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Synthesis of novel nonlinear optical chromophore containing bis(trifluoromethyl)benzene as an isolated group
Materials Letters 80 (2012) 84–86
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis of novel nonlinear optical chromophore containing bis(trifluoromethyl) benzene as an isolated group Liang Wang a, b, Jialei Liu a,⁎, Shuhui Bo a, Zhen Zhen a, Xinhou Liu a,⁎ a Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China b Graduated University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
a r t i c l e
i n f o
Article history: Received 16 April 2012 Accepted 17 April 2012 Available online 21 April 2012 Keywords: NLO Chromophore EO coefficients Isolated group
a b s t r a c t Novel NLO chromophore with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group in electron bridge was prepared for investigating the NLO character. Chromophore FTC-wl was characterized using UV–Visible spectra, nuclear magnetic resonance, and mass spectrometry and showed us excellent thermal stability. EO films prepared by poly(bisphenol A carbonate) polymer doped with this chromophore at different content had been poled to afford the highest electro optic coefficients (r33) of 28 pm/V. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Due to their high linear electro optical (EO) coefficients, ultra fast response times and promising technological abilities, organic secondorder NLO materials have been extensively studied for their wide application in photonic devices such as EO modulators, optical storage devices and so on [1]. Organic NLO chromophores as the most important part of NLO materials can be also widely used in bulk hetero junction organic solar cell and solvent detectors [2]. Large amounts of new NLO chromophores were prepared recently [3,4]. However, disadvantages of the materials hindered their practical application, such as solubility, optical loss and strong inter-molecular electrostatic interaction among the chromophore molecules [5–9]. To pursue high EO activity, the NLO chromophores must have strong electron donor, electron acceptor and relative length Electron Bridge; for good solubility and low strong inter molecular electrostatic interaction, chromophores must have large isolated groups; to reduce the optical loss, carbon-fluorine bonds should be introduced to the chromophores [10–12]. In this paper, NLO chromphore with N, N-diethylaniline as donor, 2(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) as acceptor, thiophene as electron bridge was synthesized, 3, 5bis(trifluoromethyl) benzoyl was introduced into thiophene bridge as a bulky group to reduce the intermolecular electrostatic interactions. We also provided details on the behavior of this chromophore in solution using nuclear magnetic resonance (NMR) and UV–Visible (UV–
⁎ Corresponding authors. Tel.: + 86 10 82543773; fax: + 86 10 62554670. E-mail addresses: [email protected] (J. Liu), [email protected] (X. Liu). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.04.083
vis) spectra. Furthermore, host–guest thin films containing different concentrations of this new chromophore in amorphous polycarbonate (APC) had been prepared and their EO coefficients (r33 values) were also measured. 2. Experimental section 2.1. Materials and instrumentation 1 H NMR spectra were measured on an AVANCE 400 (Bruker) spectrometer using tetramethylsilane (TMS; δ = 0 ppm) as the internal standard. The Fourier transform infrared (FT-IR) spectra were recorded on a Varian 3100 FT-IR Excalibur Series using the KBr pellet method. UV–Visible spectra were obtained using a HITACHI U-2001 spectrometer. The TGA curve was recorded with a TA-instrument Q50 with a heat rate of 10 °C/min under nitrogen atmosphere.
