Correlation between the temperature evolution of the interfacial region and the growing dynamic cooperativity length scale

We study experimentally the temperature evolution of the thickness of the interfacial layer, L-int(T), between bulk matrices and the surface of nanoparticles in nanocomposites through broadband dielectric spectroscopy. Analyses revealed a power-law dependence between the logarithm of structural relaxation time in the interfacial layer, tau(int)(T), and the L-int(T): ln tau int(T)/tau 0 proportional to Lint beta(T)/T, with tau(0) similar to 10(-12) s, and beta index similar to 0.67 at high temperatures and similar to 1.7 at temperatures close to the glass transition temperature. In addition, our analysis revealed that the L-int(T) is comparable to the length scale of dynamic heterogeneity estimated from previous nonlinear dielectric measurements and the four-point NMR [xi(NMR)(T)], with L-int(T) similar to xi(NMR)(T). These observations may suggest a direct correlation between the L-int(T) and the size of the cooperatively rearranging regions and have strong implications for understanding the dynamic heterogeneity and cooperativity in supercool liquids and their role in interfacial dynamics.