1,4- phenylenediamine-1-propylsilica hybrid xerogels were obtained for two composition at different temperatures of gelation, from 5 up to 70 degrees C. The morphological effects produced by the different gelation temperatures were investigated by using N-2 adsorption-desorption isotherms and scanning electron microscopy. The thermal stability of the organic groups and their distribution on the xerogel matrix, i. e. the fraction of the organic groups that were trapped in closed pores, formed during the xerogel synthesis, and the fraction of organic groups present on the surface, were obtained by using infrared thermal analysis. The higher porosity of the xerogels and the higher thermal stability of the organic groups were achieved for samples gelled at 25 degrees C.342189195