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Due to the simple preparation technology and appropriate crosslinking process, polyurethane was selected as the host polymer for the preparation of organic electro-optics (EO) materials. The synthesis and crosslinking process of polyurethane demanded the nonlinear optical (NLO) chromophore possessing strong stability in acid environment. Fortunately, after the introduction of azo group in the electronic bridge, the stability of this kind of chromophores in acidic environment was improved greatly. Polyurethane EO polymers and EO films based on this kind of chromophore were prepared successfully. The crosslinking process was monitored by infrared spectroscopy clearly. The crosslinking process has direct relationship with the molecular weight of the crosslinkers. Crosslinker of triethanolamine with small molecular weight showed low crosslinking temperature (80 °C) and short crosslinking time (20 min). The crosslinking temperature and time was improved to 140 °C and 60 min based on Poly(bisphenol A glycidyl ether aniline) (BPAN) crosslinker with large molecular weight. More importantly, this kind of EO polymers showed us large second order nonlinear optical coefficients (76.1 pm/V) and good long term stability (130 °C). [ABSTRACT FROM AUTHOR]

A new series of Y-type polyurethanes containing different concentrations of nonlinear optical (NLO) chromophore with aniline donor and tricyanofurane (TCF) acceptor have been successfully prepared, and characterized by FTIR, UV-Vis, and 1H-NMR spectra. New polyurethanes were synthesized with different chromophore contents by introducing diol N, N-dihydroxyethylaniline or 4-[ N, N-(dihydroxyethyl)amino]benzaldehyde. These NLO polyurethanes exhibit good film forming property and high thermal stability up to 281°C. The highest electro-optic coefficient ( r33) of polymers is up to 39 pm V−1 measured by simple reflection technique at 1310 nm, and the temporal stability of the poling-induced order at elevated temperature of 80°C was much improved through the introducing of hydrogen bonding interaction in this system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Compared with traditional inorganic second-order nonlinear optical (NLO) materials, organic second-order NLO materials have many advantages in bandwidth, dielectric constant, half-wave voltage, electro-optic (EO) coefficients, processability, and material cost. Due to their potential applications in telecommunications, computing, detection, terahertz generation, and construction of functional photonic crystals, organic NLO materials have been widely studied for several decades. Currently, the poling efficiency and long-term stability are the largest obstacles for the application of organic NLO materials. At the molecular level, these problems are mainly caused by the strong dipole–dipole intermolecular interactions between the NLO chromophores with D-π-A structures. In the molecular design of the polymer system, modification of the chromophores is considered to be an efficient pathway to solve this problem. Since 2009, many studies have been performed by our group to reduce the strong dipole–dipole intermolecular interactions between the chromophores. In this review, the development of organic NLO materials in recent years is summarized, including the following: 1) a brief introduction of organic second-order NLO materials, 2) the requirements of NLO materials for applications in devices, 3) optimization of the first-order hyperpolarizability of NLO chromophores, 4) the optimization of the chromophore loading parameters (N, ), and 5) improvements of the stabilities of organic NLO materials. • Organic second order NLO materials was briefly introduced. • Requirements of NLO materials for applications in devices were discussed. • Optimized method for first-order hyperpolarizability and loading parameters of chromophore were discussed. • Method for improving stability of organic NLO materials was included. [ABSTRACT FROM AUTHOR]

Abstract: Novel organic second-order nonlinear optical (NLO) chromophore with a large flexible rigid isolated group was prepared. The NLO properties were measured in solution and PMMA polymer films. The first order hyperpolarizabilities were equal to 4×10−28 esu and 7×10−29 esu at 1064nm Nd:YAG laser wavelength in solvent and polymer, respectively and these results are in agreement with quantum chemical calculations. Moreover, this chromophore has high thermal stability when thermal decomposition temperature is 270°C. Electrostatic interactions of the chromophores were effectively reduced by isolated group. No apparent change of the shape of UV absorption spectra versus concentration was found. [Copyright &y& Elsevier]

