Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides

Thermally Reversible Polymeric Networks from Vegetable Oils

Low cross-link density thermally reversible networks were successfully synthesized from jatropha and sunflower oils. The oils were epoxidized and subsequently reacted with furfurylamine to attach furan groups onto the triglycerides, preferably at the epoxide sites rather than at the ester ones. Under the same reaction conditions, the modified jatropha oil retained the triglyceride structure more efficiently than its sunflower-based counterpart, i.e., the ester aminolysis reaction was less relevant for the jatropha oil. These furan-modified oils were then reacted with mixtures of aliphatic and aromatic bismaleimides, viz. 1,12-bismaleimido dodecane and 1,1'-(methylenedi-4,1-phenylene)bismaleimide, resulting in a series of polymers with T_g ranging between 3.6 and 19.8 °C. Changes in the chemical structure and mechanical properties during recurrent thermal cycles suggested that the Diels-Alder and retro-Diels-Alder reactions occurred. However, the reversibility was reduced over the thermal cycles due to several possible causes. There are indications that the maleimide groups were homopolymerized and the Diels-Alder adducts were aromatized, leading to irreversibly cross-linked polymers. Two of the polymers were successfully applied as adhesives without modifications. This result demonstrates one of the potential applications of these polymers.

Chemistry, Structures, and Advanced Applications of Nanocomposites from Biorenewable Resources

Researchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources.

Photoinduced Polymerization of Eugenol-Derived Methacrylates

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses.

100th Anniversary of Macromolecular Science Viewpoint: Polymerization of Cumulated Bonds: Isocyanates, Allenes, and Ketenes as Monomers

Polymer chemistry offers exciting opportunities to tailor the properties of soft materials through control of the composition of the polymers and their interaction with each other, additives, and surfaces. Ongoing advances in the synthesis of polymeric materials demonstrate the drive for materials with tailored properties for enhanced performance in the next generation of materials and devices. One class of small molecules that can serve as monomers in chain growth polymerization are cumulated double bonds of the general form X═Y═Z. The three most common classes of these molecules are isocyanates (N═C═O), allenes (C═C═C), and ketenes (C═C═O), each of which has been explored as monomers under a variety of conditions. The orthogonality of the two pi bonds of the cumulated double bonds (i.e., lack of conjugation) enables the formation of different polymer backbones from a single monomer, provided the regioreactivity is controlled. This Viewpoint outlines the use of these three cumulated double bonds as monomers, illustrating success and current limitations to established polymerization methods. We then provide an outlook to the future of cumulated double bonds as monomers for the generation of tailored polymer compositions.

The Forgotten Pyrazines: Exploring the Dakin-West Reaction

Pyrazines are an underreported class of N-heterocycles available from nitrogen-rich biomass presenting an interesting functional alternative for current aromatics. In this work, access to pyrazines obtained from amino acids by using the 90 year old Dakin-West reaction was explored. After a qualitative screening several functional proteinogenic amino acids proved good substrates for this reaction, which were successfully scaled to multigram scale synthesis of the corresponding intermediate α-acetamido ketones. Subsequently, the conditions towards pyrazine formation using δ-amino-levulinic acid were optimized, and these were employed to synthesize a relevant set of five functional dimethylpyrazines in high purity. These pyrazines can be considered a versatile toolbox of aromatic building blocks for a wide range of applications, such as in the synthesis of polymers or metal-organic frameworks.

