The present invention relates to a polymerizable composition, comprising a) at least one compound of formula (I) (RG)--A--(Stab) (I), wherein (Stab) is a light stabilizer radical selected from the group consisting of sterically hindered amines, hydroxyphenyl-s-triazines, hydroxyphenyl-benzotriazols and o-hydroxy-benzophenones; A is a spacer group or a direct bond; and (RG) is a group containing at least one ethylenically unsaturated functional group; and either b1) a compound of formula (II) Y--X (II), wherein X represents a group having at least one carbon atom and is such that the free radical derived from X is capable of initiating polymerization and Y represents a group being such that the free radical Y.multidot. derived from it forms a stable free radical; or b2) a stable free radical Y.multidot. and a free radical source from which a radical is formed capable of initiating polymerization, or b3) a compound of formula (III) ##STR1## and a catalytically effective amount of an oxidizable transition metal complex catalyst, wherein p represents a number greater than zero and defines the number of initiator fragments; q represents a number greater than zero; [In] represents a radically transferable atom or group capable of initiating polymerization and -[Hal] represents a leaving group; and optionally c) one or more ethylenically unsaturated monomers or oligomers different from those of formula (I). Further subjects of the invention are a polymerization process, the polymers, copolymers oligomers and cooligomers obtainable by this process and the use of the polymers, copolymers oligomers and cooligomers as heat or light stabilizers.