Investigation of Structure and Dynamics in Novel Nanocomposite Membranes Douglass S. Kalika, Department of Chemical & Materials Engineering, University of Kentucky, Lexington, KY 40506 The incorporation of nanoscale particles in polymer membranes has the potential to enhance gas separation performance. In this project, working in collaboration with Prof. Benny Freeman at the University of Texas at Austin, we have undertaken a series of fundamental studies to elucidate the chemical and physical factors that govern morphology, polymer dynamics, and gas transport in model rubbery and glassy nanocomposites. The work has focused on two systems: CO2-selective nanocomposite membranes prepared via in-situ polymerization of polyethylene oxide network polymers [XLPEGDA], and polyetherimide nanocomposites formulated with modified silica particles. Dynamic mechanical analysis and broadband dielectric spectroscopy have been used to fully characterize the relaxation properties of the nanocomposites as a function of particle surface chemistry, formulation conditions and loading. Gas transport studies on the in-situ polymerized rubbery polymers revealed a decrease in permeability as a function of loading, although the introduction of diluents during crosslinking produced a modest enhancement. The dramatic increases in permeability observed previously for rubbery nanocomposites prepared by solvent-casting were not observed for the in-situ crosslinked network polymers. ACS Fall 2007