- Email: [email protected]
Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties and antibacterial activity
MOLLIQ-112248; No of Pages 7 Journal of Molecular Liquids xxx (xxxx) xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties and antibacterial activity Junyan Wu a, Hemin Gao a, Diandian Shi c, Yufei Yang a, Yadong Zhang a,b,⁎, Weixia Zhu a,⁎ a b c
School of Chemistry and Energy, Zhengzhou University, Zhengzhou 450001, China Jiyuan Research Institute, Zhengzhou University, Zhengzhou 450001, China State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 6 September 2019 Received in revised form 27 November 2019 Accepted 29 November 2019 Available online xxxx Keywords: Gemini surfactants Diamide and diester groups Surface properties Antibacterial activity
a b s t r a c t Nine novel cationic gemini surfactants containing both amide and ester groups were synthesized through a three-step reaction. These surfactants have the general formula of CnH2n+1OOCCH2N+(CH2)2-(CH2)3-NHOC(CH2)m-CONH-(CH2)3-N+(CH2)2CH2COOCnH2n+1 (with n = 8, 10, 12 and m = 2, 3, 4), named BEQA-n, PEQAn and HEQA-n (B, P, H correspond to surfactants of m = 2, 3, 4 and n = 8, 10, 12, respectively). Chemical structures, surface activity, cleavable properties, electrolytes tolerance, foam properties and antibacterial activity of these surfactants were successively investigated. The results show that the surfactants have lower critical micelle concentration (CMC) than traditional monomer surfactants. The values of CMC and the degree of counter ion dissociation (α) depend on the lengths of hydrophobic chain and spacer. The values of Krafft temperatures (Kt b 0 °C) and the standard Gibbs free energy (ΔG0mic b 0) indicate that all surfactants have good water solubility and micelle-forming ability. The simultaneous presence of the amide and ester groups makes these surfactants have good hydrolytic ability in both basic and the acidic solutions. In addition, the surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2. It is worth mentioning that EQA-8 and PEQA-12 have 200 g/L NaCl tolerance. Moreover, all of the surfactants have certain antibacterial activity against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922), and the surfactants with hydrophobic chain length n = 10 have the strongest antibacterial activity. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Gemini surfactants are composed of two hydrophobic chains and two hydrophilic head groups linked by a spacer of flexible or rigid group. These surfactants have received widespread attention since bisquaternary ammonium bromide gemini surfactants were synthesized by Bunton team [1]. Compared with conventional surfactants, gemini surfactants have lower CMC, unusual aggregation behavior, better water solubility and antibacterial activity. Therefore, Gemini surfactants are widely used in the fields of bactericides [2], corrosion inhibitors [3], clothing antistatic [4], dye adsorption [5], porous materials [6], enhanced oil recovery [7] and so on. Cationic gemini surfactants containing two cationic hydrophilic head groups are the most widely investigated gemini surfactants [8–10]. Their properties can be significantly altered by introducing different functional groups or changing the lengths of the hydrophobic chain and spacer [11,12]. For instance, the introduction of hydroxyl ⁎ Corresponding authors at: School of Chemistry and Energy, Zhengzhou University, Zhengzhou 450001, China. E-mail addresses: [email protected] (Y. Zhang), [email protected] (W. Zhu).
could significantly improve the water solubility of the cationic gemini surfactants [13], the introduction of amide, ester and Si-O-Si groups helped the cationic gemini surfactants achieve good degradation ability [14–16]. In addition, changes in the lengths of the hydrophobic chain and spacer group also gave rise to different CMC, foam properties and antibacterial activity of the cationic gemini surfactants [17,18]. Due to the widespread use of surfactants, environmental problems caused by these compounds are becoming increasingly serious. The presence of positively charged nitrogen atoms and hydrophobic chains in the cationic gemini surfactants makes them be adsorbed more easily by the sludge and penetrate into water [19]. Moreover, cationic surfactants are usually toxic to the bacteria, algae, ciliated protozoa and crustaceans [20,21]. Therefore, it is highly desirable to develop a kind of cleavable cationic gemini surfactant. In this work, nine gemini surfactants containing both amide and ester groups with different lengths of spacer and hydrophobic chain were synthesized in a three-step reaction. The effects of spacer and hydrophobic chain lengths on these surfactants' surface activity, electrolyte tolerance and foaming properties were discussed. The cleavable properties of the gemini surfactants were determined by their chemical hydrolysis. Furthermore, the antibacterial activity of these surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-
https://doi.org/10.1016/j.molliq.2019.112248 0167-7322/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
2
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
negative bacteria (E. coli ATCC 25922) were evaluated by the minimum inhibitory concentration (MIC) values. 2. Experimental 2.1. Materials and methods Butanedioic acid, pentanedioic acid, hexanedioic acid, N,N-dimethyl1,3-propane diamine, phosphorous acid, chloroacetyl chloride were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 1octanol, 1-decanol, 1-dodecanol were obtained from Shanghai McLean Biochemical Technology Co., Ltd. Xylene, dichloromethane, acetonitrile, ethyl acetate, sodium hydrogen carbonate and magnesium sulfate anhydrous were all analytically pure and purchased from Tianjin Komiou Chemical Reagent Co., Ltd. E. coli ATCC 25922 and S. aureus ATCC 25923 were obtained from Beijing Solarbio Science & Technology Co., Ltd. Water was deionized before use. FT-IR spectra of the compounds were determined on a Thermo Nicolet IR 200 spectroscope. 1H NMR spectra were performed on a Bruker ADVANCE III 400 spectrometer with CDCl3 as the solvent. 2.1.1. Synthesis of N,N-bis[3-(dimethylamine)propyl]-diamine 0.2 mol diacid (butanedioic acid/pentanedioic acid/hexanedioic acid), 0.5 mol N,N-dimethyl-1,3-propanediamine and 150 mL xylene were added into a 250 mL three-necked flask. The reaction refluxed at 160 °C for 15 h with 0.4 wt% of phosphorous acid. The process was monitored by water with a dean-stark trap apparatus, and the product was cooled to room temperature and filtered. Then, it was washed three times with ethyl acetate. The yield ranged from 93% to 95%. 2.1.2. Synthesis of n-alkyl-α-halo-acetates The synthesis of n-alkyl-α-halo-acetates was according to the literature [22] and the method was slightly changed. The process was as follows. 0.2 mol n-alkanoles (n-octanol/n-nonanol/dodecyl alcohol) and 0.24 mol chloroacetyl chloride were added into a 250 mL round bottom flask and refluxed at 50 °C for 8 h with 100 mL dichloromethane as a solvent. After completion of the reaction, the solvent was removed by a vacuum rotary evaporator, and the residue was neutralized with saturated sodium hydrogen carbonate solution. After separated and washed with deionized water, the organic layer was dried by anhydrous magnesium sulfate. The yield ranged from 96% to 97%. 2.1.3. Synthesis of cationic gemini surfactants 0.02 mol N,N-bis[3-(dimethylamine)propyl]-diamine, 0.05 mol nalkyl-α-halo-acetates, and 30 mL ethyl acetate were added into a 100 mL round bottom flask, and refluxed at 80 °C for 24 h. Then, the crude product was filtered and washed/recrystallized with a mixed solution of acetonitrile/ethyl acetate. The obtained nine cationic gemini surfactants were named as BEQA-n, PEQA-n and HEQA-n, wherein B, P, H corresponded to surfactants having methylene groups (m = 2, 3, 4) in the middle of the spacer group. E, Q, and A corresponded to ester groups, quaternary ammonium ions, and amide groups, respectively. And n represented the length of the hydrophobic chains. The yield ranged from 75% to 88%. 2.2. Electrical conductivity measurements In order to get the CMC and α values of the cationic gemini surfactants, the specific conductivities (κ) of surfactant solutions with different concentrations were obtained by a DDS-307 conductivity meter (Shanghai Leici Instrument Co. Ltd., China) at 25 °C. These CMC values were considered to be the turning point of the conductivity curves, and α values were determined by the ratio of the conductivity curve slopes before and after CMC [23–25].