2.2. Synthesis of the guest chromophore FTC-wl 2.2.1. 2-(2-(4-(diethylamino)styryl)-5-formylthiophen-3-yloxy)ethyl acetate (4) The ether solution of compound 1 (5.1 g, 10 mmol), NaH (5.5 g, 230 mmol), and compound 2 (2.14 g, 10 mmol) was stirred at room temperature for 24 h under N2 atmosphere, then poured into 200 mL ice water. The mixture was extracted twice with ether, and dried over magnesium sulfate. The product 3 was used in the next step without any characterization. Compound 3 (5.38 g, 15 mmol) in 50 mL DMF was stirred and cooled to 0 °C,then POCl3 (2 mL) was added dropwise into the solution. After the phosphorus oxychloride being added, the temperature
L. Wang et al. / Materials Letters 80 (2012) 84–86
85
was raised to 90 °C slowly, and kept for 3 h. Then the mixture was cooled down to room temperature, poured into 150 mL solution of sodium carbonate (10%), and extracted twice with chloroform. The crude product was purified by a flash chromatography, yield 54%. MS (MALDI-TOF), m/z: 387 (M +). 1H NMR (300 MHz, CD3COCD3): δ = 9.91 (s, 1H), 7.17 (d, 2H), 7.13 (d, 1H), 6.87 (d, 1H), 6.64 (d, 2H), 6.52 (s, 1H), 4.29 (t, 2H), 4.24 (t, 2H), 3.39 (q, 4H), 2.0 (s, 3H), 1.13 (t, 6H).
λmax =745 nm. 1H NMR (300 MHz, CD3COCD3): δ =8.52 (s, 2H), 8.31 (s, 1H), 8.0 (d, 1H), 7.7 (s, 2H), 7.3 (d, 2H), 7.07 (d, 2H), 6.80 (s, 1H), 6.64 (m, 2H), 4.85 (t, 2H), 4.62 (t, 2H), 3.42 (q, 4H), 1.83 (s, 6H), 1.14 (t, 6H).
2.2.2. Chromophore FTC-wl-OH Compound 4 (1.17 g, 3 mmol) was dissolved in 30 mL methanol, and 10 mL solution of potassium carbonate was added. After that, the temperature was raised to 80 °C, and kept for 3 h. The methanol was removed by rotary evaporator, and the rest part was washed by saturated brine and extracted by chloroform. The crude product was purified by a flash chromatography. 0.69 g orange solid was obtained, yield 67%. Compound 4 was used in the next step without any characterization. Compound 5 (0.35 g, 1 mmol) and tricyanofuran (TCF) acceptor (0.24 g, 1.2 mmol) were dissolved in CHCl3, then kept refluxing for 1.5 h. The chloroform was removed by rotary evaporator, the product chromophore FTC-wl-OH was purified by a flash chromatography. 0.16 g dark blue solid was obtained, yield 30%. MS (MALDI-TOF), m/z: 526(M+). IR (KBr), νmax/cm− 1: 3412 (\OH), 2980 (\CH3), 2260 (\CN), 1585 (\C_C\). UV–vis (CHCl3): λmax = 735 nm. 1H NMR (300 MHz, CD3COCD3):δ = 8.03 (d, 1H), 7.62 (s, 1H), 7.43 (d, 2H), 7.2 (d, 1H), 7.11 (d, 1H), 6.79 (s, 1H), 6.69 (d, 2H), 4.2 (t, 2H), 3.88 (t, 2H), 3.62 (s, 1H), 3.42 (q, 4H), 1.84 (s, 6H), 1.14 (t, 6H).
The synthetic route of the chromophore was sketched in Scheme 1. Chromophore FTC-wl was prepared according to a synthetic methodology as follows: the donor bridge was prepared through a Wittig condensation between thiophene bridge and Wittig salt. Then the donor bridge was subjected to Vilsmeier reactions in the presence of POCl3 and DMF, affording the desired aldehyde function on the thiophene ring. After removing the protecting group, the donor bridge was then reacted with the TCF acceptor to yield the chromophore FTC-wl-OH. Finally, the chromophore FTC-wl was prepared through the reaction between hydroxyl group on the thiophene bridge and 3,5-bis(trifluoromethyl) benzoyl chloride. The results of 1H NMR, IR and UV–vis spectra all supported the formation of the chromophore.