Poly(4-ketovalerolactone) from Levulinic acid: Synthesis and Hydrolytic Degradation

We report here the synthesis of poly(4-ketovalerolactone) (PKVL) via ring-opening transesterification polymerization (ROTEP) of the monomer 4-ketovalerolactone (KVL, two steps from levulinic acid). The polymerization of KVL proceeds to high equilibrium monomer conversion (up to 96% in the melt) to give the semicrystalline polyketoester PKVL with low dispersity. PKVL displays glass transition temperatures of 7 °C and two melting temperatures at 132 and 148 °C. This polyester can be chemically recycled through hydrolytic degradation. Under aqueous neutral or acidic conditions, the dominating pathway for polyester hydrolysis is through backbiting from the chain end. Under basic conditions, mid-chain cleavage, accelerated by the ketone carbonyl group in the backbone, promotes the hydrolysis of nearby backbone ester bonds. The final hydrolysis product is 5-hydroxylevulinic acid, the ring opened hydrolysis product of KVL. PKVL was also observed to degrade under the action of a Brønsted acid to a bis-spirocyclic dilactone natural product altaicadispirolactone, which is a dimer of KVL. This constitutes a rare example of a one-step synthesis of a secondary metabolite of non-trivial structure in which a polymer was the starting material and the sole source of matter. Analogous ROTEP of the isomeric 4-membered lactone 4-acetyl-β-propiolactone (APL) was also explored, although this chemistry was not as well-behaved as the KVL to PKVL polymerization.

Lipase-catalyzed synthesis and post-polymerization modification of new fully bio-based poly(hexamethylene γ-ketopimelate) and poly(hexamethylene γ-ketopimelate-co-hexamethylene adipate) copolyesters

A novel full bio-based ketone-containing aliphatic polyester was prepared by enzyme-catalyzed polycondensation of diethyl γ-ketopimelate (DEK) with 1,6-hexanediol (HDO) using immobilized lipase B from Candida antarctica (CALB). The influences of polymerization conditions such as temperature, time, enzyme amount, and solvent amount on the molecular weight of poly(hexamethylene γ-ketopimelate) (PHK) were investigated. New fully bio-based poly(hexamethylene γ-ketopimelate-co-hexamethylene adipate) (poly(HK-co-HA)) copolymers with narrow polydispersity and well-defined composition were synthesized by copolymerization of DEK, HDO, and diethyl adipate. The structures of PHK and poly(HK-co-HA) copolymers were characterized by nuclear magnetic resonance, and their thermal characterization was examined by thermogravimetric analysis and differential scanning calorimetry. The degradation of PHK and poly(HK-co-HA) copolymers was studied. The post-polymerization modification of these polyketoesters via oxime click chemistry was further demonstrated.

Preparation of Nanoscale Semi-IPNs with an Interconnected Microporous Structure via Cationic Polymerization of Bio-Based Tung Oil in a Homogeneous Solution of Poly(ε-caprolactone)

Nanoscale semi-interpenetrating polymer networks of bio-based poly(ε-caprolactone) (PCL) and polymerized tung oil have been prepared via in situ cationic polymerization and compatibilization in a homogeneous solution. This novel blending technique produced a nanoscale morphology of poly(ε-caprolactone) with average particle sizes as small as 100 nm dispersed in a cross-linked tung oil matrix for 20 and 30 wt % PCL blend compositions. In addition, the exothermic cationic polymerization of tung oil in the presence of the PCL homogeneous solution created a microporous morphology with open three-dimensional interconnected cluster structures. The porous morphology was found to be composition-dependent (the pore size and interconnectivity decreased with increasing PCL content in the blend). The values of the cross-link density and storage modulus in the glassy state for fully cured samples increased significantly and reached a maximum for the 20 wt % PCL blend. This simple, versatile, low-cost strategy for preparing nanoscale and interconnected three-dimensional cluster structures with a microporous morphology and desired properties should be widely applicable for new polymer systems.

100th Anniversary of Macromolecular Science Viewpoint: Polymers from Lignocellulosic Biomass. Current Challenges and Future Opportunities

Sustainable polymers from lignocellulosic biomass have the potential to reduce the environmental impact of commercial plastics while also offering significant performance and cost benefits relative to petrochemical-derived macromolecules. However, most currently available biobased polymers are hampered by insufficient thermomechanical properties, low economic feasibility (e.g., high relative cost), and reduced scalability in comparison to petroleum-based incumbents. Future biobased materials must overcome these limitations to be competitive in the marketplace. Additionally, sustainability challenges at the beginning and end of the polymer lifecycle need to be addressed using green chemistry practices and improved end-of-life waste management strategies. This viewpoint provides an overview of recent developments that can mitigate many concerns with present materials and discusses key aspects of next-generation, biobased polymers derived from lignocellulosic biomass.

