Toughening of Methacrylate Networks through Addition-Fragmentation Chain Transfer

In the broad field of photopolymers three dimensional networks are formed by free-radical polymerization. These networks have to fulfill a variety of requirements including high reactivity of the monomers and good mechanical properties. During polymerization an inhomogeneous network forms, that decreases the mechanical properties of the polymer and makes it rather brittle. To overcome this disadvantage, chain transfer agents (CTAs), which regulate the polymer network are used. These CTAs turn the chain-growth polymerization into a mixed chain-step-growth polymerization, which leads to lower shrinkage stress and better mechanical properties. Especially the toughness of the polymers could be improved by a factor of up to ten without inhibiting the polymerization process.