2.2.3. Chromophore FTC-wl FTC-wl-OH (0.53 g, 1 mmol) and a certain amount of Et3N were dissolved in 50 mL dry CH3CN, and then 3,5-bis -(trifluoromethyl) benzoyl chloride was added dropwise into the solution at 0 °C. After 2 h, acetonitrile was removed by rotary evaporator, and the rest part was purified by a flash chromatography. 0.56 g dark blue solid was obtained, yield 73%. MS (MALDI-TOF), m/z: 766(M+). IR (KBr), νmax/cm− 1: 2978 (\CH3), 2224 (\CN), 1732 (\COO\), 1542 (\C_C\). UV–vis (CHCl3):
3. Results and discussion 3.1. Synthesis and characterization
3.2. The thermal stability of the chromophore Thermal stability is very important for the chromophores' application in the process of EO devices preparation. Most of the processes of EO devices preparation need high temperature. To investigate the thermal stability of the chromophore, thermo gravimetric analysis (TGA) was used with a heating rate of 10 °C·min − 1 under nitrogen. TGA curve of the molecule is shown in Fig. 1 and the thermal decomposition temperature (Td) value obtained from TGA is 238 °C. The result indicates that chromophore FTC-wl has high thermal stability. This may be due to the large isolated group in the thiophene electron bridge, which prevent the collision between the chomophore molecules when being heated. Else, 238 °C is high enough for most of its application in the process of EO devices preparation [13].
Scheme 1. The synthesis of the guest chromophore (FTC-wl).
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Fig. 1. TGA curve of the chromophore.
3.3. Linear optical property To study the intermolecular interactions of chromophore FTC-wl, UV–vis spectra of this chromophore in chloroform with different concentration were shown in Fig. 2. The shape of UV–vis spectra has no apparent change with the increasing of concentration. These indicated that there was no strong dipole–dipole interaction among the chromophore molecules. If there is very strong dipole–dipole interaction, this kind of molecules can be easily aggregated, and they will grow up to nanocrystal via solvent exchange method (self-assembly). We have found this phenomenon in most of the chromophores, but we found there was no crystallization behavior for chromophore FTC-wl. These results confirmed that isolated group in thiophene could isolate the chromophore molecules effectively 3.4. Nonlinear optical measurements To evaluate the EO activity of the polymers, the poled thin films were prepared. The r33 were measured by simple reflection method [14]. The r33 valves of films containing chromophore FTC-wl in varying loading density were summarized in Fig. 3. With the increase in chromophore loading density, the r33 value of the films displayed a maximum of 28 pm/V at 20 wt.% and then decreased at around 25 wt.%. This saturated loading density of 25 wt.% was higher than the usual loading density of FTC chromophore without isolated groups in guest– host doped NLO polymer materials. Even if 30 wt.% of chromophore FTC-wl was loaded into the polymer matrix, no phase separation occurred in films. The high saturated loading density of film-A was
Fig. 3. EO coefficient value (r33) for chromophore FTC-wl in APC.
