CN106606992A - Asymmetric Gemini imidazole surfactant and preparation method thereof - Google Patents

Abstract

The invention discloses an asymmetric geminiidazole surfactant and a preparation method thereof. The imidazole and potassium hydroxide are reacted in the presence of a solvent DMSO, and then 1-bromoalkane is added for the reaction, and ethyl acetate is used as the mobile phase for the reaction. Long-chain alkylimidazoles are separated by column chromatography; long-chain alkylimidazoles and dibrominated alkanes undergo monobromonucleophilic substitution reaction in the presence of solvent acetone, and the mixed solvent of acetone and methanol is used as mobile phase for column chromatography to obtain Intermediate: performing nucleophilic substitution reaction between the obtained intermediate and the long-chain alkylimidazole in the presence of the solvent isopropanol, and successively recrystallizing through ethyl acetate and acetone to obtain the surfactant. The molecular structure asymmetry of surfactant of the present invention has bigger influence to the critical micelle concentration (cmc) of surfactant and thermodynamic parameter (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ), can pass Adjusting the asymmetry of the alkane backbone can regulate cmc and ΔH _m ^θ , thereby expanding the application range of gemini surfactants.

Description

Asymmetric geminimidazole surfactant and preparation method thereof

technical field

The invention relates to a series of asymmetric geminimidazole surfactants and a preparation method thereof.

Background technique

Asymmetric gemini surfactants are molecules that link together two hydrophobic chains of the same head group and different lengths, or two identical hydrophobic groups and different hydrophilic head groups, or two different head groups and different hydrophobic groups, through a linking chain , the particularity of this molecular structure adds a lot of adjustable factors to the molecular structure of gemini surfactants, and thus also obtains some novel experimental results, such as significantly increasing the enthalpy driving force of the self-organization process, positive-negative ions The head group molecules constitute a counter-ion-free system, and the long-short alkane main chain molecules successfully connect the formed vesicles in series. Asymmetric geminiidazole surfactants use cyclic imidazole as the hydrophilic head group, and exhibit some unique properties. For example, as a cationic reverse micelle system, the reverse micelle system with the cyclic large imidazole Quaternary ammonium salt cationic surfactants have stronger solubility; the strong mutual attraction between the imidazole head groups and the interaction between the π-π bonds between the aromatic rings make this type of surfactants potentially biologically Application; As a cationic micellar system, due to the polarization between imidazole head groups, they have a stronger self-aggregation tendency, which can be used as a supramolecular template in the preparation of functional materials, or change various chemical reaction types: hydrophilic Nuclear substitution reaction, decarboxylation reaction and cyclization reaction, etc. Combining the advantages of the two aspects, the present invention designs a series of preparation methods of asymmetric geminimidazole surfactants.

In 2002, Guangyue Bai et al reported the preparation of asymmetric gemini with the same total hydrophobic chain length and different symmetry degrees using N,N-dimethyl long-chain alkylamine and 1,6-dibromohexane as raw materials. Quaternary ammonium salt cationic surfactant ([C _m H _2m+1 (CH ₃ ) ₂ N(CH ₂ ) ₆ N(CH ₃ ) ₂ C _n H _2n+1 ]Br ₂ , m+n=24, m= 6,8,10,11,12). The achievement was published in "J.Phys.Chem.B" (2002,106(26):6614-6616).

In 2008, people such as Mingqi Ao reported that with imidazole, acrylonitrile, long-chain alkyl bromide, 1,4-dibromobutane prepared the symmetrical type gemini imidazole surfactant with different total hydrophobic chain lengths ([C _n -4-C _n im]Br ₂ , n=10, 12, 14). The achievement was published in "Journal of Colloid and Interface Science" (2008,326:490-495).

Contents of the invention

The object of the present invention is to provide a kind of asymmetric type geminimidazole surfactant and preparation method thereof.

