Study of solvent diffusion and solvent-induced crystallization in syndiotactic polystyrene using FT-IR spectroscopy and imaging

Kinetics of solvent diffusion (chloroform) and solvent-induced crystallization in syndiotactic polystyrene (sPS) were investigated by Fourier transform infrared (FT-TR) transmission imaging and single element detector transmission FT-IR spectroscopy. Spatially resolved information from FT-IR imaging experiments under controlled environmental conditions (temperature and solvent vapor pressure) and with uniaxial solvent diffusion into the polymer was used to monitor the appearance of 6 crystalline sPS as a function of solvent exposure time. From a series of time-resolved FT-IR images polymer crystallization kinetics at various positions in the polymer and solvent diffusion coefficients were determined. The imaging experiments proved that solvent diffusion is the limiting factor in the overall crystallization process of a sPS sample. FT-IR images revealed that the full extent of crystallinity is reached before the equilibrium concentration of the solvent in the semicrystalline polymer is established at any location in the sample. Single element detector transmission FT-IR measurements indicated that the kinetics of the crystallization process strongly depends on solvent vapor pressure. A critical value of solvent concentration in the polymer needs to be achieved in order to observe any polymer crystallization. This critical value and the crystallization kinetics in a solvent saturated atmosphere were also revealed.