Fabrication of Mesoporous Polyimide Composite Films by a Soft-Template Method Followed by Ozonolysis

抄録

Mesoporous polyimide composite films were fabricated by a soft template method using a microphase-separated structure of an amphiphilic block copolymer and porosification by ozonolysis. Poly(1,4-isoprene)-block-poly(2-vinylpyridine) was used as the template block copolymer. Poly(amic acid) (PAA), the precursor of polyimide, and resol, the cross-linker for stabilization of the nanostructure, were miscible into the poly(2-vinylpyridine) domain which is the hydrophilic domain of the template block copolymer. The mixture co-assembled and formed a periodic body-centered cubic nanostructure. The study of ozonolysis condition revealed that the reaction in hexane allowed porosification without the collapse of the nanostructure. Polyimide composite films with well-defined mesopores were successfully obtained by the sequential processes of the PAA composite film, namely, thermal annealing for crosslinking of resol, ozonolysis in hexane for the decomposition of polyisoprene domain, and thermal treatment for imidization of PAA. The domain spacing determined by small-angle X-ray scattering was 28.8 nm, and the average pore size based on scanning electron microscopy was 24 nm.