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Polymer Science and Engineering
Interactions among chain architecture, phase transitions, morphology development, and final properties are essential features of the processing behavior of polymeric materials. Research in our group centers on a number of fundamental problems where such interactions are intrinsic. Current projects include modeling flow-induced crystallization in fiber spinning and film formation, flow-induced ordering and transitions in solutions, processing-rheology interactions in dendritic and hyperbranched polymers and blends, and the dynamics of phase inversion, particularly as it relates to injectable, controlled-release drug delivery.
A number of our experiments involve the use of rheology and rheo-optics, coupled with video imaging, to generate quantitative information on the kinetics of orientation and structure development in solutions and melts under controlled flow conditions. Computational aspects involve modeling the crystallization and non-Newtonian rheological behavior of polymers, utilizing molecular and continuum approaches.
We have also developed novel optical techniques, in combination with thermo-dynamic and transport-based models, to quantify the dynamics of the diffusion, phase separation, and structuring processes that take place when a polymer-solvent mixture is quenched in a nonsolvent environment. This process, known as phase inversion, is the principal means of fabrication of asymmetric membranes that are used as energy-efficient separation devices and as drug delivery devices in the bio-pharmeceutical industry. Our current activities are centering on the application of phase inversion in polymer solutions to injectable, controlled-release delivery of bioactive agents, such as proteins. Solutions made up of a biodegradable polymer dissolved in a biocompatible solvent, along with the suspended or dissolved bioactive agent, are injected directly in vivo, forming the membrane carrier simultaneously with the release of the suspended drug. The dynamics of the membrane formation reflect the thermodynamics and mass transfer characteristics of the system (polymer solution plus physiologic surroundings) that ultimately control the drug release profile. Our studies employ dissolution baths, in combination with chromatography, electron microscopy, and scanning calorimetry to quantify protein release kinetics as a function of solution formulation (polymer type and molecular weight, solvent type, solution concentration). Modeling studies of the release kinetics are also being undertaken.