The technical solution that realizes the object of the present invention is: a kind of asymmetric type geminimidazole surfactant, and described surfactant has following structure:

R ¹ , R ² =-C ₈ H ₁₇ ,-C ₁₀ H ₂₁ ,-C ₁₂ H ₂₅ ,-C ₁₄ H ₂₉ ,-C ₁₆ H ₃₃ , R ¹ ≠R ² ; s=2,4,6.

The preparation method of asymmetric type geminimidazole surfactant of the present invention, comprises the steps:

(1) react imidazole and potassium hydroxide in the presence of solvent DMSO, then add 1-bromoalkane to react, utilize ethyl acetate as mobile phase to carry out column chromatography and separate to obtain long-chain alkylimidazole;

(2) long-chain alkylimidazole and dibromoalkane carry out monobromine nucleophilic substitution reaction in the presence of solvent acetone, and use a mixed solvent of acetone and methanol as mobile phase to carry out column chromatography separation to obtain an intermediate;

(3) Carrying out the nucleophilic substitution reaction between the obtained intermediate and the long-chain alkylimidazole in the presence of the solvent isopropanol, and successively recrystallizing through ethyl acetate and acetone to obtain the surfactant.

In step (1), 1-bromoalkane is 1-bromooctane, 1-bromodecane, 1-bromododecane, 1-bromotetradecane and 1-bromohexadecane any kind.

In step (1), the reaction time of imidazole and potassium hydroxide is more than 2 hours; after adding 1-bromoalkane, the reaction time is more than 4 hours.

In step (2), the dibromoalkane is any one of 1,2-dibromoethane, 1,4-dibromobutane and 1,6-dibromohexane.

In step (2), the reaction molar ratio of long-chain alkylimidazole and dibromoalkane is 1:2～1:6; the reaction temperature is 30～60°C; the reaction time is 8～14h; the volume of solvent acetone is the reactant 5 to 8 times the total mass.

In step (3), the reaction molar ratio between the intermediate and the long-chain alkylimidazole is 1:1-1:3, the reaction temperature is 30-80° C., and the reaction time is 8-72 hours.

Compared with the prior art, the present invention has the following advantages:

(1) the asymmetric gemini imidazole surfactant prepared by the present invention is to take the cyclic imidazole as the hydrophilic group, the hydrocarbon chains of different lengths are the hydrophobic groups, and the flexible methylene chain is the surfactant molecular structure of the linking group, So far, there is no literature report on this asymmetric molecular structure.

(2) The asymmetry of the molecular structure of this product has a great influence on the critical micelle concentration (cmc) and thermodynamic parameters (ΔG _m ^θ , ΔH _m ^θ , ΔS _m ^θ ) of the surfactant. The chain asymmetry can be used to regulate cmc and ΔH _m ^θ , thus expanding the application range of gemini surfactants.

(3) The synthesis condition of the present invention is mild, the operation is easy to control, the aftertreatment is simple, and the product purity is high.

detailed description

The synthetic route of the present invention is as follows:

R ¹ , R ² =-C ₈ H ₁₇ ,-C ₁₀ H ₂₁ ,-C ₁₂ H ₂₅ ,-C ₁₄ H ₂₉ ,-C ₁₆ H ₃₃ , R ¹ ≠R ² ; s=2, 4, 6

Example 1

Add 1g of imidazole, 0.82g of potassium hydroxide and 5mL of dimethyl sulfoxide into the reaction flask in sequence, and after stirring at room temperature for 2 h, add 2.68g of 1-bromooctane dropwise into the reaction flask, and continue stirring at room temperature for 4 h . Add 15 mL of deionized water and stir for 5 min, then transfer the solution to a separatory funnel, and extract the product with chloroform (15 mL×5). The chloroform layers were combined, anhydrous magnesium sulfate was added and allowed to stand overnight. Suction filtration and rotary evaporation gave yellow liquid, ethyl acetate was used as mobile phase column chromatography to obtain imidazole octane. ¹ H NMR (500 MHz, CDCl ₃ ) δ7.44(s,1H),7.03(s,1H),6.88(s,1H),3.90(t,2H),1.75(m,2H),1.23～1.28 (m,10H), 0.86(t,3H).