Cellulose nanocrystal/plant oil polymer composites with hydrophobicity, humidity-sensitivity, and high wet strength

The preparation of high-performance cellulose nanocrystals (CNCs)/plant oil-derived polymer composites is still a challenge, due to their poor compatibility. Here, by designing amide groups and epoxy groups on sunflower oil derived polymers, appropriate interfacial hydrogen bond interactions between the polymers and CNCs were constructed, where CNCs were homogenously dispersed in polymer matrix. Tensile tests and DMA results revealed that the incorporation of CNCs into sunflower oil derived epoxy polymers significantly enhanced the tensile strength and storage modulus. More importantly, nanocomposites with 50 wt% CNCs are still hydrophobic, which not only show a fast and reversible humidity induced modulus switch, but also exhibit high wet strength (19.9 MPa) after equilibrium water adsorption. The present work revealed that proper designed CNCs/plant oil polymer nanocomposites are good candidates for high performance and functional materials, which are able to replace petroleum-based materials in various fields.

Properties of Novel Polyesters Made from Renewable 1,4-Pentanediol

Novel polyester polyols were prepared in high yields from biobased 1,4-pentanediol catalyzed by non-toxic phosphoric acid without using a solvent. These oligomers are terminated with hydroxyl groups and have low residual acid content, making them suitable for use in adhesives by polyurethane formation. The thermal behavior of the polyols was studied by differential scanning calorimetry, and tensile testing was performed on the derived polyurethanes. The results were compared with those of polyurethanes obtained with fossil-based 1,4-butanediol polyester polyols. Surprisingly, it was found that a crystalline polyester was obtained when aliphatic long-chain diacids (>C12 ) were used as the diacid building block. The low melting point of the C12 diacid-based material allows the development of biobased shape-memory polymers with very low switching temperatures (<0 °C), an effect that has not yet been reported for a material based on a simple binary polyester. This might find application as thermosensitive adhesives in the packaging of temperature-sensitive goods such as pharmaceuticals. Furthermore, these results indicate that, although 1,4-pentanediol cannot be regarded as a direct substitute for 1,4-butanediol, its novel structure expands the toolbox of the adhesives, coatings, or sealants formulators.

Sustainable Plastics from Biomass: Blends of Polyesters Based on 2,5-Furandicarboxylic Acid

Intending to expand the thermo-physical properties of bio-based polymers, furan-based thermoplastic polyesters were synthesized following the melt polycondensation method. The resulting polymers, namely, poly(ethylene 2,5-furandicarboxylate) (PEF), poly(propylene 2,5-furandicarboxylate) (PPF), poly(butylene 2,5-furandicarboxylate) (PBF) and poly(1,4-cyclohexanedimethylene 2,5-furandicarboxylate) (PCHDMF) are used in blends together with various polymers of industrial importance, including poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalate) (PEN), poly(L-lactic acid) (PLA) and polycarbonate (PC). The blends are studied concerning their miscibility, crystallization and solid-state characteristics by using wide-angle X-ray diffractometry (WAXD), differential scanning calorimetry (DSC) and polarized light microscopy (PLM). PEF blends show in general dual glass transitions in the DSC heating traces for the melt quenched samples. Only PPF-PEF blends show a single glass transition and a single melt phase in PLM. PPF forms immiscible blends except with PEF and PBF. PBF forms miscible blends with PCHDMF and PPF, whereas all other blends show dual glass transitions in DSC and phase separation in PLM. PCHDMF-PEF and PEN-PEF blends show two glass transition temperatures, but they shift to intermediate temperature values depending on the composition, indicating some partial miscibility of the polymer pairs.

