Synthesis Of Third-order NLO Material-Polyimide Under Microwave Irradiation And The Study Of Their Film Forming Properties

Pyromellitic dianhydride (PMDA) and Sodium tetrazodiphenyl-naphthionate (STDN), 1,4-diaminoanthraquinone (DAAQ) and Benzoguanamine (BGA) as aromatic diamines were selected to be polymerized under microwave irradiation. The effects of the reaction temperature, the concentration of monomers, the monomers ratio, and the microwave irradiation time(energy) on the intrinsic viscosity and the conversion were investigated. The third-order nonlinear optical(NLO) coefficient and the response time of the polycondensates were detected by the degenerated four wave mixing (DFWM) technique. The results show that the polycondensates have excellent NLO properties (x(3)max of PI 1.476 X 10-12esu, the fastest response time of PI is 15.79ps). Quantum calculations of the molecular energy gap and energy band w:ere performed by the Crsytal98 soft package, so the relation between the third-order NLO property and the molecule structure was interpreted in theory.Modification of the polycondensates through copolymerization and grafting were carried out under microwave irradiation. The solubility of the polymers was improved. The films of the modified polymers were obtained by spinning-coat method. The result showed the film forming properties of the polymers was improved after modified. The third-order of the NLO properties of the polymer solutions and the films were detected by DFWM technique. The third-order NLO coefficient of the films is large than that of the polymers solution.