Physicochemical studies of pyridinium gemini surfactants with promethazine hydrochloride in aqueous solution

The mixed micellization and interfacial behavior of pyridinium gemini surfactants, 1,1'-(1,1'-(ethane-1,2-diylbis-(sulfanediyl))bis(alkane-2,1-diyl))dipyridinium bromide, i.e., [12-(S-2-S)-12], [14-(S-2-S)-14], [16-(S-2-S)-16] with a phenothiazine tranquilizer drug, promethazine hydrochloride (PMT), has been investigated by conductivity, surface tension and steady state fluorescence measurements. Different spectroscopic techniques like fluorescence, UV-visible and NMR were also employed to understand the nature of interactions between the pyridinium gemini surfactants and PMT. The various micellar, interfacial and associated thermodynamic parameters for different mole fractions of PMT-pyridinium gemini surfactant mixtures have been evaluated. Synergism was observed in the mixed micelle as well as the monolayer formed by these mixtures. The fluorescence quenching experiment indicates that the interactions between PMT and surfactants are hydrophobic in nature. The UV-visible measurements reveal the distinct formation of a drug-surfactant complex. The detailed mechanism for the type of interactions was further studied by NMR titrations which show cation-π interactions between PMT and pyridinium gemini surfactant molecules.     

Micellization of anionic gemini surfactants and their interaction with polyacrylamide

A series of anionic gemini surfactants have been synthesized. The surface properties and micellization process of as-prepared sulfonate gemini surfactants (SGS) and carboxylate gemini surfactant (CGS) have been studied by surface tension measurement and isothermal titration microcalorimetry. Meanwhile, the interaction of these five surfactants with polyacrylamide (PAM) was investigated using surface tension, steady-state fluorescence measurement, and isothermal titration microcalorimetry. The results show that the critical micelle concentrations (CMCs) of above-mentioned surfactants are more than 1 order of magnitude lower than those of corresponding single chain surfactants. Moreover, the enthalpy of micelle formation (ΔH _mic) for the investigated gemini surfactants is negative. In the surfactant–PAM systems, the thermodynamic parameters of binding have also been determined. The conclusion may be drawn that the binding strength of SGS onto PAM is stronger than that of CGS, resulting from more compact structure of SGS aggregates. With increasing surfactant hydrophobicity, the values of ΔH _agg become more exothermic and a ΔS _agg decrease was observed. Therefore, the interaction between SGS and PAM is enthalpy-driven.     

Interactions of cationic gemini surfactants with hydrophobically modified poly(acrylamides) studied by fluorescence and microcalorimetry

Steady-state fluorescence, time-resolved fluorescence quenching, and isothermal titration microcalorimetry have been used to study the interactions of cationic gemini surfactants alkanediyl-alpha,omega-bis(dodecyldimethylammonium bromide) (C(12)C(S)C(12)Br(2), S = 3, 6, and 12) with hydrophobically modified poly(acrylamide) (HMPAM) and unmodified poly(acrylamide) (PAM). Without addition of gemini surfactant, 0.2 wt % HMPAMs except PAM have already self-aggregated into hydrophobic aggregates. Different from single-chain surfactants, C(12)C(S)C(12)Br(2) have stronger interactions with HMPAMs to form surfactant/polymer aggregates, even with PAM. Addition of C(12)C(S)C(12)Br(2) may cause the disruption of HMPAM hydrophobic aggregates and the formation of mixed micelles. It is found that HMPAMs generate lower micropolarity of mixed micelles, larger values of enthalpy of interaction (DeltaH(ps)), and nearly constant values of Gibbs free energy of interaction (DeltaG(ps)). On the other hand, C(12)C(S)C(12)Br(2) with longer spacer brings out slightly lower micropolarity of mixed micelles, owing to the lower electrostatic repulsion between surfactant headgroups. Especially for C(12)C(12)C(12)Br(2), the values of DeltaH(ps) are much more endothermic and the values of DeltaG(ps) are much less negative. The weaker interactions of C(12)C(12)C(12)Br(2) with HMPAMs arise from the marked reduction of attraction between surfactant headgroups and polymer hydrophilic groups induced by its longer spacer.     

