Development of a novel preparation method for highly porous heat-resistant rigid polymer network films and evaluation of their properties

A rigid polymer network of poly(p-phenylene benzobisoxazole) (PBO) has excellent mechanical properties and thermal stability. Many nano voids exist within the network. However, a PBO network cannot be formed into films or fibers. Generally, PBO networks are prepared by one-step polycondensation in polyphosphoric acid. In this study, we have prepared a PBO network by a two-step method involving polymerization of a PBO network precursor (pre-PBO network) in N-methyl-2-pyrrolidone followed by thermal cyclization. Heat-resistant porous PBO network films have been successfully obtained by this two-step method. The properties of the PBO network films have been evaluated.