polymer additive being represented by the general formula: ##STR6## wherein X is an integer of 1 to 1000, inclusive, preferably 2 to 100; n is an integer having an average value of 1 to 100, inclusive, preferably 5 to 40; a is an integer having an average value of 1.1 to 100; m is 1; Y is an integer of 1 to 1000, inclusive, preferably 5 to 12; E is a member selected from the group consisting of hy