Atomistic molecular dynamics simulations have been performed to investigate the effects of introducing monofunctional polyhedral oligomeric silsesquioxanes (POSSs) as pendant groups on the polymethyl methacrylate backbone. The effect of POSS loading and of the structure of the organic substituents on the seven silicon atoms, isobutyl groups or cyclohexyl rings, was studied. Calculated volume-temperature behaviour and X-ray scattering profiles were compared with experimental results obtained on copolymers synthesized from POSS and MMA. In the limited time scale used for the simulation, no aggregation can be observed. Cohesive energy density was calculated and found to decrease as POSS was copolymerized with MMA, but in the same order of magnitude whatever the organic ligand nature is. Chain packing around the POSS cluster was evaluated through radial distribution functions. The mobility of the POSS clusters was determined via the mean square displacement. The results tend to confirm the idea that POSS incorporated as dangling groups along the macromolecular backbone behave as anchoring groups. (c) 2006 Elsevier Ltd. All rights reserved.