Removal of solvent-based ink from printed surface of HDPE bottles by alkyltrimethylammonium bromides: effects of surfactant concentration and alkyl chain length

Three alkyltrimethylammonium bromides (i.e., dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromide or DTAB, TTAB, and CTAB, respectively) were used to remove a blue solvent-based ink from a printed surface of high-density polyethylene bottles. Either an increase in the alkyl chain length or the surfactant concentration was found to increase the deinking efficiency. Complete deinking was achieved at concentrations about 3, 8, and 24 times of the critical micelle concentration (CMC) of CTAB, TTAB, and DTAB, respectively. For CTAB, ink removal started at a concentration close to or less than its CMC and increased appreciably at concentrations greater than its CMC, while for TTAB and DTAB, significant deinking was only achieved at concentrations much greater than their CMCs. Corresponding to the deinking efficiency of CTAB in the CMC region, the zeta potential of ink particles was found to increase with increasing alkyl chain length and concentration of the surfactants, which later leveled off at some higher concentrations. Wettability of the surfactants on an ink surface increased with increasing alkyl chain length and concentration of the surfactants. Lastly, solubilization of ink binder in the surfactant micelles was found to increase with increasing alkyl chain length and surfactant concentration. We conclude that adsorption of surfactant on the ink pigment is crucial to deinking due to modification of wettability, zeta potential, pigment/water interfacial tension, and dispersion stability. Solubilization of binder (epoxy) into micelles is necessary for good deinking because the dissolution of the binder is required before the pigment particles can be released from the polymer surface.     

Molecular interaction of Congo Red with conventional and cationic gemini surfactants

Interaction of tetradecyltrimethylammonium bromide (TTAB), octylophenylpolyoxyethylene ether (TX-100), sodium dodecylsulfate (SDS), N,N′-ditetradecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (14,4,14) and N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-butanediyl-diammonium dibromide (12,4,12) with an anionic diazo dye, Congo Red, was investigated using conductometry, spectroscopy, tensiometry, and pulsed field gradient NMR (PFG-NMR). The formation of dye-surfactant ion pairs, their small mixed aggregates (below the critical micelle concentration (CMC) of these surfactants) and surfactant micelles were detected successfully. Above the CMC, the dye reverted to its monomeric state and solubilized in the micelles. Job's method was used to determine the stoichiometric ratio of dye and surfactant in ion pairs and revealed the formation of more hydrophile ion pairs for geminis compared to their conventional analogs. Quantitative results obtained from tensiometry indicated the existence of considerable synergism for cationic surfactants and antagonism for anionic SDS. In addition, the synergism observed for TX-100 revealed the effect of π-π stacking and hydrophobic forces on ion pair and mixed micelle formation. The increase of dye-surfactant interactions by increasing the electrical charge and chain length of cationic surfactants confirmed the importance of both electrostatic and hydrophobic forces in binary dye/surfactant systems. The hydrodynamic radii of the micelles were determined by self-diffusion coefficient measurements. The average size of the cationic and nonionic micelles increased in the presence of CR molecules.     

FLUORESCENCE PROBE FOR MICROENVIRONMENTS: A NEW PROBE FOR MICELLE SOLVENT PARAMETERS AND PREMICELLAR AGGREGATES

Abstract— A previous study on the electronic spectroscopy of p -N,N-dialkylaminobenzylidenemalononitrile, 1, has been extended to a larger variety of organic solvents and to micelles of ionic and nonionic surfactants. By comparing the fluorescence emission (λ_F and φ_∫) of 1 in micelles and in homogeneous organic solvents, the effective polarity and the microviscosity of the micellar environments of potassium dodecanoate, sodium dodecyl sulfate, cetyltrimethylammonium bromide and Triton X-100 micelles have been determined to be 40, 40, 36 and 28, respectively and 23, 31, 34 and 28 cP, respectively. These results indicate that the fluorescence probe is located in the micelle–water interface of a micelle and this region of a micelle is polar and viscous. 1 has also been studied in different surfactants with varying surfactant concentrations. The φ_∫ of 1, a microviscosity gauge for micellar aggregates, remains unchanged at the critical micelle concentrations of various surfactants, but decreases at much lower surfactant concentrations. This is attributable to the formation of premicellar aggregates of surfactant molecules below their critical micelle concentrations.     

