Substituent Effects on Thermal and Mechanical Properties of Resorcinol‐Based Semiaromatic Polyesters

Recently biobased plastics draw attention as eco‐friendly materials, and it is important to study the effects of substituents, which are popularly found in natural products, on the characteristics of the resulted polymers. In this study, twelve resorcinol‐based semiaromatic polyesters are successfully synthesized using four types of resorcinol derivatives (resorcinol, 2‐methylresorcinol, 5‐methylresorcinol, and 2,5‐dimethylresorcinol) and three types of dicarboxylic acids (glutaric acid, adipic acid, and pimelic acid) to investigate the effect of methylation at the 2‐ and 5‐positions in resorcinol. Glass‐transition temperature of the polyesters is located from ‐3.1 to 37.9 °C, and rises with increasing the number of methyl groups in a resorcinol unit. Crystallinity of the polyesters decreases by methylation to a resorcinol unit, except the polyester from 2‐methylresorcinol and pimelic acid. The mechanical properties of the solvent‐cast films for the polyesters are tunable by the site and number of methyl groups in a resorcinol unit. The major thermal degradation of the polyesters is observed above 300 °C, and the minor thermal decomposition appears between 100 and 200 °C for the polyesters without the resorcinol methylated at the 2‐position and pimelic acid unit. Twelve resorcinol‐based semiaromatic polyesters are synthesized to investigate the effect of methylation into a resorcinol unit on their thermal and mechanical properties. The glass‐transition temperature of the polyesters rises with increasing the number of methyl groups in a resorcinol unit, and their mechanical properties are tunable by the site and number of methyl groups in a resorcinol unit.