Example 2

Add 1g of imidazole, 0.82g of potassium hydroxide and 5mL of dimethyl sulfoxide into the reaction flask in sequence, and after stirring for 2 h at room temperature, add 3.08g of 1-bromodecane dropwise into the reaction flask, and continue stirring for 4 h at room temperature . Add 15 mL of deionized water and stir for 5 min, then transfer the solution to a separatory funnel, and extract the product with chloroform (15 mL×5). The chloroform layers were combined, anhydrous magnesium sulfate was added and allowed to stand overnight. Suction filtration and rotary evaporation gave yellow liquid, ethyl acetate was used as mobile phase column chromatography to obtain imidazole decane. ¹ H NMR (500 MHz, CDCl ₃ ) δ7.43(s,1H),7.02(s,1H),6.87(s,1H),3.89(t,2H),1.75(m,2H),1.23～1.28 (m,14H), 0.86(t,3H).

Example 3

Add 1g of imidazole, 0.82g of potassium hydroxide and 5mL of dimethyl sulfoxide into the reaction flask in sequence, and after stirring for 2 hours at room temperature, add 3.47g of 1-bromododecane dropwise into the reaction flask, and continue stirring for 4 hours at room temperature. Add 15 mL of deionized water and stir for 5 min, then transfer the solution to a separatory funnel, and extract the product with chloroform (15 mL×5). The chloroform layers were combined, anhydrous magnesium sulfate was added and allowed to stand overnight. Suction filtration and rotary evaporation gave yellow liquid, ethyl acetate was used as mobile phase column chromatography to obtain imidazole dodecane. ¹ H NMR (500MHz, CDCl ₃ )δ7.43(s,1H),7.02(s,1H),6.87(s,1H),3.89(t,2H),1.75(m,2H),1.22～1.27( m,18H), 0.85(t,3H).

Example 4

Add 1g of imidazole, 0.82g of potassium hydroxide and 5mL of dimethyl sulfoxide into the reaction flask in sequence, and stir at room temperature for 2 hours, then add 3.86g of 1-bromotetradecane dropwise into the reaction flask, and continue to stir and react at 40°C 4h. Add 15 mL of deionized water and stir for 5 min, then transfer the solution to a separatory funnel, and extract the product with chloroform (15 mL×5). The chloroform layers were combined, anhydrous magnesium sulfate was added and allowed to stand overnight. Suction filtration and rotary evaporation gave yellow liquid, ethyl acetate was used as mobile phase column chromatography to obtain imidazole tetradecane. ¹ H NMR (500MHz, CDCl ₃ )δ7.44(s,1H),7.04(s,1H),6.89(s,1H),3.91(t,2H),1.76(m,2H),1.24～1.29( m,22H), 0.87(t,3H).

Example 5

Add 1g of imidazole, 0.82g of potassium hydroxide and 5mL of dimethyl sulfoxide into the reaction flask in sequence, and after stirring at room temperature for 2 hours, add 4.25g of 1-bromohexadecane dropwise into the reaction flask, and continue stirring at 55°C for the reaction 4h. Add 15 mL of deionized water and stir for 5 min, then transfer the solution to a separatory funnel, and extract the product with chloroform (15 mL×5). The chloroform layers were combined, anhydrous magnesium sulfate was added and allowed to stand overnight. Suction filtration and rotary evaporation gave yellow liquid, ethyl acetate was used as mobile phase column chromatography to obtain imidazole hexadecane. ¹ H NMR (500MHz, CDCl ₃ )δ7.45(s,1H),7.04(s,1H),6.89(s,1H),3.91(t,2H),1.77(m,2H),1.24～1.30( m,26H), 0.87(t,3H).