Benchmark chromophore C1 and counterpart chromophore C2 with the same electron donor and acceptor was designed and synthesized to compare their different electro-optic coefficients and long term stability by doping system. The electro-optic coefficient of a poled film containing 25 wt% of C1 doped in amorphous polycarbonate (25 wt% C1 /APC) afforded a value of 22 pm/V at 1310 nm, while 25 wt% C2 /APC afforded a value of 60 pm/V. After annealing at 85 °C for 500 h, the poled film of 25 wt% C2 /APC could retain more than 85% of its initial r 33 value. In contrast, only 75% of the initial r 33 value of the poled film of 25 wt% C1 /APC was kept after 300 h. The excellent thermostability and its good temporal stability in APC made C2 a favorable candidate for practical application. [ABSTRACT FROM AUTHOR]

Abstract: A novel nunchaku-like organic second order nonlinear optical chromophore containing a D–π–A backbone and a rigid biphenylene unit was prepared. The UV–vis absorption spectra studies demonstrated that the large rigid structure could suppress dipole–dipole interactions effectively. The electro-optic coefficient of a poled film containing 20% wt of the new dye doped in amorphous polycarbonate afforded a value of 39 pm/V at 1310 nm. Compared with results obtained from a similar D–π–A chromophore without the rigid isolated group, the new dye gave better performance. Moreover, the electro-optic film prepared with the new dye gave greater temporal stability, compared to a similar D–π–A doped poled film that was reported previously. These results indicated that the introduction of a biphenylene group could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores. [Copyright &y& Elsevier]

One novel chromophore C based on 4,4′-bis(diethylamino) benzophenone donor and CF 3 -Ph-TCF acceptor was synthesized. Alkoxy isolation group was introduced also. Cyclic voltammetry measurements showed that the new chromophore C had a much smaller energy gap (ΔE = 1.25 eV) than chromophore A and B. UV–Vis absorption indicated that obvious red shift (more than 100 nm) obtained for chromophore C. The doped film C containing CF 3 -Ph-TCF chromophore showed a r 33 value of 235 pm/V at the concentration of 25 wt% which is much higher than that of the TCF based chromophore A (149 pm/V) and B (163 pm/V). The thermal stability were high enough (>200 °C) to be further fabricated in devices and good EO property make application possible. [ABSTRACT FROM AUTHOR]

Two novel bichromophores YL1 and YL2 based on traditional aniline chromophore YL were synthesized by Cu(I) catalyzed click-reaction and systematically investigated in this paper. The UV–Vis, electrochemical property, thermal stability and EO activity of these chromophores were systematically studied and discussed. These two bichromophores showed good thermal stability. Then nonlinear optical polymer films were fabricated by doping chromophores into polymethylmethacrylate (PMMA). The doped films containing bichromophores YL1 and YL2 showed r 33 values of 20 and 17 p.m./V at concentration of 25 wt% at 1310 nm. These values were respectively 2.85 times and 2.43 times of the EO activity of chromophore YL (7 p.m./V). High r 33 values indicated that the new structure of bichromophores YL1 and YL2 can reduce intermolecular electrostatic interactions, thus enhancing macroscopic EO activity. These properties suggested the potential use of the new bichromophores in nonlinear optical materials. [ABSTRACT FROM AUTHOR]

A series of high performance chromophores P1 P3, based on N -(4-dibutylaminophenyl) tetrahydroquinolinyl or julolidinyl donors, and phenyl-trifluoromethyl-tricyanofuran acceptors linked together via π-conjugation through thiophene or vinylene moieties as the bridges, have been designed and synthesized. Density functional theory (DFT) was used to calculate the HOMO-LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Chromophores P1 and P3 had good thermal stabilities with glass transition temperature higher than 110 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r 33 ) in poled polymers with rational chromophore designs. In electro-optic activities, the poled films of P1/APC, P2/APC and P3/APC afforded r 33 values of 223, 283 and 278 pmV −1 , respectively, at 1310 nm at the doping concentration of 25 wt%, which showed significant enhancement over the similar EO polymer systems previously reported. [ABSTRACT FROM AUTHOR]

