Fuyang Huo

Synthesis of novel nonlinear optical chromophores: achieving excellent electro-optic activity by introducing benzene derivative isolation groups into the bridge

Three novel second order nonlinear optical (NLO) chromophores based on julolidinyl donors and tricyanofuran (TCF) acceptors linked together via modified polyene π-conjugation with rigid benzene derivative steric hindrance groups (chromophore CL1 and CL2) or unmodified polyene π-conjugation (chromophores CL) moieties as the bridges have been synthesized in good overall yields and systematically characterized. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Besides, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. Compared with CL, after introducing benzene derivative steric hindrance groups into the bridge, chromophores CL1 and CL2 had good thermal stabilities with high thermal decomposition temperatures which were 32 °C and 24 °C higher than chromophore CL, respectively. Most importantly, the introduction of rigid steric hindrance groups can effectively reduce dipole–dipole interactions to translate their relatively small β values into bulk high EO activities. By doping chromophores CL, CL1 and CL2 with a high loading of 45 wt% in APC, EO coefficients (r33) of up to 121, 197 and 202 pm V−1 at 1310 nm can be achieved, respectively. The r33 values of new chromophores CL1 and CL2 were about 1.6 times of chromophore CL. The high r33 value, good thermal stability and high yield suggest the potential use of the new chromophores in an nonlinear optical area.

Synthesis of novel nonlinear optical chromophores: achieving enhanced electro-optic activity and thermal stability by introducing rigid steric hindrance groups into the julolidine donor

A series of chromophores z1–z4 have been synthesized based on julolidine donors modified by four different rigid steric hindrance groups including benzene, 2,3,4,5,6-pentafluorobenzene, 3,5-bis(benzyloxy)benzene and 3,5-bis(2,3,4,5,6-pentafluorobenzoate)benzene, respectively, with the same thiophene bridges and strong tricyanovinyldihydrofuran (TCF) acceptors and with high yields. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Besides, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. All these four chromophores showed superb thermal stabilities with high thermal decomposition temperatures above 265 °C. Most importantly, the introduction of rigid steric hindrance groups can effectively reduce dipole–dipole interactions to translate their relatively β values into bulk high EO activities. By doping chromophores z1–z4 with a high loading of 25 wt% in APC, EO coefficients (r33) of up to 99, 104, 97 and 89 pm V−1 at 1310 nm can be achieved, respectively. The normalized r33 value was increased to 6.84 × 10−18 pm cc per (V molecules) for z4 possessing the largest steric hindrance group which indicates the weakest dipole–dipole interaction and highest polarization efficiency. The high r33 value, good thermal stability and high yield suggest the potential use of the new chromophores in nonlinear optical areas.

A novel bichromophore based on julolidine chromophores with enhanced transferring efficiency from hyperpolarizability β to electro-optic activity

Novel bichromophores YL3 based on julolidine donor chromophores were synthesized via a Cu(I) catalyzed click-reaction and systematically characterized in this paper. YL3 showed good thermal stability, solubility and transparency properties. Besides, the high molecular hyperpolarizability of bichromophores YL3 can be effectively translated into large electro-optic coefficients. In electro-optic activities, the doped film YL3-amorphous polycarbonate (APC) showed an electro-optic coefficient (r33) of 183 pm V−1. This value is much more than the electro-optic (EO) activity of the monochromophore (114 pm V−1) with similar structure. This result meant that the new structure of bichromophores YL3 can reduce intermolecular electrostatic interactions, thus enhancing macroscopic EO activity. These properties suggested the potential use of the new bichromophores in nonlinear optical materials.