Mixed micellar properties of cationic trimeric-type quaternary ammonium salts and anionic sodium n-octyl sulfate surfactants

The properties of quaternary ammonium salt-type cationic trimeric surfactants (m-2-m-2-m, m represents the carbon atom number in alkyl chain lengths of 8, 10, and 12) and oppositely charged anionic monomeric surfactant, sodium n-octyl sulfate (SOS), were characterized by employing several techniques such as static surface tension, fluorescence spectroscopy, and dynamic light-scattering measurements. The critical micelle concentrations (cmc) of m-2-m-2-m were much lower than those of the corresponding dimeric and monomeric surfactants, and decreased with increasing chain length. The addition of SOS to m-2-m-2-m solutions resulted in a further decrease of the cmc. The mixed surfactants showed higher efficiencies in lowering the surface tension than the individual surfactants. The fluorescence measurements suggested the formation of mixed micelles with a hydrophobic environment in the solutions even at lower concentrations. The dynamic light-scattering study indicated the presence of two different kinds of aggregates with different hydrodynamic diameters. The larger one was attributed to the mixed micelle of m-2-m-2-m and SOS. These results indicated a decline of the electrostatic repulsion between cationic head groups through the incorporation of anionic surfactant into the mixed surfactants.     

Surface tension and aggregation properties of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer

A series of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer were synthesized, and their surface and bulk properties were investigated by surface tension, electrical conductivity, fluorescence, viscosity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. An interesting phenomenon, that is, the obvious decline in surface tension upon increasing concentration above the critical micelle concentration (cmc), was found in these gemini surfactant solutions, and two explanations were proposed. This surface tension behavior could be explained by the rapid increase in the counterion activity in the bulk phase or the continued filling of the interface with increasing surfactant concentration above the cmc. More interestingly, not only vesicles but also the surfactant-concentration-induced vesicle to larger aggregate (spongelike aggregate) transition and the salt-induced vesicle and spongelike aggregate to micelle transition were found in the aqueous solutions of these gemini surfactants. The spongelike aggregate that is first reported in the cationic gemini surfactant-water binary system is probably caused by the adhesion and fusion of vesicles at high surfactant concentration.     

Gemini表面活性剂烷烃尾链在吸附和聚集过程中的疏水协同效应(英文)

以表面张力法测定了系列Gemini表面活性剂m-6-m以及对应单体表面活性剂CmTABr的临界胶束浓度(cmc)和降低水表面张力20mN·m-1需要的浓度(pC20).比较这些参数表明m-6-m胶束化和在界面吸附的能力均强于CmTABr,这被归结为Gemini表面活性剂烷烃尾链间的疏水协同效应.与不对称Gemini表面活性剂12-6-m比较,对称的Gemini结构更有利于表面活性剂的聚集和吸附.     

含酯基Gemini表面活性剂在有机醇-水体系中的胶束热力学及聚集行为

采用电导法研究了不同温度下含酯基Gemini表面活性剂在纯水和在质量分数为10%的甲醇-水(MAWR),乙二醇-水(EG-WR),丙三醇-水(GL-WR)四种体系中的集聚行为和胶束热力学;聚集行为参数包括临界胶束浓度(cmc)和抗衡离子的解离程度(α)以及胶束的热力学参数,包括标准吉布斯自由能(ΔG_m~o)、吉布斯迁移自由能(ΔG_(trans)~o)、吉布斯烷基链胶束化自由能(ΔG_(tail)~o)、标准焓变(ΔH_m~o)和标准熵变(ΔS_m~o),均被计算和讨论。研究表明在所有的研究体系中,cmc值随着疏水链的增加而减小,随着加入的醇结构中羟基数目的增加而增大,随温度的升高先变小,后变大呈U字形;胶束化过程都是自发进行的,并且在293.15 K下,胶束化过程是吸热的,在293.15 K上,胶束化过程是放热的;通过稳态荧光光谱法研究了表面活性剂在纯水、有机醇-水混合溶液中的微极性,结果表明,在相同溶剂中,随着烷基链长度的增加,溶液微环境的疏水性越强;对于相同的Gemini表面活性剂,随着加入含羟基数目越多的醇,其微环境的疏水性越强。并研究了Gemini表面活性剂在混合体系中形成胶束过程的焓-熵补偿曲线。     

