Water soluble amphiphilic heteratom star polymers and their use as emulsion stabilizers in emulsion polymerization

A amphiphilic heteroarm star polymer stabilized aqueous emulsion composition comprising (a) from about 10% to 80% by weight of a polymer derived from an emulsion polymerizable ethylenically unsaturated monomer or monomers;

• (b) from about 0.1 to 20% by weight of an amphiphilic heteroarm star polymer;
• (c) from about 0.01% to 1% by weight of a free radical polymerization initiating agent;
• and (d) the remainder water and optionally a buffering agent, wherein the heteroarm star polymer comprises a mercaptan core and one or more compatible vinyl monomers wherein the core is of the general formula:
• X-(Y.sub.1 -SH).sub.a (Y.sub.2 -SH).sub.b (Y.sub.3 -SH).sub.c (Y.sub.4 -SH).sub.d (Y.sub.5 -SH).sub.e (Y.sub.6 -SH).sub.f (Y.sub.7 -SH).sub.g (Y.sub.8 -SH).sub.h
• wherein X is derived from an organic radical having a valence of 3-8;
• Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4, Y.sub.5, Y.sub.6, Y.sub.7 and Y.sub.8 are the same or different and each comprise C.sub.2-10 alkanoic acids where a, b, c, d, e, f, g, h are integers from 0-8, provided that 3.ltoreq.a+b+c+d+e+f+g+h.ltoreq.8;
• and at least one of the compatible vinyl monomers comprise a functional group selected from the group consisting of hydroxyl, amine, carboxylic acid or amide group.