The performances of nanoclay, fabricated nanogold on nanoclay and modified nanoclay with assembled polymeric thiol surfactants on nanogold, were studied as heterogeneous catalysts in the bulk polymerization of methyl methacrylate (at 80 degrees C, for 5 h in inert (N-2) and in O-2 atmosphere). The polymeric thiol surfactants which assembled on gold nanoparticles are poly 6-(3-amino phenoxy) hexane-1-thiol, poly 8-(3-amino phenoxy) octane-1-thiol and poly 10-(3-amino phenoxy) decane-1-thiol. All catalyst samples were characterized using X-ray diffraction, transmission electron microscopy and fourier transform infrared spectroscopy techniques whereas the produced polymer was characterized by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy. The results indicated that the assembled polymeric thiol surfactants on gold nanoparticles exfoliated and modified the activity of nanoclay. So, the performance of these modified samples increased by increasing the alkyl chain length of surfactant monomers (C-n = C-6, C-8 and C-10) due to the creation of new active sites and exposing those deep in clay. On the other hand, O-2 may give peroxides which decomposed thermally to free radicals, also activated the exposed active sites of clay. So, the conversion% of PMMA increased by 6,9 and 14.7 times using C-6, C-8 and C-10 respectively relative to the conversion% in N-2 atmosphere. The most active sample (C-10) gave 5,3 and 78.11% PMMA in N-2 and in O-2 atmosphere respectively with better polydespersity index ((M) overbar w/(M) overbar n = 1.46 in O-2) mostly due to chain transfer.(C) 2014 Elsevier B.V. All rights reserved.