2.3. Krafft temperature measurements 1 wt% of nine cationic gemini surfactant solutions were placed in freezer at a temperature below 0 °C for at least 24 h so that the solutions became cloudy or solid. Then, the solutions were placed in a thermostat to be slowly heated. The Krafft temperature (Kt) is the temperature when the solutions become clear [16,26]. 2.4. Chemical hydrolysis 10 mL surfactant solutions (10 mmol/L) were separately added into 25 mL glass vials at 40 °C. Then, 10 mL NaOH solution (0.05 mol/L) or H2SO4 solution (2 mol/L) was added. The time when the surfactant solutions became cloudy was observed and recorded [27]. 2.5. Electrolytes tolerance 10 mL surfactant solutions (0.3 wt%) were mixed with 10 mL different concentrations of NaCl or CaCl2 solutions at 25 °C for 24 h. The transmittance (T %) of these mixed solutions was determined by a UV2600-A UV–Vis spectrophotometer (UNICO, USA). The higher transmittance means the stronger electrolytes tolerance [23]. 2.6. Foam height At room temperature, 100 mL 0.1 wt% surfactant solutions were added into 500 mL graduated cylinder and subjected to vigorous shake for 10 s then the resulting foam height (in mL) was measured. The foam stability of the solutions was measured after 3 min [28]. 2.7. Antibacterial activity The antibacterial activity of nine cationic gemini surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922) was studied by broth dilution method [29], and the minimum inhibitory concentration (MIC) values of these surfactants on the two strains were obtained. The procedure was as follows. The strains were individually inoculated into the nutrient agar plates with an inoculating loop and activated at 37 °C for 24 h. Then, the activated strains were separately inoculated into nutrient broth and configured to a bacterial suspension at a concentration of 1–2 × 106 CFU/mL. These surfactants were diluted into broth and 1 mL of each was added into a sterile tube. Finally, 1 mL of the diluted bacterial suspension was added to make the concentration of the surfactants in the range of 1–512 μg/mL, and the final concentration of the inoculum was 5–10 × 105 CFU/mL [30,31]. 3. Result and discussion 3.1. Synthesis Nine new cationic gemini surfactants containing amide and ester groups were synthesized and the specific synthetic routes were shown in Scheme 1. In the first step, the compounds 1, 2, and 3 were prepared by acylation of butanedioic acid, pentanedioic acid and hexanedioic acid with N,N-dimethyl-1,3-propanediamine, respectively. Then the n-alkanoles (n-octanol/n-nonanol/n-dodecyl alcohol) were esterified with chloroacetyl chloride and generated compounds 4, 5, and 6. Finally the gemini surfactants BEQA-8, BEQA-10, BEQA-12, PEQA-8, PEQA-10, PEQA-12, HEQA-8, HEQA-10, HEQA-12 were obtained by quaternization of these tertiary amine with ester. The tertiary amine compounds (1–3) and all the surfactants were characterized by FT-IR and 1H NMR spectra. These spectra data were listed in the supporting information section.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
3
Scheme 1. Synthetic route of the the cationic gemini surfactants containing both amide and ester groups (n = 8, 10, 12, m = 2, 3, 4).
3.2. Surface activity Fig. 1 shows the relationship between specific conductivity (κ) and concentration of nine cationic gemini surfactants at 25 °C. The CMC and α data of these surfactants are listed in Table 1. The CMC values of these surfactants ranged from 1.50 to 2.62 mmol/L. BEQA-12, PEQA-12 and HEQA-12 had significantly lower CMC than the traditional surfactants of N-dodecyl-N,N-dimethylammonium chloride (15.8 mmol/L) and N-dodecyl-N,N,N-trimethylammonium chloride (21 mmol/L) at 25 °C [32], which demonstrated that the gemini surfactants have more excellent aggregation properties than the corresponding monomer surfactants. Moreover, it could be observed that the CMC decreased with the simultaneous introduction of amide and ester groups by comparing BEQA-12, PEQA-12 and HEQA-12 with the reported surfactant named C12-PG-C12 (CMC value is 1.858 mmol/L at 25 °C) [16]. This phenomenon was because the amide and ester groups tended to form hydrogen bonds, which made the surfactants form micelles more susceptible. The conclusion is consistent with previous reports [33,34].
The CMC and α values of these surfactants decreased with the length of the hydrophobic chain increased. This was attributed to the increase of hydrophobic chain length enhanced hydrophobicity of the surfactants and made these surfactants easier to form micelles [35]. Except BEQA-12, the CMC values of these surfactants increased with the longer spacer group. This conclusion was the same with previous investigation [18,36]. This was partly related to the longer spacer group increased the distance between these surfactant head groups. On the other hand, longer methylene groups at the center of the spacer easily hindered the amide group in the surfactant spacer group to form intramolecular hydrogen bonds [37]. Accordingly, the surfactants with longer spacer formed fewer intramolecular hydrogen bonds and micelles. What was different from previous studies [38] was that the α values of the surfactants did not decrease completely with the increase of the length of the spacer. When the hydrophobic chain length was same, the α values of BEQA-n were significantly lower than PEQA-n and similar to HEQA-n. This may also be related to the shorter spacer group of the BEQA-n surfactants, which formed more intramolecular hydrogen
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
4
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
Fig. 1. Plots of conductivity versus concentration for surfactants at 25 °C. (a) BEQA-n, (b) PEQA-n, (c) HEQA-n.
bonds in the spacer group to promote the micelle formation of surfactants. The standard Gibbs free energy of micellization (ΔG0mic) was calculated by equation (Eq. (1)) [39]; ΔG0 mic ¼ RTð3−2αÞ ln CMC−RTln2
ð1Þ
where α is the degree of counter ion dissociation, CMC is the critical micelle concentration (mol/L), R is the gas constant (8.314 J/(mol·K)) and T is the temperature (K). The ΔG0mic of nine surfactants were listed in Table 1. The values of ΔG0mic ranged from −29.44 kJ/mol to −21.22 kJ/ mol. These negative values indicated all surfactants in this work had spontaneous micelle formation process. Table 1 Surface properties of nine cationic gemini surfactants. Surfactants
CMC (mmol/L)
α
Kt (°C)
ΔG0mic (kJ/mol)
tA (min)
tB (s)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
2.26 (±0.01) 2.11 (±0.01) 1.55 (±0.01) 2.56 (±0.01) 2.27 (±0.01) 1.37 (±0.01) 2.62 (±0.01) 2.48 (±0.01) 1.50 (±0.01)
0.756 0.742 0.701 0.841 0.822 0.750 0.742 0.734 0.640
b0 b0 b0 b0 b0 b0 b0 b0 b0
−24.19 −24.87 −27.34 −21.22 −22.18 −26.23 −24.06 −24.50 −29.44
1 34 210 1 41 255 1 46 340
10 15 20 10 10 20 10 15 25
CMC, critical micelle concentration; α, degree of counter ion dissociation; Kt, Krafft temperature; ΔG0mic, standard Gibbs free energy of micellization; tA, the time of acidic hydrolysis; tB, the time of basic hydrolysis.
3.3. Krafft temperature The Krafft temperature (Kt) for the nine cationic gemini surfactants was listed in Table 1. All of the surfactant solutions remained clear after 24 h in the freezer. This phenomenon indicated that the Krafft temperature of these surfactants was b0 °C, which indicated that the nine cationic gemini surfactants had good solubility in water [16].
