Resin beads having an average particle size of from 0.001 mm to 10 mm and containing a continuous phase and a particulate dispersed phase are described. The continuous phase includes elastomeric polymers; the dispersed phase includes homopolymers and/or copolymers containing repeat units resulting from the polymerization of one or more aryl polymerizable monomers. The unexpanded polymer resin beads can be prepared by dispersing an organic phase containing elastomeric polymers and one or more monomers, into droplets and polymerizing the monomers in the organic droplets in a low shear flow pattern. The beads can be impregnated with blowing agents, expanded and can be used to make molded articles. Resin beads having a continuous phase comprising a nitrile rubber, and a dispersed phase comprising one or more homopolymers and/or copolymers containing repeat units resulting form the polymerization of one or more aryl polymerizable show prolonged retention of blowing agents in unexpanded form.