Interfacial layer properties and enthalpy relaxation of polymer nanocomposites: Effect of nanoparticle dispersion

Investigating the effect of nanoparticle dispersion morphology on the properties of the interfacial layer of polymer nanocomposites (PNCs) provides an important theoretical basis for designing and regulating the macroscopic properties of PNCs. Differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS) were used to investigate the characteristic parameters of the interfacial area, segmental dynamics and enthalpy relaxation of PNCs with nanoparticle agglomerates and uniformly dispersed morphology. The volume fraction of the interfacial area (φint) and the extent of influence of the interfacial area on the enthalpy hysteresis reduction (χint) in PNCs with agglomerated nanoparticles are lower than that of PNCs with uniformly dispersed nanoparticles for the same nanoparticle loading. Because of the irregular structure of the nanoparticle aggregate morphology, the linear relationships between φint and nanoparticle content is not valid in PNCs with agglomerated nanoparticles. Interestingly, φint obtained by BDS and χint have a clearly linear relationship in all PNCs, independent of nanoparticle dispersion morphology. Such universal quantitative relationship provides a new research methodology for investigating the characteristic parameters of the interfacial area in PNCs, and facilitates the construction of a correspondence between the microscopic parameters of interfacial area and the macroscopic properties of PNCs. Highlights The linear relationships between φint and nanoparticle content are not valid in PNCs with agglomerated nanoparticles. The linear relationships between φint and the decreased degree of ΔHR can be noted in all PNCs, independent of nanoparticle dispersion morphology. The universal correspondence provides a new research methodology for investigating the characteristic parameters of the interface layer in PNCs. The correlation between relaxation enthalpy and the interfacial layer properties of polymer nanocomposites.