^ and shape recovery rate (^^^^, respectively.θ^

[0129] Chemical recycling: The chemical recycling reaction was performed according to the concept described by Liu et al.30Based on different trial results, we made some modifications to ensure the proper dissolution of our material, and the selected methodology involves the following steps. The PBDM sheet (8 g) was cut into small pieces and placed into a 250 mL flask, followed by the addition of 100 mL of 35WSLEGAL\055326\00537\41739072v5DMF and 0.4 g of TBD catalyst. The mixture was left at room temperature for 20 min to soak the material; then, it was placed in an oil bath at 130 °C under mechanical stirring for 3 h. After the reaction, the DMF was evaporated using a rotary evaporator at 80 °C under vacuum. The product obtained appeared as a brown, high-viscosity liquid. As a preliminary investigation into the potential reuse of the recycled PU material, it was evaluated as an adhesive on two different substrates to assess its bonding performance. For testing the adhesives, lap shear tests on wood (170 mm x 16 mm x 1.7 mm) and steel (170 mm x 25 mm x 1.9 mm) were performed. Steel specimens were cleaned with acetone before testing. The adhesive was evenly applied to each substrate, and then the two substrates were overlapped with a bonding area of 12.7 mm x 25 mm for the steel and 12.7 mm x 16 mm for the wood, which were kept together using binder clips. The dimensions were following ASTM D1002-10.31The specimens with the adhesives were placed in an oven at 120 °C for 12 h. The lap shear strength was measured using a Shimadzu AGS-X Universal Tensile Machine with a 1000 N static cell, at a 10 mm / min controlled rate.4At least three repetitions of the experiments were performed, and the maximal tensile force when the adhesive separated was used to calculate the shear tensile strength following Equation 10. Shear tensile strenght ^MPa^ ൌ^^^^^^^^ ^^^^^^^^ Where Fmaxrefers to the maximum force required to break the bond between the specimens, and the bond area is the length x width in mm2. Thermal-induced shape memory behavior

[0130] The PBDM sheets exhibited excellent thermal-induced shape memory performance. When samples are placed in an oven with a minimum of Tg+ 30°C, the Tgvalue is determined according to the DSC analysis. The samples with a straight initial permanent shape can be bent to a temporary shape and fixed by rapidly cooling in an ice water bath or applying force until they are cooled at room temperature. To recover the original shape, the samples were placed again in the oven according to their Tg+ 30°C. At this temperature, the samples recovered over 90% of their original shape in an average of 10 min.

[0131] Higher temperatures may reduce the recovery time. Testing at 100 and 110°C demonstrated significantly improved response time, allowing the material to release internal stress and return to its original permanent shape in less than 5 min (Figure A6a-c). Both temperatures were used to quantitatively measure shape memory performance using the fold-deploy shape memory method. At 100 36WSLEGAL\055326\00537\41739072v5°C, all the samples showed an excellent shape fixation ratio (Rf) of over 99%, maintained throughout the five tested cycles. The samples' shape recovery rate (Rr) values were between 81% and 93%, highlighting their exceptional shape memory behavior. This remarkable performance is primarily due to the shape memory effect of the PBDM sheets, which is influenced mainly by the Tg of the hard segments, essential for the storage modulus.29At room temperature, the materials are below the Tg, meaning they are in a glassy state that restricts the movement of the chain segments. When the temperature exceeds the Tg, the soft chain segments relax, permitting the material to adopt a new temporary shape, which is retained upon cooling.54Without external influences, the material can maintain its temporary shape indefinitely. In this context, the temperature-induced shape memory effect activates the recovery of its original shape. This process involves relaxing the soft segment chains and relieving the stress in the hard segments.

[0132] Based on these results, the same study of the fold-deploy memory process was carried out at 110 °C. In Figure A6d shows that the Rfand Rrof the PBDM films remain at 100 % and above 90 %, respectively, throughout five cycles of shape-memory tests. For shape memory recovery often involves releasing stored elastic energy; at 110 °C, the material might experience sufficient thermal activation to release all residual stress more effectively. According to these results, the optimal temperatures above their Tgfor shape recovery of each material are summarized in Table S2. The Rrresults from both analyses at 100 and 110 °C indicated that materials with higher concentrations of bio-oil required a slight increase in the optimal temperature above their Tg to recover properly within the timeframe of the test.

[0133] Another factor that plays a crucial role in the material's shape memory effect is its cross-linking degree. As explained above, the PBDM sheets with 0, 10, and 20 wt.% bio-oil substitution showed higher crosslinking density than the other materials, and the same required less temperature increase above its Tg to obtain an Rr over 90 %. It has been established that the Rr shape memory polymers are highly influenced by the physical or chemical crosslinkers that behave as permanent phases, mainly composed of chain entanglements and π-π interactions.56All the samples showed excellent Rfand Rrover five cycles without any physical damage, except for the PBDM60, which began to show minor deterioration in the fifth cycle tested but continued to recover its shape. Liu et al.52reported that the Rr started to decrease as lignin content increased in the PU matrix from 0.8 wt.% to 7.1 wt.%. A similar 37WSLEGAL\055326\00537\41739072v5trend was observed in this study; the more bio-oil content, the higher temperature above the Tg was needed to achieve 90% shape recovery. However, our formulation incorporated a higher bio-oil content and demonstrated that even with increased levels of polyol substitution, efficient shape recovery can still be achieved under optimized conditions. The shape memory performance of the polymer offers exceptional versatility and benefits such as customizable properties and versatility in the design, which can help to create complex shapes in a mold-free manner via solid-state plasticity.57

