The mesophase of syndiotactic polystyrene (sPS) membrane was prepared from delta-form complex, using step-wise solvent extraction method. A systematic study of FTIR and WAXD analyses was carried out for the confirmation of TTGG helices and mesophase structure of sPS membrane. respectively. The sorption isotherms of Xe to amorphous and mesophase sPS membranes were studied at 25 degreesC and the results are described by a dual mode sorption which is a combination of both Henry and Langmuir mode sorption. The sorption isotherms are concave towards the pressure axis and are well described by the dual mode sorption. The sorption amount of Xe in the mesophase membrane is extremely high when compared to the amorphous sPS membrane, depending on their structural organization. Further, the size of the molecular cavity characterized in mesophase and the microvoid in amorphous sPS membranes were attempted by means of Xe-129 NMR spectroscopy. (C) 2004 Elsevier B.V. All rights reserved.