•Four chromophore have been synthesized and systematically investigated.•There is a best match for donor and acceptor to improve nonlinear optical activity.•Chromophore d3 displayed excellent solubility and compatibility with matrix.•The poled film afforded a large r33 value of 37 pm/V after poling.In this work, a series of novel second order nonlinear optical chromophores modified by heteroatom-groups in electron-donor has been synthesized and systematically investigated. The resulting nonlinear optical chromophores exhibited both good thermal stability and good solubility in common organic solvents. UV–Vis spectra and density functional theory calculations were carried out to investigate the influence of heteroatom-groups on the electro-optic activities. The results revealed that increasing the electron-donor strength will not always improve the nonlinear optical activity of chromophore. There is a best match for electron-donor and acceptor. As to electro-optic activities, the doped polymer film-d3 displayed the highest electro-optic coefficient value of 37 pm/v at the doping concentration of 25 wt%. These results indicated that the nonlinear optical activities could be enhanced by finding the best match for electron-donor and acceptor in chromophore design.

In this work, we firstly provided a simple work-up procedure to prepare a new kind of electro-optical dendrimer with an asymmetric configuration via a Cu-(I) catalyzed Huisgen-reaction. The resulting NLO dendrimers exhibited both good thermal stability and good film-forming ability. In order to investigate the influence of the asymmetric configuration on the electro-optic (EO) activities, UV-vis spectra, density functional theory (DFT) calculations and EO performance were studied. Due to their asymmetric spherical structure, two dendrimers showed weak dipole–dipole aggregation compared with traditional dendritic electro-optical materials (DESD), but they achieved better alignment after each poling process was carried out. As expected, HJ-2 exhibited 41 pm V−1 in an EO coefficient test, which was higher than DESD and the guest–host polymeric system (C2 + PMMA) using the same chromophores.

Two novel chromophores y1 and y2 based on the same double donors and the tricyanofuran acceptor linked together via the modified thiophene π-conjugation have been synthesized and systematically investigated. Density functional theory was used to calculate the energy gaps and first-order hyperpolarizability (β) of the two chromophores. Besides, cyclic voltammetry (CV) experiments were performed to determine the different redox properties. The electro-optic coefficient of poled films containing 25 wt% of chromophore y1 and y2 doped in amorphous polycarbonate afforded values of 163 and 105 pm V−1 at 1310 nm, respectively. The obvious different results indicated that the position of the oxygen atom on the thiophene ring is essential to the linear and nonlinear optical properties, with the best results obtained when the alkoxy group was closer to the donor moiety. These results are useful in designing the nonlinear optical materials and will provide new guidance for the future research.

A series of chromophores T1–T3 based on the same thiophene π-conjugation and tricyanofuran acceptor (TCF) but with different heteroatoms in the triarylaminophenyl (TAA) donors have been synthesized and systematically investigated in this study. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Moreover, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. After introducing the heteroatom to the benzene ring of the TAA donor, reduced energy gaps of 1.28 and 0.84 eV were obtained for chromophores T2 and T3, respectively, which was much lower than for chromophore T1 (ΔE = 1.46 eV). These chromophores showed excellent thermal stability with their decomposition temperatures all above 280 °C. Compared with results obtained from the chromophore without the heteroatom (T1), these new chromophores show better intramolecular charge-transfer (ICT) absorption. Most importantly, the high molecular hyperpolarizability (β) of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in the poled polymers. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous polycarbonate (APC) afforded values of 16, 58 and 95 pm V−1 at 1310 nm for chromophores T1–T3, respectively. High r33 values indicated that introducing heteroatom to the benzene ring of the TAA donor can efficiently improve the electron-donating ability, which improves the hyperpolarizability (β). The long-chain on the benzene ring of the TAA donor, acting as the isolation group, may reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as advanced material devices.

