首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
双子表面活性剂的粘度行为   总被引:3,自引:0,他引:3  
对阳离子双子表面活性剂在溶液中的粘度行为进行了研究.发现联结基长度与双子表面活性剂在稀溶液中能否表现出粘度行为有很大关系,联结基数s = 2、3、4的双子表面活性剂稀溶液表现出显著的增粘性,但 s =4的某些双子表面活性剂的粘度具有时间依赖性,而s = 6的双子表面活性剂则没有明显的粘度行为.双子表面活性剂烷基链越长,其增粘能力也越强.联结基数s = 2或3的部分双子表面活性剂,其粘度随温度的变化有一最大值.双子表面活性剂与有机酸盐的复合物也表现出很强的增粘行为.  相似文献   

2.
Viscosity measurements on aqueous micellar solutions of cationic surfactants containing phenol with and without sodium bromide were made to study the sphere‐to‐rod transitions. Effect of surfactant structure (nonpolar tail, polar head group sizes and counterion), temperature, and phenol and sodium bromide concentration on the viscosity behavior of the surfactant solution is discussed. The sphere‐to‐rod transition is usually indicated by a marked increase in viscosity. While low temperature, high surfactant concentration, presence of salt, and hydrophobic nature of surfactant all favor the formation of rod‐like micelles, the presence of phenol showed peculiar behavior. Initial additions of phenol (up to about 2.5 wt%) showed a marked increase in viscosity, independent of the nature and concentration of surfactant and temperature; lower viscosities were observed at higher phenol concentration. Conductance and sound velocity results support the viscosity results.  相似文献   

3.
The enantioselective hydrolysis of p-nitrophenyl esters of alpha-amino acids (Phe, Leu, Ala) was accomplished in micelles formed with the surfactants bearing one or two sugar-amide headgroups. The effect of structural variations in such sugar-amide surfactants on the rates and enantioselectivity (kD/kL) for hydrolysis of p-nitrophenyl esters of D- and L-phenylalanine hydrogen bromides (D- and L-PheONp) was studied. Both the hydrolysis rate of D-PheONp and the enantioselectivity increased with an increase in the alkyl chain length as well as an increase in the number of the alkyl chains in the maltobionamide-type surfactants. Enantioselectivity also increased with an increase in the sugar chain length from bisgluconamide to bismaltobionamide (by one glucose unit per each sugar chain) in the double-sugar-chain surfactants, but enantioselectivity was no longer influenced by a further increase to bismaltotrionamide. The stereochemistry of the linkage between the sugar units in the sugar chain remarkably affected the enantioselectivity: the maltobionamide-type surfactant, in which the two sugar units are connected by an alpha-1,4-glucosidic linkage, showed high enantioselectivity (kD/kL = 5.5), whereas the surfactant bearing cellobionamide headgroups (beta-1,4-glucosidic linkage) showed no enantioselectivity. Similar trends were observed when p-nitrophenyl esters of D- and L-leucine hydrogen bromides were used as substrates. On the other hand, the rates and enantioselectivity for hydrolysis of p-nitrophenyl esters of D- and L-alanine hydrogen bromides were not so largely affected by the structural variations in the sugar-amide surfactants. Additionally, the effects of the surfactant concentration and the reaction temperature on the rates and enantioselectivity for the hydrolysis of D- and L-PheONp were examined.  相似文献   

4.
Nonionic surfactants could effectively improve the enzymatic hydrolysis efficiency of lignocellulose, while small molecule anionic and cationic surfactants usually inhibited the enzymatic hydrolysis. The results showed that the anionic surfactant sodium dodecyl sulfate (SDS) could improve the enzymatic hydrolysis efficiency of Avicel at the concentration range of 0.1–1 mM, but it did inhibit enzymatic hydrolysis at higher concentration. Cationic surfactant cetyltrimethylammonium bromide (CTAB) was used to regulate the surface charge of SDS; thereby catanionic surfactant SDS-CTAB was formed. The effect of SDS-CTAB catanionic surfactant with varied molar ratios on the enzymatic hydrolysis of pure cellulose and corn stover at various enzymatic hydrolysis environments was investigated. SDS-CTAB could increase the enzymatic hydrolysis of corn stover at high solid loading from 33.3 to 42.4%. Using SDS-CTAB could reduce about 58% of the cellulase dosage to achieve 80% of the enzymatic hydrolysis of corn stover. SDS-CTAB catanionic surfactant could regulate the surface charge of cellulase in the hydrolyzate and reduce the non-productive adsorption of cellulase on the lignin, thereby improving the enzymatic hydrolysis efficiency of lignocellulose.  相似文献   

