. "each occurrence of X2 and X3 is independently selected from the group consisting of hydrogen, R6, wherein R6 is a monovalent hydrocarbon group having from 1 to 20 carbon atoms, X1, wherein X1 is independently selected from the group consisting of ???Cl, ???Br, ???OH, ???OR6, and R6C(???O)O???, wherein R6 is a monovalent hydrocarbon group having from 1 to 20 carbon atoms, and ???OSi containing grou" . . .