Core/multishell CdSe/CdS/CdS/Cd0.75Zn0.25S/Cd0.5Zn0.5S/Cd-0.25 Zn0.75S/ZnS/ZnS QDs/PMMA bulk nanocomposites were successfully synthesized. To achieve a homogeneous and stable dispersion in MMA monomers, QDs were first modified with amphiphilic polymer of poly(ethylene glycol)-oleate (PEG-oleate). Subsequently, the transparent and homogeneous bulk composites were obtained by photopolymerization. The TEM analysis of ultramicrotome cut of composite demonstrates that QDs are well dispersed in the PMMA matrix. UV-vis transmission spectra show the nanocomposites still maintain high transmittance even with QDs content of up to 6 wt %. The thermogravimetric analysis (TGA) reveals the incorporation of the QDs significantly improves the thermal stability of composites, as evidenced by the retardation of a degradation initiation by 60 degrees C. Photoluminescence spectra suggest that the nanocomposites exhibit bright fluorescence under UV excitation. X-ray excited luminescence spectra show they have response to X-ray. All of the experimental results indicate the great promising applications of core/multishell QDs/PMMA nanocomposites in optical communication devices and radiation detectors. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1548-1553, 2013