A series of chromophores y1–y3 based on the same bis(N,N-diethyl)aniline donor and the tricyanofuran acceptor (TCF) linked together via the modified thiophene π-conjugation with different isolated groups have been synthesized and systematically investigated in this paper. 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. After introducing the isolation group into the thiophene, reduced energy gaps of 1.03 and 1.02 eV were obtained for chromophores y2 and y3, respectively, much lower compared to chromophore y1 (ΔE = 1.13 eV). These chromophores showed better thermal stability with their decomposition temperatures all above 220 °C. Besides, compared with results obtained from the chromophore (y1) without the isolated group, these new chromophores show better intramolecular charge-transfer (ICT) absorption. Most importantly, the high molecular hyperpolarizability (β) of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The electro-optic coefficient of poled films containing 25% wt of these new chromophores doped in amorphous polycarbonate (APC) afforded values of 149, 139 and 125 pm V−1 at 1310 nm for chromophores y1–y3, respectively. Besides, when the concentration was increased, the film containing chromophores y1 and y3 showed obvious phase separation, while the film with chromophore y2 showed the maximum r33 value of 146 pm V−1. Moreover, the electro-optic film prepared with these new chromophores showed greater stability. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and the isolated groups on the thiophene bridge can reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as advanced material devices.

In this work, we investigated the enhancement of the electro-optic response by introducing electron-rich heteroatoms as additional donors into the donor or bridge of a conventional second-order nonlinear optical chromophore. A series of chromophores C2–C4 based on the same tricyanofuran acceptor (TCF) but with different heteroatoms in the alkylamino phenyl donor (C2 or C3) or thiophene bridge (C4) have been synthesized and systematically investigated. Density functional theory calculations suggested that chromophores C2–C4 had a smaller energy gap and larger first-order hyperpolarizability (β) than traditional chromophore C1 due to the additional heteroatoms. Single crystal structure analyses and optimized configurations indicate that the rationally introduced heteroatom group would bring larger β and weaker intermolecular interactions which were beneficial for translating molecular β into macro-electro-optic activity in electric field poled films. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous poly-carbonate afforded values of 83 and 91 pm V−1 at 1310 nm for chromophores C3 and C4, respectively, which are two times higher than that of the traditional chromophore C1 (39 pm V−1). High r33 values indicated that introducing heteroatoms to the donor and bridge of a conventional molecular structure can efficiently improve the electron-donating ability, which improves the β. The long-chain on the donor or bridge part, acting as the isolation group, may reduce inter-molecular electrostatic interactions, thus enhancing the macroscopic EO activity. These results, together with good solubility and compatibility with the polymer, show the new chromophore's potential application in electro-optic devices.

New Y-type chromophores FTC-yh1 and FTC-yh2 containing bis(N,N-diethyl)aniline as a novel electron-donor, thiophene as a π-conjugated bridge and tricyanofuran (TCF) as an acceptor have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. These chromophores showed better thermal stability with their decomposition temperatures all above 240 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped film-A containing 25 wt% chromophore FTC-yh1 displayed a value of 149 pm V−1 at 1310 nm, and the doped film-B containing FTC-yh2 showed a value of 143 pm V−1 at the concentration of 25 wt%. These values are almost four times higher than the EO activity of usually reported traditional single (N,N-diethyl)aniline nonlinear optical (NLO) chromophores FTC. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of the new chromophores as advanced material devices.

•A series of novel second-order nonlinear optical chromophores has been synthesized and systematically characterized.•The resulting NLO chromophores exhibited both good thermal stability and good solubility in common organic solvents.•The film-C displayed the highest r33 value of 31 pm/v at the same doping concentrations of 20 wt%.A series of novel second-order nonlinear optical chromophores containing additional heteroatoms in donor moieties has been synthesized and systematically characterized. The resulting nonlinear optical chromophores exhibited both good thermal stability (the decomposition temperature in the range of 249 °C–275 °C) and good solubility in common organic solvents such as chloroform, acetone and N, N-dimethyl formamide. In order to investigate the influence of additional heteroatom on the electro-optic activities, UV–Vis spectra and density functional theory calculations were carried out. The results revealed that the donor derived from m-phenylenediamine had higher electron density compared with other three donors. As to electro-optic activities, the doped polymer film-C displayed the highest electro-optic coefficient value of 31 pm/v at the doping concentration of 20 wt%. All these results indicated that the nonlinear optical activities could be enhanced by introducing suitable additional heteroatoms into donor moiety.

