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(NaO A)制备了CTAB/NaO A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黏弹性的影响。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=0.24 mol/L时,体系中蠕虫状胶束最长,网络结构最为紧密,体系的零剪切黏度达到最大值。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模型的线性黏弹性流体。     

一种氧化胺表面活性剂pH响应蠕虫状胶束流变行为研究

利用流变学方法研究了不同pH条件下两性表面活性剂α-羧基十三烷基二甲基氧化胺(CTAO)在水溶液中的聚集行为。实验结果表明,在温度25~60℃区间内,浓度范围为55~125 mmol/L,溶液pH=6.0~6.7时,无需任何添加剂CTAO水溶液即可形成蠕虫状胶束,其流变行为符合Maxwell模型,零剪切黏度最高可达26.5 Pa·s。在溶液pH7的条件下,分子在溶液中的存在形式发生改变,分子间作用的斥力增加,蠕虫状胶束转变为球状胶束,其黏度接近于水,零剪切黏度约是pH=6.2时的1/4 000。该pH响应蠕虫状胶束体系仅由CTAO溶于水形成,其相变pH范围窄,具有制备容易、体系简单、流变性能变化显著的特点。     

十四烷基三甲基溴化铵蠕虫状胶束的形成及其线性黏弹性

以阳离子表面活性剂十四烷基三甲基溴化铵(TTAB)溶液作为反应主剂,油酸钠(NaOA)溶液作为反应助剂,制备得到了TTAB/NaOA蠕虫状胶束,并研究了表面活性剂摩尔比、主剂质量分数对蠕虫状胶束线性黏弹性的影响。结果表明,当主剂TTAB与助剂NaOA的摩尔比为2.6∶1～4.6∶1,TTAB质量分数在7%～16%之间时,溶液中均有蠕虫状胶束形成。当主剂TTAB与助剂NaOA的摩尔比为4.2∶1,TTAB质量分数为14%时,零剪切黏度可达到最大值即为η₀=15 324 mPa·s,且溶液体系的平台模量G₀和弛豫时间τ_R也达到最大值,此时溶液体系中蠕虫状胶束长度最长,网络结构最为紧密,并呈现出良好的线性黏弹性。由上述溶液体系的实际Cole-Cole图表明本文探讨研究的蠕虫状胶束体系是符合麦克斯韦模型的线性黏弹性流体。     

一种胺基型阳离子表面活性剂的合成及其溶液性能研究

该文以2-氯乙胺盐酸盐和十八烷基叔胺为原料,合成了一种胺基型阳离子表面活性剂——N-十八烷基-N,N’-二甲基-乙基-1,2-胺,通过IR和1HNMR对其结构进行了确证,并得到了优化的合成条件：物料比nb/na 为1.20,反应温度为70 oC,反应时间为7 h,pH为7。此外,采用电导法测定了该种表面活性剂的临界胶束浓度(CMC)随着pH的降低而减小。该表面活性剂在NaSal质量百分浓度为1%条件下,能形成蠕虫状胶束。流变性能测试表明,体系具有蠕虫状胶束的剪切稀释性特征和凝胶特性,同时具有pH响应,能在酸性条件下增黏,是一种智能型蠕虫状胶束体系。     

pH对油酸钠/盐酸三乙胺蠕虫状胶束流变性质的影响

用流变学方法研究了pH对油酸钠/盐酸三乙胺(NaOA/Et3NHCl)蠕虫状胶束溶液流变性质的影响。通过稳态剪切和动态流变实验发现,30℃时,NaOA(0.12 mol/L)/Et3NHCl(0.2 mol/L)溶液在pH=8.20~9.40循环变化时,pH对溶液黏度的改变具有"开关"效应,可实现黏度在3~27 649 mPa·s时反复变化3次以上。体系在pH=8.55~9.02时为蠕虫状胶束,其流变行为符合Maxwell模型。这种溶液流变性对pH的响应行为是由于pH对反离子Et3NH+与NaOA的相互作用影响而产生的。当pH降低时,反离子Et3NH+的离子势增大,导致胶束表面电荷密度降低,蠕虫状胶束进一步增长。当pH=8.64,胶束因相互吸引而析出。而在初始条件下,升高pH=9.40,反离子Et3NH+从胶束中解吸出来,蠕虫状胶束受到破坏。     

