SOLVENT EFFECTS ON THE PREPARATION OF NOVEL AMORPHOUS POLY(ARYL ETHERBENZIL)S

A synthetic approach for the preparation of amorphous poly(aryl ether benzil)s has been developed wherein the generation of the aryl ether l inkage is the polymer-forming reaction. Fluoride atoms located at the para-position of the benzil moiety were found to be very activated tow ard nucleophilic aromatic substitution. Facile displacement occurred a t these positions since the benzil moiety can accept the negative char ge developed in the transition state through a Meisenheimer complex in termediate, analogous to a conventional activating group (i.e., benzop henone). Two synthetic approaches were surveyed to determine the most efficient manner to prepare high molecular weight polymer. The convent ional potassium carbonate/ dipolar aprotic solvent route was the most effective, but only if dimethyl sulfoxide (DMSO) or sulfolane was used as the solvent. Polymer chain cleavage after initial molecular weight buildup occur;ed if. N-methylpyrrolidinone (NMP) or 1,3-dimethyl-3,4, 5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) was employed. The silylated b isphenol route in NMP containing a catalytic amount of cesium fluoride afforded high molecular weight polymers; however, long reaction times were required. The T-g's of the polymers ranged from 157 to 242 degre es C depending on the bisphenol utilized, and the thermal stability wa s comparable to that of other poly(aryl ether)s in air, with decomposi tion temperatures in the 500 degrees C range. All of the polymers prep ared in DMSO or sulfolane were formed into tough flexible films by sol ution or melt processing.