A new chromophore HK containing the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as a novel electron-donor, thiophene as a π-conjugated bridge and a tricyanofuran (TCF) acceptor has been synthesized and systematically investigated in this paper. Its corresponding chromophore FTC using 4-(diethyl amino)benzyl as the electron donor group was also prepared for comparison. This is the first time that the cis,cis-1,7-diethoxy-3-isopropyljulolidine group was introduced into NLO materials. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gap and first-order hyperpolarizability (β) of the new chromophore. The HOMO–LUMO gap was also investigated by cyclic voltammetry (CV). Upon using the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as the donor, a reduced energy gap of 1.007 eV was obtained compared with chromophore FTC (ΔE = 1.529 eV). The high molecular hyperpolarizability of the new chromophore can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped films containing the new chromophore HK showed a value of 72 pm V−1 at the concentration of 25 wt% at 1310 nm. This value is almost two times higher than the EO activity of the usually reported traditional (N,N-diethyl) aniline nonlinear optical (NLO) chromophore FTC. High r33 values indicated that the new julolidine donor can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with good solubility, suggest the potential use of the new chromophore in advanced materials devices.

Two novel non-linear optical (NLO) chromophores were designed and synthesized based on the substituted benzo[1,2-b:4,5-b′]dithiophene unit (BDT), tricyanofuran (TCF) electron acceptor and two different electron donors. These new chromophores, which exhibited good thermal stability and solubility in common organic solvents, were systematically characterized by thermogravimetric analysis, UV-Vis spectra, density functional theory (DFT) calculations and measurements of the electro-optic (EO) coefficients. Compared with the dodecyl group in chromophore BDT1 that we have previously reported, the isooctane group in BDT2 could act as a suitable isolation group, and as a result, the guest–host system containing 30% of BDT2 in amorphous polycarbonate (APC) displayed the largest EO coefficient of 102 pm V−1, which was greatly improved over BDT1 and the analogous thiophene-based chromophore with the same electron donor and acceptor. The solvatochromic analysis and DFT study demonstrated that the julolidine group in BDT3 possessed a stronger donating ability. However, the 30% BDT3/APC exhibited an EO coefficient of only 82 pm V−1, which was probably caused by the diminishment of the hyperpolarizability value of BDT3 in the polar polymer matrix. These results indicate the potential of the isooctane-substituted benzo[1,2-b:4,5-b′]dithiophene π-conjugated bridge in chromophore design and NLO materials, and further illustrate the critical role of suitable isolation groups and fine-tuning of the donor's electron-donating strength in optimizing the non-linear properties of NLO chromophores.

In this work, we investigated the enhancement of the electro-optic response by introducing electron-rich heteroatoms as additional donors into the donor or bridge of a conventional second-order nonlinear optical chromophore. A series of chromophores C2–C4 based on the same tricyanofuran acceptor (TCF) but with different heteroatoms in the alkylamino phenyl donor (C2 or C3) or thiophene bridge (C4) have been synthesized and systematically investigated. Density functional theory calculations suggested that chromophores C2–C4 had a smaller energy gap and larger first-order hyperpolarizability (β) than traditional chromophore C1 due to the additional heteroatoms. Single crystal structure analyses and optimized configurations indicate that the rationally introduced heteroatom group would bring larger β and weaker intermolecular interactions which were beneficial for translating molecular β into macro-electro-optic activity in electric field poled films. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous poly-carbonate afforded values of 83 and 91 pm V−1 at 1310 nm for chromophores C3 and C4, respectively, which are two times higher than that of the traditional chromophore C1 (39 pm V−1). High r33 values indicated that introducing heteroatoms to the donor and bridge of a conventional molecular structure can efficiently improve the electron-donating ability, which improves the β. The long-chain on the donor or bridge part, acting as the isolation group, may reduce inter-molecular electrostatic interactions, thus enhancing the macroscopic EO activity. These results, together with good solubility and compatibility with the polymer, show the new chromophore's potential application in electro-optic devices.

A new chromophore HK containing the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as a novel electron-donor, thiophene as a π-conjugated bridge and a tricyanofuran (TCF) acceptor has been synthesized and systematically investigated in this paper. Its corresponding chromophore FTC using 4-(diethyl amino)benzyl as the electron donor group was also prepared for comparison. This is the first time that the cis,cis-1,7-diethoxy-3-isopropyljulolidine group was introduced into NLO materials. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gap and first-order hyperpolarizability (β) of the new chromophore. The HOMO–LUMO gap was also investigated by cyclic voltammetry (CV). Upon using the cis,cis-1,7-diethoxy-3-isopropyljulolidine group as the donor, a reduced energy gap of 1.007 eV was obtained compared with chromophore FTC (ΔE = 1.529 eV). The high molecular hyperpolarizability of the new chromophore can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped films containing the new chromophore HK showed a value of 72 pm V−1 at the concentration of 25 wt% at 1310 nm. This value is almost two times higher than the EO activity of the usually reported traditional (N,N-diethyl) aniline nonlinear optical (NLO) chromophore FTC. High r33 values indicated that the new julolidine donor can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with good solubility, suggest the potential use of the new chromophore in advanced materials devices.

