• The preferred monovinylaromatic monomers are styrene and/or alpha-methylstyrene. [0117] A second group of monomers that may be polymerized in the presence of the polymeric backbone are acrylic monomers such as acrylonitrile, substituted acrylonitrile and/or acrylic acid esters, exemplified by acrylonitrile, and C1-C7 alkyl acrylates, such as methyl methacrylate, and the like. [0118] The acrylonitr