In this study, a series of soluble polysilsesquioxanes (PSQs) containing hydrophobic side-chain groups (PSQ-Ph, PSQ-CyC6, PSQ-C-6, and PSQ-C-11) were prepared by the facile reaction of a ladder-like PSQ containing ammonium groups with the corresponding hydrophobic carboxylic acid chlorides (i.e., benzoyl, cyclohexanecarbonyl, heptanoyl, and dodecanoyl chlorides, respectively) in the presence of triethylamine in a mixed solvent of water and N,N-dimethylformamide. The resulting hydrophobic PSQs were soluble in chloroform. The weight-average molecular weights of the hydrophobic PSQs estimated by gel permeation chromatography with chloroform as the eluent and polystyrene standards ranged from 1.92 x 10(4) to 6.49 x 10(4). The pyrolysis temperatures of PSQ-Ph estimated by thermogravimetric analyses were relatively high (T-d5 = 391 degrees C and T-d10 = 425 degrees C) due to the presence of the thermally stable phenyl side-chain groups and Si-O-Si main-chain. Moreover, hybrid films of the hydrophobic PSQs and two organic polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), were prepared by drying the chloroform solutions of the mixtures of these polymers. The PMMA/PSQ-C-6, PMMA/PSQ-C-11, and PS/PSQ-Ph hybrids were highly transparent. For PS/PSQ-Ph hybrid films, the thermal stability increased with increasing amount of PSQ-Ph. (C) 2016 Elsevier Ltd. All rights reserved.