[0134] An additional benefit of the shape memory performance of the PBDM materials is their role in enabling and enhancing gap closure. The process of repairing scratched or cut polymer is known as gap healing. The shape memory effect in the polymers inherently provides the ability to recover its original shape after some deformation, which can aid in physically closing the gaps or cracks in the material, allowing the closure process via interdiffusion of polymer chains and bond exchange mechanisms. The shape memory-assisted crack facilitated the polymer surfaces to come into molecular contact, allowing the chains to diffuse across the interface, leading to entanglement and the disappearance of the interface (Figure 14f).58The gap closure of PBDM sheets was possible at 130 °C. The material was scratched and heated in an oven to record the gap-closure process. After 1 min, the gap in the material was nearly closed, but a small hole was still visible. Completely closing took 4 min to complete. Ghosh et al.59studied the scratch repair in oxetane-substituted chitosan polyurethane and reported a Tgreduction in the damaged area due to the polymeric network disruption, but the Tg is restored once the polymer matrix is repaired. The Tgreduction facilitates the closure of the damaged area by enhancing polymer chain mobility, stress relaxation occurs, leading to a molecular motion when the material is exposed to heat. This type of gap repair is considered in different self-healing materials, denominated as shape memory components, unlike the self-healing polymer behavior that uses various types of dynamic bonds, which will lead to the kind of healing process to restore the covalent chemical linkages and heal the scratch / gap.58The shape memory components exhibit spring-like behavior, which will facilitate the repair due to the elastic response.60Temperatures above the Tg of the material will facilitate the repair of the material.58Recyclability of PBDMs

[0135] While PBDMs may prove difficult to reprocess, recycled PBDMs may be used as an adhesive. For example, using 0.4 wt.% TBD to the total weight of DMF used was enough to shorten the 38WSLEGAL\055326\00537\41739072v5dissolution time to 2.5 h at 120 °C. The soluble PBDM after reaction is composed of polymer fragments terminated by amines, alcohols, and secondary urea; these functional groups allow the new polymerization when the material is exposed to the curing temperature.30

[0136] To demonstrate the feasibility of utilizing recycled PBDMs as an adhesive, a mixture of DMF, TBD, and PBDM material was placed in a rotary evaporator at 80 °C under vacuum. This process yielded a viscous product containing less than 5% of the initial DMF added to the reaction. The recycled PBDM sheet was positioned between two specimens of wood or metal and secured with two metal binder clips. The combined specimens with the sample were then placed in an oven at 120 °C for 12 h to cure. The results shown in Fig.15c compare the bonding strength of recycled PBDM10 and PBDM20. For the PBDM20, higher shear strength was observed than for PBDM10 and slightly higher for steel than for wood. Wood substrates are more susceptible to moisture, which can weaken the bonding, leading to a reduced shear strength.4Nevertheless, the samples evaluated showed a shear strength greater than 0.7 MPa, the minimum industrial requirement for adhesives.61

[0137] TBD catalysts can be neutralized with acetic acid (10 wt.% of PBDM) to avoid uncontrolled curing reactions when using the fragment mixture to synthesize new PU films. However, the neutralization of the TBD led to reduced bonding strength; the PBDM20 was evaluated as an adhesive after adding acetic acid, resulting in a shear strength value of 0.51 MPa (not shown in the graph), while avoiding the neutralization step gave a shear strength of 1.77 MPa. Adding acetic acid to the reaction can add water, which can also react with isocyanate, and may alter the degradation of the material. In contrast, the presence of TBD led to improved curing of the recycled materials.30Neutralization is essential if the purpose is to upcycle the recycled PBDM. This step is non-negotiable, preventing a quick curing process and ensuring the material can be placed correctly in the mold. Antioxidant properties

[0138] One of the most widely used methods for assessing the antioxidant capacity of synthesized polymers that incorporate lignin is the utilization of the free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). When this stable free radical interacts with antioxidant compounds, a decolorization occurs, changing from dark purple to yellowish. This color change is accompanied by a reduction in absorbance measured through UV analysis.28,62Figure 15d shows the Radical Scavenging Activity (RSA) percentage of each sample after mixing with DPPH / methanol solution at a volume ratio of 1:1 and 39WSLEGAL\055326\00537\41739072v5stored in the dark for 1 hour before analysis. The UV absorbance at 517 nm decreased for the samples containing bio-oil. In contrast, the neat PU sample exhibited the same absorbance as the control of DPPH / methanol. This indicates that the bio-oil presence can scavenge DPPH free radicals as its content increases. The antioxidant properties are attributed to the phenolic hydroxyl groups in its chemical structure, which can neutralize the oxygen radicals from DPPH.28The higher RSA observed for the samples PBDM50 and PBDM60 may be attributed to a greater proportion of unreacted bio-oil in the PU matrix. As mentioned in previous sections, higher contents of bio-oil resulted in unreacted bio-oil dispersed in the PU network. Consequently, more free phenolic hydroxyl groups remained available within the matrix for free radical scavenging.18Interpretation

