The main mechanism of the dielectric relaxation process of ordinary hexagonal ice (ice Ih) and its temperature dependence remains unclear. The most interesting and as yet unexplained feature of ice is the presence of the dynamical crossover in relaxation time behavior around Tc = 230 ± 3 K. Since there are no phase transitions in the ice at this temperature (first or second order), we cannot correlate the origin of this crossover with any structural change. Here we present a model according to which the temperature of the crossover is defined by the polarization mechanism. The dielectric relaxation driven by the diffusion of L-D orientational Bjerrum defects (at high temperature, T > Tc) is transformed into a dielectric relaxation dominated by the diffusion of intrinsic ionic H3O(+)/OH(-) defects (at low temperature, T < Tc). In the framework of the model, we propose an analytical equation for the complex dielectric permittivity that takes into account the contribution of both types of defects.
Despite the wide use of polymer nanocomposites (PNCs) in various applications, our understanding of the microscopic parameters controlling their macroscopic properties remains limited. In this study, we examine the dielectric strength of segmental dynamics, Δε IL (T) in the interfacial polymer layer surrounding the nanoparticles in PNCs. The presented analysis reveals a significant drop in Δε IL (T) and its anomalous temperature dependence in the polymer layer adsorbed to nanoparticles. The drop in Δε IL (T) was observed in all samples regardless of whether segmental relaxation time in the interfacial layer was slower or faster than in the bulk polymer, excluding interpretation of the "dead" layer. We ascribe the observed decrease in the dielectric strength to the restricted amplitude of segmental relaxation in the interfacial/adsorbed layer. Our results provide a new perspective on discussion of dynamics in the interfacial layer in PNCs and thin polymer films, demonstrating that not only segmental relaxation time but also its amplitude can be strongly affected by the interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.