D??? is selected from the group consisting of ???O???CsH2sO???tCr???H2r??????, ???CrH2r???, ???CsH2sO???tCr???H2r??????, and ???O???CrH2r???, where r and r??? are independently integers of 0 to about 12, s is independently an integer of 1 to about 10 for each (CsH2sO), and t is an integer of 1 to about 3;