Synthesis of conjugated polymers with azobenzene moieties in the main chain

Poly(phenylenevinylene)-based conjugated polymers with azobenzene groups in the main chains were prepared by the Pd-catalyzed coupling polymerization of divinylarenes with dihaloarenes. The Pd-catalyzed coupling polymerizatio n of 4,4'-divinylazobenzene with dihaloarenes such as 1,3-dibromsbenzene, 1 ,4-dibromo-2,5-dihexylbenzene, 4,4'-dibromoazobenzene, and 4,4'-diiadoazobe nzene resulted in polymers with poor solubility. In contrast, soluble polym ers containing azobenzene moieties in the main chains were attain able from divinylbenzenes with 4,4'-dihaloazobenzenes if either or both of the monom ers possessed hexyl groups on the aromatic rings. The number-average molecu lar weight of the polymer exceeded 10,000 under optimized conditions, and t he polymer showed a remarkably redshifted absorption in the visible region (456 nm). H-1 NMR and TR spectra supported that the polymers having only tr ans-geometry for the double bonds. (C) 2000 John Wiley & Sons, Inc.