t less than about 2000 obtained by removal of active hydrogen from an active hydrogen compound selected from the group consisting of water, alcohols, thiols, carboxylic acids, carboxylic amides and amines, where the functionality of R1 is n and is in the range of 1 to 10, where E is a divalent radical selected from the group represented by the formulae ##STR4## where X is selected from the group c