NONLINEAR OPTICALLY-ACTIVE POLYMETHACRYLATES WITH HIGH GLASS-TRANSITION TEMPERATURES

A number of novel nonlinear optically (NLO) active polymethacrylates were prepared from the NLO active methacrylates 2a-d with azobenzene side groups and the bulky comonomer 1-adamantyl methacrylate. The polymers exhibit unusually high glass transition temperatures between 160 degrees C and 190 degrees C. The copolymerization parameters of the monomer pair 1-adamantyl methacrylate (1)/Disperse red methacrylate 2b (r(1) = 1,1 +/- 0,2, r(2) = 0,8 +/- 0,2) show that the two monomers are incorporated almost statistically into the polymer chain. Polymers 3a-d are soluble in common organic solvents and excellent films can be obtained by spin coating. After poling in an electric field of 120 V/mu m polymer 3b shows a large electrooptic (EO) coefficient (r(33)) of 25 pm/V at 633 nm. Within two weeks, only a negligible decay of 7% of the EO coefficient was observed at room temperature. On-line monitoring of the second harmonic generation (SHG) at 100 degrees C showed a fast initial drop (10%) of the SHG signal and subsequently a slow decay of 20% within 10 h. Afterwards, the signal remained almost constant for further 5 h at 100 degrees C. The novel polymers can thus be considered as easy processible NLO materials with a high thermal stability of the chromophore orientation obtained by poling.