Example 6

Add 1.26g of imidazole octane and 60mL of acetone into the reaction flask, slowly add 6.51g of 1,2-dibromoethane dropwise, reflux and stir at 35°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(2-bromoethyl)-3-octyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.23(s,1H),7.81(s,1H),7.37(s,1H),4.94(t,2H),4.29(t,2H),3.93(t, 2H), 1.87～1.94(m,2H), 1.22～1.32(m,10H), 0.84(t,3H).

Example 7

Add 1.26g of imidazole octane and 45mL of acetone into the reaction flask, slowly add 5.99g of 1,4-dibromobutane dropwise, and stir the reaction under reflux at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(4-bromobutyl)-3-octyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.39(s,1H),7.63(s,1H),7.40(s,1H),4.47(t,2H),4.28(t,2H),3.45(t, 2H), 2.07～2.14(m,2H), 1.86～1.95(m,4H), 1.20～1.30(m,10H), 0.82(t,3H).

Example 8

Add 1.26g of imidazole octane and 45mL of acetone into the reaction flask, slowly add 6.77g of 1,6-dibromohexane dropwise, and stir the reaction under reflux at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(6-bromohexyl)-3-octyl-1H-imidazolium bromide. ¹ H NMR(500MHz,DMSO)δ9.29(s,1H),7.83(d,2H),4.17(m,4H),3.51(t,2H),1.75～1.83(m,6H),1.36～1.43 (m,2H), 1.22～1.25(m,12H), 0.84(t,3H).

Example 9

Add 1.46g of imidazolane and 60mL of acetone into the reaction flask, slowly add 6.51g of 1,2-dibromoethane dropwise, and stir the reaction under reflux at 35°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(2-bromoethyl)-3-decyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.31(s,1H),7.80(s,1H),7.36(s,1H),4.95(t,2H),4.29(t,2H),3.93(t, 2H), 1.88～1.94(m,2H), 1.22～1.32(m,14H), 0.85(t,3H).

Example 10

Add 1.46g of imidazolane and 45mL of acetone into the reaction flask, slowly add 5.99g of 1,4-dibromobutane dropwise, and stir the reaction under reflux at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(4-bromobutyl)-3-decyl-1H-imidazolium bromide. ¹ H NMR (500MHz, DMSO) δ9.29(s,1H),7.83(d,2H),4.23(t,2H),4.16(t,2H),3.56(t,2H),1.88～1.94(m ,2H), 1.75～1.81(m,4H), 1.17～1.26(m,14H), 0.84(t,3H).

Example 11

Add 1.46g of imidazolane and 45mL of acetone into the reaction flask, slowly add 6.77g of 1,6-dibromohexane dropwise, reflux and stir at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(6-bromohexyl)-3-decyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.47(s,1H),7.56(s,1H),7.43(s,1H),4.36(t,2H),4.29(t,2H),3.35(t, 2H), 1.77～1.96(m,6H), 1.42～1.49(m,2H), 1.31～1.38(m,2H), 1.18～1.28(m,14H), 0.81(t,3H).

Example 12

Add 1.65g of imidazole dodecane and 60mL of acetone into the reaction flask, slowly add 6.51g of 1,2-dibromoethane dropwise, and stir the reaction under reflux at 35°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(2-bromoethyl)-3-dodecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.23(s,1H),7.89(s,1H),7.42(s,1H),4.92(t,2H),4.28(t,2H),3.92(t, 2H), 1.86 ~ 1.92 (m, 2H), 1.20 ~ 1.30 (m, 18H), 0.83 (t, 3H).

Example 13

Add 1.65g of imidazole dodecane and 45mL of acetone into the reaction flask, slowly add 5.99g of 1,4-dibromobutane dropwise, reflux and stir at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(4-bromobutyl)-3-dodecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.49(s,1H),7.62(s,1H),7.40(s,1H),4.48(t,2H),4.28(t,2H),3.45(t, 2H), 2.08～2.15(m,2H), 1.85～1.96(m,4H), 1.20～1.30(m,18H), 0.84(t,3H).

