含偶氮侧链聚酰胺酸合成及其三阶非线性光学性能

Synthesis and Three-order Nonlinear Optical Properties of Polyamic Acid Modified with Azo Side-chain

选取苯代三聚氰胺(BGA)和均苯四酸二酐(PMDA)为单体进行微波辐射溶液聚合反应,所得聚酰胺酸(PAA)通过重氮偶合反应引入含偶氮键的侧链,并且通过二次偶合进一步增加偶氮侧链的长度,从而合成新的具有三阶非线性光学活性的侧链型聚合物。通过红外、紫外、元素分析、拉曼等测试方法对接枝聚合物的结构进行了表征。通过简并四波混频飞秒激光系统对各个接枝聚合物的三阶非线性极化率系数进行了测定,考察了含取代基的偶氮侧链的引入对聚合物主链三阶非线性的影响,并考察了侧链上偶氮键的共轭长度对主链三阶非线性的影响。结果表明,侧链上偶氮基团的引入及其长度对提高聚合物主链三阶非线性都具有一定的影响。

P-π conjugated polyamic acid (PAA) was synthesized by the poly-condensation of benzoguanamine (BGA) and pyromellitic dianhydride (PMDA) under microwave irradiation. Then PAA was grafted with azobenzol side-chain through azo coupling reaction. The synthesized new PAAs with nonlinear optic (NLO) side-chain were characterized by FT-IR, UV-Vis, elemental analysis, 1HNMR and Fourier transform Raman spectrum (FTRR). The third-order optical NLO coefficient and response time of the polymers were measured by a phase conjugate forward, 3-dimensional degenerate, four-wave mixing (DFWM) technique. Comparing those polymers' third-order NLO coefficients measured, it is found that the X(3) value increases with the introduction of the azobenzol side-chain, and the length of azobenzol side chain can affect the X(3) value of polymer obviously. When the polymer bone is grafted with azobenzol side chain, the P-π conjugated system is extended and the fluidity of electrons is enhanced. It is also beneficial to increase polymers' third-order NLO coefficients.