侧链含偶氮苯发色团的聚酰亚胺薄膜的制备及其三阶非线性光学和光存储性能的研究

将4,4'-二氨基三苯甲烷(DTM)单体与均苯四甲酸酐(PMDA)进行缩聚反应,再与对-硝基苯基重氮氟硼酸盐进行重氮偶合反应,然后经酰亚胺化合成了侧链含偶氮苯发色团的聚酰亚胺非线性光学材料(NLOPI).通过红外光谱对产物进行了结构表征.对产物的紫外-可见吸收光谱研究发现,在330和490nm处出现侧链偶氮苯发色团的特征吸收.通过简并四波混频方法(DFWM)测定侧链含偶氮苯发色团的聚酰亚胺薄膜的三阶非线性极化率χ⁽³⁾=4.58×10^-18m²/W.在DFWM中,前向泵浦光I_f和探测光I_p是主要的写入光,而后向泵浦光I_b是主要的读出光.证实了光致偶氮分子的顺反异构能够导致光信息存储的特性.

Preparation, Third-order Nonlinear Optical Property and Optical Information Storage of Polyimide Attached with Azobenzene Chromophore Side-chain

Using aniline and benzaldehyde as raw materials, p,p'-diaminotriphenylmethane(DTM) was synthesized. Co-condensation type poly(amic acid) was prepared by using p,p'-diaminotriphenylmethane as the co-diamine monomer and pyromellitic dianhydride(PMDA) as the the dianhydride monomer. And then the nonlinear optical polyimide(NLOPI) attached with azobenzene chromophore side-chain was synthesized by diazo coupling reaction of 4-nitrobenzenediazonium tetrafluoroborate to poly(amic acid) in 1-methyl-2-pyrrolidone(NMP) and imidization reaction at 250 ℃. The designed chemical structure of production can be proved in the infrared spectrum and ultraviolet-visible absorption spectrum. The NLOPI exhibits UV-Vis absorption of the azobenzene chromophore at the wavelength of about 330 nm and 490 nm. The third-order nonlinear optical property of NLOPI was studied by degenerate four-wave mixing(DFWM). Third-order nonlinear susceptibility of NLOPI is 3.28×10-10 esu(4.58×10-18 m2/W). It is indicated that NLOPI has strong optical information storage through DFWM. Forward pumping light(If) and detecting light(Ip) are prime writing light, however backward pumping light(Ib) is principal reading light. It is proved that optical information storage can be caused by photo-induced trans-cis isomerization of azobenzene.