NONLINEAR OPTICALLY-ACTIVE POLYMETHACRYLATES WITH HIGH GLASS-TRANSITION TEMPERATURES

A number of novel nonlinear optically (NLO) active polymethacrylates w ere prepared from the NLO active methacrylates 2a-d with azobenzene si de groups and the bulky comonomer 1-adamantyl methacrylate. The polyme rs exhibit unusually high glass transition temperatures between 160 de grees C and 190 degrees C. The copolymerization parameters of the mono mer 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 i ncorporated almost statistically into the polymer chain. Polymers 3a-d are soluble in common organic solvents and excellent films can be obt ained 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 o f 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 f urther 5 h at 100 degrees C. The novel polymers can thus be considered as easy processible NLO materials with a high thermal stability of th e chromophore orientation obtained by poling.