Synthesis, properties and crosslinking of unsaturated cyano-substituted homo- and copolyesters prepared from 1-hydroxy-4-(2-cyano-2- carboxyvinyl) benzene

Abstract

4-Hydroxybenzaldehyde or 3-methoxy-4-hydroxybenzaldehyde was condensed with cyanoacetic acid to afford 1-hydroxy-4-(2-cyano-2-carboxyvinyl)benzene ( 1) and 1-hydroxy-2-methoxy-4-(2-cyano-2-carboxyvinyl)benzene ( 2) respectively. They were converted to the corresponding acid chlorides by reacting with thionyl chloride and polycondensed in the presence of pyridine to afford unsaturated cyano-substituted homopolyesters. In addition, various copolyesters were prepared from the acid chlorides of 1 and 4-hydroxybenzoic acid. The polyesters were characterized by Fourier-transform infra-red spectroscopy and differential thermal analysis as well as by inherent viscosity, X-ray and water absorption measurements. They softened between 100 and 200°C, were amorphous and showed higher hydrophilicity and solubility in certain organic solvents than did the reference polyester prepared from 4-hydroxybenzoic acid. The crosslinked polymers obtained by curing at 300°C for 48 h were remarkably more thermally stable than the cured reference polyester. They were stable up to 291–355°C in N 2 or air and afforded anaerobic char yield of 49–68% at 800°C. The thermal stabilities of cured polyesters were correlated with their composition.