Polysilalkylenes

Polysilalkylenes, in particular polydimethylsilmethylene and its structural analogs, were prepared and investigated later than polysiloxanes, which had been extensively studied as membrane materials as early as the 1960s. Polydimethylsilmethylene as well as polydimethylsiltrimethylene can be obtained by ring‐opening polymerization of 1,1,3,3‐tetramethyl‐1,3‐disilacyclobutane and 1,1‐dimethyl‐1‐silacyclobutane, respectively. Melting and crystallization processes in polydimethyltrimethylene films were studied using temperature‐modulated differential scanning calorimetry (DSC). Exposure to radiation (or plasma‐chemical treatment) leads to easily obtainable crosslinked polymers having stable films, e.g. polydimethylsiloxane films. Similar permeability coefficients of hydrocarbons for polydimethylsilmethylene and the copolymers along with their good filmmaking properties enable their application as the materials for forming various either flat‐sheet or hollow‐fiber composite membranes. It can be added that such membranes require quite small amounts of polymer materials used in thin selective layers. Random copolymers with relatively high amounts of silmethylene comonomer have amorphous structure and low glass transition temperatures.