Development of a Novel Preparation Method for Highly Porous Heat-Resistant Rigid Polymer Network Films and Evaluation of their Properties

Abstract

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 po lyme r iza tion of a PBO network precursor (pre-PBO network) in N-methyl-2-pyrrolidone followed by thermal c yc liza tion . 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.

Preparation of highly porous heat‐resistant polybenzoxazole network films and their electrical conductivities

“…Polybenzoxazole (PBO) is a representative rigid polymer and widely used for high‐performance fibers owing to their high strengths, high elastic moduli, and high thermal and chemical resistances 1 . Incorporating a certain amount of a trifunctional monomer during the synthesis of a PBO allows the formation of a three‐dimensional crosslinked polymer network (PBO network) 2,3 . As the crosslinked chains in the PBO network are rigid, they do not aggregate, forming nanometer‐scale voids.…”

“…This technique has been used to prepare PBO network films. In our previous study, 3 PBO network films were prepared via two‐step polymerization using trimethylsilane as a protecting group for monomers. However, the time for gelation was short using this method; therefore, it was difficult to prepare a uniform and defect‐free PBO network film.…”