3.4. Cleavable properties The amide and ester bonds are considered to be cleavable, by introducing these groups into the surfactants and making them cleavable [40,41]. The cleavable properties were investigated by the chemical hydrolysis of the nine cationic gemini surfactants in basic and acidic solutions [42], and these data are shown in Table 1. FT-IR spectrums of the HEQA-10 after basic and acidic hydrolysis (6 h) were shown in Fig. S3. As shown in Table 1, all of the surfactants were hydrolyzed in a 0.05 mol/L NaOH solution for b30 s, and the hydrolysis time of the surfactants in a 2 mol/L H2SO4 solution was b6 h. The characteristic peaks of amide i.e. β(N\\H) and ν(C\\N) at 1548 cm−1 and 1247 cm−1 disappeared and the characteristic peak of ester i.e. ν(C=O) at 1746 cm−1 was shifted to 1633–1634 cm−1 after basic and acidic hydrolysis (Figs. S1b and S3). These data indicated that all surfactants were susceptible to hydrolyze in both basic and acidic solutions. This was quite different from other gemini surfactants, these surfactants have been reported for harder hydrolysis in the acidic solutions [27,41]. Accordingly, the simultaneous introduction of amide and ester groups allows the
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
surfactants to have batter cleavable properties. Furthermore, as the length of the hydrophobic chain increases, the hydrolytic stability of the surfactants increases, but the influence of the length of the spacer is not significant. 3.5. Electrolytes tolerance The electrolytes could significantly decrease the water solubility of surfactants, thereby affecting the various properties of the surfactants. Fig. 2 show the transmission (T %) of nine cationic gemini surfactant solutions corresponding to the presence of different concentrations of NaCl and CaCl2. The electrolytes tolerance parameters of these surfactants were determined by the electrolytes concentration when the surfactant solutions transmittance changed sharply, and these data were listed in Table 2. It was clearly shown that these surfactants had less tolerance to CaCl2 than NaCl. It may relate to the addition of Na+ and Ca2+ reduced the hydration of the surfactants, which led to the easier precipitation of these surfactants, and the effect of Ca2+ was more pronounced [43]. As the length of the hydrophobic chain increases, the electrolyte tolerance of the surfactants to NaCl gradually decreases, which is more conspicuous than increasing the length of the spacer. Specially, both BEQA-8 and PEQA-12 exhibited excellent tolerance to NaCl and their NaCl tolerance parameters were N200 g/L. However, in the presence of CaCl2, it was very different. The surfactants exhibited lower tolerance to CaCl2 when the hydrophobic chain length was 10. This is attributed to the micellization is affected by the area of the hydrophilic head groups on the surface of the micelles, the length and size of the hydrophobic chain. And the addition of different electrolytes alters these microstructures of the surfactants [44]. 3.6. Foam properties The foam properties of surfactants have a significant impact on their practical application. Fig. 3 showed the foam height and foam stability of nine cationic gemini surfactants (0.1 wt%) at 25 °C. As the length of the hydrophobic chain increased, these surfactants were more abundant in foam and the foam stability also increased. This was attributed to the fact that the increase of hydrophobic chain enhanced the cohesion of the adsorbed molecules on the liquid membrane, which was advantageous for foaming and foam stability [45]. Compared with cationic gemini surfactants that have other spacer lengths, PEQA-n showed the best foam height, but their foam stability was relatively poor. Generally, foam stability is determined by various
5
Table 2 Electrolytes tolerance parameters of nine cationic gemini surfactants. Surfactants
NaCl(g/L)
CaCl2(g/L)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
N 200 38 30 75 26 N 200 70 28 26
23 7 18 16 6 22 18 6 20
factors such as surface tension, surface rheology, film elasticity and so on [46]. Therefore, the foam properties of these surfactants are complicated and deserve further investigation. 3.7. Minimum inhibitory concentration (MIC) Due to their unique properties, the cationic gemini surfactants exhibited excellent antibacterial activity. The antibacterial mechanism of these surfactants is presumed to be the electrostatic interaction between positively charged head groups and the negative charge on the surface of cellular cytoplasmic membrane. Meanwhile, the hydrophobic chains penetrate and disturb the selective permeability of the membrane, leading to cell death [47,48]. The antibacterial effect of the nine cationic gemini surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gramnegative bacteria (E. coli ATCC 25922) was investigated. The minimum inhibitory concentration (MIC) values were used to evaluate the antibacterial activity of surfactants, and these data were listed in Table 3. It has been found that the lengths of both the hydrophobic chain and the spacer affect the antibacterial activity of the surfactants, and these surfactants have stronger bactericidal effect when the hydrophobic chain is 10. In particular, the HEQA-10 showed the best antibacterial activity against both of E. coli ATCC 25922 and S. aureus ATCC 25923 strains. The effect of spacer lengths of these surfactants on their antibacterial activity appeared to be more complicated, and the antibacterial activity of PEQA-n was significantly lower than the surfactants with other spacer lengths. Moreover, most surfactants showed better antibacterial activity to S. aureus ATCC 25923. Which is related to the different cell wall compositions of Gram-positive bacteria and Gram-negative bacteria. The Grampositive bacterial cell wall is composed of a thick wall containing many
Fig. 2. Transmittance (T%) plots of cationic gemini surfactant solutions versus electrolytes at 25 °C. (a) NaCl, (b) CaCl2.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
6
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
Declaration of competing interest The authors declared that they have no conflicts of interest to this work. Acknowledgments The authors are grateful for the financial support provided by the National Natural Science Foundation of China (21706240) and the NSFC – He’nan Joint Fund General Project (162300410253). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.molliq.2019.112248. References Fig. 3. Plot of initial and 3 min foam properties of 0.1 wt% surfactants at 25 °C. (a: BEQA-8, b: PEQA-8, c: HEQA-8, d: BEQA-10, e: PEQA-10, f: HEQA-10, g: BEQA-12, h: PEQA-12, i: HEQA-12).
