ABA-based triblock copolymers of styrene as block ends and gelable 3-acryloxypropyltriethoxysilane (APTES) as the middle block were successfully prepared through nitroxide-mediated polymerization (NMP). The copolymers were bulk self-assembled into films and the degree of phase separation between the two blocks was evaluated by differential scanning calorimetry (DSC). Their morphology was examined through small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), whereas the mechanical properties of the corresponding crosslinked self-assembled nanostructures were characterized by dynamic mechanical analysis (DMA). Acidic treatment of the triblock copolymers favored the hydrolysis and condensation reactions of the APTES-rich nanophase, and induced a mechanical reinforcement evidenced by the increase of storage modulus values and the shift of the glass transition temperature to higher temperatures due to confinement effects. In addition, the lamellar structure of the hybrid films was retained after the removal of the organic part by calcination. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4193-4203, 2011