| With information age coming, development of science makes people show more attention on the optical functional materials. Two photon absorption (TPA) materials is one of them. It enjoys huge application prospects, such as optical limiting, optical storage, optical switch, optical polymerization, optical image and optical computing and so on. Two photon materials are required for big two photon absorption cross section and high two photon quantum yield in practical applications. Organic non linear optical material catches people’s attention, for not only its good property but also easy modification. Nowadays it is popular to find an organic two photon materials with big TPA cross section in the field of physics, chemistry and material science.In this paper, we mainly study the two photon absorption molecules and polymers with2,5-dioctylpyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione (DPP), triazine and bithiazole group. Moreover, AIE effect was found in the TPA materials. The result provides a useful guideline for the design of efficient TPA materials.In Chapter1, definition and principle of two photon absorption material were introduced. The characteristic and it’s applications in different field were mentioned as well. The design ideas were presented on that basis.In Chapter2, a new series of long wavelength compounds with2,5-dioctylpyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione (DDP) as core, different electronic donors and π-bridge structures was synthesized. The TPA cross section of those five compounds is45,51,534,754, and1056GM for DPP1to DPP5, respectively. It was found that with the different donors, those which provide higher inter molecular charge transfer show larger TPA cross section. Stronger donor and better conjugate structure provide better property. Combining them together would be the best. In addition, the optical limiting behaviors for these chromophores were studied by using a focused800nm laser beam of140fs duration. It was found that these molecules also exhibit good optical-limiting properties.In Chapter3, a novel hyperbranched polyyne (hb-DPP) with triphenylamine as the core,2,5-dioctylpyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) as the connecting unit has been designed and synthesized by Glaser-Hay oxidative coupling reaction, which was characterized by IR, NMR and UV. The polymer exhibits high molecular weight (Mw up to-6.55×104Da) and is readily soluble in common organic solvents such as toluene, chloroform, tetrahydrofuran, N, N-dimethyl formamide and so on. The one-and two-photon absorption properties have been investigated. The two-photon absorption cross section of the polymer was performed by open-aperture Z-scan experiment using120femtosecond (fs) pulse, and the two-photon absorption cross section was determined to be579GM per repeating unit at800 nm. In tetrahydrofuran, hb-DPP exhibits intense frequency up-converted fluorescence under the excitation of120fs pulses at800nm with the peaks located at584nm.In Chapter4, five new multi-branched two-photon absorption triazine chromophores (T1-T5) with different donor strength, conjugation length and the direction of charge transfer have been designed and synthesized. The one-photon fluorescence, fluorescent quantum yields and two-photon properties have been investigated. The two-photon absorption cross sections measured by the open aperture Z-scan technique were determined to be447,854,1023,603, and766GM for T1, T2, T3, T4, and T5, respectively. This result indicates that their TPA cross section values increase with increasing electron-donating strength of the end group, extending the conjugation length of the system, introducing electron-withdrawing perfluoroalkyl as side groups to the end donor and making charge transfer from the center of the triphenylamine to the triazine ends. Moreover, significant enhancement of the two-photon absorption cross-section was achieved by fusing a thiophene moiety onto conjugating C=C bond. In addition, the optical limiting behaviors for these chromophores were studied by using a focused800nm laser beam of140fs duration. It was found that these molecules also exhibit good optical-limiting properties. These initial results clearly demonstrate that multi-branched triazine chromophores are a highly suitable class of two-photon absorbing materials.In Chapter5, three novel hyper branched copolymers (J1-J3) were synthesized. They are with2,4,6-tri(p-tolyl)-l,3,5-triazine as core, triphenylamine as branch and end up with diffident terminal groups (acetaldehyde for Jl,2-(ethyl(4-(prop-l-en-l-yl)phenyl)amino) ethanol for J2, and N,N-diphenyl-4-(prop-l-en-1-yl)aniline for J3). The optical and two photon properties have been studied. All of the polymers show large two photon absorption cross section (1007,2069and426GM for J1, J2and J3, respectively). It suggests both electronic acceptor and donor as terminal groups can enhance the TPA cross section of the polymers. Moreover, strong electronic donor is the best.In Chapter6, two new AIE-active multibranched molecules containing the2,4,6-tri(p-tolyl)-1,3,5-triazine centre were synthesized and characterized. They are AIE-active molecule:virtually invisible in common organic solvents while highly emissive in the UV-blue band in the aggregation state. The on-off fluorescence switching behavior of TAPA-a and TAPA-b thin layer can be utilized for the sensing of organic vapors. Photophysical measurements indicate that introduction of multibranched donor can enrich the electron density of the system, and a change in the end group can modify the optical properties. Preliminary studies show that these TAPA-based multibranched molecules exhibit very large TPA cross-sections (4500-8629GM). This result provides a useful guideline for the design of efficient TPA materials with AIE properties.In Chapter7, two new linear and hyperbranched conjugated polymers PI and P2have been synthesized by Sonogashira coupling reaction, in which the main chain consists of bithiazole moieties as electron acceptors and triphenylamino groups as donors. The conjugated polymers were characterized by TGA, UV-vis absorption, fluorescence emission, electrochemical cyclic voltammetry, and two-photon absorption measurements. They exhibited excellent solubility in organic solvents and high thermal stability (5%of weight loss at299℃). The two-photon absorption cross sections measured by the open aperture Z-scan technique using140femtosecond (fs) pulse were determined to be1014and552GM per repeating unit for P1and P2, respectively. This result shows that the TPA cross section of linear conjugated P1is higher than that of hyperbranched P2, indicating that the linear polymer offers better intramolecular charge transfer ability. P1and P2exhibit intense frequency up-converted fluorescence under the excitation of140fs pulses at800nm in THF with the peaks located at580and548nm, respectively. Meanwhile, the optical limiting behaviors for the polymers were studied by using a focused800nm laser beam of140fs duration. It was found that these polymers also exhibit good optical-limiting properties and make them potential candidates for optical limiters in the photonic fields. |
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