5.
Synthesis and properties of a novel class of gemini pyridinium surfactants   总被引:1,自引:0,他引:1  
A novel class of gemini pyridinium surfactants with a four-methylene spacer group was synthesized, and their surface-active properties and interactions with polyacrylamide (PAM) were evaluated by surface tension, fluorescence, and viscosity measurements. A comparison between the gemini pyridinium surfactants and their corresponding monomers was also made. The cmc's of gemini pyridinium surfactants are much lower than those of the corresponding monomeric surfactants. The C20 value is about one order of magnitude lower than that of corresponding monomers, and the longer the hydrophobic chains of the surfactants, the lower the cmc value. Surface tension measurements of the surfactant-PAM mixed systems show that the critical aggregation concentration (cac) value is much lower than the cmc value of the surfactant system alone. Viscosity measurements of the surfactant-PAM mixed systems show that the relative viscosity of the surfactant-PAM system decreased with increasing concentration of surfactant. Additionally, fluorescence measurements of the surfactant-PAM mixed system suggest the formation of surfactant-polymer aggregates, and the gemini pyridinium surfactant with longer hydrophobic chains have a stronger interaction with PAM, owing to the stronger hydrophobic interaction.  相似文献   

6.
A linear and a branched nonionic cleavable surfactants containing a carbonate bond have been prepared from tetra(ethylene glycol) and an alkylchloroformate. The stability of these carbonate surfactants was determined by investigating their hydrolysis and biodegradability characteristics. The hydrolysis was catalyzed by alkali or enzymes (esterase from porcine liver and lipases from Mucor miehei and Candida antarctica B) and was monitored using 1H NMR. It was found that the stability toward alkali was higher for a carbonate surfactant than for a corresponding surfactant with an ester as weak bond. Biodegradation tests resulted in more than 60% degradation after 28 days for both carbonate surfactants. Physicochemical properties, such as critical micelle concentration (CMC), cloud point, area per molecule, and surface tension at the CMC, were determined and compared to those obtained from similar surfactants containing ester, amide, or ether bonds. It was found that the carbonate linkage is hydrophobic and that the oxycarbonyl part of the carbonate group is equivalent, in a formal sense, to an extra methylene group in the alkyl chain of the surfactant.  相似文献   

7.
Temperature-responding physical hydrogels are promising materials as injectable drug delivery carriers which could hold useful bioactive materials inside the polymer networks for further controlled releases. Aimed at desired qualities at body temperature, those gel characteristics need to be adjusted carefully. In this point of view, surfactant is one of the useful molecules to be used by simple formulations without harmful chemical reactions. In this study, thermothickening of amphiphilic nonionic polyphosphazene solution is modified by anionic and cationic surfactants with different alkyl chains and counter-ions. Specified in the thermothickening system, a maximum viscosity (ηmax) and a temperature at that point (Tmax) are changed independently reflecting unique intermolecular interactions. At low concentration (1–9 mM) of the added surfactant, the ηmax is maximized at 3 mM surfactant regardless of the surfactant type while the Tmax is increased continuously along with the surfactant concentration. From a kinetic point of view, this 3 mM surfactant at the maximized ηmax reflects a polymer-dominating interaction and highly favorable polymer–surfactant interaction with a low selectivity in the surfactant type. However, the magnitude of the maximum viscosity (ηmax) is dependent on the surfactant tail, which reflects the lifetime and the strength of the hydrophobic domains of the polymer network affected by the surfactants. Meanwhile, the magnitude of the Tmax depended on the surfactant head group, which means the interfacial tension of the polymer solutions changed by the surfactants. At high concentration (10 and 30 mM) of the cationic surfactants added to the polymer solutions with two different viscosities, the cationic surfactants are supposed to interact either with the hydrophobic parts of the aggregated polymer with high viscosity or on the backbone of the less- or non-aggregated polymer with low viscosity.Ionic surfactants change the thermothickening of the amphiphilic nonionic polyphosphazene solution in a unique tail- or head-dependent way. Moreover, the concentration of the added surfactants and the association pattern of the pure polymer solutions are also crucial for the thermothickening phase behaviors. Temperature-responsive polyphosphazenes in this work exhibit unique and controllable interactions with ionic surfactants.  相似文献   

