Gas and Vapor Transport Properties of Si-Containing and Related Polymers

This chapter considers various chemical classes of Si‐containing polymers. It particularly focuses on gas and vapor separation properties and discusses the questions of sorption thermodynamics and free volume. A much more detailed picture of free volume in membrane materials was obtained owing to systematic application of positron annihilation lifetime spectroscopy (PALS). The chapter also considers the substituents containing one or several Si‐O bonds into the side groups for several classes of polymers, and focuses on the observed gas permeation properties. In order to understand better the mechanism of transport in such polymers it is worthwhile to consider the correlations between the fractional free volume (FFV) and the gas permeabilities in conventional glassy polymers, rubbers and metathesis polymers with flexible side groups. The chapter also focuses on the main physicochemical properties of poly (vinyltrimethyl silane) (PVTMS). Synthetic chemists succeeded in introducing flexible Si–O–Si bonds into side groups in different glassy polymers.