CONFORMATIONAL ORDER IN CRYSTALLINE STATES AND GELS OF ISOTACTIC, SYNDIOTACTIC AND ATACTIC POLYSTYRENES STUDIED BY VIBRATIONAL SPECTROSCOPY

Article abstract of DOI:10.1016/0022-2860(91)87144-7

Stable conformations and their sequential order of isotactic (IPS), syndiotactic (SPS) and atactic polystyrenes (APS) in various aggregation states have been investigated by infrared (IR) spectroscopy, 13C NMR and X-ray diffraction.It has been demonstrated that the partially ordered skeletal conformation existing in IPS/CS2 gels of a (3/1) helix (TG) type having the pendant phenyl groups oriented in a disordered fashion, rather than the near-TT <(12/1)helix> form proposed previously for IPS/decalin gels.The process of conformational change during gelation of IPS/CS2 and APS/CS2 systems has been followed by IR spectroscopy, and it has been concluded that the construction of regular sequences of a particular conformation promotes the gelation of both crystallizable and non-crystallizable polystyrenes.As-cast film specimens prepared from a chloroform solution are found to be a crystalline polymer-solvent complex (the γ phase) having a TTGG conformation.On heating, the γ phase transforms to a β phase at about 120 deg C, accompanied by removal of the solvent, while the TTGG conformation is retained.On further heating, the β phase transforms to an α₁ or α₂ phase at about 200 deg C accompanied by a change in conformation from TTGG to TT.The process of conformational change (in both type and sequence) during these phase transformations has been clarified by IR spectroscopy.