8.
Electron paramagnetic resonance, viscosity, and small-angle neutron scattering (SANS) measurements have been used to study the interaction of mixed anionic/nonionic surfactant micelles with the polyampholytic protein gelatin. Sodium dodecyl sulfate (SDS) and the nonionic surfactant dodecylmalono-bis-N-methylglucamide (C12BNMG) were chosen as "interacting" and "noninteracting" surfactants, respectively; SDS micelles bind strongly to gelatin but C12BNMG micelles do not. Further, the two surfactants interact synergistically in the absence of the gelatin. The effects of total surfactant concentration and surfactant mole fraction have been investigated. Previous work (Griffiths et al. Langmuir 2000, 16 (26), 9983-9990) has shown that above a critical solution mole fraction, mixed micelles bind to gelatin. This critical mole fraction corresponds to a micelle surface that has no displaceable water (Griffiths et al. J. Phys. Chem. B 2001, 105 (31), 7465). On binding of the mixed micelle, the bulk solution viscosity increases, with the viscosity-surfactant concentration behavior being strongly dependent on the solution surfactant mole fraction. The viscosity at a stoichiometry of approximately one micelle per gelatin molecule observed in SDS-rich mixtures scales with the surface area of the micelle occupied by the interacting surfactant, SDS. Below the critical solution mole fraction, there is no significant increase in viscosity with increasing surfactant concentration. Further, the SANS behavior of the gelatin/mixed surfactant systems below the critical micelle mole fraction can be described as a simple summation of those arising from the separate gelatin and binary mixed surfactant micelles. By contrast, for systems above the critical micelle mole fraction, the SANS data cannot be described by such a simple approach. No signature from any unperturbed gelatin could be detected in the gelatin/mixed surfactant system. The gelatin scattering is very similar in form to the surfactant scattering, confirming the widely accepted picture that the polymer "wraps" around the micelle surface. The gelatin scattering in the presence of deuterated surfactants is insensitive to the micelle composition provided the composition is above the critical value, suggesting that the viscosity enhancement observed arises from the number and strength of the micelle-polymer contact points rather than the gelatin conformation per se.  相似文献   

9.
We present a large range of experimental data concerning the influence of surfactants on the well-known Landau-Levich-Derjaguin experiment where a liquid film is generated by pulling a plate out of a bath. The thickness h of the film was measured as a function of the pulling velocity V for different kinds of surfactants (C(12)E(6), which is a nonionic surfactant, and DeTAB and DTAB, which are ionic) and at various concentrations near and above the critical micellar concentration (cmc). We report the thickening factor α = h/h(LLD), where h(LLD) is the film thickness obtained without a surfactant effect, i.e., as for a pure fluid but with the same viscosity and surface tension as the surfactant solution, over a wide range of capillary numbers (Ca = ηV/γ, with η being the surfactant solution viscosity and γ its surface tension) and identify three regimes: (i) at small Ca α is large due to confinement and surface elasticity (or Marangoni) effects, (ii) for increasing Ca there is an intermediate regime where α decreases as Ca increases, and (iii) at larger (but still small) Ca α is slightly higher than unity due to surface viscosity effects. In the case of nonionic surfactants, the second regime begins at a fixed Ca, independent of the surfactant concentration, while for ionic surfactants the transition depends on the concentration, which we suggest is probably due to the existence of an electrostatic barrier to surface adsorption. Control of the physical chemistry at the interface allowed us to elucidate the nature of the three regimes in terms of surface rheological properties.  相似文献   

