An in-depth study was carried out on the structure and properties of a series of poly(ethyl acrylate)/clay nanocomposites prepared by in situ atom transfer radical polymerization (PNCIs) with well-defined molecular weights and narrow molecular weight distributions. Wide-angle Xray diffraction and transmission electron microscopy studies revealed an exfoliated clay morphology, whereas conventional solution blending generated an intercalated structure. The storage moduli of the PNCIs showed a moderate increase over that of the neat polymer [poly(ethyl acrylate)]. The sample containing 4 wt % clay (PNCI4, where the number following PNCI indicates the weight percentage of clay) exhibited the highest improvement (31.9% at 25 degrees C). In PNCIs, the beta-transition temperature showed a remarkable decrease (by 175% in PNCI4) along with a shift toward higher temperatures. This indicated the probability of the anchoring of the -OH group of the clay layers to the >C=O group of the pendant acrylate moiety, which was also confirmed by Fourier transform infrared analysis. Rheological measurements indicated a significant increase in the shear viscosity [by 9% in PNCI2,15% in PNCI4, and 6% in the poly(ethyl acrylate)/clay nanocomposite with 2 wt % clay prepared by solution blending]. The PNCIs registered enhanced thermal stability, as indicated by the shift in the peak maximum temperature (388 and 392 degrees C for the neat polymer and PNCI4, respectively) and a decrease in the rate of degradation (by 3.5% in PNCI2, 10.2% in PNCI4, and 49.3% in PNCI6). (C) 2008 Wiley Periodicals, Inc.