Intramolecular Cyclization-Induced Crystallization-Driven Self-Assembly of an Amorphous Poly(amic acid)

We propose a new concept of intramolecular cyclization-induced crystallization-driven self-assembly (ICI-CDSA) based on an amorphous poly(amic acid) (PAA). Nanobundles with high crystallinity were prepared via CDSA that was thermally induced by the imidization reaction of PAA as the crystallizable polyimide segments were introduced into its backbone. With the increase of the initial concentration of PAA, higher-order flower-shaped structures with high crystallinity and concentration-dependent petal numbers were obtained as a result of the hierarchical self-assembly of these nanobundles. The relationship between the degree of imidization and the crystallization behavior of polymers was explored. The critical degree of imidization of the polymer was 92% to form crystallized nanobundles and flower-shaped structures, below which only amorphous assemblies were obtained. In addition, nanofibers were prepared by ICI-CDSA of PAA. Overall, a new approach named ICI-CDSA was reported to self-assemble amorphous polymers into crystallized nanostructures.