The delta form, one of various crystalline forms of syndiotactic polystyrene (sPS), is a complex between sPS and solvent molecules. This crystalline form shows a solvent exchange between the originally absorbed solvent B and the newly supplied solvent A when the delta form sample was exposed to the solvent A atmosphere. We have carried out the time-resolved infrared spectral measurement during this solvent-exchange process and found that the solvent-exchange rate was almost common to any pair of solvents where the solvents A and B were toluene, chloroform, or benzene. On the other hand, when the delta form sample was heated above 150degreesC, it transferred to the gamma form having no solvent molecules in the crystal lattice. The temperature, where most of solvent molecules were evaporated from the sample, was almost common to any kind of solvent originally absorbed in the delta form, as already pointed out by Gowd et al. [Macromolecules 2002, 35, 8509]. All these phenomena, i.e., the solvent-exchange phenomenon and the solvent evaporation phenomenon, were considered to come from the characteristic features of delta form crystal: the unique columnar structure and the relatively weak interactions between sPS chains and solvent molecules; the solvent molecules are trapped in the columns made by aggregated sPS chain stems. The solvent exchange was speculated to occur easily along the column axis. The evaporation of solvent in the delta-to-gamma phase transition was considered to occur also along the column axis, and therefore almost no difference was observed for the different solvent system. When acetone was supplied to the delta form in the solvent-exchange experiment, the solvent originally trapped in the delta form was displaced by acetone molecules. But the original column structure was not affected by such a solvent exchange-different from the cases of other such solvent as toluene, benzene, or chloroform. The structure changed from delta to delta(e) (empty delta) form for the first time when acetone evaporated from the sample at room temperature.