probably attributed to the fact that the chromophore structure isolated the chromophores from each and thus reduced the inter-chromophore dipole–dipole interaction, thus improving the NLO effect at a much higher chromophore loading density level. 4. Conclusion In summary, a new NLO chromophore with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group has been synthesized and systematically investigated to explore the effects of isolated group on the macroscopic optical nonlinearity. The effects of bathochromic and solvatochromic behavior on the UV–vis absorption were also investigated to prove weaker intermolecular interactions of chromophore. In electro-optic activities, the doped film-A containing chromophore A displays a maximum r33 value of 28 pm/V at the doping concentration of 20 wt.%. Those outcomes indicate that chromophore FTC-wl with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group could efficiently reduce the interchromophore electrostatic interactions and enhance the macroscopic optical nonlinearity. This novel isolated group shows promising applications in nonlinear optical (NLO) chromophore synthesis. Acknowledgments We are grateful to the Directional Program of the CAS (KJCX2. YW.H02), Innovation Fund of CAS (CXJJ-11-M035) and National Natural Science Foundation of China (No. 11104284 and No. 61101054) for financial support. References [1] Cho M, Choi D, Sullivan P, Akelaitis A, Dalton L. Prog Polym Sci 2008;33:1013–58. [2] Cho M, Seo J, Oh H, Jee H, Kim W, Kim K, et al. J Incl Phenom Macrocycl Chem 2012;98:71–7. [3] Delower M, Bhuiyan H, Graeme A, Gainsford J, Williamson R. Mater Sci Forum 2011:700. [4] Dalton L, Benight S. Polymers 2011;3:1325–51. [5] Liu J, Huang H, Liu X, Zhen Z. Polym Adv Technol 2011, http://dx.doi.org/10.1002/ pat.1981. [6] Liu J, Bo S, Liu X, Zhen Z. J Incl Phenom Macrocycl Chem 2010;68:253. [7] Liu J, Hou W, Feng S, Qiu L, Liu X, Zhen Z. J Phys Org Chem 2011;24:439. [8] Huang H, Liu J, Zhen Z, Qiu L, Liu X, Lakshminarayana G, et al. Mater Lett 2012;75: 233–5. [9] Liu J, Xu H, Liu X, Zhen Z, Kuznik W, Kityk I. J Mater Sci Mater Electron 2011, http://dx.doi.org/10.1007/s10854-011-0569-5. [10] Li A, Wu W, Li Q, Yu G, Xiao L, Liu Y, et al. Angew Chem Int Ed 2010;49:2763. [11] Hao J, Han M, Yang Y, Shen Y, Qiu L, Meng X, et al. React Funct Polym 2006;66:832. [12] Zhou X, Luo J, Huang S, Kim T, Shi Z, Cheng Y, et al. Adv Mater 2009;21:1976. [13] Sahraoui B, Kityk I, Phu X, Hudhomme P, Gorgues A. Phys Rev B 1999;59:9229–38. [14] Teng C, Man H. Appl Phys Lett 1990;56:1734.
Fig. 2. UV–vis spectra of BP-TCF in chloroform with different concentration.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis of novel nonlinear optical chromophore containing bis(trifluoromethyl) benzene as an isolated group Liang Wang a, b, Jialei Liu a,⁎, Shuhui Bo a, Zhen Zhen a, Xinhou Liu a,⁎ a Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China b Graduated University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
a r t i c l e
i n f o
Article history: Received 16 April 2012 Accepted 17 April 2012 Available online 21 April 2012 Keywords: NLO Chromophore EO coefficients Isolated group
a b s t r a c t Novel NLO chromophore with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group in electron bridge was prepared for investigating the NLO character. Chromophore FTC-wl was characterized using UV–Visible spectra, nuclear magnetic resonance, and mass spectrometry and showed us excellent thermal stability. EO films prepared by poly(bisphenol A carbonate) polymer doped with this chromophore at different content had been poled to afford the highest electro optic coefficients (r33) of 28 pm/V. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Due to their high linear electro optical (EO) coefficients, ultra fast response times and promising technological abilities, organic secondorder NLO materials have been extensively studied for their wide application in photonic devices such as EO modulators, optical storage devices and so on [1]. Organic NLO chromophores as the most important part of NLO materials can be also widely used in bulk hetero junction organic solar cell and solvent detectors [2]. Large amounts of new NLO chromophores were prepared recently [3,4]. However, disadvantages of the materials hindered their practical application, such as solubility, optical loss and strong inter-molecular electrostatic interaction among the chromophore molecules [5–9]. To pursue high EO activity, the NLO chromophores must have strong electron donor, electron acceptor and relative length Electron Bridge; for good solubility and low strong inter molecular electrostatic interaction, chromophores must have large isolated groups; to reduce the optical loss, carbon-fluorine bonds should be introduced to the chromophores [10–12]. In this paper, NLO chromphore with N, N-diethylaniline as donor, 2(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) as acceptor, thiophene as electron bridge was synthesized, 3, 5bis(trifluoromethyl) benzoyl was introduced into thiophene bridge as a bulky group to reduce the intermolecular electrostatic interactions. We also provided details on the behavior of this chromophore in solution using nuclear magnetic resonance (NMR) and UV–Visible (UV–
⁎ Corresponding authors. Tel.: + 86 10 82543773; fax: + 86 10 62554670. E-mail addresses: [email protected] (J. Liu), [email protected] (X. Liu). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.04.083
vis) spectra. Furthermore, host–guest thin films containing different concentrations of this new chromophore in amorphous polycarbonate (APC) had been prepared and their EO coefficients (r33 values) were also measured. 2. Experimental section 2.1. Materials and instrumentation 1 H NMR spectra were measured on an AVANCE 400 (Bruker) spectrometer using tetramethylsilane (TMS; δ = 0 ppm) as the internal standard. The Fourier transform infrared (FT-IR) spectra were recorded on a Varian 3100 FT-IR Excalibur Series using the KBr pellet method. UV–Visible spectra were obtained using a HITACHI U-2001 spectrometer. The TGA curve was recorded with a TA-instrument Q50 with a heat rate of 10 °C/min under nitrogen atmosphere.
