EFFECTS OF SOLVENT AND DEGREE OF POLYMERIZATION ON THE RATE OF INTERMOLECULAR FORMALIZATION OF ETHYLENE-VINYL ALCOHOL COPOLYMER

Intermolecular formalization of ethylene-vinyl alcohol copolymers (EVOH) was studied kinetically till the gel point in dimethyl sulfoxide-water mixtures on the basis of Charlesby's theory related to gelation of polymer. At an EVOH concentration ([OH]) below 0.6 mol/l, the rate was nearly proportional to [OH] and the number of polymer molecules, and was fast in a poor solvent. But above 0.6 mol/l of [OH] the rate was fast in a good solvent and increased with increasing degree of polymerization. These results showed that the rate-determining step was the collision process between a hemiformal group of one polymer molecule and a hydroxyl group of another molecule, and the rate was affected by the excluded volume effect and accelerated with the formation of polymer entanglement.