Aggregation of sodium 1-(n-alkyl)naphthalene-4-sulfonates in aqueous solution: micellization and microenvironment characteristics

In aqueous solution, the micellization and microenvironment characteristics of the micelle assemblies of three anionic surfactants, sodium 1-(n-alkyl)naphthalene-4-sulfonates (SANS), have been investigated by steady-state fluorescence and time-resolved fluorescence decay techniques using pyrene, Ru(bpy)3(2+), and 1,6-diphenyl-1,3,5-hexatriene as fluorescence probes. The critical micelle concentrations (cmc's), effective carbon atom numbers (neff's), hydrophilic-lipophilic balances (HLBs), mean micelle aggregation numbers, micropolarities, and microviscosities of these surfactant micelles have been determined. The logarithmic cmc of the alkylnaphthalene sulfonates decreases linearly with an increase in the neff. The logarithmic aggregation number of the alkylnaphthalene sulfonates increases linearly with an increase in the neff. However, in contrast to the alkylsufonates and the alkylbenzene sulfonates, the aggregation for these alkylnaphthalene sulfonate molecules is less sensitive to the increase in the neff. The micropolarity of these alkylnaphthalene sulfonate micelles is less sensitive to the increase in the alkyl chain length and is lower than that of sodium dodecyl sulfate (SDS). The microviscosity of these alkylnaphthalene sulfonate micelles increases with an increase in the alkyl chain length and is lower than those of nonionic surfactants and zwitterionic surfactants. These results suggest that naphthyl rings have a notable effect on the micellization of SANS.     

利用荧光偏振法对表面活性剂溶液中胶束特性的研究

由表面活性剂分子所形成的胶束、囊泡等分子组合作为生物体中聚集体的模型研究已引起广泛的注意^[1]。     

Microstructure of un-neutralized hydrophobically modified alkali-soluble emulsion latex in different surfactant solutions

At low pH conditions and in the presence of anionic, cationic, and nonionic surfactants, hydrophobically modified alkali-soluble emulsions (HASE) exhibit pronounced interaction that results in the solubilization of the latex. The interaction between HASE latex and surfactant was studied using various techniques, such as light transmittance, isothermal titration calorimetry, laser light scattering, and electrophoresis. For anionic surfactant, noncooperative hydrophobic binding dominates the interaction at concentrations lower than the critical aggregation concentration (CAC) (C < CAC). However, cooperative hydrophobic binding controls the formation of mixed micelles at high surfactant concentrations (C > or = CAC), where the cloudy solution becomes clear. For cross-linked HASE latex, anionic surfactant binds only noncooperatively to the latex and causes it to swell. For cationic surfactant, electrostatic interaction occurs at very low surfactant concentrations, resulting in phase separation. With further increase in surfactant concentration, noncooperative hydrophobic and cooperative hydrophobic interactions dominate the binding at low and high surfactant concentrations, respectively. For anionic and cationic surfactant systems, the CAC is lower than the critical micelle concentration (CMC) of surfactants in water. In addition, counterion condensation plays an important role during the binding interaction between HASE latex and ionic surfactants. In the case of nonionic surfactants, free surfactant micelles are formed in solution due to their relatively low CMC values, and HASE latexes are directly solubilized into the micellar core of nonionic surfactants.     

