CTAB胶束微环境中BY增溶位置的探讨

本文用ＵＶ吸收光谱对（ＢＹ＝ＣＴＡＢ）体系胶束化过程中预胶束的形成，以及预胶束向胶束的转变过程进行了分析。采用Ｇｏｕｙ－Ｃｈａｐｍａｎ模型，建立了ＣＴＡＢ胶束微环境中ＢＹ表现解离常数与胶束结构参数之间的定量关系，根据水溶液和各种盐浓度条件下ＣＴＡＢ胶束溶液中酸碱解离常数的测量，分析了ＢＹ在ＣＴＡＢ胶束扩散层中的增溶位置，讨论了ＣＴＡＢ胶束对ＢＹ选择性吸附的特性。     

青霉素G钾盐在CTAB/n-C5H11OH/H2O体系中的水解及 其抑制

应用紫外光谱法研究了青霉素G钾盐在十六烷基三甲基溴化铵(CTAB)/n-C5H11OH/H2OO/W微乳液中的水解反应。结果表明,CTAB/n-C5H11OH/H2OO/W微乳液对青毒素G钾盐的水解具有抑制作用,此结果与此O/W微乳液能降低青霉素G钾盐(Pen-K)分子极性基团的电荷密度,减少Pen-K所处微环境的质子浓度有关。     

介质环境对辣根国氧化物酶催化荧光反应体系的影响

探讨了缓冲溶液,溶剂和表面活性剂对对羟基苯丙酸-国氧化氢- 辣根国沿化区酶反应体系反应平衡及产物荧光性质的影响,表明二聚体荧光产物中存在酸碱平衡,应荧光滴定法求得其酸离解常数pK~a≈8.3.碱式产物的荧光强于酸式, 碱性环境使酶活性降低,反应平衡时间延长,阳离子胶束溴化十六烷基三甲胺(CTMAB) 和氯化十六烷基三甲铵(CTMAC)对该体系兼有催化和增敏作用,据此提出一种更为灵敏的测定辣根过氧化物酶的方法.     

钒(Ⅴ)-桑色素-溴化十六烷基三甲铵胶束增敏荧光光度法的研究和应用

研究了在 p H 2 .5的 HCl- Na Ac介质中 ,溴化十六烷基三甲铵( CTMAB)对桑色素 ( morin)和钒 ( )配合物荧光的增敏作用 ,建立了利用钒 ( ) - morin- CTMAB胶束增敏荧光反应测定痕量钒的荧光光度新方法。方法的检出限为 0 .92μg/L ,荧光强度与钒的含量在 0 .0 1 0～ 6.0μg/1 0 m L范围内呈线性关系 ,配合物中钒 ( )与桑色素的组成比为 :V( )∶ morin=1∶ 1。方法可应用于天然水和食品中微量钒的测定     

胶束增敏紫外分光光度法测定甲砜霉素的研究

用紫外分光光度法对pH 6.00Na2 HPO4-NaH2 PO4的缓冲介质中甲砜霉素和溴化十六烷基三甲铵( CTMAB)形成的胶束配合物的性能进行了研究.利用胶束的增敏增稳作用,提出了测定甲砜霉素的紫外分光光度新方法,方法线性范围为0.25～95 μg/mL,检出限为0.12 μg/mL.已应用于片剂中甲砜霉素的测定...     

介质环境对辣根国氧化物酶催化荧光反应体系的影响

探讨了缓冲溶液,溶剂和表面活性剂对对羟基苯丙酸-国氧化氢- 辣根国沿化区酶反应体系反应平衡及产物荧光性质的影响,表明二聚体荧光产物中存在酸碱平衡,应荧光滴定法求得其酸离解常数pK~a≈8.3.碱式产物的荧光强于酸式, 碱性环境使酶活性降低,反应平衡时间延长,阳离子胶束溴化十六烷基三甲胺(CTMAB) 和氯化十六烷基三甲铵(CTMAC)对该体系兼有催化和增敏作用,据此提出一种更为灵敏的测定辣根过氧化物酶的方法.     

