Synthesis and physical properties of linear and branch phenoxies

Abstract

Linear and branch phenoxies have been synthesized by reacting difunctional epoxy and diphenol or triphenol monomer, using phosphonium salt as the catalyst. The reaction kinetics is analyzed by the ASTM E 698 method, which is suitable for a first order reaction system. The bulky structure of the bisphenol Z moiety retards the reaction; therefore, the reaction temperature required is higher- at 200 degreesC, compared to 190 degreesC for the bisphenol A based system. The introduction of a branch structure increases both molecular weight and the polydispersity of the phenoxy. A slightly branched structure tends to increase the distance between the polymer chains and results in a lower shear viscosity for easier processing. A higher branch results in light crosslinking and decreases the mobility of the polymer. The branch structure has a negligible effect on its glass transition temperature because the average distance between branches is substantially longer than the critical mainchain length for T-1's Brownian motion. The 100/1 (bisphenol/ trisphenol) system has the lowest viscosity, but its mechanical properties and the gas permeation properties are poorer than those of the others. The bisphenol Z based phenoxy shows superior mechanical properties, higher T-g, lower coefficient of thermal expansion, and lower gas permeation properties than the corresponding bisphenol A based phenoxy because of the steric hindrance structure of the bisphenol Z moiety.