2.2. Synthesis of the guest chromophore FTC-wl 2.2.1. 2-(2-(4-(diethylamino)styryl)-5-formylthiophen-3-yloxy)ethyl acetate (4) The ether solution of compound 1 (5.1 g, 10 mmol), NaH (5.5 g, 230 mmol), and compound 2 (2.14 g, 10 mmol) was stirred at room temperature for 24 h under N2 atmosphere, then poured into 200 mL ice water. The mixture was extracted twice with ether, and dried over magnesium sulfate. The product 3 was used in the next step without any characterization. Compound 3 (5.38 g, 15 mmol) in 50 mL DMF was stirred and cooled to 0 °C,then POCl3 (2 mL) was added dropwise into the solution. After the phosphorus oxychloride being added, the temperature
L. Wang et al. / Materials Letters 80 (2012) 84–86
85
was raised to 90 °C slowly, and kept for 3 h. Then the mixture was cooled down to room temperature, poured into 150 mL solution of sodium carbonate (10%), and extracted twice with chloroform. The crude product was purified by a flash chromatography, yield 54%. MS (MALDI-TOF), m/z: 387 (M +). 1H NMR (300 MHz, CD3COCD3): δ = 9.91 (s, 1H), 7.17 (d, 2H), 7.13 (d, 1H), 6.87 (d, 1H), 6.64 (d, 2H), 6.52 (s, 1H), 4.29 (t, 2H), 4.24 (t, 2H), 3.39 (q, 4H), 2.0 (s, 3H), 1.13 (t, 6H).
λmax =745 nm. 1H NMR (300 MHz, CD3COCD3): δ =8.52 (s, 2H), 8.31 (s, 1H), 8.0 (d, 1H), 7.7 (s, 2H), 7.3 (d, 2H), 7.07 (d, 2H), 6.80 (s, 1H), 6.64 (m, 2H), 4.85 (t, 2H), 4.62 (t, 2H), 3.42 (q, 4H), 1.83 (s, 6H), 1.14 (t, 6H).