胶束增敏荧光光度法测定不同蔬菜中草萘胺含量

用荧光法探索了曲拉通X-100(Triton X-100)、十二烷基硫酸钠(SDS)、β-环糊精(β-CD)、溴化十六烷基三甲铵(CTMAB)、聚氧乙烯月桂醚(Brij35)5种有序介质,及反应时间、pH条件对草萘胺荧光光谱行为的影响.结果表明,5种有序介质中CT-MAB对草萘胺荧光增敏效果最好,在λex/λem=292/338 nm处有强荧光峰.据此,建立了用CTMAB增敏荧光光度法测定草萘胺含量的新方法,方法线性范围为1.0×10-7～1.0×10-4 mol/L,相关系数R=0.9986,检出限为5.3×10-8 mol/L,对1.0×10-4mol/L草萘胺测定的相对标准偏差(RSD)为3.454％.该法已用于西红柿、芹菜、油菜、菠菜、绿尖椒、圆白菜、水萝卜、长茄子、豆角、黄瓜中草萘胺的测定.     

CTAB水溶液表面的吸附动力学

用最大气泡压力法测定了十六烷基三甲基溴化铵(CTAB)水溶液的动态表面张力,研究了CTAB水溶液表面吸附的动力学及其影响因素。结果表明,吸附过程由初始的扩散控制经混合控制过渡到势垒控制。扩散控制吸附速率快,时间短;势垒控制速率慢,时间长,吸附势垒一般为4～10kJ.mol^-^1。温度升高,动态表面张力减小,但吸附机理不变;无机盐或醇类的加入对势垒值影响不大,但对扩散控制步骤的影响较大。     

有机溶剂化效应对多元络合物显色反应作用的研究(Ⅱ)——有机溶剂对络天青S在胶束相分配系数的影响

前文曾报道有机溶剂化效应对增敏体系微环境的影响。本文从物理-有机化学及胶体化学角度,用分光光度法测定在有机溶剂存在下,铬天青S(CAS)在胶束和溶液间的分配系数(K_D),并考察分配系数与显色反应灵敏度的关系。     

Sb(Ⅲ)-甲基橙-溴化十六烷基三甲铵的高灵敏显色反应研究及应用

在ｐＨ３．５～４．５的邻苯二甲酸氢钾－ＨＣｌ缓冲介质中,Ｓｂ（Ⅲ）与甲基橙、溴化十六烷基三甲铵形成有色多元配合物的显色反应,建立了测定微量锑的高灵敏光度分析法。配合物最大吸收波长为５４０ｎｍ,表观摩尔吸光系数为４．８９×１０５Ｌ·ｍｏｌ－１·ｃｍ－１,锑的质量浓度在０～１２μｇ／２５ｍＬ范围内符合比尔定律,配合物中Ｓｂ（Ⅲ）与甲基橙（ＭＯ）的组成比为ｎ（Ｓｂ（Ⅲ））∶ｎ（ＭＯ）＝１∶１。采用巯基棉分离,可消除共存离子的影响,提高体系的选择性。已用于铜合金中微量锑的测定,结果满意。     

苯甲醇对CTAB/KBr胶束体系流变性及CTAB分子1HNMR谱影响的研究

报道了苯甲醇对CTAB/KBr胶束体系粘度的影响,利用1HNMR法研究了苯甲醇在CTAB胶束中的增溶位置.结果表明,在KBr盐溶液中,随着苯甲醇的加入,0.01mol/LCTAB胶束体系的粘度增大至最大值.对CTAB分子的1HNMR分析表明,少量的苯甲醇增溶在棒状胶束的界面,促使胶束体积增大和相互缠结,体系的粘度随之增大;当苯甲醇浓度较高时,将增溶在胶束的栅栏层靠近极性头一侧,胶束发生棒-球转变和解缠,体系的粘度降低.     

Catalytic action of CTAB/KBr/C9OH micellar media on the basic hydrolysis of crystal violet

The kinetics of basic hydrolysis of crystal violet (CV) in CTAB/KBr/C₉OH micellar media was investigated under pseudo-first-order conditions. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of CV at 590?nm. It was observed that the pseudo-first-order rate constant increases with increase in C₀. The enhancement of reaction rate with C₀ is explained on the basis of dependence of reaction rate on micellar morphology. Further, the viscosity and DLS analysis supports nonanol-induced morphological transitions. Fluorescence spectroscopy has been used to understand dye–micelles interactions. The enhancement of fluorescence intensity of CV with C₀ suggests an increase in dye–micelles interaction with C_0. The concentration of surfactant and salt had a marked effect on reaction rate. The inhibition of reaction rate at high concentration of surfactant and salt is due to the ionic competition of OH^? and Br^? ions for the reaction center. The influence of [OH^?] on CV hydrolysis was also investigated. The results show that the pseudo-first-order rate constant, k’, increases linearly with hydroxide ion concentration, indicating first-order dependence on [OH^?].     

