Abstract: A novel soluble π-conjugated polymer, poly[(3-octanoylpyrrole-2,5-diyl)-p-(N,N-dimethylamino)benz ylidene] (POPDMABE), was synthesized firstly by the condensation of 3-octanoylpyrrole with paradimethylaminobenzaldehyde.The chemical structure of the polymer was characterized by FTIR and ¹H NMR spectrometries.The polymer is a potential nonlinear optical(NLO) material.According to the function of optical forbidden band gap(E_g) and photon energy(hv), the optical forbidden band gaps of the polymer before and after ion implantation were calculated.The resonant third-order nonlinear optical properties of POPDMABE before and after ion implantation were also studied by using the degenerate four-wave mixing (DFWM) technique at 532 nm.When the energy is 25 keV and the dose is 2.2×10¹⁷ ions/cm², the polymer's optical forbidden band gap is about 1.63 eV which is smaller than that of the non-implanted sample (1.98eV) and the resonant third-order NLO susceptibility of POPDMABE is about 4.3×10^-7 esu, 1 order of magnitude higher than that of the non-implanted sample(4.1×10^-8 esu).The results show that nitrogen ion implantation is an effective method to improve the resonant third-order NLO property of the polymer.

Key words: Poly[(3-octanoylpyrrole-2,5-diyl)-p-(N,N-dimethylamino)benzylidene], Ion implantation, Optical forbidden band gap, Resonant third-order nonlinear optical property, Degenerate four-wave mixing technique