Abstract
AbstractSecond-order nonlinear optical(NLO) materials have attracted interest because of their potential application in optoelectronic technology. Organic polymer system have emerged in recent years as a new class of promising because they offer the flexibility, both molecular and bulk levels, to optimized the nonlinearity and other required properties for device application. However, some crucial issue such as thermal stability, temporal stability of dipole orientation and high frequency doubling efficiency are important challenge to materials scientists. In this work, a series of NLO polymer architecture have been designed. Thermal stability, temporal stability and frequency doubling efficiency made a leap in these NLO polymers designed.Highly thermal stability of Two dimensional nonlinear optical polyimideA new NLO-active lambda-shape main-chain polyimide containing the two-dimensional carbazole chromophore has been synthesis. This polyimide overcomes some drawbacks of head-to-tail type main-chain NLO polymers. It can be dissolved in many aprotic solvents and the thin film easily aligned under corona poling process to generate large d33 (17.2 pm/V) value. This polyimide exhibits high thermal and temporal stability. it can endure as high as 240 oC in a transient time and maintain large SH signal at 100 oC for a long time. This is due to the fact that embedding the two-dimensional chromophores onto a fully aromatic polyimide backbone effectively hinders randomization of the oriented dipole at high temperature.Fully conjugated side chain nonlinear optical polymerMost NLO organic materials are based on an aromatic π-electron system asymmetrically end-capped with electron-donating and electron-accepting electrons. Structural relationships indicate that β increases with π-conjugating length or the use of stronger electron-donating or electron-accepting moieties. Therefore, increasing conjugation length has been the usual method of modeling NLO materials. A new strategy for the self-polymerization of chromophores is investigated to develop a 2,7-carbazole-based nonlinear optical (NLO) conjugated polymer with an increasing conjugation length of chromophores. Elongation the conjugation path length in chromophores is established engineering guidelines to enhance optical nonlinearity. Compared with traditional synthesis of NLO polymer, the chromophores should be well designed at a limited conjugation spacer then incorporated into polymer matrix. Furthermore, this study marks the first research of integrating the π-electrons of chromophores and conjugated polymer. Integrating the π-electron of chromophores into the conjugated polymer provides more opportunity for simultaneously optimizing macroscopic nonlinear optical activity and temporal stability, than are associated with general NLO polymers. In an NLO conjugated polymer system, the rigid aromatic main chain may provide a high Tg, effectively suppressing the relaxation of the NLO chromophores-polymer system. Additionally the conjugated polymer parts increase the nonlinear optical coefficient. This kind of NLO polymers exhibit more potential in Electro-optic devices.Highly efficiency fully conjugated main chain nonlinear optical polymerRecent progress in developing highly efficient nonlinear optical polymers for high-performance electro-optic (EO) devices has been published. Our efforts are focused on conjugation extension on perpendicular the dipole moment of chromophore. To realize the different extention system of macro-chromophores, we observed the first hyperpolarizabilities of these macro-chromophores by solvatochromism method. The result showed that first hyperpolarizabilities would increase via extension of conjugation length without disrupted by effective conjugation length. Moreover, these integrating π-electron of chromophores into the conjugated polymer main chain system form three dimensional hollow annularity structures. Spatial isolation from the three dimensional structures decreases chromophore-chromophore electrostatic interaction As result, these fully conjugated main chain nonlinear optical polymer exhibit the excellent nonlinear optical properties may attribute the high efficiency first hyperpolarizabilities in microscopic level and site-isolation of macro-chromophores in macroscopic level.