This paper presents novel types of polysilsesquioxane (PSQ) epolymer composites formed through polycondensation of ethyltriethoxysilane in the spatially limited system of polymer pores in the presence of acid or base catalysts vapors. In addition, it gives an insight into the architecture of the PSQ network. It is shown that PSQ formed under acidic conditions is mainly composed of long ladder-like structures, whereas small three and four-membered rings are dominating structural units in the base set PSQ. Theoretical calculations extend the common interpretation of the Si-29 NMR spectra according to which signals at ca. -47, -55, and -65 ppm can be simply attributed to T-1, T-2, and T-3 Si atoms, respectively. Moreover, they indicate that T-1 and T-0 Si-29 NMR signals should be easily distinguishable from T-2, and T-3 (and among each other), since T-0 is placed upfield (-31.5 ppm) as compared to the other mentioned Si-29 signals. (c) 2018 Elsevier Ltd. All rights reserved.