10.
孪尾疏水缔合三元共聚物的粘度行为:水解度的影响   总被引:2,自引:1,他引:1  
以十二烷基硫酸钠(SDS)为表面活性剂,利用氧化还原体系、采用前加碱共聚-共水解的方法制备了孪尾疏水缔合水溶性三元共聚物聚(丙烯酰胺/丙烯酸钠/N,N-二己基丙烯酰胺)[P(AM/NaAA/DiC6AM)],研究了P(AM/NaAA/DiC6AM)稀溶液及亚浓溶液的性能。随理论水解度的增加,P(AM/NaAA/DiC6AM)水溶液的特性粘数[η]增加,Huggins常数KH减小。P(AM/NaAA/DiC6AM)水溶液的表现粘度随理论水解度的增加而增加,随温度、剪切速率的增加而降低,随剪切速率的增加开始时降低较快而后变化较小。P(AM/NaAA/DiC6AM)在盐溶液中随NaCl、CaCl2质量浓度的增加,出现盐增粘现象;理论水解度不同的P(AM/NaAA/DiC6AM)与SDS水溶液的表现粘度在wSDS=0.050~0.400g/L范围内随SDS质量浓度的变化差别不大。  相似文献   

11.
The viscosity of cholesterol dispersions in aqueous buffered surfactant solutions has been reported under progel conditions. The viscosity versus concentration curves pass through maximum which corresponds to the beginning of solubilization of cholesterol into the surfactant solutions. The stability of the dispersions has been explained by a mechanism involving formation of association complex between cholesterol and the surfactants through hydrogen bonding.  相似文献   

12.
 The electrokinetic behavior and viscosity of anatase and alumina in mixed-surfactant solutions were investigated. Sodium dodecylsulfate and nonionic polyoxyethylene ethers were investigated as model surfactants. Pure nonionic surfactants adsorbed on anatase and coated the particles, so that the zeta potential was nearly zero near the critical micelle concentration of surfactant. At higher surfactant concentrations, an increase in the zeta potentials was observed, suggesting a change in the microstructure of the adsorbed layer. Addition of nonionic surfactant to positively charged anatase and alumina with some preadsorbed sodium dodecylsulfate reversed the surface charge of the oxide to negative, indicating enhanced coadsorption of the anionic surfactant. At higher concentrations of the nonionic surfactant, the charge reversed back to positive. Nonionic surfactants did not reverse the surface charge of these oxides in the absence of the anionic surfactant. Coenhanced adsorption of nonionic and anionic surfactants was used to stabilize alumina at the isoelectric point, where neither surfactant adsorbed appreciably on its own. These results suggest a dramatic change in conformation of the surfactant chains in mixed systems. Further explanation and justification of the proposed changes in adsorbed surfactant conformation require spectroscopic evidence. Received: 12 March 1997 Accepted: 22 July 1997  相似文献   

13.
Abstract

This study investigated the effect of cationic, anionic (saturated and unsaturated), and nonionic surfactants on the formation, morphology, and surface properties of silica nanoparticles synthesized by the ammonium‐catalyzed hydrolysis of tetraethoxysilane in alcoholic media. Results indicate that at a relatively low surfactant concentration (1 × 10?3–1 × 10?6 M), cationic surfactants significantly affected the growth of silica particles as measured by dynamic light scattering and transmission electron microscopic analyses. In contrast, the anionic and nonionic surfactants showed relatively minor effects in the low concentration range. The magnitude of negative zeta potential was reduced for silica colloids that were synthesized in the presence of cationic surfactant because of charge neutralization. The presence of anionic surfactants only slightly increased the negative zeta potential while the nonionic surfactant showed no obvious effects. At high surfactant concentrations (>1 × 10?3 M), cationic and anionic surfactants both induced colloid aggregation, while the nonionic surfactant showed no effect on particle size. Raman spectroscopic analysis suggests that molecules of cationic surfactants adsorb on silica surfaces via head groups, aided by favorable electrostatic attraction, while molecules of anionic and nonionic surfactants adsorb via their hydrophobic tails.  相似文献   