Renewable Responsive Systems Based on Original Click and Polyurethane Cross-Linked Architectures with Advanced Properties

A new chemical architecture from oleic acid, consisting of a diol structure containing pendant furan rings, denoted the furan oligomer (FO) was synthesized and fully characterized. The FO was integrated into a linear rapeseed-based polyurethane (PU) backbone and cross-linked through a Diels-Alder (DA) reaction by using pendant furan rings and a short polypropylene oxide-based bismaleimide. This is the first time that a thermoreversible PU network based on vegetable oil has been reported. The effects of varying proportions of FO in linear and cross-linked systems, by DA, were studied. These materials were analyzed by classic characterization techniques. The stability and recyclability of the cross-linked materials were shown by successive reprocessing cycles and reanalyzing the mechanical properties. Self-healing properties were macroscopically exhibited and investigated by tensile tests on healed materials. The resulting cross-linked materials present a large range of properties, such as tunable mechanical and thermoresponsive behavior, good thermal recyclability, and self-healing abilities.

Synthesis of fatty ketoesters by tandem epoxidation–rearrangement with heterogeneous catalysis

Fatty ketoesters are obtained from unsaturated fatty esters in a tandem two-step process with a combination of two heterogeneous catalysts, without intermediate purification and with maximum productivity of the catalysts through recycling and reuse.

Balancing the transesterification reactivity of isosorbide with diphenyl carbonate: preferential activation of exo-OH

Exo-OH on ISB has long been asserted as a highly reactive moiety compared with endo-OH. Herein, we report that the nucleophilic attack surmounts steric hindrance in rendering endo-OH more reactive than exo-OH in case of transesterification with DPC.

Pd/Au Based Catalyst Immobilization in Polymeric Nanofibrous Membranes via Electrospinning for the Selective Oxidation of 5-Hydroxymethylfurfural

Innovative nanofibrous membranes based on Pd/Au catalysts immobilized via electrospinning onto different polymers were engineered and tested in the selective oxidation of 5-(hydroxymethyl)furfural in an aqueous phase. The type of polymer and the method used to insert the active phases in the membrane were demonstrated to have a significant effect on catalytic performance. The hydrophilicity and the glass transition temperature of the polymeric component are key factors for producing active and selective materials. Nylon-based membranes loaded with unsupported metal nanoparticles were demonstrated to be more efficient than polyacrylonitrile-based membranes, displaying good stability and leading to high yield in 2,5-furandicarboxylic acid. These results underline the promising potential of large-scale applications of electrospinning for the preparation of catalytic nanofibrous membranes to be used in processes for the conversion of renewable molecules.

Transformation of remnant algal biomass to 5-HMF and levulinic acid: influence of a biphasic solvent system

The primary commercial product from the green microalgae Dunaliella salina is β-carotene. After extracting the lipophilic fraction containing this red-orange pigment, an algal residue remains. As the carotenogenesis is induced by light stress with simultaneous nitrogen depletion, the protein content is low and the remnant is comprised largely of storage carbohydrates. In this work, we transformed the defatted remnant directly to the platform chemicals, 5-hydroxy methyl furfural (5-HMF) and levulinic acid (LA), without previous purification or any pretreatment. The batch experiments were carried out in an autoclave under biphasic solvent conditions at 453 K for 1 h using acidic ZSM-5 zeolite as a heterogeneous catalyst. Mixtures of methyl isobutyl ketone (MIBK/H₂O) or tetrahydrofuran (THF/H₂O/NaCl) with water were used to create the biphasic reactor conditions. The biphasic reaction mixtures helped to increase the 5-HMF yield and simultaneously mitigated the formation of insoluble humins. The carbon yields of 5-HMF and of LA in the MIBK/H₂O biphasic system without NaCl were 13.9% and 3.7%, respectively. The highest carbon yield of 5-HMF (34.4%) was achieved by adding NaCl to the reaction mixture containing THF/H₂O. The experimentally measured partition ratios of 5-HMF between the two liquid phases were compared to the predictions calculated by the computational method COSMO-RS, which is a quantum chemistry-based method to predict the thermodynamic equilibria of liquid mixtures and the solubilities. The COSMO-RS predicted partition ratios of 5-HMF were in line with the experimentally measured ones.