New Y-type chromophores FTC-yh1 and FTC-yh2 containing bis(N,N-diethyl)aniline as a novel electron-donor, thiophene as a π-conjugated bridge and tricyanofuran (TCF) as an acceptor have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. These chromophores showed better thermal stability with their decomposition temperatures all above 240 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped film-A containing 25 wt% chromophore FTC-yh1 displayed a value of 149 pm V−1 at 1310 nm, and the doped film-B containing FTC-yh2 showed a value of 143 pm V−1 at the concentration of 25 wt%. These values are almost four times higher than the EO activity of usually reported traditional single (N,N-diethyl)aniline nonlinear optical (NLO) chromophores FTC. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of the new chromophores as advanced material devices.

Two novel chromophores y1 and y2 based on the same double donors and the tricyanofuran acceptor linked together via the modified thiophene π-conjugation have been synthesized and systematically investigated. Density functional theory was used to calculate the energy gaps and first-order hyperpolarizability (β) of the two chromophores. Besides, cyclic voltammetry (CV) experiments were performed to determine the different redox properties. The electro-optic coefficient of poled films containing 25 wt% of chromophore y1 and y2 doped in amorphous polycarbonate afforded values of 163 and 105 pm V−1 at 1310 nm, respectively. The obvious different results indicated that the position of the oxygen atom on the thiophene ring is essential to the linear and nonlinear optical properties, with the best results obtained when the alkoxy group was closer to the donor moiety. These results are useful in designing the nonlinear optical materials and will provide new guidance for the future research.

A series of chromophores y1–y3 based on the same bis(N,N-diethyl)aniline donor and the tricyanofuran acceptor (TCF) linked together via the modified thiophene π-conjugation with different isolated groups have been synthesized and systematically investigated in this paper. 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. After introducing the isolation group into the thiophene, reduced energy gaps of 1.03 and 1.02 eV were obtained for chromophores y2 and y3, respectively, much lower compared to chromophore y1 (ΔE = 1.13 eV). These chromophores showed better thermal stability with their decomposition temperatures all above 220 °C. Besides, compared with results obtained from the chromophore (y1) without the isolated group, these new chromophores show better intramolecular charge-transfer (ICT) absorption. Most importantly, the high molecular hyperpolarizability (β) of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The electro-optic coefficient of poled films containing 25% wt of these new chromophores doped in amorphous polycarbonate (APC) afforded values of 149, 139 and 125 pm V−1 at 1310 nm for chromophores y1–y3, respectively. Besides, when the concentration was increased, the film containing chromophores y1 and y3 showed obvious phase separation, while the film with chromophore y2 showed the maximum r33 value of 146 pm V−1. Moreover, the electro-optic film prepared with these new chromophores showed greater stability. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and the isolated groups on the thiophene bridge can reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as advanced material devices.

A series of chromophores T1–T3 based on the same thiophene π-conjugation and tricyanofuran acceptor (TCF) but with different heteroatoms in the triarylaminophenyl (TAA) donors have been synthesized and systematically investigated in this study. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. Moreover, to determine the redox properties of these chromophores, cyclic voltammetry (CV) experiments were performed. After introducing the heteroatom to the benzene ring of the TAA donor, reduced energy gaps of 1.28 and 0.84 eV were obtained for chromophores T2 and T3, respectively, which was much lower than for chromophore T1 (ΔE = 1.46 eV). These chromophores showed excellent thermal stability with their decomposition temperatures all above 280 °C. Compared with results obtained from the chromophore without the heteroatom (T1), these new chromophores show better intramolecular charge-transfer (ICT) absorption. Most importantly, the high molecular hyperpolarizability (β) of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in the poled polymers. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous polycarbonate (APC) afforded values of 16, 58 and 95 pm V−1 at 1310 nm for chromophores T1–T3, respectively. High r33 values indicated that introducing heteroatom to the benzene ring of the TAA donor can efficiently improve the electron-donating ability, which improves the hyperpolarizability (β). The long-chain on the benzene ring of the TAA donor, acting as the isolation group, may reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of these new chromophores as advanced material devices.