Synthesis and characterization of isomeric polyesters based on sebacic acid and hexanediols

Abstract

AbstractIsomeric homopolymers and random copolyesters based on sebacic acid and isomeric hexanediols were synthesized by condensation techniques and characterized by NMR, GPC, intrinsic viscosity, and DSC. Among the homopolymers, only the polyester derived from the linear 1,6‐hexanediol was found to be crystalline. Typical melting points were 65–70°C, depending on molecular weight, and a Tg of −62°C was measured on a high molecular weight sample. Other isomeric homopolymers derived from the branched diols 2‐methyl‐2‐ethyl‐1,3‐propanediol and 2,5‐hexanediol were amorphous tacky fluids with glass temperatures of −69 and −66°C, respectively. In the case of the random copolymers, NMR analysis was particularly useful in determining the copolymer composition or the diol isomer ratio. DSC data indicated that all the random copolymers containing the linear 1,6‐diol were crystallizable and their melting points depended on copolymer composition. The heat of fusion per repeat unit of poly(hexamethylene sebacate) was found to be 32 cal/g from measurements of the molecular weight dependence of the melting point.