Co-reporter:Jing Lv, Weihong Qiao, and Chongqiao Xiong
Langmuir July 22, 2014 Volume 30(Issue 28) pp:8258-8267
Publication Date(Web):July 22, 2014
DOI:10.1021/la5016669
A new series of N,N′-dialkyl-N,N′-diacetate ethylenediamine, differing by the length of the carbon tails (8, 10, and 12), was synthesized in two steps. Their surface properties and aggregation behavior were studied in aqueous solution using pH titration, surface tension, zeta potential, dynamic light scattering (DLS), transmission electron microscopy (TEM), and fluorescence measurements. On the basis of the pKa values obtained, surface tension was measured, as well as key surface property parameters. Combined with the zeta potential and DLS results, the experiments produced vesicles and reflected their pH-controllability through subsequent TEM and fluorescence measurements. pH-switchability was found to be reversible by light transmittance. Emulsion stability of dodecane-in-water in different pH showed that emulsion type was reversed between “on” for the O/W emulsion type and “off” for the W/O.
Co-reporter:Qingzhao Shi
Journal of Surfactants and Detergents 2017 Volume 20( Issue 2) pp:453-458
Publication Date(Web):2017 March
DOI:10.1007/s11743-016-1912-x
Four siloxane polyether surfactants were synthesized from allyl bromide, polyethylene glycol methyl ether and heptamethyltrisiloxane (HMTS) to explore their solubility in CO2. The dissolving pressures of these surfactants were measured using a high-pressure view cell at 318–343 K to calculate their solubility in CO2. The results show that, the silicone-containing surfactants exhibit excellent solubility in CO2. The shorter the polyethylene glycol group, the better the solubility in CO2. Of the five compounds tested, HMTS showed the best solubility in CO2 which was around 2.4% as a mole percentage. The surfactants show much better solubility than the commonly used surfactants. Moreover, by investigating the effects of the pressure and temperature on the solubility, it was found that an increase in pressure benefits solubility of the compound in CO2, while an increase in temperature within the experimental range does the opposite. In addition, a linear correlation in the logarithmic values of the solubility data and the density of CO2 was found, which means the solubility follows density more directly and not the pressure.
Co-reporter:Anirudh Srivastava, Chunyu Liu, Hui Fang, Jing Lv, Weihong Qiao
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 529(Volume 529) pp:
Publication Date(Web):20 September 2017
DOI:10.1016/j.colsurfa.2017.06.053
The advantages of drug–surfactant interactions as drug delivery vehicles are valuable for developing pharmaceutical formulations. The interaction of a drug, chlorpheniramine maleate (CPM), and (N,N′-dialkyl-N,N′-diacetate ethylenediamine, Ace(m)-2-Ace(n)), amino acid gemini surfactants (GSs) was investigated for various micellar, interfacial, and thermodynamic parameters at different mole fractions of CPM and GS mixtures using surface tension techniques. The values of the interaction parameter (β) suggested that CPM (cationic drug) exhibited low synergistic interactions with anionic GSs. Using UV measurement to evaluate the binding of CPM with GS, we determined the binding constant of drugs in the presence of GS and CPM + GS mixtures. Anionic GSs bound preferentially with CPM, because of the presence of cationic ions on the head group of the drug, and as an important drug-carrier, GSs showed higher binding constant (Kb) than that of ionic surfactant even at very low mole fractions. The values of different binding constant (Kb) indicated the binding mechanism of the CPM + GS mixed system. Mixed compositions of drug–surfactants were used to stabilize silver nanoparticles in aqueous media. The UV spectroscopy, dynamic light scattering, and transmission electron microscopy indicated a strong hydrophobic and the electrostatic interaction between CPM and GS. Specific morphologies were formed by adopting different supramolecular assemblies in aqueous media, depending on the internal packing arrangements and on the numbers of methylene units [–(CH2) n–].Download high-res image (324KB)Download full-size image
Co-reporter:
Macromolecular Rapid Communications 2017 Volume 38(Issue 2) pp:
Publication Date(Web):2017/01/01
DOI:10.1002/marc.201600550
A novel co-assembly based on the block copolymer bearing photocleavable groups and macroanionic polyoxometalates Na9[Ln(W5O18)2] (LnW10, Ln = Eu, Dy) triggered by UV light is realized in aqueous solution. The copolymer synthesized by atom transfer radical polymerization (ATRP) undergoes irreversible cleavage upon UV irradiation to generate primary amine (pKa ≈ 8–9) residues which are completely protonated under a neutral pH in aqueous solution. Electrostatic attractions between the resulting positively charged copolymers and anionic LnW10 drive the formation of assemblies. In situ small angle X-ray scattering and transmission electron microscopy are used to characterize the morphology of the assemblies. The microenvironments around polyoxometalates in the core of hybrid assemblies become highly hydrophobic, resulting in dramatically enhanced photoluminescence with the obvious intensity enhancement. The solution parameters pH and salt additives show great effects on the formation of assemblies.