Synthesis and unusual properties of novel alkylbenzene sulfonate gemini surfactants

Seven new dialkyldibenzene disulfonate gemini surfactants have been synthesised. The physico-chemical properties such as their surface tensions, krafft temperatures and melting temperatures have been measured. It was found that the anionic gemini surfactants showed some aberrant properties. The results determined by drop-volume method indicated that surfactants Id, Ie at 25 °C and IIb at 50 °C showed no cmc and lowered surface tension of water hardly despite their seemingly favorable amphiphilic components. However, the three surfactants showed a sharp cmc and good surface activity with the increment of temperature. Surfactant Ie with two longer chains had a higher cmc than that for shorter chain surfactant Id. Furthermore, for this class of anionic gemini surfactants, the spacer carbon number had more important effects than the alkyl chain carbon number on their krafft temperatures and melting temperatures.     

Interactions of quaternary ammonium salt-type gemini surfactants with sodium poly(styrene sulfonate)

The interactions of cationic gemini surfactants, 1,2-bis(alkyldimethylammonio)ethane dibromide (m-2-m: m is hydrocarbon chain length, m = 10 and 12), and an anionic polymer, sodium poly(styrene sulfonate) (PSS), have been characterized by several techniques such as tensiometry, fluorescence spectroscopy, and dynamic light scattering. The surface tension of gemini surfactant/PSS mixed systems decreases with surfactant concentration, reaching break points, which are taken as critical aggregation concentrations (cac). The surface tension at the cac of mixtures is higher than that of single surfactants, and it is found that at concentrations above the cac, the surfactant molecules are associated with the polymer in the bulk. The 12-2-12/PSS mixed system shows higher surface activity than both 10-2-10/PSS and the monomeric surfactant of dodecyltrimethylammonium bromide/PSS systems. Fluorescence measurements of these mixed systems suggest the formation of a complex with a highly hydrophobic environment in the bulk of the solution. Additionally, dynamic light scattering measurements show that the hydrodynamic diameter of the 12-2-12/PSS mixed system is smaller than that of PSS only at low concentration, indicating interactions between surfactant and polymer. These result from the electrostatic attraction between ammonium and sulfate headgroups as well as the hydrophobic interaction between their hydrocarbon chains.     

Fluorescence spectroscopy of fulvic acids’ interaction with surfactants

Fluorescence spectra of two fulvic acid (FA) samples, FA0 from underground water and FA1 from forest soil, were recorded in various surfactant solutions. Alkyltrimethylammonium ions with different alkyl chain lengths induced a decrease in the fluorescence intensity for both FAs at concentrations below the critical micelle concentration (cmc) and an enhancement above the cmc. The intensity minimum thus obtained at the cmc was deeper for surfactants with longer alkyl chains. This effect was attributable to the formation of insoluble FA–surfactant complexes below the cmc and to the solubilization of the complex into micelles above the cmc. Dodecylpyridinium chloride caused a monotonic decrease in the FA fluorescence even far above the cmc. This was attributable to the quenching of FA fluorescence by the positioning of the pyridinium head group near the FA fluorophore. Anionic and nonionic surfactants showed little to no effect on the FA fluorescence.     

Adsorption and micellization behavior of novel gluconamide-type gemini surfactants

The adsorption and micellization behavior of novel sugar-based gemini surfactants (N,N(')-dialkyl-N,N(')-digluconamide ethylenediamine, Glu(n)-2-Glu(n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu(n)-2-Glu(n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100-200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu(n)-2-Glu(n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc.     

