A series of epoxy-functionalized inorganic-organic hybrid ladder-like structured polysilsesquioxanes were synthesized in one-batch via a base-catalyzed co-solvent system. Two types of epoxy functionalities were examined: aliphatic and cycloaliphatic. Obtained polymeric epoxy-functionalized ladder-like polysilsesquioxanes were cationically photopolymerized under UV irradiation over glass and plastic substrates. Obtained cross-linked films were examined as hardcoating materials as their thermal, optical, mechanical, and barrier properties were studied. These materials showed superior thermal properties ( T d > 400 °C), high optical transparency (>95%), high pencil hardness (4H-9H), low dielectric constant (3.0-3.6), and good barrier properties (WVTR < 10 1 g m −2 day −1 , OTR < 10 2 g m −2 day −1 ). A series of cationically photopolymerizable inorganic-organic hybrid epoxy-functionalized thermoplastic polysilsesquioxanes were synthesized and their thermal, mechanical, optical, and barrier properties investigated.