Specific features of the formation of the silicon dioxide phase in porous poly(propylene) prepared through the crazing mechanism

A new technique is described for preparing poly(propylene)-silica nanocomposites with the use of crazing of polymers in reactive liquid media that exhibit an adsorption capacity with respect to the polymer and contain functional groups able to enter into different chemical reactions, in particular, hydrolytic condensation. The advantage of this technique over conventional mixing is that the components can be mutually dispersed at the nanolevel without using additional modifying additives. The hydrolytic condensation of tetraethoxysilane and hyperbranched poly(ethoxysiloxane) in the presence of acid or base catalysts with the formation of a silica gel in a crazed polymer matrix is investigated. It is established that the morphology of the prepared composites is determined by the structure of the crazed polymer matrix, the nature of the precursor, and the hydrolytic polycondensation conditions. Composites are prepared in which the silica phase is located either inside the poly(propylene) matrix (in the form of a continuous phase or discrete particles) or on the surface of the polymer. Porous silicon plates are produced through heat treatment of the poly(propylene)-silicate nanocomposites at a temperature of 700°C.