Temperature dependence of the conformation of isotactic polystyrene in toluene

In order to obtain information about a possible helix–coil transition of isotactic polystyrene (i‐PS) at 80°C in toluene, as has been reported in other solvents, solution properties were examined at temperatures between 10 and 110°C. Use was made of viscometry, high‐resolution nuclear magnetic resonance, infrared spectroscopy, calorimetry, and light scattering. No distinct transition was found at 80°C but rather a second‐order transition between 62 and 65°C. A similar transition occurred in toluene solutions of atactic polystyrene. The transition may be attributed to a sudden change in the mobility of the phenyl side‐group of the polymer. From this study it is concluded that i‐PS has a helical conformation in toluene, the mean helix length decreasing smoothly with increasing temperature.