Here we report the synthesis of thermosetting resins from low molar mass Kraft lignin fractions of high functionality, refined by solvent extraction. Such fractions were fully characterized by P NMR, 2D-HSQC NMR, SEC, and DSC in order to obtain a detailed description of the structures. Reactive oxirane moieties were introduced on the lignin backbone under mild reaction conditions and quantified by simpleH NMR analysis. The modified fractions were chemically cross-linked with a flexible polyether diamine ( M ≈ 2000), in order to obtain epoxy thermosets. Epoxies from different lignin fractions, studied by DSC, DMA, tensile tests, and SEM, demonstrated substantial differences in terms of thermo-mechanical properties. For the first time, strong relationships between lignin structures and epoxy properties could be demonstrated. The suggested approach provides unprecedented possibilities to tune network structure and properties of thermosets based on real lignin fractions, rather than model compounds.

Here we investigate the relationship between thermomechanical properties and chemical structure of well-characterized lignin-based epoxy resins. For this purpose, technical lignins from eucalyptus and spruce, obtained from the Kraft process, were used. The choice of lignins was based on the expected differences in molecular structure. The lignins were then refined by solvent fractionation, and three fractions with comparable molecular weights were selected to reduce effects of molar mass on the properties of the final thermoset resins. Consequently, any differences in thermomechanical properties are expected to correlate with molecular structure differences between the lignins. Oxirane moieties were selectively introduced to the refined fractions, and the resulting lignin epoxides were subsequently cross-linked with two commercially available polyether diamines (Mn = 2000 and 400) to obtain lignin-based epoxy resins. Molecular-scale characterization of the refined lignins and their derivatives were performed by 31 P NMR, 2D-NMR, and DSC methods to obtain the detailed chemical structure of original and derivatized lignins. The thermosets were studied by DSC, DMA, and tensile tests and demonstrated diverse thermomechanical properties attributed to structural components in lignin and selected amine cross-linker. An epoxy resin with a lignin content of 66% showed a Tg of 79 °C from DMA, Young’s modulus of 1.7 GPa, tensile strength of 66 MPa, and strain to failure of 8%. The effect of molecular lignin structure on thermomechanical properties was analyzed, finding significant differences between the rigid guaiacyl units in spruce lignin compared with sinapyl units in eucalyptus lignin. The methodology points toward rational design of molecularly tailored lignin-based thermosets.

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Aromatic material constituents derived from renewable resources are attractive for new biobased polymer systems. Lignin, derived from lignocellulosic biomass, is the most abundant natural source of such structures. Technical lignins are, however, heterogeneous in both structure and polydispersity and require a refining to obtain a more reproducible material. In this paper the ethanol-soluble fraction of Lignoboost Kraft lignin is selectively allylated using allyl chloride by means of a mild and industrially scalable procedure. Analysis using 1 H-, 31 P-, and 2D HSQC NMR give a detailed structural description of lignin, providing evidence of its functionalization and that the suggested procedure is selective toward phenols with a conversion of at least 95%. The selectively modified lignin is subsequently cross-linked using thermally induced thiol−ene chemistry. FT-IR is utilized to confirm the cross-linking reaction, and DSC measurements determined the T g of the thermosets to be 45−65 °C depending on reactive group stoichiometry. The potential of lignin as a constituent in a thermoset application is demonstrated and discussed.

Aerogel microspheres of chitosan, an abundant biopolymer obtained from marine crustaceans, have been successfully applied to catalyze the asymmetric aldol reaction in water, providing the products in high yields and with good stereoselectivity (up to 93% ee) and recyclability (up to 4 runs). Yields were favourably affected by additives such as DNP and stearic acid.

A new and sustainable pathway for the synthesis of polyesters and copolyesters derived from vanillic acid is reported. The one-pot procedure does not require either solvents or purification steps. New bio-based crystalline copolymers with tunable thermal properties are obtained.

A new method for the synthesis of polyesters that combines the chemical recycling of poly(ethylene terephthalate) (PET) with the use of monomers derived from renewable resources, such as isosorbide and succinic acid, has been developed. A kinetic study has been performed in order to determine the best catalyst for PET depolymerisation with isosorbide and for the subsequent polycondensation of PET oligomers with succinic acid. Using the correct amounts of isosorbide and succinic acid it is possible to obtain polymers which well fit the properties (glass transition temperature and end-group composition) necessary for powder coating applications. The coating produced using this new environmentally friendly approach presents applicative properties similar, and in some cases superior, to those of a commercial coating obtained from non-renewable resources.

Diels or no Diels? A bifunctional organic catalyst based on the thiourea motif is able to coordinate both diene and dienophile in an unprecedented asymmetric Diels–Alder reaction of 3-vinylindole derivatives, giving a rapid access to optically active tetra- and hexahydrocarbazoles with excellent results in terms of yields, diastereoselectivities, and enantioselectivities