☆ 4.7 Article

Structural Basis for the Different Mechanical Behaviors of Two Chemically Analogous, Carbohydrate-Derived Thermosets

ACS MACRO LETTERS (2021)

Journal

ACS MACRO LETTERS

Volume 10, Issue 5, Pages 609-615

Publisher

AMER CHEMICAL SOC

DOI: 10.1021/acsmacrolett.1c00041

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Funding

National Science Foundation [CBET-1659989, CHE-1901635, CON-75851, 00074041]
National Science Foundation under the Center for Sustainable Polymers [CHE-1901635]
NSF through the MRSEC [DMR-2011401]
NNCI [ECCS-2025124]

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Abstract

Two renewable, structurally analogous monomers, isosorbide undecenoate (IU) and glucarodilactone undecenoate (GDLU), reacted with pentaerythritol tetrakis(3-mercaptopropionate) (PETT) via thiol-ene photopolymerization to form IU-PETT and GDLU-PETT thermosets. Despite their chemical similarity, uniaxial tensile testing showed that GDLU-PETT exhibited a strain-hardening behavior and is significantly tougher than IU-PETT. In situ tensile testing and wide-angle X-ray scattering experiments (WAXS) revealed that the GDLU molecules can more easily order and align during uniaxial deformation, hence increasing intermolecular interactions between the GDLU molecules and contributing to the observed strain hardening behavior of their thermosets.

Two renewable, structurally analogous monomers, isosorbide undecenoate (IU) and glucarodilactone undecenoate (GDLU) reacted with pentaerythritol tetrakis(3-mercaptopropionate) (PETT) via thiol-ene photopolymerization to form IU-PETT and GDLU-PETT thermosets. Despite their chemical similarity, uniaxial tensile testing showed that GDLU-PETT exhibited a strain-hardening behavior and is significantly tougher than IU-PETT. To understand this observation, in situ tensile testing and wide-angle X-ray scattering experiments (WAXS) were conducted. While the 2D WAXS patterns of IU-PETT displayed an isotropic halo during uniaxial deformation, they exhibited a change from an isotropic halo to a pair of scattering arcs for the GDLU-PETT samples. Density functional theory calculations further revealed that the GDLU alkyl chains are less angled than the IU alkyl chains. Based on these results, we postulate that the GDLU molecules can more easily order and align during uniaxial deformation, hence increasing intermolecular interactions between the GDLU molecules and contributing to the observed strain hardening behavior of their thermosets. This study exemplifies how molecules with subtle differences in their chemical structures can alter the structures and thermophysical properties of the resulting polymers in unpredictable ways.

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Vanillin-Derived Thermally Reprocessable and Chemically Recyclable Schiff-Base Epoxy Thermosets

Sathiyaraj Subramaniyan, Matteo Bergoglio, Marco Sangermano, Minna Hakkarainen

Summary: In order to move towards a circular bioeconomy, a paradigm shift from traditional petroleum-based non-recyclable thermosets to biobased repeatedly recyclable materials is required. Two mechanically and chemically recyclable extended vanillin-derived epoxy thermosets were successfully fabricated by introducing Schiff-base/imine covalent dynamic bonds. These thermosets exhibited good thermal and mechanical properties, stability in common organic solvents, and the ability to be thermally reprocessed through compression molding. Furthermore, they could be rapidly and completely chemically recycled to water-soluble aldehydes and amines by imine hydrolysis in 0.1M HCl solution.

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