Two series of highly efficient nonlinear optical chromophores A1-C1 and A2-C2 based on the julolidinyl donors and tricyanofuran or phenyl-trifluoromethyl-tricyanofuran acceptors (CF 3 -Ph-TCF) linked together via π-conjugation through thiophene or pyrrole or tetraene moieties as the bridges, have been synthesized and investigated. The ultraviolet absorption, solvatochromic, thermal stabilities and electro-optic activities of these chromophores were systematically studied to illustrate structure-performance relationships within the six chromophores. All the chromophores exhibited good thermal stabilities with the decomposition temperatures (T d ) higher than 200 °C. Appropriate combination of the π-conjugated bridge, electron-donor and electron-acceptor as well as the isolated group in the chromophores plays an important role in achieving larger electro-optic activities. Exemplified by the chromophore A2 with CF 3 -Ph-TCF acceptor, it gave a very large r 33 value of 223 pmV −1 at 1310 nm at the doping concentration of 25 wt%. [ABSTRACT FROM AUTHOR]

A novel chromophore based on N -(4-dibutylaminophenyl)tetrahydroquinolinyl donor group was synthesized to compare with traditional chromophores based on either diethylaminophenyl or triarylaminophenyl donor groups. Cyclic voltammetry measurements showed that the new chromophore had a much smaller energy gap than the structurally related chromophores. Density functional theory calculations suggested that the molecular quadratic hyperpolarizability (μβ) value of tetrahydroquinolinyl chromophore is 65% and 110% larger than that of either the diethylaminophenyl or triarylaminophenyl chromophores, respectively. The doped film containing the tetrahydroquinolinyl chromophore showed an r 33 value of 126 pm/V at the concentration of 25 wt% which is much higher than the electro-optic activity of the diethylaminophenyl derived chromophore (39 pm/V) and six times higher than that of the traditional triarylaminophenyl chromophore (19 pm/V). The tetrahydroquinolinyl chromophore possesses much higher thermal stability (with its onset decomposition temperature above 280 °C) than those of commonly used alkyl chromophores. [ABSTRACT FROM AUTHOR]

A series of second-order nonlinear optical chromophores containing an identical π-bridge and electron acceptor but different, aromatic amine electron-donating groups have been synthesized and systematically investigated. The donors studied here include traditional donors carbazole, triphenylamine and N , N -diethylaniline and novel donor phenothiazine, phenoxazine and N -(4-methoxyphenyl)phenoxazine. The ultraviolet absorption, solvatochromic, redox properties, density functional theory calculations, thermal stabilities and electro-optic activities of these chromophores were systematically studied to compare the strength of the donors and illustrate the structure–performance relationships within six chromophores. The results show that the new donors have stronger electron-donating ability than traditional donors. Moreover, they show reduced energy gap, much larger molecular quadratic hyperpolarizability (μβ) and r 33 value. Exemplified by the N -(4-methoxyphenyl)phenoxazine chromophore, it showed nearly three times higher μβ and more than four times higher r 33 value than that of the N -hexylcarbazole containing chromophore. [ABSTRACT FROM AUTHOR]

Two novel chromophores based on the phenoxazine (chromophore L1) or phenothiazine (chromophore L2) donor, and tricyanofuran acceptors linked together via thiophene as the bridges have been synthesized and systematically investigated. Cyclic voltammetry measurements showed that chromophore L1 had smaller energy gap than chromophore L2 due to the stronger electron-donating ability. Moreover, Density functional theory calculations suggested that the β value of chromophore L1 is 17% larger than that of chromophore L2. The doped film containing the chromophore L1 showed an r 33 value of 49 pm/V at the concentration of 25 wt% which is two times higher than the EO activity of the chromophore L2 (23 pm/V) and the traditional aryl chromophore (10–20 pm/V). High r 33 value, high thermal stability (onset decomposition temperatures higher than 220 °C) suggests the potential use of the new chromophore in nonlinear optical materials. [ABSTRACT FROM AUTHOR]