Nonlinear optical active polymethacrylates

Chromophore relaxation is still one of the major problems of NLO polymers. Two strategies have been developed to overcome this problem. One of them is crosslinking after poling. We synthesized new polymers with methylfuryl acryloyl side groups. Upon irradiation with UV- light, they undergo a (2 + 2) cycloaddition which leads to a highly crosslinked material. Compared to cinnamoyl gorups frequently used in such polymers, the absorption of the novel crosslinker is shifted to longer wavelengths. This allows to use a cutoff filter during irradiation and therewith minimizes chromophore decomposition. The second way to suppress chromophore relaxation is the use of polymers with high glass transition temperatuers. We have prepared a number of polymers by copolymerization of NLO-active methacrylates with the bulky adamantyl methacrylate. This leads to polymers with glass transition temperatures up to 190 degrees C. The synthesis and properties of these polymers are reported in detail. The polymers shown a good long term stability of the electro-optic coefficient (r33) with its relaxation approximately following a KWW-function.