Vanillyl alcohol, a lignin derived aromatic diol, is a potential platform chemical for the production of renewable epoxy thermosets. A bio-based bisphenolic analogue, bisguaiacol (BG), was synthesized via electrophilic aromatic condensation of vanillyl alcohol and guaiacol, from which diglycidyl ether of BG (DGEBG) was prepared. In addition, three single aromatic diglycidyl ethers were synthesized from vanillyl alcohol (DGEVA), gastrodigenin (DGEGD), and hydroquinone (DGEHQ). All epoxies were characterized via 1H NMR, 13C NMR, FTIR, MS, and GPC. Dynamic mechanical analyses of the epoxies by themselves or blended with a commercial epoxy resin and cured with a diamine were conducted to determine the effect of the methoxy and methylene moieties on polymer properties. The thermomechanical results indicate that the methoxy lowers the glass transition temperature (T g) yet increases the glassy storage modulus at 25 °C, while the methylene spacer between the aromatic ring and the epoxide further lowers the T g in cured epoxy–amine systems.

Stereolithography (SLA) is a well-established additive manufacturing (AM) technique that allows a resin to be photopolymerized into high resolution parts with rapid production times. Vanillin, a naturally occurring molecule as well as a derivative easily obtained from biomass, including lignin, can be used as a building block for vinyl ester resins (VERs) and AM-ready materials. A vanillin-based VER, prepared via a 100% atom efficient and solventless technique, was investigated for AM applications due to its low viscosity and demonstrated ability to photopolymerize. The resin was additively manufactured via SLA and the effect of postprocessing after printing was investigated. The extent of cure between the printed and postprocessed samples was found to have the highest effect on polymer properties, increasing extent of cure by approximately 23%. With postprocessing, the printed material was shown to have a glass transition temperature (T g ) of 153 °C and Young’s modulus of 4900 MPa, comparable to the same resin cured via traditional thermal techniques. This resin system has the potential to be used as a standalone high strength and high T g material for SLA. Furthermore, the resin system also has potential as a formulation base for tunable SLA cure characteristics and final desired printed polymer properties while retaining significant biobased content.

No abstract

The macromolecular properties, including the glass transition temperature (T g ) and solvent resistance, of lignin-inspired poly(dimethoxyphenyl methacrylate)s were controlled by varying the position of the dimethoxy substituents in the constituent monomers. For the four dimethoxyphenyl methacrylate isomers investigated, with substituents at different locations on the phenyl ring (i.e., 3,5-; 2,3-; 2,4-; and 2,6-), the T g 's of the resulting polymers spanned a wide range from less than 100 °C to greater than 200 °C. Rotational freedom and segmental interactions were responsible for the varying T g 's. The polymers were thermally stable in air up to ∼300 °C, providing a suitable thermal processing window. The poly(dimethoxyphenol methacrylate) homopolymers also exhibited remarkably different solvent resistances to organic solvents, including tetrahydrofuran and chloroform. Furthermore, by copolymerizing various dimethoxyphenyl methacrylate isomers, the T g and solvent resistance of the resulting macromolecules could be tuned independently to gain enhanced control over materials design. The ability to manipulate properties through isomer composition in this lignin-inspired system may facilitate usage in applications such as components in coatings, thermoplastics, thermoplastic elastomers, and other materials.

No abstract