Rubber‐elastic mesophase siloxane systems

Abstract

Abstract Thermotropic poly(diethylsiloxane) is a new type of the mesophase elastomers. Mechanical Measurements in extension and contraction and stretching calorimetric measurements of heat and energy effects resulting from extension and contraction were combained with thermo‐mechanical measurements under constant loads and opto‐mechanical measurements to obtain molecular understanding of the deformational behaviour of these mesophase rubber‐like materials in a wide temperature range with particular emphasis on the temperature range of the mesophase stability as a function of extension. The stress‐strain curves of semi‐mesomorphic films resemble the strain‐strain behaviour of crystalline polymers with a very low degree of crystallinity. During stretching of amophous films the strain‐induced mesophase occurs. The influence of stress on the temperature range of the stability of the strain‐induced mesophase is very strong due to a very small heat of isotropization. The cyclic deformations of the mesophase elastomers are accompanied by the necking‐renecking phenomena resulting from the train‐induced mesophase formation on stretching followed by the immediate isotropization during contraction. Some potential practical applications of the mesophase elastomers are considered.