Example 14

Add 1.65g of imidazole dodecane and 45mL of acetone into the reaction flask, slowly add 6.77g of 1,6-dibromohexane dropwise, reflux and stir at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(6-bromohexyl)-3-dodecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.57(s,1H),7.50(s,1H),7.39(s,1H),4.38(t,2H),4.31(t,2H),3.38(t, 2H), 1.80～1.98(m, 6H), 1.45～1.52(m,2H), 1.34～1.41(m,2H), 1.26～1.31(m,18H), 0.84(t,3H).

Example 15

Add 1.85g of imidazolium tetradecane and 60mL of acetone into the reaction flask, slowly add 6.51g of 1,2-dibromoethane dropwise, reflux and stir at 35°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(2-bromoethyl)-3-tetradecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.32(s,1H),7.82(s,1H),7.36(s,1H),4.91(t,2H),4.29(t,2H),3.94(t, 2H), 1.86 ~ 1.93 (m, 2H), 1.20 ~ 1.31 (m, 22H), 0.85 (t, 3H).

Example 16

Add 1.85g of imidazolium tetradecane and 45mL of acetone into the reaction flask, slowly add 5.99g of 1,4-dibromobutane dropwise, reflux and stir at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(4-bromobutyl)-3-tetradecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, DMSO) δ9.25(s,1H),7.81(d,2H),4.22(t,2H),4.16(t,2H),3.56(t,2H),1.88～1.95(m ,2H), 1.73～1.81(m,4H), 1.17～1.28(m,22H), 0.84(t,3H).

Example 17

Add 1.85g of imidazolium tetradecane and 45mL of acetone into the reaction flask, slowly add 6.77g of 1,6-dibromohexane dropwise, and stir the reaction under reflux at 50°C, and monitor the reaction progress by thin layer chromatography (TLC). The reaction solution was rotary evaporated and then washed with n-hexane for 4-5 times to obtain a viscous liquid. The mobile phase was separated by column chromatography using acetone:methanol=10:1 to obtain the intermediate 1-(6-bromohexyl)-3-tetradecyl-1H-imidazolium bromide. ¹ H NMR (500MHz, CDCl ₃ )δ10.47(s,1H),7.55(s,1H),7.42(s,1H),4.36(t,2H),4.29(t,2H),3.36(t, 2H), 1.77～1.96(m,6H), 1.42～1.49(m,2H), 1.31～1.38(m,2H), 1.18～1.28(m,22H), 0.82(t,3H).

Example 18

Add 1.47g of 1-(2-bromoethyl)-3-octyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.76g of imidazole hexadecane dropwise, reflux and stir at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid precipitated out. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₈ -2-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.33(d,2H),8.84(d,2H),7.15(d,2H), 5.30(s,4H),4.15(t,4H),1.91(m, 4H), 1.24～1.34 (m, 36H), 0.87 (t, 6H).

Example 19

Add 1.57g of 1-(4-bromobutyl)-3-octyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.76g of hexadecane of imidazolium dropwise, reflux and stir at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid precipitated out. It was filtered with suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₈ -4-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.19(s,2H),8.05(s,2H),7.21(s,2H),4.58(s,4H),4.24(t,4H),2.19(d, 4H), 1.87～1.90(m,4H), 1.23～1.32(m,36H), 0.86(t,6H).

Example 20

Add 1.68g of 1-(6-bromohexyl)-3-octyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.76g of imidazole hexadecane dropwise, and react under reflux at 60°C for 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₈ -6-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.51(s,2H),7.88(s,2H),7.19(d,2H),4.46(t,4H),4.29(t,4H),2.05(m, 4H), 1.91(m, 4H), 1.52(t, 4H), 1.22～1.34(m, 36H), 0.87(t, 6H).