layers of peptidoglycan and teichoic acids, while the Gram-negative bacteria cell wall is composed of high lipopolysaccharides and porins. These proteins limit the entry of the hydrophobic chain into the Gram-negative bacteria [49–51]. 4. Conclusion Nine new cationic gemini surfactants containing both amide and ester groups were synthesized and characterized by FT-IR and 1H NMR spectra. The CMC values of the surfactants decrease as the length of the hydrophobic chain increases and most of the CMC values increase when the spacer length increases. The introduction of the amide and ester groups makes the surfactants readily to form micelles and cleave. These surfactants are susceptible to hydrolyze in both basic and acidic solutions. The surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2, and it is worth mentioning that the NaCl tolerance parameters of BEQA-8 and PEQA-12 are both N200 g/L. The surfactants with longer hydrophobic chains have better foam properties and PEQA-n produce more foam than the surfactants with other spacer lengths. Moreover, most of the cationic gemini surfactants showed good antibacterial activity against both Gram-negative and Gram-positive bacteria and HEQA-10 had the optimal performance. CRediT authorship contribution statement Junyan Wu: Conceptualization, Formal analysis, Investigation, Writing - original draft, Writing - review & editing. Hemin Gao: Investigation. Diandian Shi: Writing - review & editing. Yufei Yang: Writing - review & editing. Yadong Zhang: Writing - review & editing, Resources, Supervision. Weixia Zhu: Writing - review & editing, Resources, Supervision. Table 3 MIC values of nine cationic gemini surfactants for different strains. Compounds
E. coli ATCC 25922 (μg/mL)
S. aureus ATCC 25923 (μg/mL)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
512 128 256 512 256 256 256 64 128
512 64 128 512 128 256 256 32 64
[1] C.A. Bunton, L.B. Robinson, J. Schaak, M. Stam, J. Org. Chem. 36 (1971) 2346. [2] Y. Bao, Y. Zhang, J. Guo, J. Ma, Y. Lu, J. Clean. Prod. 206 (2019) 430. [3] M. Pakiet, I. Kowalczyk, R. Leiva Garcia, R. Moorcroft, T. Nichol, T. Smith, R. Akid, B. Brycki, Bioelectrochemistry 128 (2019) 252. [4] W. Zieliński, K.A. Wilk, G. Para, E. Jarek, K. Ciszewski, J. Palus, P. Warszyński, Colloids Surf. A Physicochem. Eng. Asp. 480 (2015) 63. [5] H. Zeng, M. Gao, T. Shen, F. Ding, Colloids Surf. A Physicochem. Eng. Asp. 555 (2018) 746. [6] S. Wang, Z. Zheng, B. He, C. Sun, X. Li, X. Wu, X. An, X. Xie, Appl. Organomet. Chem. 32 (2018) e4145. [7] S. Hussain, M.S. Kamal, M. Murtaza, Energies 12 (2019) 1731. [8] Y. Han, Y. Wang, Phys. Chem. Chem. Phys. 13 (2011) 1939. [9] K. Parikh, B. Mistry, S. Jana, S. Gupta, R.V. Devkar, S. Kumar, J. Mol. Liq. 206 (2015) 19. [10] B. Li, Q. Zhang, Y. Xia, Z. Gao, Colloids Surf. A Physicochem. Eng. Asp. 470 (2015) 211. [11] A.R. Tehrani-Bagha, J. Kärnbratt, J.-E. Löfroth, K. Holmberg, J. Colloid Interface Sci. 376 (2012) 126. [12] C. Yang, Z. Song, J. Zhao, Z. Hu, Y. Zhang, Q. Jiang, Colloids Surf. A Physicochem. Eng. Asp. 523 (2017) 62. [13] M. Mahdavian, A.R. Tehrani-Bagha, E. Alibakhshi, S. Ashhari, M.J. Palimi, S. Farashi, S. Javadian, F. Ektefa, Corros. Sci. 137 (2018) 62. [14] L.-H. Lin, K.-M. Chen, Colloids Surf. A Physicochem. Eng. Asp. 275 (2006) 99. [15] H. Liu, X. Zhou, X. Zhang, G. Shi, J. Hu, C. Liu, B. Xu, J. Chem. Eng. Data 63 (2018) 1304. [16] D. Xu, X. Ni, C. Zhang, J. Mao, C. Song, J. Mol. Liq. 240 (2017) 542. [17] A. Laschewsky, K. Lunkenheimer, R.H. Rakotoaly, L. Wattebled, Colloid Polym. Sci. 283 (2005) 469. [18] M.H. Alimohammadi, S. Javadian, H. Gharibi, A. reza Tehrani-Bagha, M.R. Alavijeh, K. Kakaei, J. Chem. Thermodyn. 44 (2012) 107. [19] E. Grabinska-Sota, J. Hazard. Mater. 195 (2011) 182. [20] G. Nałęcz-Jawecki, E. Grabińska-Sota, P. Narkiewicz, Ecotoxicol. Environ. Saf. 54 (2003) 87. [21] G. Jing, Z. Zhou, J. Zhuo, Chemosphere 86 (2012) 76. [22] E. Obłąk, A. Piecuch, A. Krasowska, J. Łuczyński, Microbiol. Res. 168 (2013) 630. [23] Y. Wang, Y. Jiang, T. Geng, H. Ju, S. Duan, Colloids Surf. A Physicochem. Eng. Asp. 563 (2019) 1. [24] O. Kaczerewska, B. Brycki, I. Ribosa, F. Comelles, M.T. Garcia, J. Ind. Eng. Chem. 59 (2018) 141. [25] N. Fatma, M. Panda, W.H. Ansari, Kabir-ud-Din, J. Mol. Liq. 211 (2015) 247. [26] X.-P. Liu, J. Feng, L. Zhang, Q.-T. Gong, S. Zhao, J.-Y. Yu, Colloids Surf. A Physicochem. Eng. Asp. 362 (2010) 39. [27] M. Abo-Riya, A.H. Tantawy, W. El-Dougdoug, J. Mol. Liq. 221 (2016) 642. [28] N.A. Negm, S.M. Tawfik, J. Ind. Eng. Chem. 20 (2014) 4463. [29] J. Ma, N. Liu, M. Huang, L. Wang, J. Han, H. Qian, F. Che, J. Mol. Liq. 294 (2019). [30] M.C. Murguía, L.M. Machuca, M.E. Fernandez, J. Ind. Eng. Chem. 72 (2019) 170. [31] A. Maneedaeng, S. Phoemboon, P. Chanthasena, N. Chudapongse, Korean J. Chem. Eng. 35 (2018) 2313. [32] A. Mozrzymas, B. Różycka-Roszak, J. Math. Chem. 49 (2010) 276. [33] J. Hoque, S. Gonuguntla, V. Yarlagadda, V.K. Aswal, J. Haldar, Phys. Chem. Chem. Phys. 16 (2014), 11279. [34] A. Bhadani, T. Endo, K. Sakai, H. Sakai, M. Abe, Colloid Polym. Sci. 292 (2014) 1685. [35] Y. Liang, H. Li, M. Li, X. Mao, Y. Li, Z. Wang, L. Xue, X. Chen, X. Hao, J. Mol. Liq. 280 (2019) 319. [36] J. Mao, J. Tian, W. Zhang, X. Yang, H. Zhang, C. Lin, Y. Zhang, Z. Zhang, J. Zhao, Colloids Surf. A Physicochem. Eng. Asp. (2019) 123619. [37] M. Pisárčik, M. Polakovičová, M. Markuliak, M. Lukáč, F. Devínsky, Molecules 24 (2019) 1481. [38] H. Ju, Y. Jiang, T. Geng, Y. Wang, C. Zhang, J. Mol. Liq. 225 (2017) 606. [39] R. Zana, Langmuir 12 (1996) 1208. [40] J. Hoque, P. Akkapeddi, V. Yarlagadda, D.S. Uppu, P. Kumar, J. Haldar, Langmuir 28 (2012), 12225. [41] A. Tehrani-Bagha, K. Holmberg, C. Van Ginkel, M. Kean, J. Colloid Interface Sci. 449 (2015) 72.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx [42] A. Tehrani-Bagha, K. Holmberg, Curr. Opin. Colloid Interface Sci. 12 (2007) 81. [43] Z. Liu, L. Zhang, X. Cao, X. Song, Z. Jin, L. Zhang, S. Zhao, Energy Fuel 27 (2013) 3122. [44] J.-H. Mu, G.-Z. Li, X.-L. Jia, H.-X. Wang, G.-Y. Zhang, J. Phys. Chem. B 106 (2002) 11685. [45] Y. You, X. Wu, J. Zhao, Y. Ye, W. Zou, Colloids Surf. A Physicochem. Eng. Asp. 384 (2011) 164. [46] L. Wang, R.-H. Yoon, Int. J. Miner. Process. 85 (2008) 101. [47] S.M. Shaban, I. Aiad, H. Moustafa, A. Hamed, J. Mol. Liq. 212 (2015) 907.
