Conformation of substituted poly-norbornene polymers studied by hyper-Rayleigh scattering at 1064 nm

Hyper-Rayleigh scattering with a conventional 1064 nm laser source is employed to study the conformation of substituted poly-norbornene polymers that contain the non-linear optical chromophores as pendant groups. The dispersion-free first-hyperpolarizabilities (β₀) of the polymers and pendant chromophores are determined and compared. A large enhancement of the β₀ values for the polymer samples is observed. Each of the chromophores is found to contribute 39% of its β₀ value to that of the polymer, in close agreement with the result of a simple calculation. This agreement supports the syndiotactic polymer conformation already predicted with the open-force-field calculation. Two-photon absorption-induced fluorescence (TPF) exists for most monomers but not for polymers in this study. The absence of TPF in the polymers may be due to the excited-state electronic interaction between pendant chromophores.