Example 21

Add 1.57g of 1-(2-bromoethyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, reflux and stir at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder, and the surfactant [C ₁₀ -2-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.31(d,2H),8.80(d,2H),7.17(d,2H),5.28(s,4H),4.16(t,4H),1.92(m, 4H), 1.22～1.31 (m, 36H), 0.87 (t, 6H).

Example 22

Add 1.69g of 1-(4-bromobutyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, reflux and stir at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₀ -4-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.27(s,2H),7.96(s,2H),7.15(s,2H),4.58(t,4H),4.24(t,4H),2.22(d, 4H), 1.88～1.93(m, 4H), 1.22～1.33(m, 36H), 0.87(t, 6H).

Example 23

Add 1.80g of 1-(6-bromohexyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, and react under reflux at 60°C for 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₀ -6-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.49(s,2H),7.90(s,2H),7.20(s,2H),4.46(t,4H),4.28(t,4H),2.05(m, 4H), 1.90(m, 4H), 1.51(s, 4H), 1.24～1.33(m, 36H), 0.87(t, 6H).

Example 24

Add 1.57g of 1-(2-bromoethyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazole hexadecane dropwise, reflux and stir at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₀ -2-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz,DMSO)δ9.17(s,2H),7.80(s,2H),7.68(s,2H),4.69(s,4H),4.13(t,4H),1.71(m,4H ), 1.19～1.23(m,40H), 0.84(t,6H).

Example 25

Add 1.69g of 1-(4-bromobutyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of hexadecane of imidazolium dropwise, and react under reflux at 60°C for 48h . Ethyl acetate was added after rotary evaporation, and a white solid precipitated out, which was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder, and the surfactant [C ₁₀ -4-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.26(s,2H),8.00(s,2H),7.17(s,2H),4.58(s,4H),4.24(t,4H),2.23(d, 4H), 1.90(m, 4H), 1.24～1.33(m, 40H), 0.87(t, 6H).

Example 26

Add 1.80g of 1-(6-bromohexyl)-3-decyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of hexadecane imidazolium dropwise, and react under reflux at 60°C for 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₀ -6-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.31(s,2H),7.91(s,2H),7.26(s,2H),4.44(t,4H),4.27(t,4H),2.02(m, 4H), 1.89(m, 4H), 1.48(m, 4H), 1.23～1.31(m, 40H), 0.85(t, 6H).

Example 27

Add 1.69g of 1-(2-bromoethyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuum to obtain a white powder, and the surfactant [C ₁₂ -2-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz,DMSO)δ9.18(s,2H),7.81(s,2H),7.70(s,2H),4.68(s,4H),4.12(t,4H),1.73(m,4H ), 1.18～1.23(m,40H), 0.85(t,6H).

Example 28

Add 1.80g of 1-(4-bromobutyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuum to obtain a white powder, and the surfactant [C ₁₂ -4-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.28(s,2H),7.96(s,2H),7.15(s,2H),4.58(t,4H),4.24(t,4H),2.23(s, 4H), 1.86 ~ 1.93 (m, 4H), 1.24 ~ 1.33 (m, 40H), 0.87 (t, 6H).

Example 29

Add 1.91g of 1-(6-bromohexyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.58g of imidazolium tetradecane dropwise, reflux and stir at 60°C 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₂ -6-C ₁₄ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.25(s,2H),7.90(s,2H),7.27(s,2H),4.43(t,4H),4.27(t,4H),2.01(m, 4H), 1.85～1.91(m,4H), 1.48(m,4H), 1.19～1.31(m,40H), 0.85(t,6H).

Example 30

Add 1.69g of 1-(2-bromoethyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₂ -2-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz,DMSO)δ9.07(s,2H),7.80(s,2H),7.64(s,2H),4.67(s,4H),4.11(t,4H),1.72(m,4H ), 1.18-1.23 (m, 44H), 0.84 (t, 6H).

