The present study examined ion exchange of layered silicate clay by ammonium ions and investigated thermal dissociation of ammonium ions and the presence of nadic endgroups in ammonium ions on the potential of clay exfoliation in nanocomposites of PMR-15 (an oligomer with molecular weight 1500). A novel method of organoclay exfoliation was used. It involved organoclay intercalation by lower molecular weight PMR-5 oligomer, dispersion of PMR-5/clay mixture in higher molecular weight PMR-15 resin, and curing of the resultant mixtures at approximately 315 degrees C. The PMR-5 resin residing inside the clay galleries underwent crosslinking during curing and produced higher elastic forces to facilitate clay platelets exfoliation against a slower rising viscous force in the matrix PMR-15 resin. It was found that the ammonium ions with nadic endgroups participated in intra-gallery PMR-5 resin crosslinking reactions and promoted better exfoliation compared to non-reactive arnmonium ions. Improvements in thermal and mechanical properties were also observed. (C) 2007 Elsevier Ltd. All rights reserved.