7
[48] L. Tavano, M.R. Infante, M.A. Riya, A. Pinazo, M.P. Vinardell, M. Mitjans, M. Manresa, L. Perez, Soft Matter 9 (2013) 306. [49] F.F. Sperandio, Y.-Y. Huang, M.R. Hamblin, Recent Patents on Anti-Infective Drug Discovery 8 (2013) 108. [50] L. Pérez, M.T. Garcia, I. Ribosa, M.P. Vinardell, A. Manresa, M.R. Infante, Environ. Toxicol. Chem. Int. J. 21 (2002) 1279. [51] K. Taleb, M. Mohamed-Benkada, N. Benhamed, S. Saidi-Besbes, Y. Grohens, A. Derdour, J. Mol. Liq. 241 (2017) 81.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties and antibacterial activity Junyan Wu a, Hemin Gao a, Diandian Shi c, Yufei Yang a, Yadong Zhang a,b,⁎, Weixia Zhu a,⁎ a b c
School of Chemistry and Energy, Zhengzhou University, Zhengzhou 450001, China Jiyuan Research Institute, Zhengzhou University, Zhengzhou 450001, China State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012, China
a r t i c l e
i n f o
Article history: Received 6 September 2019 Received in revised form 27 November 2019 Accepted 29 November 2019 Available online xxxx Keywords: Gemini surfactants Diamide and diester groups Surface properties Antibacterial activity
a b s t r a c t Nine novel cationic gemini surfactants containing both amide and ester groups were synthesized through a three-step reaction. These surfactants have the general formula of CnH2n+1OOCCH2N+(CH2)2-(CH2)3-NHOC(CH2)m-CONH-(CH2)3-N+(CH2)2CH2COOCnH2n+1 (with n = 8, 10, 12 and m = 2, 3, 4), named BEQA-n, PEQAn and HEQA-n (B, P, H correspond to surfactants of m = 2, 3, 4 and n = 8, 10, 12, respectively). Chemical structures, surface activity, cleavable properties, electrolytes tolerance, foam properties and antibacterial activity of these surfactants were successively investigated. The results show that the surfactants have lower critical micelle concentration (CMC) than traditional monomer surfactants. The values of CMC and the degree of counter ion dissociation (α) depend on the lengths of hydrophobic chain and spacer. The values of Krafft temperatures (Kt b 0 °C) and the standard Gibbs free energy (ΔG0mic b 0) indicate that all surfactants have good water solubility and micelle-forming ability. The simultaneous presence of the amide and ester groups makes these surfactants have good hydrolytic ability in both basic and the acidic solutions. In addition, the surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2. It is worth mentioning that EQA-8 and PEQA-12 have 200 g/L NaCl tolerance. Moreover, all of the surfactants have certain antibacterial activity against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922), and the surfactants with hydrophobic chain length n = 10 have the strongest antibacterial activity. © 2019 Elsevier B.V. All rights reserved.
1. Introduction Gemini surfactants are composed of two hydrophobic chains and two hydrophilic head groups linked by a spacer of flexible or rigid group. These surfactants have received widespread attention since bisquaternary ammonium bromide gemini surfactants were synthesized by Bunton team [1]. Compared with conventional surfactants, gemini surfactants have lower CMC, unusual aggregation behavior, better water solubility and antibacterial activity. Therefore, Gemini surfactants are widely used in the fields of bactericides [2], corrosion inhibitors [3], clothing antistatic [4], dye adsorption [5], porous materials [6], enhanced oil recovery [7] and so on. Cationic gemini surfactants containing two cationic hydrophilic head groups are the most widely investigated gemini surfactants [8–10]. Their properties can be significantly altered by introducing different functional groups or changing the lengths of the hydrophobic chain and spacer [11,12]. For instance, the introduction of hydroxyl ⁎ Corresponding authors at: School of Chemistry and Energy, Zhengzhou University, Zhengzhou 450001, China. E-mail addresses: [email protected] (Y. Zhang), [email protected] (W. Zhu).
could significantly improve the water solubility of the cationic gemini surfactants [13], the introduction of amide, ester and Si-O-Si groups helped the cationic gemini surfactants achieve good degradation ability [14–16]. In addition, changes in the lengths of the hydrophobic chain and spacer group also gave rise to different CMC, foam properties and antibacterial activity of the cationic gemini surfactants [17,18]. Due to the widespread use of surfactants, environmental problems caused by these compounds are becoming increasingly serious. The presence of positively charged nitrogen atoms and hydrophobic chains in the cationic gemini surfactants makes them be adsorbed more easily by the sludge and penetrate into water [19]. Moreover, cationic surfactants are usually toxic to the bacteria, algae, ciliated protozoa and crustaceans [20,21]. Therefore, it is highly desirable to develop a kind of cleavable cationic gemini surfactant. In this work, nine gemini surfactants containing both amide and ester groups with different lengths of spacer and hydrophobic chain were synthesized in a three-step reaction. The effects of spacer and hydrophobic chain lengths on these surfactants' surface activity, electrolyte tolerance and foaming properties were discussed. The cleavable properties of the gemini surfactants were determined by their chemical hydrolysis. Furthermore, the antibacterial activity of these surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-
https://doi.org/10.1016/j.molliq.2019.112248 0167-7322/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
2
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
negative bacteria (E. coli ATCC 25922) were evaluated by the minimum inhibitory concentration (MIC) values. 2. Experimental 2.1. Materials and methods Butanedioic acid, pentanedioic acid, hexanedioic acid, N,N-dimethyl1,3-propane diamine, phosphorous acid, chloroacetyl chloride were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 1octanol, 1-decanol, 1-dodecanol were obtained from Shanghai McLean Biochemical Technology Co., Ltd. Xylene, dichloromethane, acetonitrile, ethyl acetate, sodium hydrogen carbonate and magnesium sulfate anhydrous were all analytically pure and purchased from Tianjin Komiou Chemical Reagent Co., Ltd. E. coli ATCC 25922 and S. aureus ATCC 25923 were obtained from Beijing Solarbio Science & Technology Co., Ltd. Water was deionized before use. FT-IR spectra of the compounds were determined on a Thermo Nicolet IR 200 spectroscope. 1H NMR spectra were performed on a Bruker ADVANCE III 400 spectrometer with CDCl3 as the solvent. 2.1.1. Synthesis of N,N-bis[3-(dimethylamine)propyl]-diamine 0.2 mol diacid (butanedioic acid/pentanedioic acid/hexanedioic acid), 0.5 mol N,N-dimethyl-1,3-propanediamine and 150 mL xylene were added into a 250 mL three-necked flask. The reaction refluxed at 160 °C for 15 h with 0.4 wt% of phosphorous acid. The process was monitored by water with a dean-stark trap apparatus, and the product was cooled to room temperature and filtered. Then, it was washed three times with ethyl acetate. The yield ranged from 93% to 95%. 2.1.2. Synthesis of n-alkyl-α-halo-acetates The synthesis of n-alkyl-α-halo-acetates was according to the literature [22] and the method was slightly changed. The process was as follows. 0.2 mol n-alkanoles (n-octanol/n-nonanol/dodecyl alcohol) and 0.24 mol chloroacetyl chloride were added into a 250 mL round bottom flask and refluxed at 50 °C for 8 h with 100 mL dichloromethane as a solvent. After completion of the reaction, the solvent was removed by a vacuum rotary evaporator, and the residue was neutralized with saturated sodium hydrogen carbonate solution. After separated and washed with deionized water, the organic layer was dried by anhydrous magnesium sulfate. The yield ranged from 96% to 97%. 2.1.3. Synthesis of cationic gemini surfactants 0.02 mol N,N-bis[3-(dimethylamine)propyl]-diamine, 0.05 mol nalkyl-α-halo-acetates, and 30 mL ethyl acetate were added into a 100 mL round bottom flask, and refluxed at 80 °C for 24 h. Then, the crude product was filtered and washed/recrystallized with a mixed solution of acetonitrile/ethyl acetate. The obtained nine cationic gemini surfactants were named as BEQA-n, PEQA-n and HEQA-n, wherein B, P, H corresponded to surfactants having methylene groups (m = 2, 3, 4) in the middle of the spacer group. E, Q, and A corresponded to ester groups, quaternary ammonium ions, and amide groups, respectively. And n represented the length of the hydrophobic chains. The yield ranged from 75% to 88%. 2.2. Electrical conductivity measurements In order to get the CMC and α values of the cationic gemini surfactants, the specific conductivities (κ) of surfactant solutions with different concentrations were obtained by a DDS-307 conductivity meter (Shanghai Leici Instrument Co. Ltd., China) at 25 °C. These CMC values were considered to be the turning point of the conductivity curves, and α values were determined by the ratio of the conductivity curve slopes before and after CMC [23–25].
