Mid-Segment Polydispersity as a New Tool for Manipulating ABA Triblock Copolymer Morphologies and Properties

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TECHNICAL SUMMARYApplications of commodity and specialty block copolymers rely on their useful combinations of properties, which stem from covalently linking two or more dissimilar homopolymer segments into a single macromolecule. By virtue of their thermodynamically driven self-assembly into complex yet well-defined nanoscale morphologies, block copolymers are useful as thermoplastics and thermoplastic elastomers, advanced molecular separations membranes, and new templates for fabricating next-generation microelectronics. Modern polymerization techniques enable access to a plethora of copolymers containing unusual combinations of chemical functionalities with useful physical properties, at the expense of introducing significant segmental dispersity into one or more blocks of the copolymers. However, the role of broad segmental dispersity on block copolymer phase behavior is not well understood. This project will directly investigate the effects of mid-segment polydispersity on the phase behavior of ABA-type triblock copolymers. Model polydisperse triblock copolymers with varying segmental interaction parameters will be synthesized by tandem polymerization techniques for studies of their composition-dependent phase behavior, using small-angle X-ray scattering, electron microscopy, polymer rheology, and various transport measurements. Characterization of samples near the order-disorder transition (ODT) will help to identify the variables that parameterize the phase behavior of these multicomponent block copolymer mixtures. Ultimately this study aims to transform segmental polydispersity into a new tool for manipulating the morphologies of block copolymers with technologically useful bulk properties.NON-TECHNICAL SUMMARYThe development of innovative polymeric materials possessing unusual combinations of chemical functionalities and useful physical properties is crucial in their myriad applications as high-strength structural materials, water and gas purification membranes, components in organic photovoltaic cells, and materials for high power lithium-ion batteries. Within a highly interdisciplinary research environment, this project will challenge undergraduate and graduate students to conduct hypothesis-driven, crosscutting research at the interface between chemistry, chemical engineering, and materials science. By using modern methods in synthetic polymer chemistry to generate new materials and by characterizing their structures and attendant physical properties, this project will aim to uncover new tools for designing innovative, functional polymers with unusual morphologies and novel properties for a variety of potential applications. An undergraduate polymer chemistry lab and two polymer-oriented lecture demonstrations will be developed for use in general chemistry instruction and in public outreach lectures.