Equilibrium and dynamic surface tension properties of partially fluorinated quaternary ammonium salt gemini surfactants

The equilibrium and dynamic surface tension properties of a partially fluorinated quaternary ammonium salt gemini surfactant 1,2-bis[dimethyl-(3-perfluoroalkyl-2-hydroxypropyl)ammonium]ethane bromide (C(n)(F)C3-2-C3C(n)F, where n represents fluorocarbon chain lengths of 4, 6, and 8) were investigated, and the effects of the fluorocarbon chain length and the number of chains on them were discussed. The plot of the logarithm of the critical micelle concentration (cmc) against the fluorocarbon chain length for C(n)(F)C3-2-C3C(n)F showed a linear decrease with an increase in chain length. On the basis of the slope of this plot, it was found that the variation in cmc with respect to the chain length is large for fluorinated gemini surfactants. The surface tension at the cmc decreased significantly; this surface tension value is lower than that of conventional fluorinated monomeric surfactants. In particular, the lowest value was 13.7 mN m(-1) for n = 8. Furthermore, it was confirmed that the kinetics of adsorption at the interface decrease with an increase in the fluorocarbon chain length and the concentration.     

混合胶束中Gemini阳离子表面活性剂14-s-14与常规表面活性剂的协同作用:连接臂及反离子效应(英文)

The mixed micelle formation of binary cationic 14-s-14 gemini with conventional single chain surfactants was studied by conductivity measurements.The critical micelle concentration(cmc) and the degree of counterion binding values(g) of the binary systems were determined.The results were analyzed by applying regular solution theory(RST) to calculate micellar compositions(X),activity coefficients(f1,f2),and the interaction parameters(β).The synergistic interactions of all the investigated cationic gemini+conventional surfactant combinations were found to be dependent upon the length of hydrophobic spacer of the gemini surfactant.The excess Gibbs free energy of mixing was evaluated,and it indicated relatively more stable mixed micelles for the binary combinations.     

Conductometric and fluorometric investigations on the mixed micellar systems of cationic surfactants in aqueous media

Micellar properties of binary mixtures of hexadecyldiethylethanolammonium bromide surfactant with tetradecyldimethylammonium, trimethylammonium, triphenylphosphonium, diethylethanolammonium, and pyridinium bromide surfactants have been characterized employing conductometric and fluorescence techniques. The critical micelle concentration (cmc*) and the degree of counter-ion binding values (delta) of the binary systems were determined from the conductivity measurements. The results were analyzed in light of various existing theories to calculate micellar composition, activity coefficients, and the interaction parameter (beta). Partial contribution of each surfactant, cmc1*, cmc2*, to the overall cmc* value was also evaluated. Aggregation numbers and micropolarity of the mixed micelles were determined from fluorescence measurements. The results were discussed in terms of synergetic interactions in these systems on the basis of the head group/head group and tail/tail interactions and the counter-ion binding.     

Synthesis and surface properties of anionic gemini surfactants with amide groups

Novel anionic gemini surfactants, 1,2-bis(N-beta-carboxypropanoyl-N-alkylamino)ethane (2CnenAm; n is hydrocarbon chain length of 6, 8, 10, 12, or 14), with two hydrocarbon chains, two carboxylate groups, and two amide groups, were synthesized by three-step reactions. Their solution properties were characterized by equilibrium and dynamic surface tension, steady-state fluorescence spectroscopy of pyrene, and dynamic light-scattering techniques. The surface tension measurements of 2CnenAm give low critical micelle concentrations (cmc), great efficiency in lowering the surface tension, and strong adsorption at air/water interface. Gemini surfactants behave normally with the logarithm of cmc decrease linearly with the chain length. In addition, adsorption and micellization behavior of 2CnenAm was estimated by parameter of pC20, cmc/C20, and standard free energy (DeltaG(0)mic and DeltaG(0)ads); they are significantly influenced by hydrocarbon chain length, and the adsorption is promoted more than the micellization as chain length becomes longer. The results of dynamic light-scattering and fluorescence quenching indicate that small micelles of 2CnenAm are observed at the concentrations above the cmc, and further large particles are also seen. Further, from the dynamic surface tension measurements, it is found that the shorter hydrocarbon chain length of 2CnenAm, the faster the rate of decrease of surface tension.     

