A fluorescence probe technique was used to investigate the role of the solvent in the syndiotactic polystyrene (sPS) thermoreversible gel system. Four probe molecules with different molecular sizes were dispersed throughout the gels, and their fluorescence anisotropy values were examined in detail for a range of sPS concentrations. The results showed that solvent molecules are mobile in the area where solvent gathers in the gels and that, in sPS/chloroform gels consisting of 2(1)-helical sPS chains forming a polymer-solvent molecular compound with chloroform, there exists a distribution of free volume in an area where the sPS chains associate and into which molecules smaller than 1,5-dimethylnaphthalene are able to penetrate. The size of the free volume between the sPS chains is consistent with that of the cavity size in the delta-empty crystalline form of sPS solids. However, in the sPS/trans-decalin gels having a spherulitic morphology, almost all NP molecules were assumed to be excluded out of the clathrate 6 crystalline form not due to their cavity size but rather due to the growing process of the solvated crystalline forms.