2.3. Krafft temperature measurements 1 wt% of nine cationic gemini surfactant solutions were placed in freezer at a temperature below 0 °C for at least 24 h so that the solutions became cloudy or solid. Then, the solutions were placed in a thermostat to be slowly heated. The Krafft temperature (Kt) is the temperature when the solutions become clear [16,26]. 2.4. Chemical hydrolysis 10 mL surfactant solutions (10 mmol/L) were separately added into 25 mL glass vials at 40 °C. Then, 10 mL NaOH solution (0.05 mol/L) or H2SO4 solution (2 mol/L) was added. The time when the surfactant solutions became cloudy was observed and recorded [27]. 2.5. Electrolytes tolerance 10 mL surfactant solutions (0.3 wt%) were mixed with 10 mL different concentrations of NaCl or CaCl2 solutions at 25 °C for 24 h. The transmittance (T %) of these mixed solutions was determined by a UV2600-A UV–Vis spectrophotometer (UNICO, USA). The higher transmittance means the stronger electrolytes tolerance [23]. 2.6. Foam height At room temperature, 100 mL 0.1 wt% surfactant solutions were added into 500 mL graduated cylinder and subjected to vigorous shake for 10 s then the resulting foam height (in mL) was measured. The foam stability of the solutions was measured after 3 min [28]. 2.7. Antibacterial activity The antibacterial activity of nine cationic gemini surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gram-negative bacteria (E. coli ATCC 25922) was studied by broth dilution method [29], and the minimum inhibitory concentration (MIC) values of these surfactants on the two strains were obtained. The procedure was as follows. The strains were individually inoculated into the nutrient agar plates with an inoculating loop and activated at 37 °C for 24 h. Then, the activated strains were separately inoculated into nutrient broth and configured to a bacterial suspension at a concentration of 1–2 × 106 CFU/mL. These surfactants were diluted into broth and 1 mL of each was added into a sterile tube. Finally, 1 mL of the diluted bacterial suspension was added to make the concentration of the surfactants in the range of 1–512 μg/mL, and the final concentration of the inoculum was 5–10 × 105 CFU/mL [30,31]. 3. Result and discussion 3.1. Synthesis Nine new cationic gemini surfactants containing amide and ester groups were synthesized and the specific synthetic routes were shown in Scheme 1. In the first step, the compounds 1, 2, and 3 were prepared by acylation of butanedioic acid, pentanedioic acid and hexanedioic acid with N,N-dimethyl-1,3-propanediamine, respectively. Then the n-alkanoles (n-octanol/n-nonanol/n-dodecyl alcohol) were esterified with chloroacetyl chloride and generated compounds 4, 5, and 6. Finally the gemini surfactants BEQA-8, BEQA-10, BEQA-12, PEQA-8, PEQA-10, PEQA-12, HEQA-8, HEQA-10, HEQA-12 were obtained by quaternization of these tertiary amine with ester. The tertiary amine compounds (1–3) and all the surfactants were characterized by FT-IR and 1H NMR spectra. These spectra data were listed in the supporting information section.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
3
Scheme 1. Synthetic route of the the cationic gemini surfactants containing both amide and ester groups (n = 8, 10, 12, m = 2, 3, 4).
3.2. Surface activity Fig. 1 shows the relationship between specific conductivity (κ) and concentration of nine cationic gemini surfactants at 25 °C. The CMC and α data of these surfactants are listed in Table 1. The CMC values of these surfactants ranged from 1.50 to 2.62 mmol/L. BEQA-12, PEQA-12 and HEQA-12 had significantly lower CMC than the traditional surfactants of N-dodecyl-N,N-dimethylammonium chloride (15.8 mmol/L) and N-dodecyl-N,N,N-trimethylammonium chloride (21 mmol/L) at 25 °C [32], which demonstrated that the gemini surfactants have more excellent aggregation properties than the corresponding monomer surfactants. Moreover, it could be observed that the CMC decreased with the simultaneous introduction of amide and ester groups by comparing BEQA-12, PEQA-12 and HEQA-12 with the reported surfactant named C12-PG-C12 (CMC value is 1.858 mmol/L at 25 °C) [16]. This phenomenon was because the amide and ester groups tended to form hydrogen bonds, which made the surfactants form micelles more susceptible. The conclusion is consistent with previous reports [33,34].
The CMC and α values of these surfactants decreased with the length of the hydrophobic chain increased. This was attributed to the increase of hydrophobic chain length enhanced hydrophobicity of the surfactants and made these surfactants easier to form micelles [35]. Except BEQA-12, the CMC values of these surfactants increased with the longer spacer group. This conclusion was the same with previous investigation [18,36]. This was partly related to the longer spacer group increased the distance between these surfactant head groups. On the other hand, longer methylene groups at the center of the spacer easily hindered the amide group in the surfactant spacer group to form intramolecular hydrogen bonds [37]. Accordingly, the surfactants with longer spacer formed fewer intramolecular hydrogen bonds and micelles. What was different from previous studies [38] was that the α values of the surfactants did not decrease completely with the increase of the length of the spacer. When the hydrophobic chain length was same, the α values of BEQA-n were significantly lower than PEQA-n and similar to HEQA-n. This may also be related to the shorter spacer group of the BEQA-n surfactants, which formed more intramolecular hydrogen
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
4
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
Fig. 1. Plots of conductivity versus concentration for surfactants at 25 °C. (a) BEQA-n, (b) PEQA-n, (c) HEQA-n.
bonds in the spacer group to promote the micelle formation of surfactants. The standard Gibbs free energy of micellization (ΔG0mic) was calculated by equation (Eq. (1)) [39]; ΔG0 mic ¼ RTð3−2αÞ ln CMC−RTln2
ð1Þ
where α is the degree of counter ion dissociation, CMC is the critical micelle concentration (mol/L), R is the gas constant (8.314 J/(mol·K)) and T is the temperature (K). The ΔG0mic of nine surfactants were listed in Table 1. The values of ΔG0mic ranged from −29.44 kJ/mol to −21.22 kJ/ mol. These negative values indicated all surfactants in this work had spontaneous micelle formation process. Table 1 Surface properties of nine cationic gemini surfactants. Surfactants
CMC (mmol/L)
α
Kt (°C)
ΔG0mic (kJ/mol)
tA (min)
tB (s)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
2.26 (±0.01) 2.11 (±0.01) 1.55 (±0.01) 2.56 (±0.01) 2.27 (±0.01) 1.37 (±0.01) 2.62 (±0.01) 2.48 (±0.01) 1.50 (±0.01)
0.756 0.742 0.701 0.841 0.822 0.750 0.742 0.734 0.640
b0 b0 b0 b0 b0 b0 b0 b0 b0
−24.19 −24.87 −27.34 −21.22 −22.18 −26.23 −24.06 −24.50 −29.44
1 34 210 1 41 255 1 46 340
10 15 20 10 10 20 10 15 25
CMC, critical micelle concentration; α, degree of counter ion dissociation; Kt, Krafft temperature; ΔG0mic, standard Gibbs free energy of micellization; tA, the time of acidic hydrolysis; tB, the time of basic hydrolysis.
3.3. Krafft temperature The Krafft temperature (Kt) for the nine cationic gemini surfactants was listed in Table 1. All of the surfactant solutions remained clear after 24 h in the freezer. This phenomenon indicated that the Krafft temperature of these surfactants was b0 °C, which indicated that the nine cationic gemini surfactants had good solubility in water [16].
