Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups. 1. Adsorption and micellization

Zwitterionic heterogemini surfactants with two hydrocarbon chains and two different hydrophilic groups, N,N-dimethyl-N-[2-(N'-alkyl-N'-beta-carboxypropanoylamino)ethyl]-1-alkylammonium bromides (2C(n)AmCa, where n represents the hydrocarbon chain lengths of 8, 10, 12, and 14), were synthesized by N,N-dimethylethylenediamine with alkyl bromide, followed by reaction with succinic anhydride. One of the hydrophilic groups is a carboxylate anion, and the other is an ammonium cation. Their physicochemical properties were characterized by measuring equilibrium and dynamic surface tension, fluorescence intensity of pyrene, and light-scattering intensity. A relationship between a logarithm of critical micelle concentration (cmc) and hydrocarbon chain length showed a linear decrease upon increasing chain length and then a departure from linearity at n = 14. This is due to the existence of premicellar aggregations at concentrations below the cmc for n = 14. The surface tension of 2C(n)AmCa reached 27-30 mN m(-1) at each cmc, indicating efficiencies typical of hydrocarbon chain surfactants. The adsorbing rate at the air/water interface became slow with an increase of the chain length. From the fluorescence intensity ratios of 373 and 384 nm using pyrene as a probe, for n = 8, 10, and 14, the pyrene was solubilized in surfactant micelles at around the cmc, whereas for n = 12 the pyrene was solubilized from a concentration of 10-fold the cmc. The scattering intensities by dynamic light scattering also increased from around these concentrations for each chain length, showing the formation of aggregates in solution.     

Star-shaped trimeric quaternary ammonium bromide surfactants: adsorption and aggregation properties

Novel star-shaped trimeric surfactants consisting of three quaternary ammonium surfactants linked to a tris(2-aminoethyl)amine core were synthesized. Each ammonium had two methyls and a straight alkyl chain of 8, 10, 12, or 14 carbons. The adsorption and aggregation properties of these tris(N-alkyl-N,N-dimethyl-2-ammoniumethyl)amine bromides (3C(n)trisQ, in which n represents alkyl chain carbon number) were characterized by equilibrium and dynamic surface tension, rheology, small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM) techniques. 3C(n)trisQ showed critical micelle concentrations (CMC) 1 order of magnitude lower than that of the corresponding gemini surfactants with an ethylene spacer and the corresponding monomeric surfactants. The logarithm of the CMC decreased linearly with increasing hydrocarbon chain length for 3C(n)trisQ. The slope of the line, which is well-known as Klevens equation, was larger than those of the monomeric and gemini surfactants; however, considering the total carbon number in the chains, the slope was shallower than the monomeric and was close to the gemini. Through the results such as surface tensions at the CMC (32-34 mN m(-1)) and the parameters of standard free energy, CMC/C(20) and pC(20), it was found that 3C(n)trisQ could adsorb densely at the air/water interface despite the strong electrostatic repulsion between multiple quaternary ammonium headgroups. Moreover, dynamic surface tension measurements showed that the kinetics of adsorption for 3C(n)trisQ to the air/water interface was slow because of their bulky structures. Furthermore, the results of rheology, SANS, and cryo-TEM determined that 3C(n)trisQ with n = 10 and 12 formed ellipsoidal micelles at low concentrations in solution and the structures transformed to threadlike micelles with very few branches for n = 12 as the concentration increased, but for n = 14 threadlike micelles formed at relatively low concentrations.     

Synthesis of novel quaternary ammonium surfactants containing adamantane

A series of novel quaternary ammonium surfactants containing adamantane were designed and synthesized from 1-adamantanecarboxylic acid.The structures of target surfactants were confirmed by]H NMR,elements analysis and FTIR.Surface properties of these surfactants were investigated.Due to the lipophilicity of adamantane,the critical micelle concentration（CMC） and C₂₀ values of the synthesized quaternary ammonium surfactants are lower than that of conventional quaternary ammonium surfactants.     

Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups 2: aggregation behavior studied by SANS, DLS, and cryo-TEM

Metallo-meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrins (metallo-TPPSs), such as ZnTPPS, have been widely used as photosensitizers. However, their vulnerability to photodegradation significantly limits their applications. In this contribution, we demonstrate a method to enhance the photostability of metallo-TPPSs while retaining photoactivity via encapsulation inside cores of complex micelles. Poly(ethylene glycol)-b-poly(4-vinylpyridine) (PEG-b-P4VP) and metallo-TPPSs can form complex micelles in acidic solution through electrostatic interactions and then undergo axial coordination with the pyridine moieties of PEG-b-P4VP when the pH is adjusted to 7.4. In this way, metallo-TPPSs are entrapped in the hydrophobic, compact micellar cores, which effectively prevents photodegradation of the metallo-TPPSs that would otherwise occur in aqueous solution. In addition, the photodebromination of 2,3-dibromo-3-phenylpropionic acid (DPP) sensitized with ZnTPPS has been used as a model reaction to study the photosensitive activity of ZnTPPS entrapped in complex micelles. The entrapped ZnTPPSs exhibit pronounced activity and have much higher efficiency and faster photosensitive reaction rates than free ZnTPPS.     

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.     

Molecular aggregates of partially fluorinated quaternary ammonium salt gemini surfactants

The size and shape of novel partially fluorinated gemini surfactant 1,2-bis[dimethyl-(3-perfluoroalkyl-2-hydroxypropyl)ammonium]ethane bromide (CnFC3-2-C3CnF, where n=4, 6, and 8) were investigated in aqueous solution by means of light scattering and transmission electron microscopy (TEM). The sizes of these molecular aggregates changed with increasing carbon number of the alkyl chain and concentration. For example, the apparent hydrodynamic radius by dynamic light scattering was 18 nm at a concentration of cmcx5 for n=4, 115 nm at the cmcx15 for n=6, and 62 nm at the cmcx30 for n=8, at 298.2 K. The shapes of CnFC3-2-C3CnF aggregates drastically changed with the alkyl chain length; the aggregates were mainly in the form of large or irregular small aggregates (n=4), string-like aggregates (n=6), and vesicles (n=8). The bromide-ion activity was measured using a bromide-ion-selective electrode to determine the degree of counterion binding to the aggregates. The degree of counterion binding to aggregate was very small compared with that in the typical hydrogenated gemini surfactants. These results indicated that the small curvature of large aggregates was not influenced by an electrostatic repulsion between the cationic head groups in the case of the bulky molecular volume of fluorinated gemini surfactants.     

Physicochemical properties of quaternary ammonium bromide-type trimeric surfactants

Trimeric surfactants of quaternary ammonium bromide (m-2-m-2-m, where m is the hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three hydrophilic groups connected by two ethylene spacer chains were synthesized by the reaction of N,N,N',N",N"-pentamethyldiethylenetriamine and the corresponding alkyl bromide. Their physicochemical properties were characterized by surface tension, static and dynamic light-scattering, and fluorescence spectrum of pyrene techniques. The critical micelle concentrations (cmc's) of m-2-m-2-m shifted to lower concentrations with increasing hydrocarbon chain length, and their values were smaller by about one to three orders of magnitude than those of the corresponding dimeric (m-2-m) and monomeric surfactants (C(m)TAB) with the same hydrocarbon chain length. Of these surfactants, 10-2-10-2-10 showed the greatest efficiency in lowering the surface tension and provided the smallest occupied area per molecule, indicating that it adsorbs more compactly at the air/water interface. In addition, from the static and dynamic light-scattering measurements, the aggregation numbers of the trimeric surfactants at the cmc were very small, and two hydrodynamic diameters above the cmc were observed.     

Lipophilic counterion effect on aggregation and adsorption behavior of quaternary ammonium surfactants

The obvious different aggregation and adsorption behavior of six newly quaternary ammonium surfactants with different lipophilic counterions has been discoverd by measurements of equilibrium and dynamic surface tension, fluorescence and conductivity. Interestingly, the critical micelle concentration (CMC) and its surface tension γ_CMC decrease with the increasing counterion chain length. However, three methods have confirmed that an exception of CMC increases slightly from C₁₆NC₁ to C₁₆NC₂. According to experimental results, a balanced mechanism between hydrophobicity and electrostatic of counterion is proposed. Besides, the dynamic surface tension results show the diffusion coefficient increases with the increasing counterion length both at a short time (D_t?→?0) and long time (D_t?→?∞), which indicates a faster adsorption process. Unlike the inorganic counterion, the diffusion coefficient decreases with the increase of hydrophobic chain length. This is attributed to the strong electrostatic interactions between counterions and cationic headgroups.     

