FOURIER-TRANSFORM INFRARED SPECTROSCOPIC STUDIES OF GELATION AND CRYSTALLIZATION OF POLYSTYRENE CARBON-DISULFIDE SOLUTIONS

Dried gel and solution-cast films of atactic (at-) and isotactic (iso-)polystyrene/carbon disulfide (PS/CS2) systems were investigated by Fourier transform infra-red spectroscopy (FTI.r.) and the relation between gelation and crystallization was studied. Iso-PS gel films dried at gelation temperature were less turbid than homogeneous solution-cast films made at room temperature. No difference was found in the i.r. spectrum of dried gel and solution-cast films of at-PS/CS2. However, the i.r. spectrum of iso-PS dried gel film was different from that of solution-cast film. Comparison of these spectra indicated that spectral changes occurred at the bands near 1200, 560, 1085-1052 and 907-922 cm-1. There were two bands at 909 and 922 cm-1 for solution-cast films, while for dried gel films there was only one which shifted from 912 to 921 cm-1 with increasing polymer concentration (10 to 40 g l-1) of the original gel. I.r. spectra of dried gel films of low concentration gels were like those of solution and quenched iso-PS samples. The intensity of the crystalline band at 983 cm-1 decreased with decreasing iso-PS gel concentration. This means that gel containing no crystals should be formed at very low polymer concentration; this is consistent with our previous conclusion that gelation of the PS/CS2 system is independent of crystallization.