Epoxy–Amine Route to Tough and Degradable Aromatic Polyester Thermosets

We report polyester thermosets from diepoxide and diamine monomers that contain aromatic ester linkages and short aliphatic spacers between the phenylene units. The influences of aromatic substitution pattern, spacer length, and ester content were studied. An increase in the spacer length or in the level of meta-substitution depressed glass transition temperature consistently. Tensile and flexural strengths and moduli increased with meta-substitution and ester content and decreased as spacer length increased. Properties of reference thermosets derived from monomeric/oligomeric diglycidyl ether of bisphenol A (DGEBA) and para or meta-substituted aromatic amines were compared, and several parallels in strength and modulus were observed. Consistently higher fracture toughness (2.0-3.4×) and impact resistance (5.1-6.9×) were observed for the polyester thermosets - potentially attributable to enhanced molecular mobility and differences in secondary interactions. Additionally, the presence of ester functionality in every network strand enabled glycolytic degradation under ambient pressure - a potential route for end-of-use processing.