Nanopore Foams of High Temperature Polymers

Abstract

A method of generating high temperature polymer foams with pore sizes in the nanometer regime has been developed. The nanofoams were prepared by casting a block copolymer comprised of a thermally stable and a thermally labile block, followed by a subsequent thermal treatment to degrade the labile material and generate the pores. The morphology of the block copolymer film was made up of a high temperature polymer matrix, with the labile component as the dispersed phase. Thermolysis of the labile block affords pores where the size and shape of the pores are dictated by the initial copolymer morphology. Nanopore foam formation is described for triblock copolymers of poly(phenylquinoxaline) (PPQ) with poly(propylene oxide) (PO) as the labile block. Foam formation led to a 10–15% reduction in density, consistent with the PO composition, and a dielectric constant as low as 2.3. SAXS and TEM measurements indicated pore sizes of approximately 10 nm. © 1992 IEEE