Precise Acid Copolymers and Ionomers: Morphology, Dynamics and Mechanical Properties

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TECHNICAL SUMMARYPrecise acid copolymers are novel materials having functional groups spaced exactly evenly along a linear polyethylene. For example, a phosphonic acid group can be placed on every 9th, 15th or 21st carbon. The proposed project involves nine precise acid copolymers and one random acid copolymer having carboxylic acid and phosphonic acid groups with mono- or geminal-substitution. These materials have established synthetic routes. Winey's morphological studies of the acid copolymers will use X-ray scattering, HAADF STEM, and electron diffraction to establish the crystalline structure of the polyethylene segments and the nature of the acid group assemblies. The acid copolymers will be neutralized with Li, Na, Cs, and Zn to form partially- and fully-neutralized ionomers in which Winey will probe the size, shape, spatial arrangement, and composition of the ionic aggregates. The precision of these acid copolymers and ionomers is known to yield remarkable uniformity in the morphologies, making data interpretation and comparisons with simulations more rigorous. The dynamics and mechanical properties will be studied for the first time in three precise acid copolymers and one random acid copolymer, along with their ionomers. The property measurements will include melt rheology, small-strain compression testing to explore elastic deformations, and large-strain, cyclic compression testing to study plastic deformation. The PI's group has highly specialized expertise to study the morphology, dynamics, and mechanical properties of these remarkable polymers in terms of both demonstrated prior work and existing collaborations. NON-TECHNICAL SUMMARYThe PI will study an extraordinary set of functional polymers with the ultimate goal of knowing how the functional groups are arranged and thereby how their arrangement dictates their mechanical properties. These functional polymers have an acid group on every 9th, 15th or 21st carbon atom along a polyethylene molecule. The unprecedented precision in these molecules will lead to better structural order at both the micro- and nanoscale, which, in turn, enable improved correlations between molecular structure and properties. The PI has established collaborations with synthetic chemists, spectroscopists, and theorists to explore these remarkable materials, and within this interdisciplinary team the teaching, learning, and training of more students and researchers will be significantly enriched. These precise polymers are based on polyethylene, which constitutes the largest class of commercial polymers. This project involves the first dynamical and mechanical property measurements of these materials and in so doing will evaluate their commercial potential.