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 (phi int) as TMDSC and BDS. The parameter (chi int) corresponding to the decreased degree of enthalpy hysteresis (Delta HR) related to the contribution of the interfacial layer, is identical with phi int estimated from BDS, while presents only similar dependence on nanoparticle loading with phi int 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 relaxa-tion. 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.

Automated summary

The accurate characterization of the interfacial layer is essential for understanding the structure-property relationship in polymer nanocomposites (PNCs). In this study, enthalpy relaxation and interfacial layer properties of model PNCs with attractive interactions were investigated using temperature-modulated differential scanning calorimetry (TMDSC) and broadband dielectric spectroscopy (BDS). Enthalpy relaxation accurately quantified the volume fraction of the interfacial layer, which was consistent with the results from BDS. The parameter (chiint) related to the contribution of the interfacial layer showed similar dependence on nanoparticle loading as the volume fraction estimated from TMDSC. This correlation between enthalpy and dielectric relaxation provides a new approach to characterize the interfacial layer properties and understand the impact on the glass transition behavior in PNCs.