The Structural, Mechanical, and Osmotic Properties of Acrylic Triblock Copolymer Gels Determined by Self-Consistent Mean Field Theory and Experiment

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In recent years, research has expanded the uses of triblock copolymer gels to a wide variety of applications including everything from ceramics processing to regenerative medicine and drug delivery. The research presented in this dissertation focuses on a physically crosslinked, block copolymers gel system in a selective solvent. This system undergoes a rapid thermally reversible gel transition, from a viscous liquid at elevated temperatures to an elastic solid at room temperature. The research presented in this text was motivated by a desire to develop a more detailed understanding of the interplay between the structural, osmotic, and mechanical properties that determine the properties of physically crosslinked triblock copolymer networks. A more refined understanding of the forces at work in such a system will provided a basis for the design of future systems with specific predetermined properties. Self-consistent field theory is a useful tool in modeling complex polymeric systems. A SCFT based model of acrylic triblock copolymer gels was formulated and used to simulate the equilibrium properties of acrylic triblock copolymers for a range of temperatures, volume fractions, and two different midblock architectures. Theoretical results are compared to experimental rheometric, SAXS, swelling, and osmometry data. Both SCFT and experiment showed that between 55°C and 80°C the gel structure undergoes considerable rearrangement. Rheometry provided mechanical characterization of the acrylic triblock copolymer gels and showed that the visco-elastic gel to liquid transition occurs between 65°C and 80°C. Osmotic pressure measurements demonstrated that the complete dissolution of the endblock aggregate network occurs between 75°C and 80°C, but is only detectable when the elastic restoring force plays a large role in determining osmotic properties when compared to the volume fraction of osmotically active polymer. In conjunction with SCFT, the experimental results obtained provide a more detailed understanding of the relationship between the mechanical, structural, and osmotic properties of acrylic triblock copolymers.

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  • 09/13/2018
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