3.4. Cleavable properties The amide and ester bonds are considered to be cleavable, by introducing these groups into the surfactants and making them cleavable [40,41]. The cleavable properties were investigated by the chemical hydrolysis of the nine cationic gemini surfactants in basic and acidic solutions [42], and these data are shown in Table 1. FT-IR spectrums of the HEQA-10 after basic and acidic hydrolysis (6 h) were shown in Fig. S3. As shown in Table 1, all of the surfactants were hydrolyzed in a 0.05 mol/L NaOH solution for b30 s, and the hydrolysis time of the surfactants in a 2 mol/L H2SO4 solution was b6 h. The characteristic peaks of amide i.e. β(N\\H) and ν(C\\N) at 1548 cm−1 and 1247 cm−1 disappeared and the characteristic peak of ester i.e. ν(C=O) at 1746 cm−1 was shifted to 1633–1634 cm−1 after basic and acidic hydrolysis (Figs. S1b and S3). These data indicated that all surfactants were susceptible to hydrolyze in both basic and acidic solutions. This was quite different from other gemini surfactants, these surfactants have been reported for harder hydrolysis in the acidic solutions [27,41]. Accordingly, the simultaneous introduction of amide and ester groups allows the
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
surfactants to have batter cleavable properties. Furthermore, as the length of the hydrophobic chain increases, the hydrolytic stability of the surfactants increases, but the influence of the length of the spacer is not significant. 3.5. Electrolytes tolerance The electrolytes could significantly decrease the water solubility of surfactants, thereby affecting the various properties of the surfactants. Fig. 2 show the transmission (T %) of nine cationic gemini surfactant solutions corresponding to the presence of different concentrations of NaCl and CaCl2. The electrolytes tolerance parameters of these surfactants were determined by the electrolytes concentration when the surfactant solutions transmittance changed sharply, and these data were listed in Table 2. It was clearly shown that these surfactants had less tolerance to CaCl2 than NaCl. It may relate to the addition of Na+ and Ca2+ reduced the hydration of the surfactants, which led to the easier precipitation of these surfactants, and the effect of Ca2+ was more pronounced [43]. As the length of the hydrophobic chain increases, the electrolyte tolerance of the surfactants to NaCl gradually decreases, which is more conspicuous than increasing the length of the spacer. Specially, both BEQA-8 and PEQA-12 exhibited excellent tolerance to NaCl and their NaCl tolerance parameters were N200 g/L. However, in the presence of CaCl2, it was very different. The surfactants exhibited lower tolerance to CaCl2 when the hydrophobic chain length was 10. This is attributed to the micellization is affected by the area of the hydrophilic head groups on the surface of the micelles, the length and size of the hydrophobic chain. And the addition of different electrolytes alters these microstructures of the surfactants [44]. 3.6. Foam properties The foam properties of surfactants have a significant impact on their practical application. Fig. 3 showed the foam height and foam stability of nine cationic gemini surfactants (0.1 wt%) at 25 °C. As the length of the hydrophobic chain increased, these surfactants were more abundant in foam and the foam stability also increased. This was attributed to the fact that the increase of hydrophobic chain enhanced the cohesion of the adsorbed molecules on the liquid membrane, which was advantageous for foaming and foam stability [45]. Compared with cationic gemini surfactants that have other spacer lengths, PEQA-n showed the best foam height, but their foam stability was relatively poor. Generally, foam stability is determined by various
5
Table 2 Electrolytes tolerance parameters of nine cationic gemini surfactants. Surfactants
NaCl(g/L)
CaCl2(g/L)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
N 200 38 30 75 26 N 200 70 28 26
23 7 18 16 6 22 18 6 20
factors such as surface tension, surface rheology, film elasticity and so on [46]. Therefore, the foam properties of these surfactants are complicated and deserve further investigation. 3.7. Minimum inhibitory concentration (MIC) Due to their unique properties, the cationic gemini surfactants exhibited excellent antibacterial activity. The antibacterial mechanism of these surfactants is presumed to be the electrostatic interaction between positively charged head groups and the negative charge on the surface of cellular cytoplasmic membrane. Meanwhile, the hydrophobic chains penetrate and disturb the selective permeability of the membrane, leading to cell death [47,48]. The antibacterial effect of the nine cationic gemini surfactants against Gram-positive bacteria (S. aureus ATCC 25923) and Gramnegative bacteria (E. coli ATCC 25922) was investigated. The minimum inhibitory concentration (MIC) values were used to evaluate the antibacterial activity of surfactants, and these data were listed in Table 3. It has been found that the lengths of both the hydrophobic chain and the spacer affect the antibacterial activity of the surfactants, and these surfactants have stronger bactericidal effect when the hydrophobic chain is 10. In particular, the HEQA-10 showed the best antibacterial activity against both of E. coli ATCC 25922 and S. aureus ATCC 25923 strains. The effect of spacer lengths of these surfactants on their antibacterial activity appeared to be more complicated, and the antibacterial activity of PEQA-n was significantly lower than the surfactants with other spacer lengths. Moreover, most surfactants showed better antibacterial activity to S. aureus ATCC 25923. Which is related to the different cell wall compositions of Gram-positive bacteria and Gram-negative bacteria. The Grampositive bacterial cell wall is composed of a thick wall containing many
Fig. 2. Transmittance (T%) plots of cationic gemini surfactant solutions versus electrolytes at 25 °C. (a) NaCl, (b) CaCl2.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
6
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx
Declaration of competing interest The authors declared that they have no conflicts of interest to this work. Acknowledgments The authors are grateful for the financial support provided by the National Natural Science Foundation of China (21706240) and the NSFC – He’nan Joint Fund General Project (162300410253). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.molliq.2019.112248. References Fig. 3. Plot of initial and 3 min foam properties of 0.1 wt% surfactants at 25 °C. (a: BEQA-8, b: PEQA-8, c: HEQA-8, d: BEQA-10, e: PEQA-10, f: HEQA-10, g: BEQA-12, h: PEQA-12, i: HEQA-12).