Synthesis and properties of side chain liquid crystalline ionomers containing quaternary ammonium salt groups

New thermotropic side chain liquid crystalline ionomers (LCIs), containing 4-(4-allyloxybenzyloxy)-4'-alkoxybiphenyl (IM) as mesogenic unit and allyltriethylammonium bromide (ATAB) as non-mesogenic unit, were synthesized by graft copolymerization upon polymethylhydrosiloxane. The chemical structures of the polymers were confirmed by IR spectroscopy. Differential scanning calorimetry (DSC) was used to measure the thermal properties of these polymers; the mesogenic properties were characterized by polarizing optical micrography, DSC and X-ray diffraction. The influence of the alkoxy chain length on the clearing temperatures of the ionomers is clearly shown in an odd-even effect, similar to other side chain liquid crystal polymers. The mesomorphic behaviour of the ionomers is compared with that of isomeric ionomers synthesized in previous work. The results demonstrate that the phase behaviour of the two series of isomeric ionomers is similar, but with the difference that the melting temperature of ionomers with biphenyl located at the end of the mesogen is higher than for ionomers with biphenyl located at the middle of the mesogen. The latter are more useful for smectic orientational order than the former.     

两性离子表面活性剂的合成及其表面性质

合成了一类含季铵基和磺酸基结构的非对称Gemini两性离子表面活性剂;利用红外光谱、质谱、离子定性试验验证了合成产物的分子结构,并测定了其表面性质.结果表明,目标产物的分子结构符合设计预期;五种非对称Gemini两性离子表面活性剂的表面张力在30mN/m左右,临界胶束浓度达到10-4~10-5数量级.此外,虽然非对称Gemini两性离子表面活性剂的起泡性能比相应单链型表面活性剂的稍差,但其稳泡性明显优于后者.     

含三个硬脂酰胺基的树枝状季铵盐的制备

由三羟甲基丙烷三丙烯酸酯(TMPTA)和乙二胺(EDA)直接进行M ichael加成反应,合成端基为3个NH2的树枝状大分子G(NH2)3,用硬脂酰氯将其端氨基进行酰胺化得到端基为3个硬脂酰基的树枝状大分子GS(R)3,产率为82.4%。GS(R)3进一步与碘甲烷反应,其分子中的3个仲氨基被季铵化,生成树枝状季铵盐GI(R)3,产率为82.0%。讨论了反应温度、反应时间和原料配比对GS(R)3和GI(R)3产率的影响,并用红外、核磁和元素分析对GS(R)3和GI(R)3的结构进行表征。     

Synthesis and properties of quaternary ammonium Gemini surfactants with hydroxyl groups

The article describes synthesis of four hydroxyethyl alkylene–double alkyl bromide through substitution of nucleophilic d iethanolamine, 1-bromododecane, and 1,4-dibromobutane. The structure of the new hydroxyl cationic surfactant (HDCS) was characterized by ¹H NMR and FTIR spectra. The aqueous solution of HDCS showed critical micelle concentration, i.e., 5.6 × 10^?2 mM, and could reduce oil/water interfacial tension to 3.28 × 10^?3 mN m^?1. The surface tension measurements provided a series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γ_CMC), adsorption efficiency (pC₂₀), and effectiveness of surface tension reduction (Π_CMC). In addition, maximum surface excess concentration (Г_max) and minimum surface area/molecule (A_min) at the air/water interface were obtained by the Gibbs adsorption isotherm. The influence of inorganic salts (sodium chloride, calcium chloride) and organic salts (sodium benzoate) on the surface tension of HDCS in aqueous solution was investigated. For wettability alteration measurement, contact angle measurement as a quantitative method was utilized. Meanwhile, foam ability, foam stability, and emulsifying property of the synthesized surfactant were also examined at different concentration. HDCS also had excellent viscosity property.     

