Dynamics in Miscible Polymer Systems

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Polymers in multicomponent systems exhibit complex dynamics. An understanding of these dynamics should lead to the ability to predict the rheological properties of miscible polymer mixtures. Experiments that probe the influence of mixing on dynamics in a number of miscible polymer systems are proposed. In all cases, NMR relaxation time measurements will be used to characterize the segmental dynamics of individual components in these mixtures. For some systems, these measurements will be supplemented by work performed by collaborators (solid-state NMR measurements of segmental dynamics, diffusion measurements, and computer simulations). Specific systems to be studied include polybutadiene/poly(vinyl ethylene) blends, low molecular weight blends of polystyrene and polyisoprene, isotopic blends of two different molecular weight polystyrenes, a series of blends containing polystyrene as a dilute component, blends of poly(ethylene oxide) and poly(vinyl phenol), and styrene-isoprene block copolymers. Together, these activities will couple macroscopic measurements of blend dynamics at both the segmental and terminal level with microscopic simulations. Specific issues to be addressed include the microscopic origin of distinct component dynamics in miscible blends, the prediction of segmental dynamics, and the relationship between segmental and terminal dynamics. If the proposed work is funded, significant progress in our ability to predict blend dynamics and rheology based upon homopolymer properties is anticipated. This work will have impact beyond the field of miscible polymer blends. Insights obtained about how nearby segments or surfaces impact polymer dynamics will be required for understanding the properties of composites of polymers with nanomaterials or biological structures. The detailed comparisons between experiment and simulation proposed here provide a sensitive test of the simulation potentials and will lead to improved potentials that will positively impact simulations in biology, other materials areas, and beyond. The funding of this proposal would also advance the training of both graduate students and students at the K-12 level. If this proposal is funded, those supported will help run (and refine the curriculum for) a summer education activity at the University of Wisconsin Madison for high school sophomores. This three-week activity is part of a larger program for students who otherwise would be unlikely to go to college.