molecular weight modifiers are employed particularly such as the mercaptan molecular weight modifiers can enjoy the application of our invention polymers prepared by suspension polymerization systems range from various resinous types such as polystyrene poly methyl methacrylate styrene acrylonitrile copolymers to elastomeric or rubbery types such as butadiene styrene copolymers or mixed polymers of the butadiene acrylonitrile type and the like monomeric starting materials may be employed or suspensions can be made of rubbery polymers such as polybutadiene or butadiene styrene copolymers dissolved in monomers such as styrene or styrene and acrylonitrile and the rubber in monomer solution placed in a suspension system for further co and graft polymerization of the polymerizable monomer onto the polymer monomers employed as monomeric materials in suspension polymerization systems include polymerizable monovinyl substituted aromatic compounds and other polymerizable monomers such as the nitriles esters of acrylic acids or of alkacrylic acids and vinyl esters such suspension system polymerizable monomers most commonly include the monovinyl substituted aromatic compounds of 8 to 20 carbon atoms per molecule vinyl nitriles of 8 to 20 carbon atoms per molecule alpha beta unsaturated nitriles esters of acrylic acid and vinyl esters of up to 20 carbon atoms per molecule and the like while polymerizable monomers such as the conjugated dienes are not employed as monomers in our suspension polymerization sytem these monomers commonly are employed in polymerization systems such as solution polymerization with organoalkali metal.