where (x) represents the degree of polymerization (i.e. 10-2,300) or number of repeating units in the polymer chain and is dependent on the molecular weight of the polymer, (n) is zero or a positive integer, (A) is a capping group as defined herein, i.e. an --H, amino, carboxy, halo, C1-6 alkyl or other activating group and (A') is the same as (A) or another (A) moiety.