title: Free volume expansion and nanofoaming of supercritical carbon dioxide treated polystyrene.
abstract: Free volume of polystyrene films treated with supercritical carbon dioxide (SCCO 2) were examined by positron annihilation lifetime spectroscopy. Variation of the free volume sizes after the SCCO 2 treatment due to the release of trapped CO 2 and structural relaxation of the polymer was observed. After 500 h from the depressurization, the free volume of the treated films free from CO 2 was approximately 0.306 nm in radius and much larger than that of the untreated films of approximately 0.295 nm in radius due to the freezing of the swollen structure caused by the large solubility of CO 2.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan. t-oka@aist.go.jp
authors.forename: Toshitaka
authors.initials: T
authors.lastname: Oka
authors.forename: Kenji
authors.initials: K
authors.lastname: Ito
authors.forename: Chunqing
authors.initials: C
authors.lastname: He
authors.forename: Cedric
authors.initials: C
authors.lastname: Dutriez
authors.forename: Hideaki
authors.initials: H
authors.lastname: Yokoyama
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kobayashi