Example 31

Add 1.80g of 1-(4-bromobutyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuum to obtain a white powder, and the surfactant [C ₁₂ -4-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.31(s,2H),7.98(s,2H),7.15(s,2H),4.58(s,4H),4.24(t,4H),2.23(s, 4H), 1.86 ~ 1.92 (m, 4H), 1.22 ~ 1.33 (m, 44H), 0.87 (t, 6H).

Example 32

Add 1.91g of 1-(6-bromohexyl)-3-dodecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and reflux and stir at 60°C 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder, and the surfactant [C ₁₂ -6-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ ) δ10.56(d,2H),7.80(d,2H),7.18(d,2H),4.46(t,4H),4.29(t,4H),2.02～2.09( m,4H), 1.88～1.94(m,4H), 1.53(t,4H), 1.24～1.34(m,44H), 0.87(t,6H).

Example 33

Add 1.80g of 1-(2-bromoethyl)-3-tetradecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid precipitated out. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₄ -2-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz,DMSO)δ9.17(s,2H),7.81(s,2H),7.63(s,2H),4.69(s,4H),4.12(t,4H),1.71(m,4H ), 1.18～1.24(m,48H), 0.86(t,6H).

Example 34

Add 1.91g of 1-(4-bromobutyl)-3-tetradecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and stir under reflux at 60°C Reaction 48h. Ethyl acetate was added after rotary evaporation, and a white solid precipitated out. It was filtered by suction, recrystallized three times with acetone, and dried in vacuo to obtain a white powder. The surfactant [C ₁₄ -4-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, CDCl ₃ )δ10.30(s,2H),7.99(s,2H),7.16(s,2H),4.58(s,4H),4.24(t,4H),2.22(s, 4H), 1.88 ~ 1.91 (m, 4H), 1.24 ~ 1.33 (m, 48H), 0.87 (t, 6H).

Example 35

Add 2.02g of 1-(6-bromohexyl)-3-tetradecyl-1H-imidazolium bromide and 12mL of isopropanol into the reaction flask, then add 1.75g of imidazolium hexadecane dropwise, and reflux and stir at 60°C 48h. Ethyl acetate was added after rotary evaporation, and a white solid was precipitated, which was filtered by suction, recrystallized three times with acetone, and dried in vacuum to obtain a white powder, and the surfactant [C ₁₄ -6-C ₁₆ im]Br ₂ was obtained. ¹ H NMR (500MHz, DMSO) δ9.21(s, 2H), 7.80(d, 4H), 4.15(t, 8H), 1.78(m, 8H), 1.22～1.25(m, 52H), 0.85(t ,6H).

performance measurement

From all the synthesized final products, three kinds of asymmetric geminiidazole surfactants with a total hydrophobic carbon chain length of 24 and 4 methylene groups as intermediate linking groups were selected, and the asymmetry of the alkane main chain was investigated by the conductivity method The ^test _results ^{are shown} in _{Table 1} .

