Epoxy Resin Thermosets Derived from Trehalose and β-Cyclodextrin

Epoxy resins are ubiquitous in high-performance composite applications because of their excellent mechanical strength, thermal and chemical resistance, strong adhesion, and low shrinkage after curing. Bio-based epoxy resins derived from natural products such as carbohydrates offer tremendous potential for creating new polymeric materials. Sugars and their derivatives often offer great biodegradability and functionality such as the presence of multiple hydroxyl groups that impart highly cross-linked polymer networks. Moreover, their ring structures can afford polymers with high glass transition temperatures. To develop epoxy resins containing sustainably sourced feedstocks, we designed and synthesized trehalose- and β-cyclodextrin-based carboxylic acid hardeners for epoxy resins and examined the thermal, mechanical, and adhesive properties of the resulting materials. Trehalose and β-cyclodextrin were succinylated with excess succinic anhydride, and the resulting carboxylic acid hardeners formed homogeneous mixtures with trimethylolpropane triglycidyl ether (TTE) in different carboxyl–epoxide ratios. The cured resins were found to be thermally stable (Td5 > 300 °C) and display high Young's moduli of up to 1.4 and 1.8 GPa with mechanical strengths of 47 and 64 MPa for the trehalose- and β-cyclodextrin-based epoxy resins, respectively. Preliminary adhesion tests showed that the cured resins exhibit excellent lap-shear strengths of 3600 and 2100 psi, respectively. The resins were also degradable into water-soluble components in both aqueous acidic and basic solutions but were relatively stable from hydrolysis in neutral aqueous conditions. These results imply that this novel class of hardeners are promising feedstocks for renewable high performance epoxy resins.