KINETICS AND MECHANISM OF THERMAL CYCLIZATION OF POLYAMIC ACIDS.

Abstract

Polyamic acids with different chemical structure and molecular weights have been used to analyze the kinetic relationships of their transformation into polyimides. Models describing the cyclization of polyamic acids under both isothermal and non-stationary conditions are developed. Cyclization is regarded as a two-stage physico-chemical process in which both the molecular mobility of the polymer matrix and the physical state of intrachain groups transformed into the imide rings play an important role. The nature of non-equivalent physical states of amic acid groups is discussed.