Table 1 The cmc and thermodynamic parameters of [C _m -4-C _n im]Br ₂

The spontaneous micellization process (ΔG _m ^θ <0) comes from the joint influence of two factors, entropy and enthalpy. Studies have shown that the association of ordinary single-head group and single-alkane chain surfactants in aqueous solution to form micelles is mainly driven by entropy. The entropy-driven mechanism believes that when surfactant molecules are dissolved in water, the water molecules will surround the alkane chains and combine with hydrogen bonds to form structured water, that is, the iceberg structure, resulting in a decrease in the entropy of water. The water system will try to repel the alkane chains of the surfactant molecules so as to destroy the iceberg structure and increase the entropy of the system, thereby promoting the aggregation of these alkane chains to form micelles. The enthalpy change (ΔH _m ^θ ) of the micellization process mainly comes from the following factors: van der Waals force and hydrophobic interaction between alkane chains, head group repulsion, and for gemini surfactants, there are also changes in the configuration of the linkage chain. energy changes, etc. The significant increase in the contribution ratio of ΔH _m ^θ to ΔG _m ^θ has important scientific significance. As mentioned above, the entropy drive is derived from the iceberg structure formed by the hydrogen bond association between solvent and water molecules, and most of the surfactant self-organization behaviors currently investigated need to rely on solvents with strong hydrogen bond tendencies. Significant self-organization is less likely to exist in solvents that form hydrogen bonds. If the enthalpy contribution is dominant in the self-organization process of surfactants, it is expected that the self-organization behavior will occur through those solvents that do not rely on hydrogen bonds (such as some ionic liquid solvents with green characteristics).

It can be seen from Table 1 that as the asymmetry m/n increases, cmc gradually decreases, and both ΔG _m ^θ and ΔH _m ^θ become more negative. The change of ΔG _m ^θ indicates that the micellization process of geminimidazole surfactants with larger asymmetry degree m/n is more likely to proceed spontaneously. In addition, with the increase of asymmetry m/n, the contribution of ΔH _m ^θ to the negative value of ΔG _m ^θ increases obviously. Therefore, cmc and ΔH _m ^θ can be adjusted by adjusting the asymmetry of the alkane backbone, and the contribution ratio of ΔH _m ^θ to ΔG _m ^θ can be increased, thereby expanding the application range of gemini surfactants and further understanding molecular self-organization behavior essential law.

Claims (7)

1. a kind of asymmetric Shuangzi imidazoles surfactant, it is characterised in that structure is as follows：

Wherein, R¹,R²=-C₈H₁₇、-C₁₀H₂₁、-C₁₂H₂₅、-C₁₄H₂₉、-C₁₆H₃₃,R¹≠R²；S=2,4,6.

2. a kind of preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 1, its It is characterised by, comprises the steps：

(1) imidazoles and potassium hydroxide are reacted in the presence of solvent DMSO, adding 1- brominated alkanes is carried out Reaction, carries out column chromatography for separation using ethyl acetate as mobile phase and obtains chain alkyl imidazoles；

(2) chain alkyl imidazoles carries out single bromine nucleophilic substitution in the presence of solvent acetone with dibromoalkane hydrocarbon, Column chromatography for separation is carried out as mobile phase using the mixed solvent of acetone and methanol and obtain intermediate；

(3) intermediate for obtaining and chain alkyl imidazoles are carried out into nucleophilic displacement of fluorine in the presence of solvent isopropanol anti- Should, be successively recrystallized to give by ethyl acetate and acetone described in surfactant.

3. the preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 2, its feature It is that, in step (1), 1- brominated alkanes are 1- bromooctanes, 1- bromodecanes, Dodecyl Bromide, 1- In bromotetradecane and 1- bromohexadecanes any one.

4. the preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 2, its feature It is that, in step (1), imidazoles is more than 2h with the response time of potassium hydroxide；After adding 1- brominated alkanes Reaction more than 4h.

5. the preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 2, its feature It is that, in step (2), dibromoalkane hydrocarbon is glycol dibromide, Isosorbide-5-Nitrae-dibromobutane and 1,6- dibromo-hexane In any one.

6. the preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 2, its feature It is that, in step (2), the reaction mol ratio of chain alkyl imidazoles and dibromoalkane hydrocarbon is 1:2～1:6；Reaction Temperature is 30～60 DEG C；Response time is 8～14h；5～8 times for reactant gross mass of solvent acetone volume.

7. the preparation method of asymmetric Shuangzi imidazoles surfactant as claimed in claim 2, its feature It is that, in step (3), the reaction mol ratio of intermediate and chain alkyl imidazoles is 1:1～1:3, reaction temperature For 30～80 DEG C, the response time is 8～72h.