1. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6393; Department of Chemical Engineering, College of Engineering, Florida Agricultural and Mechanical University and Florida State University, Tallahassee, Florida 32310; Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306; Baytown Polymers Center, EXXON Chemical Company, Baytown, Texas 77522