Polarized-light-induced enhancement of the electro-optic properties in a photoreactive maleimide copolymer

A photocrosslinkable maleimide copolymer has been synthesized using a tricyanopyrrolidene (TCP)-based chromophore. The 2-(3-Cyano-4-(2-{4-[hexyl-(6- hydroxy-hexyl)-amino]-phenyl}-vinyl)-5-oxo-1-{4- [4- (3-oxo-3-phenyl-propenyl)- phenoxy]-butyl}-1,5-dihydro-pyrrol-2-ylidene)-malononitrile chromophore (DHATCP-CH) exhibits nonlinear optical activity and contains a chalcone moiety that is highly sensitive to UV light for crosslink formation. The maleimide monomer was also functionalized with chalcone moieties. The electro-optic signal can be varied under irradiation with linearly polarized light. The enhancement of the electro-optic effect in the copolymer is attributed to an angular selective photocrosslink formation upon illumination with p-polarized UV light. A possible mechanism that can explain this phenomenon is presented.