Rationalizing the interfacial layer in polymer nanocomposites: Correlation between enthalpy and dielectric relaxation

The accurate and convenient characterization of the interfacial layer is a crucial prerequisite for understanding the relationship between structure and macroscopic properties in polymer nanocomposites (PNCs). Herein, enthalpy relaxation and interfacial layer properties estimated from temperature-modulated differential scanning calorimetry (TMDSC) and broadband dielectric spectroscopy (BDS) of model PNCs with attractive interactions are investigated. We demonstrate that enthalpy relaxation enables the accurate quantification of the volume fraction of the interfacial layer (φint) as TMDSC and BDS. The parameter (χint) corresponding to the decreased degree of enthalpy hysteresis (ΔHR) related to the contribution of the interfacial layer, is identical with φint estimated from BDS, while presents only similar dependence on nanoparticle loading with φint estimated from TMDSC. This interesting phenomenon can be ascribed to the consistency between enthalpy and dielectric relaxation, which both characterize the dynamic change of polymer mainly originating from segmental relaxation. Such an unexpected correlation between enthalpy and dielectric relaxation provides a new approach to characterize the interfacial layer properties of PNCs and understand its impact on the glass transition behavior.