Effects of Heterogeneous Segmental Friction on the Decoupling of Segmental and Chain Dynamics

Segmental and chain dynamics often deviate from Rouse model predictions due to dynamic heterogeneity introduced by interfaces or temperature reduction. However, the effect of heterogeneous segmental friction on such multi-scale dynamics of polymers remains poorly understood. This work aims to elucidate a possible mechanism for the decoupling of segmental and entire chain motion by systematically altering segmental friction in statistical copolymers. A model statistical copolymer of styrene and 2-vinyl pyridine (2VP) is loaded with amine functionalized silsesquioxane nanoparticles. These nanoparticles form hydrogen bonds with 2VP, while not interacting strongly with styrene monomers. Thus, the heterogeneous polymer architecture leads to heterogeneous segment-nanoparticle friction. Segmental relaxation is studied by differential scanning calorimetry, while the chain relaxation is studied by rheology. These measurements suggest that segmental and entire chain dynamics are slowed due to increasing copolymer-nanoparticle friction by increasing nanoparticle loading and/or increasing the 2VP content of the polymer. The relationship between segmental and entire chain dynamics of these copolymer/nanoparticle composites will be discussed in this presentation.