芥酸钾/三羟乙基苄基氯化铵蠕虫状胶束的黏度行为

以阴离子表面活性剂芥酸钾(KEU)与有机反离子三羟乙基苄基氯化铵(BTHEAC)通过自组装形成的蠕虫状胶束为主要研究对象,苯乙烯与N,N-孪尾取代丙烯酰胺(DiC_nAM)为可聚合单体,偶氮二异丙基咪唑啉盐酸盐(VA-044)为引发剂,在一定温度下,合成了系列增溶单体并聚合的蠕虫状胶束,通过黏度法研究了该合成条件对蠕虫状胶束表观黏度的影响。结果表明,当单体增溶并聚合后,蠕虫状胶束表观黏度显著增大。当苯乙烯的浓度为0.02mol/L、摩尔比n(KEU):n(BTHEAC)=5:3、n(苯乙烯):n(DiC₈AM)=5:2时,合成的蠕虫状胶束表观黏度最大,为1320mPa·s,明显大于KEU/BTHEAC蠕虫状胶束的表观黏度,且耐温性能良好。     

表面活性剂蠕虫状胶束研究现状

本文主要介绍了蠕虫状胶束的一种制备方法,以及当前应用比较多的蠕虫状胶束粘弹性的评定方法。使用冷冻刻蚀电镜直接观察形成胶束的形貌。使用流变手段评价蠕虫状胶束粘弹性,可分为静态流变性和动态粘弹性两部分进行。     

简述离子表面活性剂构筑蠕虫状胶束的研究现状

粘弹性蠕虫状胶束具有特殊的微观结构,其流变性能在不同领域具有重要的应用。本文介绍了表面活性剂构筑的蠕虫状胶束的结构特点、应用及研究现状。传统离子表面活性剂构筑蠕虫状胶束通常需要一些外加作用,Gemini表面活性剂因其结构优势,可以自身形成蠕虫状胶束。     

AES/Na_2CO_3蠕虫状胶束溶液流变性研究

采用流变学方法分别考察了脂肪醇聚氧乙烯醚硫酸钠(AES)质量分数、碳酸钠(Na_2CO_3)质量分数、AES水解和温度对AES/Na_2CO_3蠕虫状胶束溶液流变性能的影响。结果表明,Na_2CO_3的加入可以促进AES蠕虫状胶束的生长。与氯化钠相比,碳酸钠对AES溶液的增黏机制更加复杂。碳酸钠加量小时,反离子Na~+作用小而增黏能力弱;加量高的碳酸钠溶液碱性强,可拟制AES水解,导致活性分子数量增加,表现出较强的增黏能力。同时发现,缩短AES酸性水解时间,有利于改善蠕虫状胶束体系的黏弹性。随着温度升高,AES/Na_2CO_3体系黏弹性逐渐减弱,超过70℃后,体系呈黏性流体。     

聚合物影响蠕虫状胶束流变性能的机理研究

本文基于流变学和中子小角度散射法,研究了不含聚合物的普通支化的蠕虫状胶束和嵌有聚4-乙烯基吡啶的支化蠕虫状胶束的流变性能。研究结果表明无聚合物蠕虫状胶束的平台模量不受分支数增加的影响。同时,由于含有聚合物的蠕虫状胶束的轮廓长度较短,混合蠕虫状胶束平台模量较低。聚4-乙烯基吡啶有利于形成额外的分支,并且加速破坏/重组过程。该研究结果可为嵌入聚合物的蠕虫状胶束作为增稠剂提供理论依据。     

CO2/N2-紫外光双重响应蠕虫状胶束制备

通过N,N-二甲基十二烷基胺（DMA）、十六烷基三甲基溴化铵（CTAB）以及肉桂酸钠（CA）构建了一种具有CO₂/N₂-紫外光双重响应的蠕虫状胶束体系。研究发现DMA、CTAB、CA组成的体系黏度较低,不能形成蠕虫状胶束,向上述体系中引入CO₂后会引起DMA的质子化,从而导致表面活性剂分子在体系中的排列方式发生改变并形成蠕虫状胶束。在通入N₂后蠕虫状胶束会可逆地转变为球状胶束。进一步研究发现,由于CA可以在紫外光的照射下实现反式结构与顺式结构的转变,对已经形成的蠕虫状胶束体系照射紫外光也可以形成黏度较低的球状胶束。     

Gel shrinking resulting from uneven distribution of ionic micelles between the inside and the outside of the polymer gel network

