Two types of SAN/silicate nanocomposites were prepared to set up the relationship between the composition of monomers and the resultant morphology of the composites using a pristine sodium montmorillonite (Na-MMT). SAN I series were synthesized with acrylonitrile in initial stage and a mixture of styrene and acrylonitrile in increment stage. SAN II series were prepared with the mixture of styrene and acrylonitrile throughout polymerization. SAN I series showed exfoliated states but SAN II series exhibited intercalated states because SAN I series consisted of hydrophilic AN initially. The chemical affinity between monomer and silicate had a strong influence on the morphology of SAN/silicate nanocomposites. The exfoliated SAN I series had enhanced moduli and glass transition temperatures, T-g, compared to the intercalated SAN II series and pure SAN. (C) 2003 Elsevier Ltd. All rights reserved.