2.2.2. Chromophore FTC-wl-OH Compound 4 (1.17 g, 3 mmol) was dissolved in 30 mL methanol, and 10 mL solution of potassium carbonate was added. After that, the temperature was raised to 80 °C, and kept for 3 h. The methanol was removed by rotary evaporator, and the rest part was washed by saturated brine and extracted by chloroform. The crude product was purified by a flash chromatography. 0.69 g orange solid was obtained, yield 67%. Compound 4 was used in the next step without any characterization. Compound 5 (0.35 g, 1 mmol) and tricyanofuran (TCF) acceptor (0.24 g, 1.2 mmol) were dissolved in CHCl3, then kept refluxing for 1.5 h. The chloroform was removed by rotary evaporator, the product chromophore FTC-wl-OH was purified by a flash chromatography. 0.16 g dark blue solid was obtained, yield 30%. MS (MALDI-TOF), m/z: 526(M+). IR (KBr), νmax/cm− 1: 3412 (\OH), 2980 (\CH3), 2260 (\CN), 1585 (\C_C\). UV–vis (CHCl3): λmax = 735 nm. 1H NMR (300 MHz, CD3COCD3):δ = 8.03 (d, 1H), 7.62 (s, 1H), 7.43 (d, 2H), 7.2 (d, 1H), 7.11 (d, 1H), 6.79 (s, 1H), 6.69 (d, 2H), 4.2 (t, 2H), 3.88 (t, 2H), 3.62 (s, 1H), 3.42 (q, 4H), 1.84 (s, 6H), 1.14 (t, 6H).
The synthetic route of the chromophore was sketched in Scheme 1. Chromophore FTC-wl was prepared according to a synthetic methodology as follows: the donor bridge was prepared through a Wittig condensation between thiophene bridge and Wittig salt. Then the donor bridge was subjected to Vilsmeier reactions in the presence of POCl3 and DMF, affording the desired aldehyde function on the thiophene ring. After removing the protecting group, the donor bridge was then reacted with the TCF acceptor to yield the chromophore FTC-wl-OH. Finally, the chromophore FTC-wl was prepared through the reaction between hydroxyl group on the thiophene bridge and 3,5-bis(trifluoromethyl) benzoyl chloride. The results of 1H NMR, IR and UV–vis spectra all supported the formation of the chromophore.
2.2.3. Chromophore FTC-wl FTC-wl-OH (0.53 g, 1 mmol) and a certain amount of Et3N were dissolved in 50 mL dry CH3CN, and then 3,5-bis -(trifluoromethyl) benzoyl chloride was added dropwise into the solution at 0 °C. After 2 h, acetonitrile was removed by rotary evaporator, and the rest part was purified by a flash chromatography. 0.56 g dark blue solid was obtained, yield 73%. MS (MALDI-TOF), m/z: 766(M+). IR (KBr), νmax/cm− 1: 2978 (\CH3), 2224 (\CN), 1732 (\COO\), 1542 (\C_C\). UV–vis (CHCl3):
3. Results and discussion 3.1. Synthesis and characterization
3.2. The thermal stability of the chromophore Thermal stability is very important for the chromophores' application in the process of EO devices preparation. Most of the processes of EO devices preparation need high temperature. To investigate the thermal stability of the chromophore, thermo gravimetric analysis (TGA) was used with a heating rate of 10 °C·min − 1 under nitrogen. TGA curve of the molecule is shown in Fig. 1 and the thermal decomposition temperature (Td) value obtained from TGA is 238 °C. The result indicates that chromophore FTC-wl has high thermal stability. This may be due to the large isolated group in the thiophene electron bridge, which prevent the collision between the chomophore molecules when being heated. Else, 238 °C is high enough for most of its application in the process of EO devices preparation [13].
Scheme 1. The synthesis of the guest chromophore (FTC-wl).
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L. Wang et al. / Materials Letters 80 (2012) 84–86
Fig. 1. TGA curve of the chromophore.