layers of peptidoglycan and teichoic acids, while the Gram-negative bacteria cell wall is composed of high lipopolysaccharides and porins. These proteins limit the entry of the hydrophobic chain into the Gram-negative bacteria [49–51]. 4. Conclusion Nine new cationic gemini surfactants containing both amide and ester groups were synthesized and characterized by FT-IR and 1H NMR spectra. The CMC values of the surfactants decrease as the length of the hydrophobic chain increases and most of the CMC values increase when the spacer length increases. The introduction of the amide and ester groups makes the surfactants readily to form micelles and cleave. These surfactants are susceptible to hydrolyze in both basic and acidic solutions. The surfactants exhibit greater electrolyte tolerance to NaCl than CaCl2, and it is worth mentioning that the NaCl tolerance parameters of BEQA-8 and PEQA-12 are both N200 g/L. The surfactants with longer hydrophobic chains have better foam properties and PEQA-n produce more foam than the surfactants with other spacer lengths. Moreover, most of the cationic gemini surfactants showed good antibacterial activity against both Gram-negative and Gram-positive bacteria and HEQA-10 had the optimal performance. CRediT authorship contribution statement Junyan Wu: Conceptualization, Formal analysis, Investigation, Writing - original draft, Writing - review & editing. Hemin Gao: Investigation. Diandian Shi: Writing - review & editing. Yufei Yang: Writing - review & editing. Yadong Zhang: Writing - review & editing, Resources, Supervision. Weixia Zhu: Writing - review & editing, Resources, Supervision. Table 3 MIC values of nine cationic gemini surfactants for different strains. Compounds
E. coli ATCC 25922 (μg/mL)
S. aureus ATCC 25923 (μg/mL)
BEQA-8 BEQA-10 BEQA-12 PEQA-8 PEQA-10 PEQA-12 HEQA-8 HEQA-10 HEQA-12
512 128 256 512 256 256 256 64 128
512 64 128 512 128 256 256 32 64
[1] C.A. Bunton, L.B. Robinson, J. Schaak, M. Stam, J. Org. Chem. 36 (1971) 2346. [2] Y. Bao, Y. Zhang, J. Guo, J. Ma, Y. Lu, J. Clean. Prod. 206 (2019) 430. [3] M. Pakiet, I. Kowalczyk, R. Leiva Garcia, R. Moorcroft, T. Nichol, T. Smith, R. Akid, B. Brycki, Bioelectrochemistry 128 (2019) 252. [4] W. Zieliński, K.A. Wilk, G. Para, E. Jarek, K. Ciszewski, J. Palus, P. Warszyński, Colloids Surf. A Physicochem. Eng. Asp. 480 (2015) 63. [5] H. Zeng, M. Gao, T. Shen, F. Ding, Colloids Surf. A Physicochem. Eng. Asp. 555 (2018) 746. [6] S. Wang, Z. Zheng, B. He, C. Sun, X. Li, X. Wu, X. An, X. Xie, Appl. Organomet. Chem. 32 (2018) e4145. [7] S. Hussain, M.S. Kamal, M. Murtaza, Energies 12 (2019) 1731. [8] Y. Han, Y. Wang, Phys. Chem. Chem. Phys. 13 (2011) 1939. [9] K. Parikh, B. Mistry, S. Jana, S. Gupta, R.V. Devkar, S. Kumar, J. Mol. Liq. 206 (2015) 19. [10] B. Li, Q. Zhang, Y. Xia, Z. Gao, Colloids Surf. A Physicochem. Eng. Asp. 470 (2015) 211. [11] A.R. Tehrani-Bagha, J. Kärnbratt, J.-E. Löfroth, K. Holmberg, J. Colloid Interface Sci. 376 (2012) 126. [12] C. Yang, Z. Song, J. Zhao, Z. Hu, Y. Zhang, Q. Jiang, Colloids Surf. A Physicochem. Eng. Asp. 523 (2017) 62. [13] M. Mahdavian, A.R. Tehrani-Bagha, E. Alibakhshi, S. Ashhari, M.J. Palimi, S. Farashi, S. Javadian, F. Ektefa, Corros. Sci. 137 (2018) 62. [14] L.-H. Lin, K.-M. Chen, Colloids Surf. A Physicochem. Eng. Asp. 275 (2006) 99. [15] H. Liu, X. Zhou, X. Zhang, G. Shi, J. Hu, C. Liu, B. Xu, J. Chem. Eng. Data 63 (2018) 1304. [16] D. Xu, X. Ni, C. Zhang, J. Mao, C. Song, J. Mol. Liq. 240 (2017) 542. [17] A. Laschewsky, K. Lunkenheimer, R.H. Rakotoaly, L. Wattebled, Colloid Polym. Sci. 283 (2005) 469. [18] M.H. Alimohammadi, S. Javadian, H. Gharibi, A. reza Tehrani-Bagha, M.R. Alavijeh, K. Kakaei, J. Chem. Thermodyn. 44 (2012) 107. [19] E. Grabinska-Sota, J. Hazard. Mater. 195 (2011) 182. [20] G. Nałęcz-Jawecki, E. Grabińska-Sota, P. Narkiewicz, Ecotoxicol. Environ. Saf. 54 (2003) 87. [21] G. Jing, Z. Zhou, J. Zhuo, Chemosphere 86 (2012) 76. [22] E. Obłąk, A. Piecuch, A. Krasowska, J. Łuczyński, Microbiol. Res. 168 (2013) 630. [23] Y. Wang, Y. Jiang, T. Geng, H. Ju, S. Duan, Colloids Surf. A Physicochem. Eng. Asp. 563 (2019) 1. [24] O. Kaczerewska, B. Brycki, I. Ribosa, F. Comelles, M.T. Garcia, J. Ind. Eng. Chem. 59 (2018) 141. [25] N. Fatma, M. Panda, W.H. Ansari, Kabir-ud-Din, J. Mol. Liq. 211 (2015) 247. [26] X.-P. Liu, J. Feng, L. Zhang, Q.-T. Gong, S. Zhao, J.-Y. Yu, Colloids Surf. A Physicochem. Eng. Asp. 362 (2010) 39. [27] M. Abo-Riya, A.H. Tantawy, W. El-Dougdoug, J. Mol. Liq. 221 (2016) 642. [28] N.A. Negm, S.M. Tawfik, J. Ind. Eng. Chem. 20 (2014) 4463. [29] J. Ma, N. Liu, M. Huang, L. Wang, J. Han, H. Qian, F. Che, J. Mol. Liq. 294 (2019). [30] M.C. Murguía, L.M. Machuca, M.E. Fernandez, J. Ind. Eng. Chem. 72 (2019) 170. [31] A. Maneedaeng, S. Phoemboon, P. Chanthasena, N. Chudapongse, Korean J. Chem. Eng. 35 (2018) 2313. [32] A. Mozrzymas, B. Różycka-Roszak, J. Math. Chem. 49 (2010) 276. [33] J. Hoque, S. Gonuguntla, V. Yarlagadda, V.K. Aswal, J. Haldar, Phys. Chem. Chem. Phys. 16 (2014), 11279. [34] A. Bhadani, T. Endo, K. Sakai, H. Sakai, M. Abe, Colloid Polym. Sci. 292 (2014) 1685. [35] Y. Liang, H. Li, M. Li, X. Mao, Y. Li, Z. Wang, L. Xue, X. Chen, X. Hao, J. Mol. Liq. 280 (2019) 319. [36] J. Mao, J. Tian, W. Zhang, X. Yang, H. Zhang, C. Lin, Y. Zhang, Z. Zhang, J. Zhao, Colloids Surf. A Physicochem. Eng. Asp. (2019) 123619. [37] M. Pisárčik, M. Polakovičová, M. Markuliak, M. Lukáč, F. Devínsky, Molecules 24 (2019) 1481. [38] H. Ju, Y. Jiang, T. Geng, Y. Wang, C. Zhang, J. Mol. Liq. 225 (2017) 606. [39] R. Zana, Langmuir 12 (1996) 1208. [40] J. Hoque, P. Akkapeddi, V. Yarlagadda, D.S. Uppu, P. Kumar, J. Haldar, Langmuir 28 (2012), 12225. [41] A. Tehrani-Bagha, K. Holmberg, C. Van Ginkel, M. Kean, J. Colloid Interface Sci. 449 (2015) 72.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248
J. Wu et al. / Journal of Molecular Liquids xxx (xxxx) xxx [42] A. Tehrani-Bagha, K. Holmberg, Curr. Opin. Colloid Interface Sci. 12 (2007) 81. [43] Z. Liu, L. Zhang, X. Cao, X. Song, Z. Jin, L. Zhang, S. Zhao, Energy Fuel 27 (2013) 3122. [44] J.-H. Mu, G.-Z. Li, X.-L. Jia, H.-X. Wang, G.-Y. Zhang, J. Phys. Chem. B 106 (2002) 11685. [45] Y. You, X. Wu, J. Zhao, Y. Ye, W. Zou, Colloids Surf. A Physicochem. Eng. Asp. 384 (2011) 164. [46] L. Wang, R.-H. Yoon, Int. J. Miner. Process. 85 (2008) 101. [47] S.M. Shaban, I. Aiad, H. Moustafa, A. Hamed, J. Mol. Liq. 212 (2015) 907.
7
[48] L. Tavano, M.R. Infante, M.A. Riya, A. Pinazo, M.P. Vinardell, M. Mitjans, M. Manresa, L. Perez, Soft Matter 9 (2013) 306. [49] F.F. Sperandio, Y.-Y. Huang, M.R. Hamblin, Recent Patents on Anti-Infective Drug Discovery 8 (2013) 108. [50] L. Pérez, M.T. Garcia, I. Ribosa, M.P. Vinardell, A. Manresa, M.R. Infante, Environ. Toxicol. Chem. Int. J. 21 (2002) 1279. [51] K. Taleb, M. Mohamed-Benkada, N. Benhamed, S. Saidi-Besbes, Y. Grohens, A. Derdour, J. Mol. Liq. 241 (2017) 81.
Please cite this article as: J. Wu, H. Gao, D. Shi, et al., Cationic gemini surfactants containing both amide and ester groups: Synthesis, surface properties an..., Journal of Molecular Liquids, https://doi.org/10.1016/j.molliq.2019.112248