Selective surface modification of syndiotactic polystyrene films: A study by Fourier transform- and confocal-Raman spectroscopy

A helical crystalline modification of syndiotactic polystyrene (sPS), the delta-form, was employed to prepare solution-cast films electively sulfonated on the surface. This result was achieved because of the unusual transport characteristics of the delta-form, exhibiting comparatively large diffusivity and solubility values for low-molecular weight compounds such as chloroform, which can be effectively used as a carrier solvent. The results of sulfonation of the d-form are compared with those obtained with a trans-planar crystalline modification of sPS (beta-form). The latter was found unsuitable for selective surface modification. The analysis of the sulfonated films was carried out by FT-Raman and confocal-Raman spectroscopy. The first technique was used to investigate the average composition of the samples in terms of sulfonation degree and crystalline structure. It also allowed us to construct calibration curves to be used in connection with the confocal-Raman data. The latter technique was employed to generate images with spectroscopic contrast and to quantitatively characterize the depth-profiles of the investigated films.