Phase Behavior of Block and Graft Styrene Copolymers in Near Critical and Supercritical Solvents

University Of Wyoming, Laramie WY

Investigators

Abstract

Maciej Radosz University of Wyoming "Phase Behavior of Block and Graft Styrene Copolymers in Near Critical and Supercritical Solvents." The overall goal of this research is to understand the phase behavior of block and graft styrene copolymers in compressible fluids, such as near critical- and supercritical solvents and monomers. Such understanding is needed not only to improve existing manufacturing processes, but also to develop new polymeric materials and new polymer processing approaches that are more efficient and more environmentally acceptable. This research is a synthesis of experiment and thermodynamic modeling. The approach would be to: 1) synthesize novel graft and block copolymers, such as polyisobutene-g-polystyrene (PIBg-PS), polybutadiene-g-polystyrene (PBD-g-PS), and polybutadiene-b-polystyrene (PBDb-PS) from atom transfer radical polymerization and living anionic polymerization followed by partial or complete hydrogenation (for polymers containing polybutadiene); 2) characterize these polymers upon microphase separation and bulk phase transitions (fluid-liquid and fluid solid) in high-pressure experiments; and 3) develop equation-of-state-based thermodynamic models that can explicitly account for and predict the phase behavior of graft and block copolymers. The research builds on a current NSF-funded project on fluid-solid equilibria in solutions of crystallizable polymers, and on a series of preliminary but promising seed experiments and computer simulations using recent versions of Statistical Associating Fluid Theory (SAFT), such as SAFT1, and a recent Lennard-Jones equation of state with self-consistent theoretical framework for vapor, liquid, and solid phases. This research could enhance our understanding of how the macromolecular structure affects the phase behavior of copolymers with complex backbone architecture. Such understanding could provide a basis for future research on phase equilibria for other polymers with even more complex architecture, such as triblock copolymers and graft copolymers with double branches (centipede), and more predictive thermodynamic models. In addition to building a knowledge base in this area, and seeding future research, the project could have a broader impact on the existing and future commercial polymer technology. For example, the theoretical model can be used to provide rapid predictions of cloud points, micelle formation, crystallization, and melting of graft or block copolymers in supercritical fluids. Such predictions are needed to control desirable and undesirable phase transitions in production lines. The model itself can also be used to optimize advanced polymerization schemes in supercritical fluids, such as ATRP and living anionic polymerization. This may lead to unique products and efficient, environmentally benign processes. Other examples of a broader social impact include contributions to education (graduate students and post-doctoral researchers) and to broadening participation of underrepresented groups.