14.
Aqueous solutions of synthetic clay minerals have been studied in the presence of surfactants and water-soluble polyvinylalcohol (PVA). The PVAs (PVA 1, PVA 2) had a molecular weight of about 105 Dalton and a degree of hydrolysis of 82%. The PVA-samples were surface active and lowered the surface tension to 43 mN/m. As a consequence of their amphiphilic nature the PVA molecules bind strongly to clay mineral particles. On saturation the clay mineral particles adsorb the fivefold weight of PVA of their own weight. It is concluded that the thickness of the adsorbed layers on both sides of the clay mineral is in the range of the hydrodynamic diameter of the PVA-coils in the bulk phase.When the clay mineral particles are not saturated with PVA, they act as cross-linking agents for the PVA. The whole systems are physically cross-linked and assume gel-like properties. Rheological measurements show that samples behave like soft matter with a yield stress value. All of them have a frequency independent storage modulus which is an order of magnitude larger than the loss modulus. The hydrogels become stronger as PVA concentration increases.Small amounts of cationic surfactants bind on the clay mineral. The interface of the clay mineral becomes more hydrophobic and the binding of the PVA on the clay mineral is strengthened. With rising concentration of the surfactant the surfactant molecules bind on PVA and the PVA becomes hydrophilic. As a consequence the PVA can no longer bind on the clay mineral and the gels transform to viscous and turbid solutions. Small amounts of cationic surfactants therefore stiffen the hydrogels while larger amounts cause phase separation and a solution with low viscosity. Anionic surfactants like SDS do not bind on the clay mineral, but strongly on the PVA. With increasing SDS concentration, the hydrogels become stiffer at first but thereafter they break and transform to viscous fluids.In PVA-solutions without the clay minerals both cationic and anionic surfactants bind to the PVAs in the aqueous solution. With increasing concentration of surfactant, the viscosities of the solutions pass over a maximum. In this respect the PVAs behave like hydrophobically modified water soluble polymers. The surfactants bind to the hydrophobic microdomain and thereby crosslink the polymer molecules. On saturation the polyvinyl alcohol with anionic surfactant become hydrophilic and the network character disappears to a certain extent.  相似文献   

15.
Oil-in-water emulsions stabilised by anionic surfactant and gelatin provide the bulk of photographic coating fluids. Their rheology is of crucial importance to the fluids' performance in coating and their concentration in drying. Gelatin complexes with non-adsorbed micelles and adsorbs to the oil-surfactant-water interface, which effects an increase in the viscosity of the continuous phase and the volume of the nano-sized oil droplets, respectively. The consequences of these interactions are high viscosity and strong shear thinning. Here, the effects on the emulsion rheology of a series of bulk, commercially available surfactants were studied. These co-surfactants were chosen so as to weaken the interactions between gelatin and the anionic surfactant and hence reduce viscosity and thinning thus enabling the emulsions to be concentrated. The co-surfactants had polar head groups of three types: simple nonionic based on polyethylenenoxide, simple cationic based on a quaternary alkyltrimethyl ammonium, and combined nonionic-cationic based on a quaternised bis-ethoxylated primary amine. This last type proved the most effective at reducing the low-shear viscosity of the emulsion and reducing the shear thinning, although, at high concentrations the polyethoxylated cationic surfactants induced flocculation and coalescence of the oil droplets.  相似文献   

