Conformational order in crystalline states and gels of isotactic, syndiotactic and atactic polystyrenes studied by vibrational spectroscopy

• Published in: Journal of molecular structure 1991-01, Vol.242, p.315-331
• Main Authors: Nakaoki, Takahiko, Kobayashi, Masamichi
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/0022-2860(91)87144-7

Stable conformations and their sequential order of isotactic (IPS), syndiotatic (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 demostrated that the partially ordered skeletal conformation existing in IPS/CS2 gels is 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 or 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 crystalline polymer-solvent complex (the γ phase) having a TTGG conformation. On heating the γ phase transforms to a β phase at about 120°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°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.