Volume fraction of polymer

1. 10x40 20x40 30x40 Time Volume fraction of polymer 3.08x10-2 7.21x10-2 Development of a Simulation Tool to Model Complex Dynamics Anna C. Balazs, University of Pittsburgh, DMR-ITR-0312115 Modeling Self-Oscillating Polymer Gels Polymeric gels constitute optimal candidates for use as soft “active” materials because they can undergo large-scale, reversible changes in volume or shape. Chemo-responsive gels involved in the Belousov-Zhabotinsky (BZ) reaction can expand and contract periodically without external stimuli. Such self-oscillating gels could be used in autonomous devices, such as micro-actuators for pulsatile drug release. We have developed an efficient approach to modeling large-scale, two-dimensional deformations and chemical reactions within a swollen polymer network. The 2D calculations allow us to probe not only volume changes, but also changes in the shape of the sample. By applying our new technique to responsive gels undergoing the BZ reaction, we observed traveling waves of local swelling that form a rich variety of dynamic patterns, and give rise to distinctive oscillations in the gel’s shape. The observed patterns depend critically on the gel’s dimensions (see figure on right). Our studies can further facilitate the design of devices that harness chemo-mechanical energy conversion to exhibit self-sustained rhythmic action in multiple directions. Science 2006, in press

2. Modeling Self-Oscillating Polymer Gels Anna C. Balazs, University of Pittsburgh, DMR-ITR-0312115 Broader Research Impact • Education • The funds supported Dr. Victor Yashin as a postdoctoral researcher • Collaboration with other research labs in the U.S. and abroad • We shared our computational models with Prof. Julia Yeomans and her group at Oxford University, UK • Dissemination of Knowledge • We also shared our computational models with researchers at the Dow Chemical Company. • Outreach • Dr. Yashin has given contributed talks on this subject at the MRS and APS meetings and Prof. Balazs has given invited talks at various universities on this topic.