A method of generating high-temperature polymer foams with pore sizes in the nanometer regime was developed. The nanofoams were prepared by casting a block copolymer composed 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), with poly(propylene oxide) as the labile block. Foam formation led to a 10-15% reduction in density, consistent with the poly(propylene oxide) composition, and a dielectric constant of 2.3. SAXS and TEM (transmission electron microscopy) measurements indicated pore sizes of approximately 10 nm.
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