十六烷基三甲基溴化铵/油酸钠混合体系蠕虫状胶束流变性研究

阴、阳离子表面活性剂之间强烈的相互作用利于形成自由弯曲的蠕虫状胶束。本文利用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)和阴离子表面活性剂油酸钠(Na OA)制备了CTAB/Na OA蠕虫状胶束,研究了两表面活性剂的混合比和表面活性剂总浓度的变化对蠕虫状胶束体系稳态流变性及动态粘弹性的影响。结果表明,蠕虫状胶束在剪切过程中的解缠、拟网状结构的破坏以及最终沿剪切速度方向取向等是蠕虫状胶束产生剪切稀释特性的原因。两表面活性剂的混合比和表面活性剂总浓度的变化导致表面活性剂之间的静电作用、疏水作用发生较大的变化,最终引起体系内部表面活性剂聚集体形态的差异。体系内蠕虫状胶束长度、体系结构复杂程度、蠕虫状胶束形成的网络结构的致密度等都影响着体系的流变行为。在混合比R=3.6、总浓度CT=0.24mol/L时,体系中蠕虫状胶束最长,网络结构最为紧密,体系的零剪切粘度达到最大值。表面活性剂浓度一定时,混合比的提高有助于蠕虫状胶束的定向生长,弛豫时间τR和储能模量高频区平台模量G0提高,R=3.6时两者皆达到极大值,此后由于蠕虫状胶束的分枝化及(或)胶束破裂导致τR及G0下降。在表面活性剂混合比一定(R=3.6)时,表面活性剂浓度的提高利于蠕虫状胶束的增长或者分枝化,增加了胶束网络结构缠绕(融合)点的密度,导致G0逐渐增大。Cole-Cole图证实本文研究的蠕虫状胶束体系是符合Maxwell模型的线性粘弹性流体。     

Effect of alkaline materials on interfacial rheological properties of oil-water systems

Interfacial rheological properties of a model crude oil-water system were studied in the presence of sodium hydroxide. The interfacial viscosity, the non-Newtonian flow behavior and the activation energy of viscous flow were determined as a function of shear rate, alkali concentration and aging time. The fundamental conclusion of the experimental results is that the interfacial viscosity drastically decreases in the presence of alkaline materials and the change under favorable conditions may exceed 3 or 4 orders of magnitude. Simultaneously, the sodium hydroxide effectively suppresses the non-Newtonian flow behavior of the interfacial layer. The experimental observations are explained by simultaneous chemical processes taking place in the boundary layer. The present data may help to elucidate the formation, stability and breaking of alkali-containing oil-water emulsions and they provide additional information for better understanding of the displacement mechanism and for the formulation of alkaline flooding as a potential chemically enhanced oil-recovery method. Received: 6 April 1998 Accepted: 18 August 1998     

Effect of ethoxylated nonyl-phenols on interfacial rheological properties of oil/water systems

 Interfacial rheological properties of different Hungarian crude oil/water systems were determined in wide temperature and shear rate range and in presence of ethoxylated nonyl-phenols with ethoxy group number between 10 and 40. The fundamental conclusion of the experimental results is that the interfacial viscosity, the non-Newtonian flow behavior and the activation energy of the viscous flow drastically decrease in presence of non-ionic surfactants. Modification of these interfacial rheological properties increase with decreasing ethoxy group number and increasing tenside concentration and temperature. The most radical change was observed in presence of NPEO₁₀. As a summary it was evidenced that the interfacial rheology is an efficient and powerful detection technique, which may enhance our knowledge on formation, structure, properties and behavior of interfacial layers formed in oil/water systems. Thus, similar studies will probably accelerate the progress significantly not only in oil recovery but also in all areas of colloid science and technology. Received: 10 August 1996 Accepted: 29 November 1996     

Investigation on rheological properties of carbon nanotube nanofluids

The effective viscosity of carbon nanotube nanofluids is strongly dependent on the temperature and concentration. The aggregation behaviour that carbon nanotubes exhibit in solution and the orientation variation of single carbon nanotube make rheological properties of nanofluids more complex. With the increase of shear rate, the degree of dispersion and orientation of carbon nanotubes will be improved. Based on previous studies and the fact mentioned above, a reasonable expression for viscosity of carbon nanotube nanofluids has been given, which is associated with the shear rate and aspect ratios of carbon nanotubes. The expression has been validated comparing with previous experimental data.     