Enhancement of electro-optic properties of bis(N,N-diethyl)aniline based second order nonlinear chromophores by introducing a stronger electron acceptor and modifying the π-bridge

A series of highly polarizable chromophores y1, y2, yz1 and yz2 based on the same bis(N,N-diethyl)aniline donor, a tricyanofuran acceptor (TCF) and a CF3-Ph-TCF acceptor linked together via thiophene and modified thiophene π-conjugation have been synthesized and are systematically investigated in this paper. Density functional theory (DFT) calculations suggested that the molecular quadratic hyperpolarizability (β) value of the CF3-Ph-TCF based chromophore is 16.8% (yz1 compared with y1) and 46.8% (yz2 compared with y2) larger than those TCF based chromophores. These chromophores showed good thermal stability and their decomposition temperatures were all above 230 °C. Compared with the results obtained from the chromophores (y1 and y2) with the TCF acceptor, the new chromophores (yz1 and yz2) with the CF3-Ph-TCF acceptor show better intramolecular charge-transfer (ICT) absorption (108 nm and 97 nm red-shift). By doping chromophores y1, y2, yz1 and yz2 with a high loading of 25 wt% in amorphous polycarbonate (APC), electro-optic (EO) coefficients (r33) of up to 149, 139, 142 and 252 pm V−1 at 1310 nm can be achieved, respectively. A normalized r33 value of 15.57 × 10−18 pm cc per (V molecules) and an order parameter of (Φ) up to 27.3% was obtained for yz2 possessing the bis(N,N-diethyl)aniline donor, the alkoxy chain modified thiophene bridge and the CF3-Ph-TCF acceptor, which indicated that the structure–property relationship was essential. The high r33 value, good thermal stability and high yields suggest the potential use of new chromophores in a nonlinear optical area.

Synthesis and characterization of two novel second-order nonlinear optical chromophores based on julolidine donors with excellent electro-optic activity

Julolidine and its derivatives are excellent electron-rich structures thus two novel second order nonlinear optical (NLO) chromophores based on julolidine donors and tricyanofuran (TCF) acceptors linked via isophorone bridge (zh-1) and modified isophorone bridge (zh-2) have been synthesized. Density functional theory (DFT) was used to optimize the geometrical structures, calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Besides, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. The optimized structures suggest that chromophore zh-1 possesses better planarity which increases the ability of electron delocalization. These chromophores showed good thermal stability with their decomposition temperatures all above 210 °C. The electro-optic coefficients (r33) of poled films containing 25 wt% of these chromophores doped in amorphous polycarbonate (APC) afforded values of 170 and 101 pm V−1 at 1310 nm for chromophores zh-1 and zh-2, respectively. These properties show the potential use of the new chromophores as advanced material devices.

Low-voltage polymer-stabilised blue-phase liquid crystals with oleic acid (OA)-modified LaF3 nanoparticles

ABSTRACT The resultant oleic acid (OA)-modified LaF3 (OA-LaF3) NPs were easily dispersed well in common organic solvents or liquid crystals (LCs). Usually, the stability of BPs depends on a well-arranged double-twisted alignment and a stable defect. Theoretical simulation shows that the BPLCs is likely to trap the doped nanoparticles due to the elastic interactions.By means of the OA-LaF3 NPs we synthesized and doping into conventional polymer-stabilized blue phase liquid crystals (PS-BPLCs), it was observed that the on-state voltage can be reduced by 41% when the PS-BPLCs doped with 0.8wt. % OA-LaF3 NPs compared with that PS-BPLCs without OA-LaF3 NPs. It showed significant effects on the driving voltage when doping OA-LaF3 NPs to PS-BPLCs. Our studies will certainly provide an effective and simple method to stabilize cubic BP structures and improve the electronic-optical performances, leading to potential applications in areas of displays as well as optoelectronic devices. Graphical Abstract

Influence of monomer structure on the properties of blue phase liquid crystal

ABSTRACT In this paper, four kinds of polymer-stabilized blue phase liquid crystals (PS-BPLCs) with different monomer were designed and prepared. The morphology, temperature ranges and electro-optical properties of the blue phase were studied and discussed. The temperature ranges of four BPLCs are more than 90°C, and all samples can be stabilized well at room temperature. Referring to electro-optical performance, on-state voltage for mono-functional monomers systems is reduced from 75 V to 65 V at 497 nm. On-state voltage for tri-functional monomers systems is reduced from 107 V to 85 V at 497 nm. These results are helpful to the application of display and photonic devices. GRAPHICAL ABSTRACT