Partial phase behavior and micellar properties of tetrabutylammonium salts of fatty acids: unusual solubility in water and formation of unexpectedly small micelles

The tetrabutylammonium (TBA) salts of fatty acids, from dodecanoic acid (C12) to octacosanoic acid (C28), have been prepared by direct neutralization of the fatty acid by TBA hydroxide. Unexpectedly, all of these surfactants have been found to be soluble in water under the form of micelles at a sufficiently high temperature. For instance, the solubility of TBA octacosanoate in water is of about 7 wt % at 46 degrees C. Starting from TBA docosanoate, the aqueous solutions of the surfactants gelled below a certain temperature. The gelling temperature increased linearly with the fatty acid carbon number. Upon increasing temperature, the TBA octocosanoate showed a relatively complex phase behavior that has been investigated. The micellar solutions of these surfactants did not cloud at high temperatures, up to 98 degrees C, contrary to TBA alkylsulfates. The aggregation numbers of micelles of the various TBA alkylcarboxylates have been measured and found to be smaller than those for the maximum spherical micelle that a surfactant with the same alkyl chain length can form. The micelle micropolarity and microviscosity (as sensed by fluorescent probes) decreased and increased, respectively, with the fatty acid carbon number.     

Mechanism of surfactant micelle formation

The mechanism of micelle formation of surfactants sodium dodecyl sulfate (SDS), n-hexyldecyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) in heavy water solutions was studied by 1H NMR (chemical shift and line shape) and NMR self-diffusion experiments. 1H NMR and self-diffusion experiments of these three surfactants show that their chemical shifts (delta) begin to change and resonance peaks begins to broaden with the increase in concentration significantly below their critical micelle concentrations (cmc's). At the same time, self-diffusion coefficients ( D) of the surfactant molecules decrease simultaneously as their concentrations increase. These indicate that when the concentrations are near and lower than their cmc's, there are oligomers (premicelles) formed in these three surfactant systems. Carefully examining the dependence of chemical shift and self-diffusion coefficient on concentration in the region just slightly above their cmc's, one finds that the pseudophase transition model is not applicable to the variation of physical properties (chemical shift and self-diffusion coefficient) with concentration of these systems. This indicates that premicelles still exist in this concentration region along with the formation of micelles. The curved dependence of chemical shift and self-diffusion coefficient on the increase in concentration suggests that the premicelles grow as the concentration increases until a definite value when the size of the premicelle reaches that of the micelle, i.e., the system is likely dominated by the monomers and micelles. Additionally, the approximate values of premicelle coming forth concentration (pmc) and cmc were obtained by again fitting chemical shifts to reciprocals of concentrations at a different perspective, and are in good accordant with experimental results and literature values and prove the former conclusion.     

Miscibility of dodecyltrimethylammonium bromide and dodecyltrimethylammonium chloride in surface-adsorbed film and micelle

Surface tension of aqueous solutions of mixtures of dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium chloride (DTAC) has been measured and analyzed by using thermodynamic relations. The adsorbed film has been found to contain more DTAB molecules than the solution. The shape formed by the curves of the total molality at constant surface tension against the solution and surface compositions indicates the ideal mixing of the DTAB and DTAC molecules in the adsorbed film. Micellar composition has been estimated at the critical micelle concentration (CMC). The micelles have been found to be richer in DTAB than the solution, but poorer in DTAB than the adsorbed film at the CMC. The DTAB and DTAC molecules have been shown to mix ideally in the micelles. From the comparison with the results on the system of decylammonium bromide and decylammonium chloride, it has been concluded that, on the mixing of surfactants differing only in counter ions, the adsorbed film is influenced more significantly by the ionic head group of the surfactant than the micelle.     

Determination of the Critical Micelle Concentration of Cationic Surfactants by Capillary Electrophoresis

The determination of the critical micelle concentration (CMC) of cationic surfactants by capillary electrophoresis was demonstrated. In this study, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DoTAB) were selected as cationic surfactants and propazine was chosen as test solute. In the evolution of the effective electrophoretic mobility of propazine as a function of surfactant concentration, a dramatic change in slope at a particular concentration is a good indication of the CMC of this surfactant. The CMC values determined experimentally were further confirmed by a curve-fitting approach. Simulation of the electrophoretic mobility curves as a function of surfactant concentration in both micellar electrokinetic chromatography and capillary zone electrophoresis using cationic surfactants as an electrolyte modifier was performed for propazine, and the intersection of these two mobility curves allowed us to precisely predict the CMC of the surfactant. The CMC values determined for TTAB and DoTAB are 1.6 ± 0.1 and 11.0 ± 0.1 mM, respectively, in the case of an electrolytic solution consisting of 70 mM phosphate buffer at pH 6.0. Moreover, the applicability of the electroosmotic mobility as a parameter for the determination of the CMC was examined.     

