ABSTRACT
In most studies of the chemical transformation in solid polyamic acids, during their thermal treatment attention is focused only on the main reaction. This is cyclodehydration: the formation of intrachain imide rings with simultaneous water elimination. This chapter discusses some models that allow the mathematical analysis of imidization kinetics at various temperatures and times, the nature of the kinetic nonequivalence of amic acid groups, and the mechanism for resynthesis of chains in solid phase based on a new phenomenon — relay transfer of chemical functionality. The solutions obtained are general and seem to be useful for the study of the two-stage synthesis of many other thermally stable polymers. Chemical cross-linking of polymer chains in the latest high temperature stage of thermal imidization is very important for the physical properties of polyimides. The chapter mentions a large number of polyamic acids and polyimides of various chemical structures.
