Abstract: A novel soluble π-conjugated polymer, poly[(3-octanoylpyrrole-2,5-diyl)-p-nitrobenzylidene](POPNBE), was synthesized by a five-step reaction.As a result of introducing a long aeyl to pyrrole at 3-position, the polymer can be easily solved in polar solvents and be processed into films.The chemical structures of the intermediates and POPNBE were characterized by FTIR, ¹H NMR, and UV-Vis-NIR spectrometries.The absorption band in the range of 400-600 nm in the UV-Vis-NIR spectrum is due to the π-π^* band gap transition.The optical band gap of POPNBE obtained from the optical absorption is about 1.72eV.The resonant third-order nonlinear optical property of POPNBE at 532 nm was studied by using the degenerate fourwave mixing (DFWM) technique.The resonant third-order nonlinear optical susceptibility of POPNBE is about 3.42×10^-8 esu.

Key words: Poly[(3-octanoylpyrrole-2,5-diyl)-p-nitrobenzylidene], Small optical band gap, Degenerate four wave-mixing technique, Third-order non linear optical property