Polyethylene-Silica Nanocomposites with the Structure of Semi-Interpenetrating Networks

Organic-inorganic nanocomposites with the structure of interpenetrating or semi-interpenetrating networks are considered as advanced materials, since they have improved thermal and mechanical properties. An alternative approach to the preparation of such hybrid systems is proposed. It is based on the synthesis of silica from the precursor of hyperbranched polyethoxysiloxane by the hydrolytic condensation reaction in the volume of pores of a polymer matrix (bulk porosity is 40 vol%) stretched via the environmental crazing mechanism. Polyethylene-silica nanocomposites with the structure of semi-interpenetrating networks when the content of silica is not less than 20-25 wt% are obtained. These composites can undergo an additional phase separation at a temperature of 160 degrees C (above the melting point of polyethylene), which is accompanied by an increase in the size of the polymer phase with the formation of macrophases. At the same time, the environment (orthophosphoric acid), in which the composite is heated, fills the pores that have appeared. As a result, the content of the third component with the new functionality increases up to 50 wt%, which allowed us to impart proton-conducting properties to the composite material and preserve its shape stability.