Aggregation behavior of hexadecyltrimethylammonium surfactants with various counterions in aqueous solution

Both thermodynamic and microenvironmental properties of the micelles for a series of cationic surfactants hexadecyltrimethylammonium (C16TAX) with different counterions, F-, Cl-, Br-, NO3-, and (1/2)SO4(2-), have been studied. Critical micelle concentration (CMC), degree of micelle ionization (alpha), and enthalpy of micellization (DeltaH(mic)) have been obtained by conductivity measurements and isothermal titration microcalorimetry. Both the CMC and the alpha increase in the order SO4(2-) < NO3- < Br- < Cl- < F-, consistent with a decrease in binding of counterion, except for the divalent anion sulfate. DeltaH(mic) becomes less negative through the sequence NO3- < Br- < Cl- < F- < SO4(2-), and even becomes positive for the divalent sulfate. The special behavior of sulfate is associated with both its divalency and its degree of dehydration. Gibbs free energies of micellization (DeltaG(mic)) and entropies of micellization (DeltaS(mic)) have been calculated from the values of DeltaH(mic), CMC, and alpha and can be rationalized in terms of the Hofmeister series. The variations in DeltaH(mic) and DeltaS(mic) have been compared with those for the corresponding series of gemini surfactants. Electron spin resonance has been used to assess the micropolarity and the microviscosity of the micelles. The results show that the microenvironment of the spin probe in the C16TAX surfactant micelles depends strongly on the binding of the counterion.     

Effects of Spacer Chain Length and Additives on Solution Properties of Cationic Gemini Surfactant

The critical micelle concentration (CMC) has been determined for the gemini surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium bromide)12-s-12,2Br^?1 by means of electricity conductivity measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, geminis have CMC values well below those of conventional single-chain cationic surfactants. The CMC of 12-3-12 reduces with the addition of n-alcohol except ethanol and with the increase of n-alcohol chain length as well as increase of concentration of n-butanol and sodium chloride. Steady-state fluorescence quenching technology has been employed to study the aggregation number of micelle, which increases with increase in the length of n-alcohol. The Kraft temperature measurements also indicate that the stability of solid surfactant hydrate decreases along with the improvement of concentration of n-butanol and sodium chloride.     

Hydrolysis of 2,4-Dinitrochlorobenzene Catalyzed by Cationic Micelles

Micellar catalysis by nine cationic surfactants of the basic hydrolysis of 2,4-dinitrochlorobenzene(DNCB) was studied. The results obtained are as follows: (I) The second-order constants k₂ for the hydrolysis reaction of DNCB catalized by the cationic micelles increase by a factor of 11–100 than that in water. Plots of k₂ against the surfactant concentration show an S-type curve, and the catalytic effect is observed below the critical micelle concentration(CMC) of the surfactants. (2) For a series of surfactants, there is an optimal chain length for the alkyl of the surfactants to show the greatest catalytic effect. (3) The hydrolysis rate of DNCB decreases as the base concentration increases. (4) For the surfactants with the same hydrophilic and hydrophobic groups, chlorides have advantage over bromides in enhancing the reaction rate. These results can be interpreted in term of the changes in CMC, micelle size, solubilization capacity of the micelles, binding degree of counterion et al.     

