1. School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, Ohio Aerospace Institute, 22800 Cedar Point Road, Cleveland, Ohio 44142, Department of Chemistry, University of MissouriRolla, Rolla, Missouri 65409, and Materials Division-Polymers Branch, NASA Glenn Research Center, 21000 Brookpark Road, M.S. 49-1, Cleveland, Ohio 44135