Infrared spectroscopy study on crystalline and conformational changes in solution-cast syndiotactic polystyrene

Fourier transform infrared (FT-IR) analysis was used to investigate the con formation and the effects on crystals in syndiotactic polystyrene (sPS) sub jected to different solvent and/or thermal treatments. It was found that th e original helical conformation in sPS cast from a solution of 1,1,2,2-tetr achloroethane could transform to an all-trans planar conformation as the sP S was heated to temperatures above 200 degreesC. The spectra of sPS showed that the helical conformation chain varied with different casting solvents and the band positions and relative intensities also differed slightly owin g to different interactions between the solvent molecule and the delta -typ e sPS crystalline phase. The solution-casting temperature also had a signif icant effect on the crystal forms in sPS. Lower temperatures (casting below similar to 100 degreesC) produced helical crystals while the higher temper atures (casting above 120 degreesC) yielded all-trans crystals. In addition , spectra evidence of different crystals (alpha- and beta -crystals: in all -trans conformation) in sPS are discussed and identified in this study.