Co-reporter:Lei Bao;Hanwei Wang;Yongbin Wu;Xingmin Li
Journal of Surfactants and Detergents 2016 Volume 19( Issue 5) pp:979-987
Publication Date(Web):2016 September
DOI:10.1007/s11743-016-1843-6
A series of alkyl phenol polyoxyethylene glycidyl ether (NP-n-O) and alkyl phenol polyoxyethylene ether hydroxypropyl sulfonate (NP-n-S) surfactants was synthesized to explore emulsification viscosity reduction. The optimum sulfonation conditions were obtained through orthogonal experiments, the ratio of alkyl phenol polyoxyethylene glycidyl ether and sodium bisulfite 1:1.5, 100 °C, and 6 h. The effects of concentrations of the synthesized surfactants, pH values, emulsifying temperature (40 and 60 °C) and water content on emulsification viscosity reduction and the stability of the emulsion to Venezuela’s Orinoco heavy oil were investigated. The water diversion ratio of emulsion at the reservoir temperature (55 °C) in 30 days was taken as an index, the results show that under the conditions of a temperature of 40 °C, an oil/water ratio of 7:3 and a surfactant NP-4-S concentration of 0.5 %, emulsions can be formed with a viscosity reduction rate reaching up to 99.69 % and with a water diversion ratio in 30 days reaching 9.38 %; while at 60 °C and an oil/water ratio of 7:3, at an NP-4-S concentration of 1 %, the viscosity reduction rate can reach 99.55 % and water diversion ratio is merely 4.23 % in 30 days. The mixture of NP-n-S, xanthan gum and cocamidopropyl dimethylamine oxide (CAO-30) at suitable concentration can greatly improve the emulsification viscosity reduction and emulsion stability, which gives an emulsion viscosity rate of over 98 %. Moreover, the emulsion can be stable for at least 30 days without water emerging.
Co-reporter:Jing Lv, Weihong Qiao, Zongshi Li
Colloids and Surfaces B: Biointerfaces 2016 Volume 146() pp:523-531
Publication Date(Web):1 October 2016
DOI:10.1016/j.colsurfb.2016.06.054
•Reversible transition from micelle to vesicle is accomplished by regulating pH.•The key to pH-regulated gemini amino-acid surfactants is the protonation between H+ and NCH2COO−.•Vesicles fabricated as nanocapsules can be effectively transported into cells.Reversible transition from micelles to vesicles by regulating pH were realized by gemini amino-acid surfactants N,N’-dialkyl-N,N’-diacetate ethylenediamine. Measurement results of ζ-potential at different pH and DLS at varying solvents revealed that the protonation between H+ and double NCH2COO− groups (generating NH+CH2COO−), expressed as pKa1 and pKa2, is the key driving force to control the aggregation behaviors of gemini surfactant molecule. Effect of pH on the bilayer structure was studied in detail by using steady-state fluorescence spectroscopy of hydrophobic pyrene and Coumarin 153 (C153) respectively and fluorescence resonance energy transfer (FRET) from C153 to Rhodamine 6G (R6G). Various pH-regulated and pH-reversible self-assemblies were obtained in one surfactant system. Vitamin D3 was encapsulated in vesicle bilayers to form nano-VD3-capsules as VD3 supplement agent for health care products. By using the electrostatic attraction between Ca2+ and double −COO− groups, nano-VD3-capsules with Ca2+ coated outermost layers were prepared as a formulation for VD3 and calcium co-supplement agent. DLS and TEM were performed to check stability and morphology of the nano-capsules. It is concluded that the pH-regulated gemini amino-acid surfactants can be used to construct colloidal systems for delivering hydrophobic drugs or nutritions without lipids at human physiological pH level.