Degree of micelle ionization and micellar growth for gemini surfactants detected by 6-methoxy-N-(3-sulfopropyl)quinolinium fluorescence quenching

The degree of micelle ionization of gemini surfactants has been investigated by using halide-sensitive fluorescence probes (e.g., 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ)). The fluorescence is quenched by the free bromide ions dissociated from surfactants. The degree of micelle ionization increased with increasing spacer chain length, but it decreased with increasing surfactant concentration. The Stern-Volmer plot gave two inflection points (i.e., not only at the cmc but also far above the cmc). The second inflection point suggested spherocylindrical micellar growth with decreases in the degree of micelle ionization. The spherocylindrical micellar growth was depressed with increasing spacer chain length, whereas it was enhanced with increasing tail chain length. The degree of micelle ionization of spherocylindrical micelles depended on the concentration and chain length of gemini surfactants. The change in SPQ fluorescence spectra upon hydrogenation was utilized to evaluate the solubilization site in micelle solutions. The dissolved SPQ in water was instantly reduced by the addition of NaBH4, resulting in abrupt changes in fluorescence intensity and spectral shift. All of the SPQ in micelle solution was also instantly reduced by NaBH4, indicating the existence of SPQ in the water bulk phase, but its fluorescence intensity increased upon the solubilization of hydrogenated SPQ into micelles.     

Self-assembled Gemini surfactant film-mediated dispersion stability

The force-distance curves of 12-2-12 and 12-4-12 Gemini quaternary ammonium bromide surfactants on mica and silica surfaces obtained by atomic force microscopy (AFM) were correlated with the structure of the adsorption layer. The critical micelle concentration was measured in the presence or absence of electrolyte. The electrolyte effect (the decrease of CMC) is significantly more pronounced for Gemini than for single-chain surfactants. The maximum compressive force, F(max), of the adsorbed surfactant aggregates was determined. On the mica surface in the presence of 0.1 M NaCl, the Gemini micelles and strong repulsive barrier appear at surfactant concentrations 0.02-0.05 mM, which is significantly lower than that for the single C(12)TAB (5-10 mM). This difference between single and Gemini surfactants can be explained by a stronger adsorption energy of Gemini surfactants. The low concentration of Gemini at which this surfactant forms the strong micellar layer on the solid/solution interface proves that Gemini aggregates (micelles) potentially act as dispersing agent in processes such as chemical mechanical polishing or collector in flotation. The AFM force-distance results obtained for the Gemini surfactants were used along with turbidity measurements to determine how adsorption of Gemini surfactants affects dispersion stability. It has been shown that Gemini (or two-chain) surfactants are more effective dispersing agents, and that in the presence of electrolyte, the silica dispersion stability at pH 4.0 can also be achieved at very low surfactant concentrations ( approximately 0.02 mM).     

Adsorption of a polymeric siloxane surfactant on carbon black particles dispersed in mixtures of water with polar organic solvents

The adsorption of a rake-type polymeric siloxane surfactant (polydimethylsiloxane-graft-polyether copolymer) on carbon black (CB) particles dispersed in mixtures of water with polar organic solvents (ethanol, formamide, or glycerol) has been investigated. The adsorption obeys the Langmuir isotherm at low surfactant concentrations (below the critical micelle concentration, CMC). At these conditions, the average surface area occupied by one siloxane surfactant follows the sequence water+glycerol mixture >plain water >water+ethanol mixture. At higher surfactant concentrations in the solution in contact with the particles, a sharp increase in the adsorbed amount is observed. The adsorbed layer thickness has been determined by dynamic light scattering. Below the CMC the adsorbed layer thickness is less than 10 nm. Above the CMC, the adsorbed layer thickness increases to 20-30 nm, a length scale comparable to the diameter of the siloxane surfactant micelles in aqueous solution. This fact, together with SANS data that we have obtained in the absence of added polar organic solvent, indicates that the structure of the adsorbed layer is similar to that of micelles. The findings presented here are relevant to waterborne coatings and ink formulations, where polymeric surfactants are used in conjunction with polar organic solvents.     