Effect of head group polarity and spacer chain length on the aggregation properties of gemini surfactants in an aquatic environment

The aggregation behavior of cationic gemini surfactants with respect to variation in head group polarity and spacer length is studied through conductance, surface tension, viscosity, and small-angle neutron-scattering (SANS) measurements. The critical micellar concentration (cmc), average degree of micelle ionization (beta(ave)), minimum area per molecule of surfactant at the air-water interface (A(min)), surface excess concentration (gamma(max)), and Gibb's free energy of micellization (delta G(mic)) of the surfactants were determined from conductance and surface tension data. The aggregation numbers (N), dimensions of micelles (b/a), effective fractional charge per monomer (alpha), and hydration of micelles (h(E)) were determined from SANS and viscosity data, respectively. The increasing head group polarity of gemini surfactant with spacer chain length of 4 methylene units promotes micellar growth, leading to a decrease in cmc, beta(ave), and delta G(mic) and an increase in N and b/a. This is well supported by the observed increase in hydration (h(E)) of micelles with increase in aggregation number (N) and dimension (b/a) of micelle.     

Effects of organic salt additives on the behavior of dimeric ("gemini") surfactants in aqueous solution

The effects of a series of aromatic anions, so-called hydrotropes, on characteristic solution properties of a family of ammonium gemini surfactants with dodecyl chains were explored. The stoichiometric addition of the organic salts to the geminis can result in clear solutions or in phase separation/precipitation, depending on the detailed nature of the added counterions and on the spacer group of the gemini surfactant. Many organic anions induce synergistic effects, strongly reducing the critical micellization concentration (cmc) and the surface tension at the cmc. Furthermore, a number of combinations of organic anions and geminis exhibit thickening of their aqueous solutions. The effects of the added salts are strongly enhanced for the gemini surfactants compared to the monomeric analogue N-dodecyl-N,N,N-trimethylammonium chloride. Even anions such as benzoate may be effective for thickening, and viscoelastic solutions can be obtained with salicylate despite the relatively short alkyl chains.     

两相催化体系中双子表面活性剂对1-十二烯氢甲酰化反应的助催化作用

合成了几种具有刚性连接基团的双子表面活性剂,研究了它们在Rh-TPPTS体系中催化长链烯烃氢甲酰化反应中的助催化作用.结果表明,在水/有机两相催化体系中,新型双子表面活性剂的助催化作用比单链表面活性剂CTAB更好,在较低的表面活性剂浓度下能得到较高的反应转化率.这归因于此类表面活性剂有较低的cmc,降低界面张力的能力和对1-十二烯的增溶能力比CTAB更强.     

Synergistic interactions in the mixed micelles of cationic gemini with zwitterionic surfactants: fluorescence and Krafft temperature studies

Pyrene fluorescence and Krafft temperature measurements have been carried out for various combinations of cationic gemini (m-2-m) with zwitterionic surfactants by changing the length of the hydrophobic tail over the whole mixing range. The results have been evaluated by using the regular solution theory. All the mixtures of cationic gemini+zwitterionic surfactants indicate the presence of synergistic interactions which largely decrease at higher hydrophobicity of both components. A greater amount of gemini component in the mixed micelles induces stronger synergism which reduces with the increase in the length of hydrophobic tail of the gemini component. The Krafft temperature measurements also indicate the presence of strong synergistic interactions, which decrease with increase in the length of hydrophobic tail of both components.     

Interaction between biosurfactant surfactin and cationic surfactant cetyl trimethyl ammonium bromide in mixed micelle

An anionic/cationic mixed surfactant aqueous system of surfactin and cetyl trimethyl ammonium bromide (CTAB) at different molar ratios was studied by surface tension and fluorescence methods (pH 8.0). Various parameters that included critical micelle concentration (cmc), micellar composition (X ₁), and interaction parameter (β ^m) as well as thermodynamic properties of mixed micelles were determined. The β ^m was found to be negative and the mixed system was found to have much lower cmc than pure surfactant systems. There exits synergism between anionic surfactin and cationic CTAB surfactants. The degree of participation of surfactin in the formation of mixed micelle changes with mixing ratio of the two surfactants. The results of aggregation number, fluorescence anisotropy, and viscosity indicate that more packed and larger aggregates were formed from mixed surfactants than unmixed, and the mixed system may be able to form vesicle spontaneously at high molar fraction of surfactin.