1. Departamento de Ciencia de los Materiales, Grupo de Polímeros USB, Apartado 89000-A, Caracas, Venezuela; Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu 30013, Taiwan; National Synchrotron Radiation Research Center, Hsin-Chu 300, Taiwan; and Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431