Nonlinear Optical Properties and Ultrafast Dynamics of a New Blue-Light Emitting Polymer

The nonlinear optical properties and the excited state dynamics of a new blue-light emitting polymer poly[5-(diphenylamino)-1,3-phenylenevinylene] (Yu1) and its starting material 5-(N,N-diphenylamino)benzene-1,3-dicarbaldehyde (Yu0) were studied. In contrast to the monomer Yu0, the two-photon absorption (TPA) properties of Yu1 were found to be significantly enhanced upon polymerization. The TPA cross section of Yu1 (per repeating unit) increased about tenfold compared to Yu0. Femtosecond pump-probe experiments were carried out to study the excited state dynamics of the two materials. An investigation of the ultrafast dynamics demonstrated that different relaxation processes occurred in the Yu0 and Yu1 samples. Apparent optical anisotropy was observed from a one-color pump-probe experiment of the polymer Yu1 at 400 nm. The fast component observed in the parallel configuration of Yu1 disappeared when the perpendicular polarization configuration was used because of the high orientation of exciton migration. The nonlinear optical study and the ultrafast dynamics results indicated that the onlinear optical properties were enhanced because of monomer polymerization.