Defatted algal remnant is transformed to 5-HMF and LA.

Totally green cellulose conversion into bio-oil and cellulose citrate using molten citric acid in an open system: synthesis, characterization and computational investigation of reaction mechanisms

The simultaneous transformation of crystalline or amorphous cellulose into a furan-based bio-oil and cellulose citrate was realized avoiding the use of strong inorganic acids, drastic conditions, enzymatic treatments or microorganism fermentation. This innovative method is very eco-friendly and involves the use of molten citric acid under solvent free conditions at atmospheric pressure. An accurate discussion on chemical composition of the bio-oil enriched in bioprivileged molecules as well as structural and morphological characterization of cellulose citrate was reported. Moreover, mechanistic hypotheses were formulated on the basis of experimental findings and detailed DFT quantum-mechanical simulations were carried out to confirm, step by step, the proposed reaction paths.

Innovative and efficient conversion of cellulose in furan-based bio-oil and cellulose citrate.

2-Activated 1,3-enynes in enantioselective synthesis

The rapid enantioselective synthesis of valuable building blocks and pharmaceutically important compounds from easily accessible precursors is one of the major areas of focus in organic chemistry. In this context, 2-activated 1,3-enyne has emerged as a powerful synthon in recent years for the efficient synthesis of enantioenriched furans, allenes, 4-H-pyrans, and 4-isoxazolines, which are privileged scaffolds in bioactive compounds and natural products. This review will cover the history of the development of 2-activated 1,3-enyne in enantioselective synthesis along with the corresponding mechanisms, which may motivate further development in this area to forge more complex and valuable molecules.

Transition metal-free catalytic reduction of primary amides using an abnormal NHC based potassium complex: integrating nucleophilicity with Lewis acidic activation

An abnormal N-heterocyclic carbene (aNHC) based potassium complex was used as a transition metal-free catalyst for reduction of primary amides to corresponding primary amines under ambient conditions. Only 2 mol% loading of the catalyst exhibits a broad substrate scope including aromatic, aliphatic and heterocyclic primary amides with excellent functional group tolerance. This method was applicable for reduction of chiral amides and utilized for the synthesis of pharmaceutically valuable precursors on a gram scale. During mechanistic investigation, several intermediates were isolated and characterized through spectroscopic techniques and one of the catalytic intermediates was characterized through single-crystal XRD. A well-defined catalyst and isolable intermediate along with several stoichiometric experiments, in situ NMR experiments and the DFT study helped us to sketch the mechanistic pathway for this reduction process unravelling the dual role of the catalyst involving nucleophilic activation by aNHC along with Lewis acidic activation by K ions.

An abnormal N-heterocyclic carbene (aNHC) based potassium complex was used as a transition metal-free catalyst for reduction of primary amides to corresponding primary amines under ambient conditions.

Cellulose-Derived Functional Polyacetal by Cationic Ring-Opening Polymerization of Levoglucosenyl Methyl Ether

The unsaturated bicyclic acetal levoglucosenyl methyl ether was readily obtained from sustainable feedstock (cellulose) and polymerized by cationic ring-opening polymerization to produce a semicrystalline thermoplastic unsaturated polyacetal with relatively high apparent molar mass (up to ca. 36 kg mol-1 ) and decent dispersity (ca. 1.4). The double bonds along the chain can undergo hydrogenation and thiol-ene reactions as well as crosslinking, thus making this polyacetal potentially interesting as a reactive functional material.

