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(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, τ(T), and the L(T): lnτ(T)/τ∝L (T)/T, with τ ∼ 10 s, and β index ∼0.67 at high temperatures and ∼1.7 at temperatures close to the glass transition temperature. In addition, our analysis revealed that the L(T) is comparable to the length scale of dynamic heterogeneity estimated from previous nonlinear dielectric measurements and the four-point NMR [ξ(T)], with L(T) ∼ ξ(T). These observations may suggest a direct correlation between the L(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.