vinyl propionate, and nitriles, more particularly those comprising from 3 to 12 carbon atoms, such as acrylonitrile and methacrylonitrile. [0098] Use is preferably made of the following monomers: [0099] styrene and styrene derivatives, such as ??-methylstyrene or vinyltoluene, [0100] vinyl nitriles, [0101] dienes, for example butadiene or isoprene. [0102] The term ???(meth)acrylic esters??? denote