Multicomponent Polymer Nanocomposites: Characterization Of Interfacial Interactions And Their Effects On Bulk Properties

Abstract

Polymer blending and copolymerization provide techniques to engineer polymeric materials with desired properties. Inorganic particles may also be added to the polymers to further enhance mechanical properties. In particular, clay nanoparticles, with their large surface area per unit weight, can both reinforce polymers and change polymer structure. In copolymers and polymer blends, nanoparticles can suppress crystallinity and stabilize domain morphology. This thesis details the effects of clay nanoparticles on multicomponent polymer systems. The first part of the thesis focuses on butadiene-styrene copolymer interactions with clay nanoparticles and the effect of those interactions on the kinetics of copolymer intercalation. Dielectric relaxation spectroscopy was used to measure interfacial polymer relaxations which are a measure of interaction strength. Copolymers of different compositions were studied, and the copolymers with higher styrene concentration had slower polymer dynamics. Dielectric spectroscopy results were compared to the intercalation kinetics measured with xray diffraction. Copolymers with higher styrene concentration intercalated the clay nanoparticles faster indicating that there is a correlation between strong copolymer interactions and fast intercalation kinetics. The second part of the thesis focuses on characterizing various polymer blend nanocomposites to determine what variables control blend morphology and properties. Both thermodynamic variables (such as polymer-polymer and polymer-clay interactions) and kinetic variables (such as viscosities of the matrix and domain phases) control domain size. To stabilize the domain morphology in blend nanocomposites and improve the mechanical properties, clay nanoparticles need to interact favorably with both polymers to reduce the interfacial tension. To reduce domain size, the nanoparticles should also change the viscosities of the domain and matrix phases so that they are comparable.