1. Studies on Polymer Glasses, Melts, and Solutions Jane E. G. Lipson, Dartmouth College, DMR 0804593 A polymeric sample in the bulk is characterized, in part, by its glass transition, Tg, the temperature at which it transforms from a glassy to a rubbery solid. In the mid-1990s experimental results 1 revealed that the glass transition temperature for thin polymeric films could be considerably shifted, relative to the bulk. Since then numerous studies have appeared, in part driven by the myriad practical applications of polymeric films. There has also been strong theoretical interest, motivated by a number of observations: substrate effects may (not always) raise Tg relative to the bulk value; surface effects always work to lower Tg; effects may persist over many tens of nanometers, yet the bulk Tg transition is correlated with local molecular motions; sample molecular weight appears to play a role, but only in free-standing films. We 2 have developed two models : In one (see left) as T is lowered, local regions become dense (black); adjacent regions can connect (blue). At a sufficiently low temperatures connected regions span the sample (‘percolate’); it becomes glassy. A strongly interacting support can provide a short cut to create and connect dense regions (green). The result is that Tg may be significantly shifted to higher temperatures. In a second model (see right) the presence of one (or two) free surfaces acts as both a source and sink for kinks of free volume that may travel through the sample on polymer loops (and bridges).This ‘imported’ free volume works against glassiness, and leads to a significant suppression of Tg. These models each capture some observed behavior, but not all. Future efforts are aimed at comprehensive model that is simple to execute, yet sophisticated in its predictions. 1. Keddie et al Europhys. Lett. 27 59 (1994) 2. With S.T. Milner: Model 1:Eur.Phys.J 72 133 (2009); Model 2: two manuscripts in review. The presence of substrate (left) enhances ‘glassiness’ (grey); a free surface inhibits it. Model 1 snapshot: note large glassy region at substrate, other large connected regions in blue. Model 2:sample chain in blue illustrates loops and bridges.

2. The Lipson group: a research home for women scholars at all stages 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 work here at Dartmouth, alone. Jutta Luettmer-Strathmann, a former postdoctoral fellow with the PI, is now an Associate Professor of Physics at the University of Akron. Former postdoctoral fellow Hannah Sevian is an Associate Professor as well as Associate Director for the Center of Science and Mathematics at the University of Massachussetts at Boston. Graduate student Virginia Anderson earned her Master’s degree at Dartmouth and is now a Ph.D. student in the Chemistry Department at the University of Colorado at Boulder. Meanwhile, current Ph.D. graduate student Elizabeth Clark is involved in research and undergraduate laboratory teaching here in the Chemistry Department at Dartmouth. With respect to undergraduates, Laura Muller joined the group as an NSF-REU undergraduate; she is now Associate Professor of Chemistry at Wheaton College. Lisa Hall, whose first foray into research was also in the Lipson group under the auspices of the NSF-REU program, recently earned her Ph.D. in the Materials Science and Engineering Department at the University of Illinois; and is now a scientist at Sandia National Labs. Kallie Willets, Dartmouth undergraduate and NSF-REU participant, undertook a senior major thesis with the PI and was a co-author on a paper resulting from that research. She went on to graduate and postgraduate studies, and is now Assistant Professor in the Chemistry Department at the University of Texas at Austin. Former group members currently work at a variety of institutions, ranging from research universities, to undergraduate colleges, to national labs. NSF’s investment in education and research collaboration creates opportunities for scientists at all levels to develop skills that are transportable to other environments. Studies on Polymer Glasses, Melts, and Solutions Jane E. G. Lipson, Dartmouth College, DMR 0804593