3.3. Linear optical property To study the intermolecular interactions of chromophore FTC-wl, UV–vis spectra of this chromophore in chloroform with different concentration were shown in Fig. 2. The shape of UV–vis spectra has no apparent change with the increasing of concentration. These indicated that there was no strong dipole–dipole interaction among the chromophore molecules. If there is very strong dipole–dipole interaction, this kind of molecules can be easily aggregated, and they will grow up to nanocrystal via solvent exchange method (self-assembly). We have found this phenomenon in most of the chromophores, but we found there was no crystallization behavior for chromophore FTC-wl. These results confirmed that isolated group in thiophene could isolate the chromophore molecules effectively 3.4. Nonlinear optical measurements To evaluate the EO activity of the polymers, the poled thin films were prepared. The r33 were measured by simple reflection method [14]. The r33 valves of films containing chromophore FTC-wl in varying loading density were summarized in Fig. 3. With the increase in chromophore loading density, the r33 value of the films displayed a maximum of 28 pm/V at 20 wt.% and then decreased at around 25 wt.%. This saturated loading density of 25 wt.% was higher than the usual loading density of FTC chromophore without isolated groups in guest– host doped NLO polymer materials. Even if 30 wt.% of chromophore FTC-wl was loaded into the polymer matrix, no phase separation occurred in films. The high saturated loading density of film-A was
Fig. 3. EO coefficient value (r33) for chromophore FTC-wl in APC.
probably attributed to the fact that the chromophore structure isolated the chromophores from each and thus reduced the inter-chromophore dipole–dipole interaction, thus improving the NLO effect at a much higher chromophore loading density level. 4. Conclusion In summary, a new NLO chromophore with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group has been synthesized and systematically investigated to explore the effects of isolated group on the macroscopic optical nonlinearity. The effects of bathochromic and solvatochromic behavior on the UV–vis absorption were also investigated to prove weaker intermolecular interactions of chromophore. In electro-optic activities, the doped film-A containing chromophore A displays a maximum r33 value of 28 pm/V at the doping concentration of 20 wt.%. Those outcomes indicate that chromophore FTC-wl with 3, 5-bis(trifluoromethyl) benzoyl as the isolated group could efficiently reduce the interchromophore electrostatic interactions and enhance the macroscopic optical nonlinearity. This novel isolated group shows promising applications in nonlinear optical (NLO) chromophore synthesis. Acknowledgments We are grateful to the Directional Program of the CAS (KJCX2. YW.H02), Innovation Fund of CAS (CXJJ-11-M035) and National Natural Science Foundation of China (No. 11104284 and No. 61101054) for financial support. References [1] Cho M, Choi D, Sullivan P, Akelaitis A, Dalton L. Prog Polym Sci 2008;33:1013–58. [2] Cho M, Seo J, Oh H, Jee H, Kim W, Kim K, et al. J Incl Phenom Macrocycl Chem 2012;98:71–7. [3] Delower M, Bhuiyan H, Graeme A, Gainsford J, Williamson R. Mater Sci Forum 2011:700. [4] Dalton L, Benight S. Polymers 2011;3:1325–51. [5] Liu J, Huang H, Liu X, Zhen Z. Polym Adv Technol 2011, http://dx.doi.org/10.1002/ pat.1981. [6] Liu J, Bo S, Liu X, Zhen Z. J Incl Phenom Macrocycl Chem 2010;68:253. [7] Liu J, Hou W, Feng S, Qiu L, Liu X, Zhen Z. J Phys Org Chem 2011;24:439. [8] Huang H, Liu J, Zhen Z, Qiu L, Liu X, Lakshminarayana G, et al. Mater Lett 2012;75: 233–5. [9] Liu J, Xu H, Liu X, Zhen Z, Kuznik W, Kityk I. J Mater Sci Mater Electron 2011, http://dx.doi.org/10.1007/s10854-011-0569-5. [10] Li A, Wu W, Li Q, Yu G, Xiao L, Liu Y, et al. Angew Chem Int Ed 2010;49:2763. [11] Hao J, Han M, Yang Y, Shen Y, Qiu L, Meng X, et al. React Funct Polym 2006;66:832. [12] Zhou X, Luo J, Huang S, Kim T, Shi Z, Cheng Y, et al. Adv Mater 2009;21:1976. [13] Sahraoui B, Kityk I, Phu X, Hudhomme P, Gorgues A. Phys Rev B 1999;59:9229–38. [14] Teng C, Man H. Appl Phys Lett 1990;56:1734.
Fig. 2. UV–vis spectra of BP-TCF in chloroform with different concentration.