16.
Interactions in solution between a hydrophobic polymer and surfactants were studied by viscometry, light scattering and conductimetry measurements. One polymer, poly(2-ethyl hexyl methacrylate) (P2EHMA), five surfactants, sodium dodecyl sulfate (SDS), hexadecyl trimethylammonium bromide (HTAB), hexadecyl pyridinium chloride (HPCl), and ethoxylated nonyl phenol containing 10 or 25 segments of ethylene oxide (NP10 or NP25), and one solvent mixture, THF/6 vol% H2O were used in this work. For the P2EHMA/surfactant mixtures in THF/6 vol% H2O, the viscosity versus surfactant concentration curves are similar in shape for all surfactants. They show a minimum at low surfactant concentration followed at higher concentration by a maximum and a plateau. An interpretation of these curve shapes is proposed. The relevance of these findings to the problem of the polymer/surfactant interactions in latexes and latex films is also discussed.  相似文献   

17.
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.  相似文献   

18.
Acid labile surfactants containing an ortho ester link are used as emulsifiers for an aliphatic oil, squalane. The emulsions were made in the presence of a cationic polymer, either polyamine or the corresponding hydrophobically modified polyamine. Spontaneous hydrolysis of the surfactant resulted in emulsions stabilized by polymer together with degradation products from the surfactant. The effect of breakdown of the surfactant on the emulsion was evaluated by means of droplet size measurements and kinetic stability. One linear and one branched nonionic ortho ester surfactant with the same number of oxyethylene units were characterized and used for the purpose. The ortho ester surfactants are complex mixtures of components, ranging from very hydrophilic to very hydrophobic species. The chemical shift of the central methine proton in the ortho ester link is extremely sensitive to the substitution pattern and it was possible to identify by (1)H NMR the components that make up the surfactants, as has been reported earlier. The change in emulsion stability, the change in droplet size and the rate of surfactant hydrolysis were studied at acidic pH at room temperature. Both gas chromatography and (1)H NMR were used in order to monitor the surfactant degradation. The presence of a polymer gave a more sluggish breakdown of the surfactants, probably due to hydrophobic shielding by the polymer. There was a good correlation between increase of droplet size and degree of surfactant decomposition.  相似文献   

19.
表面活性剂对海藻酸钠稀水溶液剪切粘度的影响   总被引:1,自引:0,他引:1  
通过粘度法考察了不同pH值时, 阴离子聚电解质海藻酸钠(NaAlg)与阴离子表面活性剂十二烷基硫酸钠(SDS)、阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)、非离子表面活性剂辛基酚聚氧乙烯醚(TritonX-100)以及它们的复配体系的相互作用. 研究表明, 在酸性条件下, SDS和TritonX-100与NaAlg之间主要是疏水作用, 随着表面活性剂浓度的增加, 体系粘度下降直到基本不变, CTAB与NaAlg主要发生静电作用和疏水作用, 体系粘度随CTAB浓度的增加呈现先上升后下降的趋势. 在实验条件下, TritonX-100浓度为0.05 mmol·L-1时, SDS的加入, 使得NaAlg/TritonX-100体系的零剪切粘度下降, 而CTAB的加入, 在pH=3.0和5.0时, NaAlg/TritonX-100体系的零剪切粘度出现上升, 在pH=6.4时, 该体系零剪切粘度下降.  相似文献   

20.
Critical parameters playing a role in oil recovery by capillary imbibition of surfactant solutions were studied. Experiments conducted on sandstone and carbonate samples using different oil and surfactant types were evaluated for surfactant selection. In this evaluation interfacial tension (IFT), surfactant type, solubility characteristics of surfactants, rock type, initial water (pre-wet rock), and surfactant concentration were considered. In addition to these, a new technique was adopted to facilitate the surfactant screening process. This technique is based on assigning inorganic and organic property values and plotting organic conception diagrams (OCD) for surfactants. OCD defines the property of a compound in terms of physical chemistry in such a way that the property that depends much on the van der Waals force is called "organic" and the one that depends much on electric affinity is called "inorganic." Correlations between the capillary imbibition recovery performance and the properties of surfactant and oil (organic value (OV), inorganic value (IV), and IFT of surfactant solutions, oil viscosity, and surfactant type) were obtained. These correlations are expected to be useful in selecting the proper surfactant for improved oil recovery as well as identifying the effects of surfactant properties on the capillary imbibition performance.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号