Surface Spectroscopic Studies of Polymer Surfaces and Interfaces: Poly(tetramethyl-p-silphenylenesiloxane)

Surface spectroscopic (ESCA, FTIR) studies of changes in the morphology of fractionated poly(TMpS) solution-grown crystal mats (I), melt-cast mats (II), melt-quenched mats (III), and solution-cast films (IV) have been correlated with thermal (differential scanning calorimetry), crystallographic (small angle X-ray scattering), and gas phase (HF) reaction studies. These results provide a complete picture of the surface structure of this well-ordered macromolecular material, demonstrating for the first time the use of ESCA to analyze the morphology of an ordered homopolymer. ESCA analyses of various degrees of crystallinity of poly(TMpS) (I > II > III > IV) were correlated with FTIR results yielding the conclusion that the surface (amorphous) region of each material consists of surface-segregated Si-C₆H₄-Si-O linkages, most likely in the form of folds or loops of the long chains back into the rod-like crystalline core of the materials. Chemical etching studies were accomplished with gaseous HF (diluted with He 10:30 v/v) which selectively reacts with and removes the less-ordered surface amorphous regions, thereby increasing the overall crystallinity. This process was followed both spectroscopically and with DSC and SAXS analysis, providing results which demonstrate the efficacy of these methods and confirm the surface chemistry and morphology of the polymer system.