Organically modified aluminosilicate hybrid materials incorporating polystyrene and poly(styrene-co-hydroxypropyl acrylate) latexes, (3-glycidyloxypropyl) trimethoxysilane, and aluminum sec-butoxide [Al((OBu)-Bu-s)(3)] were synthesized by a sol-gel process. The bulk materials obtained were macroscopically homogeneous dispersions with good mechanical properties. Dynamic mechanical and dielectric analyses of these new hybrid materials as a function of the Al((OBu)-Bu-s)(3) concentration and copolymer composition revealed a series of transitions that represented relaxation processes of the incorporated polymer (glass transition), =Al-O-Si=, the =Si-O-Si= part of the network, and segmental motion of unreacted =Si-(CH2)(3)OCH2CHCH2O chains. (C) 2001 John Wiley & Sons, Inc.