A New Valuable Synthesis of Polyfunctionalized Furans Starting from β-Nitroenones and Active Methylene Compounds

Highly functionalized furans are the key scaffolds of many pharmaceuticals and bioactive natural products. Herein, we disclose a new fruitful synthesis of polyfunctionalized furans starting from β-nitroenones and α-functionalized ketones. The protocol involves two steps promoted by solid supported species, and it provides the title targets from satisfactory to very good overall yields and in an excellent diastereomeric ratios.

A Brønsted Acidic Ionic Liquid as an Efficient and Selective Catalyst System for Bioderived High Molecular Weight Poly(ethylene 2,5-furandicarboxylate)

Green synthesis of bioderived high-molecular-weight poly(ethylene 2,5-furandicarboxylate) (PEF) over metal-free catalysts is a significant challenge. This study focuses on PEF prepared from ethylene glycol and 2,5-furandicarboxylic acid (FDCA) through a direct esterification method with ecofriendly metal-free ionic liquids (ILs) as catalysts. The catalytic activities of a series of imidazolium cations in the presence of various anions are systematically investigated and found to be mainly governed by the anions. Among the ILs studied, 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂ MIM]BF₄ ) is identified as the best catalyst, showing excellent catalytic activity, selectivity, and stability, even at low catalyst loadings (0.1 mol % w.r.t. FDCA). Optimization of the polymerization parameters enables [C₂ MIM]BF₄ -catalyzed production of PEF with a high number-average molecular weight (M_n =5.25×10⁴  g mol^-1 ). The relationship between Brønsted acidity and catalytic activity is also investigated and the results show that the trend in catalytic activity is in good agreement with that in Brønsted acidity, as determined by the Hammett method. Additionally, on the basis of experimental results and density functional theory calculations, an electrophilic activation mechanism induced by hydrogen bonds is proposed. This strategy of adjustable acidity and anion structure in ILs provides an opportunity to develop other ILs for bio-based polyesters through green synthesis pathways.

Study of the Influence of the Reprocessing Cycles on the Final Properties of Polylactide Pieces Obtained by Injection Molding

This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

Copolymerization of Natural Camphor-Derived Rigid Diol with Various Dicarboxylic Acids: Access to Biobased Polyesters with Various Properties

In this work, alicyclic (1R,3S)-1,2,2-trimethylcyclopentane-1,3-dimethanol (TCDM), derived from natural camphor, was copolymerized with linear α,ω-diacids, terephthalic acid (TPA), and 2,5-furandicarboxylic acid (FDCA), affording a series of polyesters with functional properties. 2D NMR spectroscopy revealed that the stereoconfiguration of TCDM was preserved after polymerization. The TCDM polyester based on TPA showed high thermostability, high T_g value (115 °C), high modulus (1.3 GPa), and high ultimate strength (29.8 MPa). The TCDM polyester based on 1,4-succinic acid exhibited excellent ductility and resilience. Lastly, the rigidity analysis based on van Krevelen's group contribution method, coupled with the comparisons between TCDM- and sugar-based polyesters, confirmed that TCDM is a highly reactive and rigid diol. Results indicate that TCDM polyesters are suitable for a wide range of applications, including hot-filled containers and transparent packaging materials. This work addresses some critical needs for high performance biopolymers such as achieving high T_g values, high thermostability, and high transparency.

Synthesis of Resins Using Epoxies and Humins as Building Blocks: A Mechanistic Study Based on In-Situ FT-IR and NMR Spectroscopies

The combination of eco-respectful epoxy compounds with the humins, a by-product of biomass chemical conversion technologies, allow the obtention of materials with high added value. In this work, we propose a chemical connection study of humins with two aliphatic bis-epoxides through copolymerization reactions to synthesize sustainable, bio-based thermosets. The mechanism insights for the crosslinking between the epoxides and humins was proposed considering the different functionalities of the humins structure. Fourier Transform InfraRed (FT-IR), one dimensional (1D) and two-dimensional (2D) Nuclear Magnetic Resonance (NMR) spectroscopy techniques were used to build the proposed mechanism. By these techniques, the principal chain connections and the reactivity of all the components were highlighted in the synthesized networks.