The volume change of crosslinked nonionic poly (N‐isopropylacrylamide) (NIPA) polymer gel immersed in tetradecyldimethylaminoxide (C14DMAO) surfactant solutions at 0.1M NaCl, were investigated to distinguish between binding and nonbinding polymer gel/C14DMAO surfactants. Also, the aggregation behavior of C14DMAO surfactants the inside and the outside the polymer hydrogels has been studied through solubilization of Sudan III dye. For the C14DMAO surfactants at the degrees of ionization (α) of 0.5 and 1, they bind to the NIPA gel at low surfactant concentration (C_D) that enhance the gel swelling due mainly to the osmotic pressure contribution from the counter ions (regime I, C_D<10mM). However, the deswelling behavior was observed as the surfactant concentration increases above 10 mM (regime II). The solubilization experiments indicated that the surfactant concentration inside the gel is lower than that outside the gel in the regime II, which may be due to the large micelle size that cannot accommodate the mesh size of the gel. It was suggested that the uneven distribution of the ionic micelles leads to the reduction of the net swelling osmotic pressure of the gel (i.e., the decrease of the gel volume). In the case of the nonionic C14DMAO at α = 0, on the other hand, the deswelling behavior was not clearly observed and the surfactant concentration inside the gel and outside the gel was almost identical even at 30 mM. For the nonionic surfactant, it was also found that the gel volume increases with the surfactant concentration at low surfactant concentration less than 1mM. This may be attribute to the dipole‐dipole repulsion of N‐O headgroups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2001–2006, 2004     

Wormlike Micelles in Mixed Amino Acid‐Based Anionic Surfactant and Zwitterionic Surfactant Systems

The formation of wormlike micelles in aqueous solutions of an amino acid‐based surfactant, sodium lauroyl sarcosinate (LS) and a zwitterionic surfactant, cocamidopropyl betaine (CAPB) has been investigated. Holding the total concentration of LS and CAPB constant at 12 wt%, the synergistic effects of mass ratio of CAPB and LS and pH of the micelle solution on rheological behaviors of CAPB/LS micelles were studied. The viscosity of CAPB/LS micelle systems with a mass ratio from 4:8 to 9:3 increases to maximum values and then decreases as pH increases from 4.0 to 5.6. The maximum viscosity of the transparent CAPB/LS micelle solution is nearly 5500 mPa·s with a mass ratio of CAPB/LS = 8:4 at pH 5.10. It is suggested that the proper pH for CAPB and LS to form wormlike micelles should be close to the isoelectric point of the CAPB/LS solution. The results of thixotropy measurements show that the appropriate mass ratio of CAPB/LS can improve the stability of the network structure of wormlike micelles. In addition, viscosity curves of CAPB/LS wormlike micelles follow a nonlinear co‐rotational Jeffreys model, and the linear viscoelasticity of CAPB/LS wormlike micelles can be described by a linear viscoelastic Jeffreys model. The network of wormlike micelles is confirmed by Cryo‐TEM images.     

Self-assembling of star-like amphiphilic block copolymers with polyelectrolyte blocks. Effect of pH

The self-assembling behaviour of a four-arm amphiphilic star block copolymer, (PMMA₇₃-b-PAA₁₄₃)₄, with poly(methyl methacrylate) inner blocks and poly(acrylic acid) outer blocks in ratio 1:2 (PMMA:PAA) has been investigated in aqueous solutions as a function of pH by dynamic light scattering and cryo-transmission electron microscopy. At low pH (pH ≤ 5) the amphiphile forms in the presence of salt both spherical and worm-like micellar aggregates that coexist in solution. At high pH (pH > 12) the solution contains mainly spherical micelles and a small number of larger aggregates that have ‘pearl-necklace’ structure, indicating the disintegration of the worm-like species. In addition to the experiments, computer simulations of the four-arm amphiphilic star block copolymer with the same ratio of the blocks as above were conducted using a coarse-grained model. The simulations predict the formation of the worm-like micellar aggregates at low pH and the spherical ones at high pH. The changes in the morphology of the aggregates are related to the higher degree of ionization of poly(acrylic acid) blocks at high pH and to the swelling of the corona of the micelles by the higher osmotic pressure due to trapped counterions.     

Effects of ph on foam stability of dimethyldodecylamine oxide and n-dodecyl-2-anninopropionic acid in aqueous solutions

Foam stability of aqueous solutions of dimethyl-dodecylamine oxide (DMAO) and N-dodecyl-2-aminopropionic acid (DAPA) has been studied in relation to pH by means of the dynamic method. The foam of DMAO solution is stabilized in the acidic pH region, while with the DAPA solution, the foam is stable in either the acidic or basic pH range and unstable between them. The results suggest that the foam stability of the solutions of these two surfactants is governed by the formation of ionic species of the surfactants. It can be presumed that the adsorption of the ionic species of the surfactant molecules at the surface of foam films establishes an electric double-layer which makes the foams stable.     