三烷基季铵盐阳离子表面活性剂的合成与性能测定

用柠檬酸、十二烷基二甲基叔胺与环氧氯丙烷反应合成了柠檬酸三酯三烷基季铵盐阳离子表面活性剂。实验结果表明,在异丙醇溶剂中,反应体系在80℃,反应时间12h,产物的收率为91.5%。用红外光谱、元素分析、高效液相色谱对其结构进行了表征,通过测定其临界胶束浓度、Krafft点及泡沫性能,对产物表面活性进行了分析。     

Synthesis and properties of new polymeric surfactant with quaternary ammonium salt

The polymeric surfactant with quaternary ammonium salt (PQ) was synthesized by cationic ring-open polymerization using boron trifluoride diethyletherate as cationic catalyst. The chemical structure and aggregation behavior of PQ were studied by ¹H NMR, surface tension, static light scattering, dynamic laser light scattering, electrical conductivity, and fluorescence measurement. The results show the surface tension (γ_cmc) and critical micelle concentration (cmc) of PQ decrease with increasing of sodium chloride concentration. The cmc and γ_cmc values of PQ measured by electrical conductivity and fluorescence measurements mainly identify with that obtained by surface tension measurements. The thermodynamic parameters (DG_m⁰ \Delta G_m^0 ,DH_m⁰ \Delta H_m^0 ,DS_m⁰ \Delta S_m^0 ) from electrical conductivity indicated that the micellization of PQ was mainly the process of entropy-driven. In addition, the results from the viscosity stability between hydrolyzed polyacrylamide (HPAM) and PQ showed that the viscosities of mixed system for HPAM and PQ are higher than the viscosity of HPAM.     

Aggregation behavior of nitrophenoxy-tailed quaternary ammonium surfactants

Cationic surfactants N,N,N-trimethyl-10-(4-nitrophenoxy)decylammonium bromide (N10TAB) and N,N,N',N'-tetramethyl-N,N'-bis[10-(4-nitrophenoxy)decyl]-1,6-hexanediammonium dibromide (N10-6-10N), bearing aromatic nitrophenoxy groups in the ends of their hydrophobic chains, have been synthesized, and their self-assembling properties in aqueous solutions have been studied by conductivity, isothermal titration microcalorimetry, 1H NMR spectroscopy, and dynamic light scattering. Below the critical micelle concentration, N10-6-10N can form premicelles with 2 or 3 surfactant molecules. Beyond the critical micelle concentration, the two surfactants have strong self-aggregation ability and can form micelles of rather small size and with small aggregation numbers N, which are 30 +/- 3 for N10TAB and 20 +/- 2 for N10-6-10N, respectively. Also, the variations in 1H NMR signals at different surfactant concentrations provide the information on the environmental change of the surfactants upon their micellization progress. The most prominent phenomenon is the shielding effect of the aromatic groups over the protons in the aliphatic chains, implying that the nitrophenoxy groups partially insert into the micelles and face the several middle methylenes of the hydrophobic side chains.     

Highly selective iodide-sensing silicone ladder polymer membranes containing a porphyrin and a quaternary ammonium salt.

It has been demonstrated that a glass-like silicone ladder-type polymer permits one to homogeneously incorporate high amounts of ionophores into the covalently-bonded double chain structure. Furthermore, by making use of this feature, we have successfully fabricated an iodide ion-sensitive field-effect transistor based on two kinds of ionophores and silicone ladder polymer matrix. As ionophores, 5,10,15,20-tetraphenyl-21H,23H-porphyrin and dimethyloctadecyl-3-trimethoxylsilylpropylammonium chloride were homogeneously incorporated into the matrix. The ion-sensitive field-effect transistor showed a linear potential response ranging in the I- concentration between 1.0 x 10(-5) and 1.0 x 10(-1) M. The selectivity coefficients for I- towards interferences of ClO4- and NO3- were estimated to be Kpot(I-,ClO4-) approximately 6.2 x 10(-4) and Kpot(I-,No3-) approximately 4.9 x 10(-4). The matrix has proved to be so stable that the selectivity coefficients have not been altered over six months.     

