TY - JOUR A1 - Pietsch, Ullrich A1 - Bhattacharya, M. K. A1 - Sanyal, M. K. A1 - Geue, Thomas T1 - Glass transition in Ultrathin Polymer Films : a Thermal Expansion Study N2 - The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T-g) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T-g was found to be very small. The existence of reversible negative and positive thermal expansion below and above T-g increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T-g variation as a function of depth expected from sliding motion could explain the results Y1 - 2005 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Bhattacharya, M. K. A1 - Mukherjee, M. A1 - Sanyal, M. K. A1 - Geue, Thomas A1 - Grenzer, Jörg T1 - Energy dispersive x-ray reflectivity technique to study thermal properties of polymer films Y1 - 2003 ER - TY - JOUR A1 - Mukherjee, M. A1 - Bhattacharya, M. K. A1 - Sanyal, M. K. A1 - Geue, Thomas A1 - Grenzer, Jörg A1 - Pietsch, Ullrich T1 - Temperature dependent thickness and surface tension of polymer films Y1 - 2000 SN - 81-7371295-6 ER -