[0139] References in the specification to "one embodiment", "an embodiment", etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element or feature may be combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

[0140] It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as "solely," "only," and the like, in connection with the recitation of claim elements or use of a "negative" limitation. The terms "preferably," "preferred," "prefer," "optionally," "may," and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

[0141] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase "one or more" is readily understood by one of skill in the art, particularly when read in context of its usage. 40WSLEGAL\055326\00537\41739072v5

[0142] The term "about" can refer to a variation of ± 5%, ± 10%, ± 20%, or ± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" can include one or two integers greater than and / or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited value or range that are equivalent in terms of the functionality of the composition, or the embodiment.

[0143] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. A recited range includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.

[0144] As will also be understood by one skilled in the art, all language such as “between”, "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number(s) recited and such terms refer to ranges that can be subsequently broken down into sub-ranges as discussed above. In the same manner, all ratios recited herein also include all sub-ratios falling within the broader ratio. References

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Claims

CLAIMS 1. A polyurethane comprising cross-linked polyols and lignin degradation products produced by depolymerizing lignin by mixing the lignin with a solvent comprising a short-chain alcohol and a short chain carboxylic acid and heating the mixture to between about 100° C to about 300° C.

2. The polyurethane of claim 1 wherein the lignin degradation products have a number-average molecular weight of between about 600 to about 1500 g / mol, an average molecular weight of about 1200 to about 2900 g / mol, with a polydispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g.

3. The polyurethane of claim 1 or 2, wherein the short-chain alcohol is isopropanol and the short chain carboxylic acid is formic acid.

4. The polyurethane of claim 1, 2 or 3, wherein the polyols comprise aromatic polyester polyols.

5. A method of producing a polyurethane, comprising the steps of: a. depolymerizing lignin by mixing the lignin with a solvent comprising a short-chain alcohol and a short chain carboxylic acid, optionally with a nickel catalyst, and heating the mixture to between about 100° C to about 300° C to produce bio-oil, and b. polymerizing a blend of bio-oil and polyol with a polyfunctional isocyanate.

6. The method of claim 3, wherein the blend comprises between about 1% to about 60 wt% bio-oil.

7. The method of claim 4 wherein the blend comprises between about 10% to about 20 wt% bio-oil.

8. The method of any one of claims 5-7 wherein the bio-oil comprises oligomeric lignin degradation compounds, and having an number-average molecular weight of about 600 to about 1500 g / mol and an average molecular weight of about 1200 to about 2900 g / mol, with a polydispersity index between about 1.9 to about 2.3, and a hydroxyl value of about 290 to about 330 mg of KOH / g.

9. The method of any one of claim 5-8, wherein the isocyanate comprises 4, 4’-Methylenebis (phenyl isocyanate) (MDI).

10. The method of any one of claims 5-9, wherein the polyol comprises aromatic polyester polyols.

11. The method of any one of claims 5-10, wherein the biooil is first dissolved in a solvent, such as dimethylformamide, in a ratio of about 1:10 by weight. SLEGAL\055326\00537\41739072v512. The method of any one of claims 5-11, comprising a vacuum step to remove gas bubbles generated during step b.

13. The method of any one of claims 5-12 wherein the heating step comprises irradiating the mixture with microwaves, and the mixture is heated to between about 100° C to about 200° C.

14. The method of any one of claims 5-13, wherein the heating step comprising heating the mixture in a sealed reactor, such as a Parr reactor, to about 200° to about 300° C with an optional nickel catalyst.

15. The method of any one of claims 5-14, wherein the short chain alcohol comprises methanol, ethanol, propanol, isopropanol or butanol.

16. The method of any one of claims 5-15, wherein the short chain carboxylic acid comprises formic acid, acetic acid, or propanoic acid.

17. The method of claim 15 or 16 wherein the short chain alcohol comprises isopropanol and the short chain carboxylic acid comprises formic acid.

18. The method of claim 17 wherein the ratio of lignin to formic acid is between about 0.0033 g to about 0.67 g per 1.0 ml of formic acid.

19. The method of claim 18 wherein the ratio of lignin to formic acid is between about 0.053 g to about 0.33 g per 1.0 ml of formic acid.

20. The method of any one of claims 13-19, wherein the reaction time is between about 5 min and 120 min.

21. The method of any one of claims 5-20, comprising the further step of recovering biochar produced during production of bio-oil in step a.

22. The method of any one of claims 5-21, wherein a nickel catalyst is added to step a.

23. The method of any one of claims 5-22, wherein step b. is performed without a catalyst.

24. A biochar produced by a depolymerization of lignin, for use as a metal absorbent material.SLEGAL\055326\00537\41739072v5

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