Such comonomers include a vinyl cyanide monomer such as acrylonitrile or methacrylonitrile, an unsatulated carboxylic acid monomer such as acrylic acid, methacylic acid, itaconic acid or crotonic acid, a methacrylate monomer such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate or glycidyl methacrylate, a vinyl ether monomer such as methyl vinyl ether, ethy