The aim of this work is to study the internal structure, thermal properties and rheological properties in molten state for polymer blends nanocomposites based on PMMA-PEO blends and Laponite. Polymer blends and their nanocomposites were prepared by a combination of solution mixing to generate PEO protected Laponite particles and melt dispersion to blend the PEO/Laponite master batch with PMMA and PEO. PMMA/PEO blends appear to be miscible at room temperature only for PEO concentration less than 30wt%. In the molten state, rheological data indicate miscisbility between PMMA and PEO. The introduction of Laponite particles which are, in the master batch, located inside the PEO phase does not lead to their dispersion in the blend. However, diffusion of PEO inside the PMMA phase is observed in the molten state since glass transition temperature and rheological properties of the blends with 20wt% PEO are almost identical to those of the pristine melt with the same composition. On the contrary, at high concentrations of PEO, it has been demonstrated that a continuity of the PEO phase is observed where most of Laponite particles are located. Some particles (Their fraction cannot be estimated( seem to be inside the matrix. These types of nanocomposite blends show a non-vanishing zero frequency storage modulus. Its origin is attributed to the formation of a Laponite PEO network as in PEO melts filled with Laponite1. These results show that Laponite particles, such as those used in this study, i.e. protected by PEO chains, do not act as compatibilizer in these blends in contrast to other layered silicate nanocomposites. On the opposite, TEM micrographs showed that Laponite particles partially hinder the diffusion of PEO in PMMA/PEO blends and thereby limit its miscibility. ______________________________________________________________________ 1. (a) Jose, J.; Omar, A. A.; Brotons, G.; Tassin, J.-F. In Influence of Preparation Method and Molecular parameters on the Rheology