Synthesis of Main-chain Polyimides Containing Azoaryl and Their Third-order NLO Properties

摘要

A series of main-chain polyimides containing azo aryl with different substituted groups have been synthesized by a condensation of corresponding N, n-dichloroethylaminoaryl azo compounds with 4,4'-(hexafluoroisopropylidene) diphthalic bis-imide in an alkaline DMF solution, which have high thermal stability and good solubility in organic solvents. The third-order NLO measurements made with Z-scan technique at 532 nm indicate that the polyimides containing p-nitrophenylazo and nitrobenzothiazole azo group (P2 and P3) have larger third-order nonlinear absorption coefficient (β) and the nonlinear refractive coefficient (n_2).