Co-reporter:Jing Lv and Weihong Qiao
Soft Matter 2015 vol. 11(Issue 13) pp:2577-2585
Publication Date(Web):09 Feb 2015
DOI:10.1039/C5SM00041F
A new series of pH-regulated asymmetric amino-acid gemini surfactants N,N′-dialkyl-N,N′-diacetate ethylenediamine (Ace(m)-2-Ace(n)), differing by the asymmetric degree and length of the carbon tails (m = 8 and 10, n = 10, 12, 14, and 16), were synthesized in three steps. On the basis of pKa values obtained by pH titration, surface tension, fluorescence, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements were performed to study the surface adsorption and aggregation properties in aqueous Ace(m)-2-Ace(n) solution. The new compounds have higher surface activity and better pH adaptability in comparison with that of symmetric gemini surfactants Ace(n)-2-Ace(n). The molecule behavior of Ace(m)-2-Ace(n) can be adjusted by either the hydrophobic group or the pH. With increasing alkyl chain length, the surface adsorption declines but its ability to form aggregates increases. We find that pH can promote the self-assembly transition of Ace(m)-2-Ace(n) from surfactant monomers to aggregates through protonation between H+ and the tertiary nitrogen group. TEM data further confirm the pH-regulated molecular self-assembly process and the existence of vesicles at neutral or weak acidic pH. pH-recyclability is found to be reversible by pH-light transmittance recycle tests.
Co-reporter:Zhibo Zheng;Chenyu Liu
European Journal of Lipid Science and Technology 2015 Volume 117( Issue 10) pp:1673-1678
Publication Date(Web):
DOI:10.1002/ejlt.201400429
Responsive vesicles have attracted great attention because they can undergo reversible changes in response to external stimuli and possess prospective applications in different environments. A pH-responsive and CO2-responsive vesicle formed by N-decylimidazole was prepared. By dynamic light scattering (DLS) and transmission electron microscopy (TEM), it is shown that spherical vesicles are formed spontaneously in N-decylimidazole aqueous solution at pH 5.8∼6.2. By HCl/NaOH adjustment, the vesicle radius increases from 73.8 to 100.8 nm as the solution pH increases from 5.8 to 6.2. By CO2/Ar adjustment, the vesicles also can be formed in N-decylimidazole aqueous solution at suitable pH. The CO2-responsive vesicle can be repeatedly formed without change of vesicle size.
Practical applications: The vesicles can be spontaneously formed in N-decylimidazole aqueous solution at pH 5.8∼6.2 either by HCl/NaOH adjustment or CO2/Ar stimuli. Therefore, they can be used as pH-responsive or CO2-responsive vesicles for potential applications in drug-delivery, size-selective release, biochemical reactions, and so on.
In order to fabricate pH-responsive and CO2-responsive vesicles, the authors studied vesicle formation using N-decylimidazole, by HCl/NaOH or CO2/Ar adjustment. These vesicles have potential applications in drug delivery and other biochemical applications.
Co-reporter:Qingzhao Shi; Lishuai Jing; Chongqiao Xiong; Chenyu Liu
Journal of Chemical & Engineering Data 2015 Volume 60(Issue 8) pp:2469-2476
Publication Date(Web):July 24, 2015
DOI:10.1021/acs.jced.5b00345
The experiment utilizes a high-pressure view chamber that mainly aims at identifying the effect of surfactant architecture on solubility in CO2. First, when solubility pressures of three series of nonionic hydrocarbon surfactants are measured, results reveal that surfactants with a methylated tail exhibit the best solubility. Unexpectedly, surfactants with a branched tail show worse solubility than linear surfactants. This is conjectured to be caused by attractive molecule–molecule interactions. TX45 that possesses the shortest ethylene oxide chain and a highly methylated tail performs the best in CO2 solubility. Additionally, the experimental study on the solubility of TX45 in CO2 at T = (318 to 343) K demonstrates that solubility has a direct correlation with pressure and CO2 density, while it is inversely related to temperature. Finally, when we look at effects of the added alcohols on surfactant TX45 solubility, the results indicate that hexanol is the most effective alcohol in enhancing solubility. The reason is assumed to be that hexanol molecules could insert themselves between surfactant tails and hinder molecule–molecule interactions.
Co-reporter:Zhibo Zheng;Chongqiao Xiong
European Journal of Lipid Science and Technology 2014 Volume 116( Issue 8) pp:961-967
Publication Date(Web):
DOI:10.1002/ejlt.201400032
By dynamic light scattering (DLS) and transmission electron microscopy (TEM), it is shown that spherical vesicles are formed spontaneously in the mixed systems consisting of sodium dodecyl benzene sulfonate (SDBS) and N′-dodecyl-N,N-dimethylacetamidinium bicarbonate (DAB). These vesicles can be successfully tuned by alkali, but not CO2-switch due to the unsuitable pKa of DAB. In SDBS/DAB system, alkalinity increase can substantially expand the vesicle size in DAB-rich zone, but same effect is indistinguishable in SDBS-rich zone. Only DAB solution can also form vesicles when the solution pH is close to the pKa of DAB.
