New crystalline nanostructured inorganic-organic hybrid materials containing isotactic polystyrene (iPS) are prepared by means of hydrosilylation coupling of vinyl-terminated iPS with octakis(dimethylsilyloxy) silsesquioxane (Q(8)M(8)H). The number average molar mass of the iPS chains varies between 2000 and 6000 g mol(-1). As a function of the iPS/Q(8)M(8)H ratio, using excess reagent, the formation of linear or star-shaped hybrid architectures is achieved. Via fractionation, it is possible to isolate well-defined linear hybrids containing one iPS chain and seven ethyl groups per silica core (iPS-Q(8)M(8)E(7)) as well as star-shaped hybrids containing up to eight iPS side chains (iPS(6-8)-Q(8)M(8)). These new iPS/polyhedral oligomeric silsesquioxane hybrid materials crystallize when the number average molar mass of iPS side chain exceeds 5500 g mol(-1). The hydrosilylation coupling reaction and the resulting linear iPS-Q(8)M(8)E(7) and star-shaped iPS(6-8)-Q(8)M(8) are characterized by NMR spectroscopy, size exclusion chromatography (gel permeation chromatography), and polarized light microscopy. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 947-953