Syntheses of Poly[(tetraphenyl-p-silphenylenesiloxane)-co-(tetramethyl-p-silphenylenesiloxane)]s and the Physical Properties of Their Films

Abstract

In order to obtain a polysilarylenesiloxane having a high glass transition temperature (Tg), a high thermal degradation temperature (Td), and a good solubility in common solvents to prepare a film, the copolycondensation of 1,4-bis(hydroxydiphenylsilyl)benzene with 1,4-bis(hydroxydimethylsilyl)benzene was studied. Their thermal properties were studied by using a differential scanning calorimetry and a thermogravimetry analysis. The physical properties of copolymer films were also investigated. All the copolymers exhibited the Tg’s, and those increased with the increase of the molar ratio of the units based on 1,4-bis(hydroxydiphenylsilyl)benzene (PS units). The Tg of one of the copolymers, CP-a, reached to 127 °C. CP-c having a relatively high molecular weight showed the highest thermal stability in air, whose Td5 was 524 °C. Tough self-standing films were obtained from the copolymers by the casting method. These films had much lower gas permeability coefficients than that of polydimethylsiloxanes and low surface energy similarly to the silicon-containing polymers having a phenylene moiety. The gas permeability coefficients of the films decreased, and the densities and the tensile strength of films increased with the increase of the molar ratio of PS units. These results indicated that dense and tough films were obtained from these copolymers.