Polymer mixture thermodynamics and applications for functional, microstructured films

Date
2017
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University of Delaware
Abstract
Polymer blend films are used in applications including organic optoelectronics and pressure sensitive adhesives. The film microstructure (domain size and composition) is a critical component that determines the material properties (e.g. friction coefficient). The morphology in these films is dictated by the thermodynamics and kinetics of phase separation in addition to the processing conditions, such as solvent evaporation, during film generation. ☐ In this dissertation, the relationships between phase separation and casting conditions on microstructure and the effect of the resulting morphology on the friction coefficient were studied to produce targeted structures in multicomponent, hierarchical polymer blend films. First, a robust method was developed and implemented to measure polymer-solvent interaction parameters, which were used to predict the phase diagram in polymer blend solutions. The influence of the phase separation on the casting behavior was captured using in situ techniques. Second, the casting behavior and morphology of polymer blends was tuned through the addition of nanoparticles. The solvent quality, a parameter that has not previously been explored in polymer blend nanocomposites, was shown to impact the effect of the nanoparticles on the microstructure. Third, the relationships between the structure, composition, and friction coefficient were established to provide insight into rational design of tribologically-relevant materials like pressure sensitive adhesives. Finally, the techniques and methodologies developed in this dissertation were applied to renewable polymers to study the solvent-polymer interactions, surface energies, and friction coefficients towards incorporating these sustainable materials into green, structured coatings. ☐ Overall, this dissertation provides enhanced understanding and robust methods to characterize and control interactions in polymer blend films. These insights afford control over the final material properties through modifying the film morphology. The methods outlined in this work can be applied to polymer blend systems of interest for rational design of functional, hierarchical materials.
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