Dynamics of Molecules in Complex Molecular Materials

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The aim of this project is to investigate the dynamics and intermolecular interactions in complex condensed matter molecular systems. A wide variety of materials will be studied, including glasses, supercooled liquids, liquid crystals, hydrogen bonded clusters, micelles, reverse micelles, polymers, and polymer micelles. Cynamics in complex molecular systems can span a wide range of time scales. Therefore, the experiments ae directed toward observations over a sufficiently wide range of times to provide a detailed picture of the dynamics. Ultrafast infrared vibrational echo experiments combined with infrared pump-probe experiments will be used to study vibrational dynamics which reflect the dynamics of the medium in which the vibrational oscillator is embedded and the nature of the intermolecular interactions that couple dephasing dynamics to be extracted from systems that are inhomogeneous, and, therefore, cannot be studied with convention linear spectroscopy. The vibrational echo studies will be extended to include other vibrational coherence experiments including stimulated vibrational echoes and various types of two dimensional vibrational echo experiments. Stimulated vibrational echoes will provide information on longer time scale dynamics, i.e., vibrational spectral diffusion. The first tow-dimensional vibrational echo experiments, Vibrational Echo Spectroscopy, was demonstrated in the previous grant period. This technique, which provides a method for the suppression of unwanted background absorptions in a vibrational spectrum, will be developed further. Two time 2D experiments that probe the coupling between different mechanical degrees of freedom will also be developed. Vibrational echo experiments, and the related non-linear vibrational coherence experiments, will be used to study dynamics in high temperature glass, supercooled liquids, water in the core of reverse micelles, hydrogen bonded clusters of water and alcohols in solvents, pure liquids, and proteins. Transient grating optical Kerr effect experiments, heterodyne amplified optical Kerr effect experiments, and a new method, density induced heterodyne amplified rotational dynamics, will be applied to the study of dynamics in complex molecular systems over vast ranges of time, from tens of femtoseconds to milliseconds and longer, Work during the current grant period has shown that a combination of these techniques, which provide tremendous dynamic range in signal and time, can provide fundamentally new information about the nature of complex systems. The techniques will be applied to supercooled liquids, micelles, polymer micelles, polymers, and liquids crystals.The emphasis in this study is on complex condensed matter systems such as supercooled liquids, micelles, polymer micelles, polymers, and liquids crystals and on the optimization of materials processing for applications such as optical flat panel desplay devices and structural materials.