Various types of polysiloxanes studied by positron annihilation lifetime spectroscopy

Based on free volume sizes determined by this method, relations between cross-link densities in the investigated systems have been established. They have been compared with the results of swelling experiments conducted in the work and to efficiency of cross-linking reaction evaluated in our previous FTIR investigations of the systems. It has been found that PALS and swelling measurements lead to the same conclusions concerning cross-link densities in the networks prepared from low-molecular siloxanes. Discrepancies have been observed in the case of polymer-derived systems. Additionally, it is demonstrated that PALS is capable of revealing the presence of free carbon phase in SiCO materials formed upon pyrolysis of polysiloxane networks.