Synthesis and aggregation behavior of a hexameric quaternary ammonium surfactant

A star-shaped hexameric quaternary ammonium surfactant (PAHB), bearing six hydrophobic chains and six charged hydrophilic headgroups connected by an amide-type spacer group, was synthesized. The self-assembly behavior of the surfactant in aqueous solution was studied by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. The results reveal that there are two critical aggregate concentrations during the process of aggregation, namely C(1) and C(2). The aggregate transitions are proved to be caused by the changes of the surfactant configuration through hydrophobic interaction among the hydrocarbon chains. Below C(1), PAHB may present a star-shaped molecular configuration due to intramolecular electrostatic repulsion among the charged headgroups, and large aggregates with network-like structure are observed. Between C(1) and C(2), the hydrophobic interaction among the hydrophobic chains may become stronger to make the hydrophobic chains of the PAHB molecules curve back and pack more closely, and then the network-like aggregates transfer to large spherical aggregates of ～100 nm. Beyond C(2), the hydrophobic interaction may become strong enough to cause the PAHB molecular configuration to turn into a pyramid-like shape, resulting in the transition of the spherical large aggregates to spherical micelles of ～10 nm. Interestingly, the PAHB displays high emulsification ability to linear fatty alkyls even at very low concentration.     

Synthesis and antimicrobial activity of a perfluoroalkyl-containing quaternary ammonium salt

A novel perfluoroalkyl-containing quaternary ammonium salt 5 was designed and synthesized. Consequently, the antimicrobial activities of compound 5 were measured with Escherichia coli 8099 as a Gram-negative strain and Staphylococcus aureus ATCC 6538 as a Gram-positive strain. Both the minimum inhibitory concentration (MIC, the lowest concentration of compound 5 that inhibits microbial growth) values of quaternary ammonium salt 5 against Escherichia coli 8099 and Staphylococcus aureus ATCC 6538 were 7.8 μg/ml.     

Aggregation properties of supralong-chain surfactants with double or triple quaternary ammonium head groups

Double or triple quaternary ammonium head groups were designed to improve the solubility of supralong alkyl chain surfactants. In the surfactant head group, quaternary ammonium groups are connected by an ethylene spacer. Micellar shapes of divalent surfactants [C(n)H(2n)(+1)N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(3) 2Br(-): C(n)-2Am (n=18, 20, and 22)] and trivalent surfactants [C(n)H(2n)(+1)N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(2)-(CH(2))(2)-N(+)(CH(3))(3) 3Br(-): C(n)-3Am (n=18, 20, and 22)] were studied in aqueous solutions by means of dynamic light scattering (DLS) and transmission electron microscopy (TEM). Changes in the surfactant concentration have a small influence on the apparent hydrodynamic radii (r(h)) of the molecular aggregates in both surfactant series. Average values of r(h) of aggregates are 60-90 nm for C(n)-2Am (n=18, 20, and 22) and 2-40 nm for C(n)-3Am (n=18, 20, and 22). TEM micrographs showed that aggregates of C(n)-2Am (n=18, 20, and 22) typically formed rod-like micelles. In contrast, trivalent surfactants of C(n)-3Am (n=18, 20, and 22) formed spherical (C(18)-3Am) or ellipsoidal micelles (C(20)-3Am and C(22)-3Am). Moreover, the degree of micellar counterion binding for these surfactants was determined by using a bromide ion-selective electrode, which indicated relatively high values (0.8-0.9) for C(n)-2Am (n=18, 20, and 22) and more common values (0.5-0.8) for C(n)-3Am (n=18, 20, and 22). The size of the aggregates is closely related to the degree of counterion binding.     

联接基对双子表面活性剂12-s-12表面活性的影响

双子表面活性剂是通过一个联接基将两个传统表面活性剂分子在其亲水头基或接近亲水头基处联接在一起而形成的 类新型表面活性剂,属于低聚表面活性剂范畴[1-3],通常表示为m-s-m·2X,其中m表示两个疏水尾基的碳原子数,s表示联接基中亚甲基,X代表反离子.