Proton conducting poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) ultrathin layer was deposited on sol-gel-derived phenylsilsesquioxane (PhSiO3/2) particles via layer-by-layer (LbL) assembly technique. Spherical and size-controlled particles in the range of 0.3-4.0 mu m were successfully prepared by varying the condensation reaction. One PAMPS layer with 1.5 nm thickness was deposited on the particle, the volume fractions of Primer/PAMPS-multilayer varied from 0.7 to 11 vol.%. Sheet-like composite electrolytes in which PAMPS layer percolated throughout the sample can be obtained by hot-pressing the PAMPS-deposited PhSiO3/2 particles. The sample prepared using unmodified PhSiO3/2 exhibited a very low proton conductivity of 10(-9) S cm(-1) at 80 degrees C, whereas the conductivity of the composite electrolytes increased significantly with a very small amount of PAMPS-multilayer (similar to 1 vol.%). The composite with 11 vol.% PAMPS exhibited 2 x 10(-3) S cm(-1) at 80 degrees C and 95% of relative humidity. (C) 2010 Elsevier B.V. All rights reserved.