When a new material is created through the combination of several components all properties are affected, not just the ones of particular interest. The response of the mixture depends on the property of interest. It may be a weighted sum of the constituent responses; alternatively, there may be a range of responses, as in the set of experimental traces for the glass transition shown below. 1 These data for polystyrene and dibutylphthalate in both pure and mixed states show that the effect of adding a second component is to shift not only the temperature of the transition, but also its breadth. Similar broadening of response is found in other data, for example dielectric relaxation, and can be understood by accounting for how the neighborhood (local environment) sampled by segments of each component, is changing with composition. The cartoon (at right) depicts an equal mixture of red and blue chains. One red chain has been highlighted, and four of its sections ‘blown up’ in the accompanying figures. While this two-component system appears well-mixed, the close-ups reveal that a ‘walk’ along one chain (bolder red) leads through neighborhoods ranging in composition (of unconnected neighbors) from all red to all blue. What about connected neighbors ? These play a very important role, although questions remain about the extent of their influence. We have developed 2 a simple model which accounts quantitatively for how the neighborhood around a segment affects its contribution to certain experimental properties of the sample. Our work has revealed some answers and also some new questions about the connections between molecular environment and macroscopic properties. We hope our results provoke new research on the role of these issues in determining properties of simple and complex mixtures. 80% DBP80% PS pure PS pure DBP 1. Data from Savin et al, J. Polym.Sci., part B, Polym.Phys. 442, (2004). 2. Lipson and Milner, J. Polym.Sci., part B, Polym.Phys. 44, (2006). Studies on Fluids and Fluid Mixtures: Connecting Theory with Experiment Jane E.G. Lipson, Dartmouth College, DMR DBP = dibutylphthalate PS = polystyrene T(°C)

Studies on Fluids and Fluid Mixtures: Connecting Theory with Experiment Jane E.G. Lipson, Dartmouth College, DMR Education and Outreach NSF support of the research being carried out by the PI and her group has lead to a broader reach into the learning community than would be visible from focusing on her work here at Dartmouth, alone. James Porter, a postdoc working in the group at the start of this grant, is currently teaching undergraduate Physics at Colby College, a liberal arts institution in Maine. Jutta Luettmer-Strathmann, a former postdoctoral fellow with the PI, just earned tenure in her position as a Physics professor at the University of Akron. Graduate student Michael Tambasco finished his Ph.D. within the last year and is now a postdoctoral Fellow in the Chemical Engineering Department at Columbia University. Meanwhile, current graduate student Elizabeth Clark is involved in research and undergraduate laboratory teaching here in the Chemistry Department at Dartmouth. With respect to undergraduates, Lisa Hall, whose first foray into research was in the PI’s group under the auspices of the NSF-REU program, is in the process of earning her Ph.D. in the Materials Science and Engineering Department at the University of Illinois; she was recently a co-author on a paper in Physical Review Letters. Kallie Willets, who (as a Dartmouth undergraduate) undertook a senior major thesis with the PI and was a co-author on a paper resulting from that research, went on to graduate and postgraduate studies, and has just started as an Assistant Professor in the Chemistry Department at the University of Texas at Austin. All of these transitions, and others not mentioned, are related to the ongoing education and participation which scientists at all levels experience as part of a community of scholars. The range of institutions at which these current and former group members have chosen to spend this part of their respective careers clearly illustrates that the investment in learning within one kind of environment yields skills which are transportable to other environments.