The paper reports the synthesis of new silsesquioxanes with methacrylate and/or vinyl units, obtained by combining the sol-gel technique with radical polymerization in the presence of 2,2'-azobis(2-methylpropionitrile) as initiator and a cationic surfactant, cetyltrimethylammonium bromide. The thermal behaviour was investigated through simultaneous thermogravimetric and differential scanning calorimetry analysis (TG/DSC) coupled on-line with Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS), as well as by pyrolysis and gas chromatography-mass spectrometry (GC-MS). The aim of the investigation consists in drawing useful information on the influence of both chemical structure and chain end double bonds and silanol units on the resistance of such compounds against thermal degradation. (C) 2013 Elsevier B.V. All rights reserved.