C7-C18 aryl-substituted alkyl, C2-C12 alkoxycarbonyl, C7-C18 aryloxycarbonyl, C8-C18 alkyl-substituted aryloxycarbonyl, C8-C18 aryl-substituted alkoxycarbonyl, nitrile, formyl, imidate, and thiocarboxylate; and wherein Y is a divalent group selected from the group consisting of wherein R14 and R15 are each independently selected from the group consisting of hydrogen and C1-C12 alkyl. 29.