Physical gelation of syndiotactic polystyrene in the presence of large molar volume solvents induced by volatile guests of clathrate phases

Cooling of syndiotactic polystyrene (s-PS) solutions with bulky solvents, unsuitable as guests of s-PS clathrate phases, results in the formation of pastelike gels characterized by a trans-planar chain conformation and poor mechanical properties. Strong elastic gels with s(2/1)2 helical polymer chains forming a three-dimensional network can be, instead, obtained with the same bulky solvents by the temporary presence of a volatile solvent which is instead a suitable guest for a s-PS clathrate phase. After gel formation, the volatile solvent can be easily removed without breaking the gel structure, and the big size solvent molecules remain entrapped in the three-dimensional polymer network. The gel structures have been investigated by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and rheological measurements.