Rational designs of multifunctional polymers

To manifest photorefractive effects, a polymer must possess a photocharge generator, a charge transporter, a charge trapping center, and a nonlinear optical chromophore. We utilized the Stille coupling reaction to synthesize a novel type of multifunctional polymer that contains a conjugated backbone and a second-order NLO chromophore. The expectation that the polymers will possess photorefractivity is the design idea behind the structure of the polymers. Because the conjugated backbone absorbs photons in the visible region and is photoconductive, it is expected to play the triple role of charge generator, charge transporter, and backbone. Thus, the four functionalities necessary to manifest the PR effect will exist simultaneously in a single polymer. The second harmonic generation and the photoconductivity measurements revealed that the polymers are nonlinear-optically active and photoconductive. Two beam-coupling experiments clearly indicated asymmetric optical energy exchange, which is an unambiguous demonstration of photorefractivity.