Evaluation of thermal stability of syndiotactic polystyrene/toluene complex by spectroscopic analysis

The syndiotactic polystyrene membranes containing the δ-form which is a clathrated crystal with some solvent molecules as a guest and so-called “complex”, were prepared by casting from its toluene solution at 85°C and room temperature. In order to evaluate the thermal stability of the complex in the two membranes, WAXD and timeresolved FT-IR measurements at various temperatures were performed. WAXD profiles suggested that the content of the complex in the membrane cast at room temperature was higher than that in one cast at 85°C. The transformation from TTGG helical to TT planar conformation were observed for the both membranes, but only above 190°C for the membrane cast at room temperature, indicating the retention of the helical conformation at a wide range of temperature.

Fig. 3. Relative absorbance of (a) TTGG, and (b) TT conformation in cast-85 with respect to annealing time. The sPS membranes containing the complex with toluene were prepared by casting from a toluene solution at room temperature and 85°C, and the characterization of the complex and the in situ observation of conformational change in annealing at various temperatures were performed by WAXD and time-resolved FT-IR methods, respectively. WAXD profiles and the thermal behaviors of conformational change evaluated by FT-IR introduced that the content of the complex in the membrane cast at room temperature was higher than that in one cast at 85°C. The transformation from TTGG helical to TT planar conformation were confirmed for the both membranes, but the remarkably temperature-dependence of this transformation for the membrane with low complex content, whereas a critical variation of this transformation below or above 190°C for the membrane with high complex content, indicating the retention of the TTGG conformation at a wide range of temperature. From these results, it was concluded that the casting condition in preparation of the sPS membranes containing the complex with solvent is one of the important factors on the control of the complex content and the thermal stability for TTGG conformation. Furthermore, these factors must strongly affect the yield in the preparation of the mesophase. The detailed investigations about the release behavior of guest molecules and the high ordered structure of the mesophase will be published in near future.