The ladder polymethylsilsesquioxane (PMSQ) nanoparticles with average diameter size of 15 and 20 nm were synthesized by hydrolysis and condensation of methyltrimethoxysilane (MTMS). An ex situ kinetic study in acidic medium of MTMS hydrolysis was followed by Raman spectroscopy. The PMSQ nanoparticles was studied by infrared spectroscopy, Si-29 and C-13 nuclear magnetic resonance and by X-ray diffraction. The thermal stability was examined by thermogravimetric analysis. PMSQ nanoparticles have a degradation temperature of 390 degrees C under nitrogen and 380 degrees C under oxygen, an excellent specific area (397.21 m(2)/g), a density of 1.42 g/m(3) and hydrophobic surface (apparent contact angle 148 degrees +/- 3). (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.