Senior seminar
November 19, 2009

Dynamics of glass forming liquids and polymer under hydrostatic pressure
By: Riccardo Casalini

Last seminar Dr Riccardo Casalini talked about glass formation under pressure. His research is focused on the concept of dielectric spectroscopy. Dielectric Spectroscopy, the measurement separates molecular process on the basis of response time, providing a unique relaxation frequency along with a signature variation with frequency. If an electric field is applied on dipoles, we get polarization. Broadband polarization was applied in time and frequency domains. Dr. Casalini talked abut how a sample can be analyzed when it is immersed into a high pressure cell in Dielectric spectrometer. In the broadband dielectric system under hydrostatic pressure and broad range of frequency the sample is analyzed. Dr. Casalini also talked abut the transition states of liquid to super-cooled liquids then to glass, which are the major phase transitions related in glass formation. At transition point’s temperature Tg, a laser light is applied to heat polymer materials. Using pressure as a constant variable and temperature as a changing variable it is possible to model the glass transition state. He used some mathematical models that he had tested on glass transition dynamics. In his lab more than seventy materials were identified or verified using thermodynamical scaling models. Moreover he talked about how Lenard Jones potential plot and soft-sphere potential can be used to verify repulsive forces that reside in intramolecular potentials and experimental evidences that depicted intramolecuar potentials for materials in their amorphous states.