Practical applications: The vesicles can be spontaneously formed by mixing DAB and SDBS aqueous solution at various concentrations and mole fractions. These vesicles can expand gradually as the solution pH increases. They can be used as pH-response vesicles for application in drug-delivery, size-selective release, biochemical reactions, and so on.
Mixing SDBS and DAB aqueous solution can spontaneously form vesicles at various concentration and mole fraction. The vesicles cannot be tuned by CO2/Ar stimuli. The pH increase by adding NaOH can expand the vesicle size in DAB-rich zone, but the same effect is indistinguishable in SDBS-rich zone.
Co-reporter:Mingfeng Chai;Zhibo Zheng;Lei Bao
Journal of Surfactants and Detergents 2014 Volume 17( Issue 3) pp:383-390
Publication Date(Web):2014 May
DOI:10.1007/s11743-014-1569-2
In order to overcome the hydrolysis of 2-alkyl-1-hydroxyethyl imidazoline and its unsatisfactory emulsification–demulsification switchability to water-alkane, the long-chain N-alkylimidazole compounds were synthesized by n-octyl bromide, n-decyl bromide, n-dodecyl bromide, n-tetradecyl bromide and n-hexadecyl bromide with imidazole, respectively and characterized by MS, 1H NMR and FTIR. The long-chain N-alkylimidazole compounds can be reversibly transformed into charged surfactants by exposure to CO2. Surface tension values indicated that N-alkylimidazolium bicarbonates had excellent surface activity compared with corresponding conventional surfactants with a lower γCMC. The surface behaviors of the five surfactants can be illustrated by Amin. Five conductivity cycles by bubbling CO2 and N2 alternately indicated that these surfactants could be switched by CO2 reversibly and repeatedly. Emulsions were repeatedly stabilized for five cycles by N-alkylimidazolium bicarbonate and broken by bubbling N2 through the solutions to reverses the reaction, releasing CO2.
Co-reporter:Lishuai Jing;Limei Luo;Huan Peng
Journal of Surfactants and Detergents 2014 Volume 17( Issue 4) pp:629-636
Publication Date(Web):2014 July
DOI:10.1007/s11743-013-1555-0
The design, synthesis and interfacial behaviors of six asymmetric carboxyl betaine surfactants (BCm−n, m, n = 8, 10, 12, or 14, m ≠ n) derived from s-triazine, which were prepared from cyanuric chloride, aliphatic amines, N,N-dimethylpropane-1,3-diamine, followed by the reaction with sodium chloroacetate, are reported. The structures were confirmed by MS, 1H NMR and FT-IR. Compared with symmetric surfactants (BCn−n, n = 8, 10, 12, or 14) we previously synthesized, the asymmetric series show superior surface activity. The γCMC of surfactants BC10−8, BC12−8, BC14−8 and BC12−10 is all below 30 mN/m. The minimum alkane carbon number of these ten surfactants is determined to be between 10 and 14. The interfacial behaviors between the alkanes and the solutions of triazine carboxyl betaine surfactants show that surfactants with a total carbon number in hydrophobic chains between 16 and 22 exhibit the ability to reduce the interfacial tension to an ultra-low value (10−3 mN/m). The surfactants with longer hydrocarbon chains display strong affinity to the alkanes with longer chains.
Co-reporter:Jing Lv, Weihong Qiao, and Chongqiao Xiong
Langmuir 2014 Volume 30(Issue 28) pp:8258-8267
Publication Date(Web):2017-2-22
DOI:10.1021/la5016669
A new series of N,N′-dialkyl-N,N′-diacetate ethylenediamine, differing by the length of the carbon tails (8, 10, and 12), was synthesized in two steps. Their surface properties and aggregation behavior were studied in aqueous solution using pH titration, surface tension, zeta potential, dynamic light scattering (DLS), transmission electron microscopy (TEM), and fluorescence measurements. On the basis of the pKa values obtained, surface tension was measured, as well as key surface property parameters. Combined with the zeta potential and DLS results, the experiments produced vesicles and reflected their pH-controllability through subsequent TEM and fluorescence measurements. pH-switchability was found to be reversible by light transmittance. Emulsion stability of dodecane-in-water in different pH showed that emulsion type was reversed between “on” for the O/W emulsion type and “off” for the W/O.
