Entwicklung photosensitiver Polymernetzwerke mit Formgedächtniseigenschaften

In the present thesis a polymer system with shape-memory properties is developed. The shape-memory effect is triggered by irradiation of the polymer with UV-light with different wavelength. The irradiation causes a reversible change of network density of the elastomer. By that, the elastic properties of the material are changed in a way that the fixing of a temporary shape by UV-irradiation is possible. Irradiation of the fixed sample with another UV-light releases the fixing and the permanent shape of the polymer sample is recovered. Network-density of the elastomers is controlled by the light-induced [2+2]-cycloaddition of cinnamates. The synthesis of amorphous covalently linked polyacrylate networks is reported. Acrylate monomers containing cinnamic acid groups lead to photoreactive groups in polymer side- chains. Those monomers are prepared by esterification of hydroxyalkylacrylates and – methacrylates with cinnamic acid. The amorphous covalently linked polyacrylate networks are prepared by free-radical bulk polymerization of mixtures with different amounts of butylacrylate, hydroxyethylmethacrylate (HEMA), cinnamic acid groups-containing monomers and poly(propyleneglycol)dimethacrylate (Mw = 560) as cross-linker. To quantify the shape-memory properties a measuring method is established, which is able to determine mechanical properties of elastomers in cyclic photomechanical experiments. Shape fixity rates (Rf) up to 50% were realized. The shape recovery rate (Rr) was nearly 100%. Thermal and mechanical properties of the photosensitive networks are controlled by the composition of the polymer networks. The elastic properties of the networks are decreasing with an increasing content of cinnamic acid groups. Stiffening of the polymers is observed. The shape-memory properties are controlled by irradiation time and content of cinnamic acid groups.