Thermodynamics of micellization of multiheaded single-chain cationic surfactants

The energetics of micelle formation of three single-chain cationic surfactants bearing single (h = 1), double (h = 2), and triple (h = 3) trimethylammonium [(+)N(CH(3))(3)] headgroups have been investigated by microcalorimetry. The results were compared with the microcalorimetric data obtained from well-known cationic surfactant, cetyl trimethylammonium bromide (CTAB), bearing a single chain and single headgroup. The critical micellar concentrations (cmc's) and the degrees of counterion dissociation (alpha) of micelles of these surfactants were also determined by conductometry. The cmc and the alpha values increased with the increase in the number of headgroups of the surfactant. The relationship between the cmc of the surfactant in solution and its free energy of micellization (DeltaG(m)) was derived for each surfactant. Exothermic enthalpies of micellization (DeltaH(m)) and positive entropies of micellization (DeltaS(m)) were observed for all the surfactants. Negative DeltaH(m) values increased from CTAB to h = 1 to h = 2 and decreased for h = 3 whereas DeltaS(m) values decreased with increase in the number of headgroups. The DeltaG(m) values progressively became less negative with the increase in the number of headgroups. This implies that micelle formation becomes progressively less favorable as more headgroups are incorporated in the surfactant. From the steady-state fluorescence measurements using pyrene as a probe, the micropolarities sensed by the probe inside various micelles were determined. These studies suggest that the micelles are more hydrated with multiheaded surfactants and the micropolarity of micelles increases with the increase in the number of headgroups.     

Micelle Formation and Aggregate Morphology Transition from Vesicle to Rod Micelle for Allyl Alkyldimethylammonium Bromide Cationic Surfactant

A series of cationic surfactants of allyl alkyldimethylammonium bromide (AA_nDB), where n=12, 16, 18, were synthesized, and the adsorption behavior of AA_nDB at the air–water interface and the aggregation morphology in bulk solution were reported. The critical micelle concentration (CMC) was determined by the drop volume technique and steady state fluorescence. The surface excess concentration of AA_nDB surfactants was calculated from the surface tension versus log concentration curves by applying the Gibbs' adsorption isotherm. The values of surface area per molecule calculated by using Gibbs' equation were 2.9–1.4 nm², indicating the relatively large size of the AA_nDB surfactants. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements reveal that, at low surfactant concentration of allyl dodecyl dimethylammonium bromide (AA₁₂DB) above CMC, vesicles can be spontaneously formed. However, with increasing surfactant concentration, vesicles tend to be transformed into rod‐like micelles.     

表面活性剂双水相的性质及其应用 Ⅰ. 表面活性剂双水相的微环境性质

阴、阳离子表面活性剂混合体系, 在一定浓度及混合比范围内, 可以形成两个互不相溶、平衡共存的水相, 称为表面活性剂双水相。其中阳离子表面活性剂过量的双水相体系, 称为阳离子双水相。本文分别以芘和罗丹明B作为探针, 用荧光探针法研究了摩尔比为1.6:1的C12NE和SDS混合体系成形成的阳离子双水相,测定其上层和下层的胶束微环境的极性和微粘度, 取得了有意义的结果。     

表面活性剂胶束形状随浓度转变的核磁共振研究

运用核磁共振一维氢谱和自扩散实验方法研究了聚乙烯乙二醇异辛酚醚(TX-100)、十二烷基苯磺酸钠(SDBS)和十四烷基三甲基溴化铵(TTAB)三种不同类型的表面活性剂在重水溶液中的胶束形状转变, 发现它们在临界胶束浓度以上的各自相应浓度都有胶束形状的变化(由球状转变为椭球状或棒状). 在常温常压和没有其他添加剂的情况下, 表面活性剂溶液浓度高于其临界胶束浓度时, 球状胶束开始形成. 核磁共振一维氢谱和自扩散实验的结果显示, 当溶液浓度继续增加到一定程度时, 溶液中表面活性剂分子的化学位移和自扩散系数的变化速率都有明显的转折, 这说明溶液中球状胶束开始发生转变. 进一步通过仔细分析对比核磁共振一维氢谱中各基团谱峰, 发现表面活性剂胶束亲水表面上的质子的化学位移变化速率要远高于其疏水内核中的质子, 据此推测胶束形状很可能由球状转变为椭球状或棒状.