Shear-dependent rheological properties of starch/bentonite composite gels

 Rheological properties of starch/bentonite gels (5.3–8.2% solids, 0–100% starch) were investigated at shear rates 0.0083–0.33 s^-1 (Brookfield viscometer). Prior to these measurements the strain introduced during preparation of the gel was kept as low as possible. Under these conditions six different types of structural units could be identified in the gel: bentonite particles associated in a band-type structure; bands coated with starch polymers; bundles of bands interlaced and enveloped by starch polymers (strands); individual bentonite platelets dispersed in a polymer matrix; starch polymer networks; and swollen granules. A power-law model was fitted to the experimental viscosity data: μ_app= Kγ ^n-1 . In all cases n was found to be less than 0.5. Its value decreased with the ability of the structural components to reorient under applied shear. K was found to be proportional to the compaction and/or entanglement of the structural units. These trends in K and n were further confirmed by the index of thixotropy (IT) and complex modulus of shear elasticity (G ^* ) measurements. Received: 12 August 1996 Accepted: 7 January 1997     

Influence of the monomer properties on the rheological behavior of chemically crosslinked hydrogels

The rheological behavior of two hydrogels, poly(sodium acrylate) and polyacrylamide gels, synthesized in the presence of the same crosslinking agent molecule, N,N′-methylene bis-acrylamide, has been investigated. The variation of the norm of the complex shear modulus |G*| vs. the monomer concentration (sodium acrylate or acrylamide) exhibited a different power law, depending on the nature of the monomer molecule. This discrepancy was ascribed to the influence of the properties of the monomer molecules on the crosslinked structure of the gelified networks. The analysis of the experimental results have allowed the suggestion that the elasticity exponent value was dependent on the length and on the conformation of the polymer chains connecting the junctions points of the network. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2535–2541, 1997     

Dielectric model and theoretical analysis of cationic reverse micellar solutions in CTAB/isooctane/n-hexanol/water systems

Dielectric relaxation spectra of CTAB reverse micellar solutions, CTAB/isooctane/n-hexanol/water systems with different concentrations of CTAB and different water contents, were investigated in the frequency range from 40 Hz to 110 MHz. Two striking dielectric relaxations were observed at about 10(4) Hz and 10(5) Hz, respectively. Dielectric parameters were obtained by fitting the data using the Cole-Cole equation with two Cole-Cole dispersion terms and the electrode polarization term. These parameters show different variation with the increase of the concentration of CTAB or the water content. In order to explain the two relaxations systematically and obtain detailed information on the systems and the inner surface of the reverse micelles, an electrical model has been constituted. On the basis of this model, the low-frequency dielectric relaxation was interpreted by the radial diffusion of free counterions in the diffuse layer with Grosse model. For the high-frequency dielectric relaxation, Hanai theory and the corresponding analysis method were used to calculate the phase parameters of the constituent phases in these systems. The reasonable analysis results suggest that the high-frequency relaxation probably originated from the interfacial polarization. The structural and electrical information of the present systems were obtained from the phase parameters simultaneously.     

Thermal and rheological properties of gelatin-dextran hydrogels

Hydrogels prepared by crosslinkage of gelatin with dextran dialdehyde have been characterized by dynamic shear oscillation measurements at small strain. Isothermal as well as temperature scan measurements were performed. The results obtained demonstrated that the final polymer network is a result of a chemical gelatin-dextran dialdehyde interaction as well as a gelatin-gelatin (physical association) and a polymer-solvent interaction. This balance is strongly dependent on the composition of the system, the polymer concentration, the storage temperature and the storage time.We found that a short cryogenic treatment at –20°C of physically structured gels, significantly increases the chemical crosslinkage. DSC measurements at low cooling rate confirm these results and demonstrate a chemical reaction enthalpy contribution.This work was supported by the Flemish Institute for Science and Technology (IWT) and the Belgian Government (PAI-III-40).The authors also express their gratitude to Systèmes Bio Industries Benelux for providing free samples of well characterized gelatin.