Lauryl alcohol and amine oxide as foam stabilizers in the presence of hardness and oily soil

The effects of two potential foam boosters, n-dodecanol (or lauryl alcohol: LA) and tetradecyldimethylamine oxide (C₁₄DMAO), were investigated for two situations in which foam made from a 0.01 wt% solution of a common alkylethoxy sulfate surfactant was highly unstable in the presence of oil drops consisting of an n-hexadecane/oleic acid mixture. In one case in which dissolved CaCl₂ was present at alkaline pH, insoluble calcium oleate particles formed in situ and facilitated foam breakage. In the other, a much higher concentration of calcium was present at neutral pH, and drops of a microemulsion phase formed but no calcium oleate. In both cases, 0.005 wt% LA reduced the entry coefficient, E, of the oil to the air-water surface sufficiently to prevent drop entry and stabilized the foam. In contrast, 0.005 wt% C₁₄DMAO caused smaller reductions in E and was ineffective as a foam booster. LA was more effective because it was able to form a more compact monolayer with the surfactant than C₁₄DMAO at the air-water surface, which led to lower surface tensions and hence lower values of E.     

Mizellare Extraktion von Zink mit Di(2‐ethylhexyl)phosphorsäure in Gegenwart des Tensids Cetyltrimethylammoniumbromid

Addition of surfactants can influence extraction processes. In the case were the surfactant concentration is above the critical micelles concentration the mass transfer rate increases by the formation of inverse micelles and therefore the micellar extraction mechanism of zinc. The influence of the added surfactant cetyltrimethylammonium bromide (CTAB) on zinc extraction with the cation exchanger di(2‐ethylhexyl)phosphoric acid (D₂EHPA) is analysed based on extraction equilibriums and mass transfer experiments. The observed experimental results are explained phenomenologically.     

检测环境水体中银离子含量的新型碳基光学传感器

以木质素磺酸钙为原料,通过常温下分子自组装和超声波辅助法制备木质素基碳量子点(CQDs),探究木质素磺酸钙和NaBH_(4)对CQDs荧光性能的影响并优化CQDs合成条件。研究结果显示:优化后的CQDs合成条件为木质素磺酸钙质量浓度60 g/L,还原剂NaBH_(4)质量浓度50 g/L。利用透射电子显微镜(TEM)、红外光谱(FT-IR)、X射线光电子能谱(XPS)、紫外-可见光谱(UV-vis)和荧光光谱(FL)对CQDs的结构形貌及光学特性进行分析,结果显示:CQDs粒径小((9.5±0.5)nm)且分布均匀、无团聚现象,光学性能优异且荧光量子产率达12.4%。此外,基于CQDs探究不同银离子浓度对其荧光强度的影响,结果表明:CQDs对Ag^(+)具有较好的荧光识别性和灵敏度,在0~250μmol/L范围内CQDs荧光淬灭强度比值与Ag^(+)浓度呈线性关系(R^(2)=0.998),检测限可达525 nmol/L。同时,CQDs荧光选择性优异且表现出较低的细胞毒性,有望在生物传感和环境检测领域展现出潜在应用价值。     

pH-Sensitive Micelles Based on Double-Hydrophilic Poly(methylacrylic acid)-Poly(ethylene glycol)-Poly(methylacrylic acid) Triblock Copolymer

pH-sensitive micelles with hydrophilic core and hydrophilic corona were fabricated by self-assembling of triblock copolymer of poly(methylacrylic acid)-poly(ethylene glycol)-poly(methylacrylic acid) at lower solution pH. Transmission electron microscopy and laser light scattering studies showed micelles were in nano-scale with narrow size distribution. Solution pH value and the micelles concentration strongly influenced the hydrodynamic radius of the spherical micelles (48–310 nm). A possible mechanism for the formation of micelles was proposed. The obtained polymeric micelle should be useful for biomedical materials such as carrier of hydrophilic drug.     

Supramolecular assemblies of amphiphilic PMMA-block-PAA stars in aqueous solutions

Self-assembling properties of an amphiphilic star block copolymer, 4-arm (PMMA-b-PAA)₄ with poly(methyl methacrylate) core and poly(acrylic acid) shell, have been investigated in aqueous solutions. The stars have been observed to aggregate in a complex manner in aqueous solutions, depending on the presence or absence of salt. Screening of the electrostatic repulsion between the polyelectrolyte blocks by adding salt triggers the formation of worm-like micelles. The presence of worm-like micelles in saline solutions was revealed by Kratky analysis of the light scattering data. The coexistence of different micellar morphologies was visualized by direct imaging by cryoTEM. Due to the balance between the electrostatic and hydrophobic interactions semidilute solutions show interesting rheological properties. Shear thinning behavior of salt-free solutions and their time-dependent gelation have been observed, thus indicating the strong tendency of the polymers to aggregate.