Nature offers a wide selection of biobased molecules, many of which have similar chemical structures with only slight differences in the types of substituents present. However, such slight differences may significantly impact the physical properties of the resulting polymers. To demonstrate this concept, two renewable, structurally analogous monomers, isosorbide 10-undecenoate (IU) and glucarodilactone 10-undecenoate (GDLU), were synthesized and reacted with pentaerythritol tetrakis(3−mercaptopropionate) (PETT) via thiol-ene photopolymerization to form IU−PETT and GDLU−PETT thermosets. Uniaxial tensile testing of the thermosets revealed that GDLU−PETT is significantly tougher than IU−PETT. In situ tensile testing and wide- angle x-ray scattering experiments (WAXS) showed that while IU−PETT only displayed an isotropic halo, GDLU−PETT displayed a transition from an isotropic halo to a pair of scattering arcs. To understand this observation, the optimized structures of GDLU and IU monomers were obtained via density functional theory calculations, which revealed that GDLU has less puckered bicyclic rings and less angled alkyl chains than IU. We postulate that such differences enabled GDLU chains to align more easily during uniaxial deformation, hence increasing the intermolecular interactions between the GDLU molecules and contributing to the improved toughness of GDLU−PETT thermosets. These results demonstrate how subtle differences in monomer structures can significantly affect the physical properties of the resulting polymers in unpredictable ways. Finally, in addition to forming thermoset films, these materials were processed into thermoset nonwovens via in-situ UV curing and electrospinning. Fibers containing GDLU were successfully produced and readily degraded into small soluble molecules in basic aqueous media via base-catalyzed hydrolysis, hence demonstrating a potential strategy for addressing the problem of microfibers pollution.

Thermoset films and nonwovens from two chemically analogous, carbohydrate-derived monomers

ACS Fall 2021

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