Molecular Dynamics of Polymer Composites Using Rheology and Combined RheoNMR on the Example of TiO2-Filled Poly(n-Alkyl Methacrylates) and Trans-1,4-Polyisoprene

Abstract

The determination of the interplay between polymeric matrices and filler particles in composites is of great interest to understand structure-property relationships and develop predictive theories. To study the molecular dynamics of polymers in composites, model systems based on poly(n-alkyl methacrylates), trans-1,4-polyisoprene (gutta percha), and titania (TiO2) were prepared and characterized using rheometry and a combined RheoNMR technique. Apparent entanglement molecular weights were obtained from small amplitude oscillatory shear (SAOS) experiments, which are related to the increasing physical cross-link density as a function of the filler content. Large amplitude oscillatory shear (LAOS) experiments were performed and analyzed within the FT-rheometry framework. The filler had a strong impact on the scaling behavior of the normalized third harmonic. A combined RheoNMR technique was used to simultaneously study the molecular dynamics via NMR and the corresponding mechanical response via rheometry. A strong correlation between the macroscopic mechanical properties and microscopic molecular dynamics was found, which might lead to a new understanding of polymer melt dynamics.