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cool to recover former density

Why do some thin polymer films melt so far below the bulk ? Jane E.G. Lipson, Dartmouth College, DMR 1104658. Bulk sample in the melt has a characteristic density at T. Bulk polymer goes from melt to glass at the glass transition temperature, T g . Changing to a thin film

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cool to recover former density

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  1. Why do some thin polymer films melt so far below the bulk ?Jane E.G. Lipson, Dartmouth College, DMR 1104658 Bulk sample in the melt has a characteristic density at T Bulk polymer goes from melt to glass at the glass transition temperature, Tg. Changing to a thin film sample can lower Tg by tens of degrees. The reasons for this are still not completely understood. top and bottom lose neighbours extract a slice from the middle cool to recover former density fewer interactions  film swells We have a very simple theory that starts with a model for polymer melts and blends in the bulk. It captures the experimental trends for polystyrene films. We are now working to extend it to other polymers and their mixtures, as well as layered polymers. Need to cool melt film to lower T than did the bulk in order to get glass Why is this important ?Tg is a key reference point for polymers. Lowering it may affect material behaviour over a wide range of T. A greater understanding of the physics behind the shift in Tg will allow us to optimize these materials for new applications. White & Lipson Phys. Rev. E 84 041801 ‘11; Data: J. Mattsson et al Phys. Rev. E 62, 5187 ‘00.

  2. Lipson Group Members Reaching OutJane E.G. Lipson, Dartmouth College, DMR 1104658 Lipson has begun working with a colleague in Media Studies at Dartmouth to involve undergrads in promoting fundamental science to the general public From our collaboration with Dame Julia Higgins of Imperial College (London) Research Associate Ron White has created new links between basic material properties and the tendency to form mixtures Graduate student Nick Tito participated in an American Chemical Society (ACS) student exchange to Germany; he also co-chaired the inaugural Gordon Research Seminar on Polymer Physics, and was part of the ACS Summer Institute, whose purpose was to “redefine how our science is published, distributed, and incorporated into the research and learning workflow The Lipson group welcomed 2nd year undergrad Amanda Cahoy to the group. She worked on glassy thin films and learned about polymers, and glasses, as well as how to use Mathematica

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