to assist with maintaining a relatively uniform suspension of monomer droplets within the suspending medium illustrative suspending agents are gelatin polyvinyl alcohol magnesium hydroxide hydroxyethylcellulose methylhydroxyethylcellulose methylcellulose and carboxymethyl methylcellulose other suitable suspending agents are disclosed in u s pat no 4 419 245 the amount of suspending agent used can vary widely depending on the monomers and suspending agents employed latex inhibitors such as sodium dichromate may be used to minimize latex formation polymerization of the first monomer reaction mixture may be conducted to a point short of substantially complete conversion of the monomers to copolymer or alternatively to substantially complete conversion if incomplete conversion is desired the resulting partially polymerized seed particles advantageously contain a free radical source therein capable of initiating further polymerization in subsequent polymerization stages the term u201c free radical source u201d refers to the presence of free radicals a residual amount of free radical initiator or both which is capable of inducing further polymerization of ethylenically unsaturated monomers in such an embodiment of the invention it is preferable that from about 20 to about 95 weight percent of the first monomer reaction mixture based on weight of the monomers therein be converted to copolymer and more preferably from about 50 to about 90 weight percent due to the presence of the free radical source the use of a free radical initiator in a subsequent polymerization stage would be optional for.