Co-reporter:Weihong Qiao;Min Zhou;Limei Luo
Journal of Surfactants and Detergents 2014 Volume 17( Issue 2) pp:261-268
Publication Date(Web):2014 March
DOI:10.1007/s11743-013-1474-0
Two double chain cationic lipids QAS Cn-2-S (n = 12, 14) derived from thio galactose and carbamate-linkage tertiary amine were synthesized and their structures were confirmed by MS, TOF-MS, 1H NMR and 13C NMR. The QAS C12-2-S revealed superior surface activity compared with QAS C14-2-S with lower CMC and γCMC. Though Lipo C12-2-S displayed large average particle-size with high polydispersity, positive charged Lipo Cn-2-S can be combined with the negative charged DNA, also negatively stained TEM images confirmed the formation of vesicles. All the above prove that the Lipo Cn-2-S is helpful for gene transfection.
Co-reporter:Weihong Qiao;Yangyang Qiao
Journal of Surfactants and Detergents 2013 Volume 16( Issue 6) pp:821-828
Publication Date(Web):2013 November
DOI:10.1007/s11743-012-1432-2
Two series of surfactants based on glycine and serine were synthesized with aproic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid and hexadecanoic acid. All the surfactants were characterized by MS and 1H NMR, the structures of the synthesized surfactants are correct and the signals in MS and 1H NMR can be explained. The reaction conditions, surface properties and foam properties were studied. For the two series of surfactants, critical micelle concentration (CMC) and γCMC (surface tension at CMC) decrease and surface activity is enhanced as the length of carbon chain increases. The surfactants with tetradecanoyl and hexadecanoyl groups show a good foaming property and especially, the long-chain acyl-serine performs better. These are all related to the hydromethyl group in the serine.
Co-reporter:Weihong Qiao;Zhibo Zheng;Qingzhao Shi
Journal of Surfactants and Detergents 2012 Volume 15( Issue 5) pp:533-539
Publication Date(Web):2012 September
DOI:10.1007/s11743-012-1332-5
Switchable surfactants are environment-friendly compounds, which can be separated from the system or lose surface activity after completing their function during one stage of a process. In order to study switchable properties of a kind of CO2 switchable surfactant with an imidazoline group, four 2-alkyl-1-hydroxyethylimidazolines were synthesized by condensation of N-(2-hydroxyethyl)ethanediamine with dodecanoic, tetradecanoic, hexadecanoic, and octadecanoic acids. Then, the series of long-chain alkyl imidazoline compounds were reacted with dry ice to produce imidazolinium bicarbonates cationic surfactants. The critical micelle concentration (CMC) and surface tension at CMC (γcmc) measured by the Wilhelmy plate technique show that these surfactants have excellent surface activity. The changes of conductivity before and after bubbling CO2 show the conversion between imidazolines and imidazolinium bicarbonates cationic surfactants. Conductivity cycles indicated that these surfactants could be switched by CO2 reversibly and repeating this three times. However, their switchable function on the emulsification-demulsification of water-alkane was dissatisfactory due to the emulsibility of amide which was hydrolyzed from 2-alkyl-1-hydroxyethylimidazoline. Therefore, the application of these switchable surfactants needed to be studied further.
Co-reporter:Qingzhao Shi, Lishuai Jing, Weihong Qiao
Journal of CO2 Utilization (March 2015) Volume 9() pp:29-38
Publication Date(Web):1 March 2015
DOI:10.1016/j.jcou.2014.12.002
•We measured solubility of n-alkanes in CO2.•Temperature and alkane chain length will increase cloud point pressure.•x Rises with pressure, temperature increase will reduce x.•The solubility of n-alkanes has direct access to density of CO2.Poor solubility of heavy hydrocarbons in CO2 has limited the application of CO2-EOR (enhanced oil recovery) in modern oil recovery industry to some extent. Therefore, it is crucial to investigate the solubility regularity of different hydrocarbons in supercritical carbon dioxide (scCO2) in the first place. In this paper, our objective is to explore the solubility of n-alkanes (C6H14–C18H38) in scCO2. To measure cloud point pressures, the experiment utilizes high-pressure view chamber, and results for accuracy and repeatability of the experimental method and instrument are evidently positive. Then, cloud point pressures for n-alkanes from 318 K to 343 K show a proximately linear and positive correlation with the temperature; they also increase with expanding chain length of n-alkanes. In addition, the result of x (molar fraction of n-alkane at cloud point pressure) indicates that x has a positive correlation with the pressure at identical temperature, and when pressure is constant, temperature increase will reduce x. Finally, relationship studies between density of CO2 and x reveal that, density of CO2 has a positive influence on the solubility of n-alkane, and the Chrastil model corrects ln ρ and ln S data. The measured data align with the Chrastil model, with a maximum AARD value of 9.85%.Download full-size image
