取代基结构对聚[(3-烷基)噻吩-2,5]-取代苯甲烯衍生物三阶非线性光学性能的影响

Effects of Substituents on the Third Order Nonlinear Optical Properties of Poly[(3-alkylthiophene-2,5-diyl)- (benzylidenequinomethene-2,5-diyl)] Derivatives

采用3-烷基噻吩与对硝基苯甲醛和对二甲氨基苯甲醛的聚合反应得到了5种聚(3-烷基)噻吩取代苯甲烯衍生物:聚(3-丁基)噻吩对硝基苯甲烯(PBTNBQ)、聚(3-己基)噻吩对硝基苯甲烯(PHTNBQ)、聚(3-丁基)噻吩对二甲氨基苯甲烯(PBTDMABQ)、聚(3-己基)噻吩对二甲氨基苯甲烯(PHTDMABQ)和聚(3-辛基)噻吩对二甲氨基苯甲烯(POTDMABQ).计算其光学禁带宽度分别为PBTNBQ(1.82eV),PHTNBQ(1.85eV),PBTDMABQ(1.71eV),PHTDMABQ(1.78eV)和POTDMABQ(1.67eV).利用简并四波混频技术测量了5种聚合物薄膜的三阶非线性极化率,分别为1.74×10-8,1.82×10-8,5.62×10-9,8.64×10-9和1.22×10-8esu,均具有较大的三阶非线性光学性能.针对取代基结构对聚(3-烷基)噻吩取代苯甲烯衍生物的三阶非线性光学性能的影响从分子内极化程度和主链电子的离域程度两个方面进行了讨论.

Five poly[(3-alkylthiophene) benzylidenequinomethene] derivatives: poly[(3-butylthiophene-2,5-diyl)-(p-nitrobenzylidenequinomethene-2,5-diyl)](PBTNBQ), poly[(3-hexylthiophene-2,5-diyl)-(p-nitrobenzylidenequinomethene-2,5-diyl)](PHTNBQ), poly[(3-hexylthiophene-2,5-diyl)-(p-N,N-dimethylamino)-benzylidenequinomethene-2,5-diyl](PBTDMABQ), poly[(3-hextylthiophene-2,5-diyl)-(p-N,N-dimethylamino)benzylidenequinomethene-2,5-diyl](PHTDMABQ) and poly[(3-octylthiophene-2,5-diyl)[(p-N,N-dimethylamino)benzylidenequinomethene-2,5-diyl](POTDMABQ) were synthesized. According to the function of band gap and energy of the incident photons, the band gaps of these polymers are calculated as 1.82, 1.85, 1.71, 1.78 and 1.67 eV, respectively. The homogenous films of these five polymers are prepared and their third-order nonlinear optical properties are studied with the backward degenerate four-wave mixing(DFWM) at 532 nm. By using the relative measurement technique, the third-order nonlinear optical susceptibilities of PBTNBQ, PHTNBQ, PBTDMABQ, PHTDMABQ and (POTDMABQ) films are measured as big as 1.74×10^(-8), 1.82×10^(-8), 5.62×10^(-9), 8.64×10^(-9) and (1.22×)10^(-8) esu respectively. It is found that the substitutents have a strong effects on nonlinear optical properties of poly[(3-alkylthiophene) benzylidenequinomethene] derivatives, the effects of substituents on the third order nonlinear properties of poly-[(3-alkylthiophene) benzylidenequinomethene] derivatives are illuminated with the delocalization degree of conjugated π electronics and the polarity of the polymers.