大离子诱导聚电解质/表面活性剂复合物的解离

采用分子动力学模拟方法研究了大离子与聚电解质/表面活性剂复合物的相互作用, 考察了大离子的电性、直径、表面电荷、浓度等对其与复合物相互作用的影响. 结果表明, 与聚电解质所带电性相同的大离子对复合物作用不明显, 只有当大离子所带电荷较多时, 才会引导少量表面活性剂从复合物中脱离. 当大离子所带电荷与聚电解质所带电荷电性相反时, 大离子的加入会诱导复合物的解离, 表面活性剂从复合物中释放出来, 甚至导致聚电解质/表面活性剂复合物的完全解离, 从而形成聚电解质/大离子复合物; 大离子所带电荷越多, 诱导作用越明显. 大离子的直径及浓度对其与复合物之间的作用也有很大的影响, 对于所带电荷数相同的大离子而言, 直径越小, 其与复合物的作用越显著, 越容易引导表面活性剂从复合物中解离, 若大离子的表面电荷密度相同, 大离子直径越小, 反而与复合物的作用越弱; 大离子浓度越高, 越易引起复合物的解离, 复合物中聚电解质链上结合的大离子数增多直至饱和, 相应的会出现电荷反转现象.     

聚电解质与相反电荷表面活性剂的相互作用

通过透光度测定、电导滴定和粘度法考察了阳离子聚电解质聚苯乙烯 4 乙烯基吡啶硫酸甲酯盐与阴离子表面活性剂十二烷基硫酸钠 (SDS)的相互作用。研究表明 ,在表面活性剂未过量时 ,二者之间的静电作用占主导地位 ,并且当二者电荷总量相等时 ,生成的复合物沉淀最多 ;在表面活性剂过量后 ,复合物可部分溶解 ,溶解的原因是疏水相互作用。本文初步阐述了二者的作用机理     

高分子与表面活性剂在水相中的相互作用

按照组分荷电属性的不同,高分子/表面活性剂体系可大致划分为三种:中性高分子/离子表面活性剂体系、带电高分子/离子表面活性剂体系、高分子/非离子表面活性剂体系。本文对这三种体系在水相中的高分子/表面活性剂相互作用研究进行综述。在大多数情况下,水相中高分子与表面活性剂共存时都能发生相互作用并形成复合物,其驱动力主要包括疏水作用、静电作用和氢键作用。根据高分子与表面活性剂的荷电情况及结构性质(如疏水链长度)的不同,上述驱动力可以单独或组合作用。此外,温度、pH值、电解质等外界因素对复合物形成过程及结构也具有不同程度的影响。     

阳离子Gemini表面活性剂12-3-12与DNA在模拟体液中的相互作用研究

采用紫外透射光谱、透射电镜、原子力显微镜、圆二色谱(CD)等方法探讨了阳离子Gemini表面活性剂C12H25N+(CH3)2-(CH2)3-(CH3)2N+C12H25·2Br-(12-3-12)与DNA在模拟体液(SBF)中的相互作用。结果表明,SBF中较高反离子浓度不但屏蔽了DNA和12-3-12之间的静电吸引作用,而且促进了12-3-12聚集体的产生和生长,导致低盐条件下体系中出现的沉淀溶解现象的消失。SBF中DNA与12-3-12之间存在强烈的相互作用;随着12-3-12的加入,表面活性剂分子在DNA链周围聚集,类网络结构的DNA逐渐变为类似于串珠的复合物,随后出现尺寸较大的类球形复合物以及较大复合物与较小表面活性剂聚集体共存的现象。CD谱结果显示,SBF中12-3-12可以诱导DNA的构象发生改变,由自然的B构型变成高度致密的ψ相。分子动力学模拟的离子液体中表面活性剂与带相反电荷聚电解质的相互作用过程及模式与实验结果吻合良好。模拟结果也表明,SBF中较高的反离子浓度提高了聚电解质的可压缩程度,导致相同条件下SBF中聚电解质的均方回旋半径远小于稀盐水溶液(10mmol/L Na Br)体系中的聚电解质均方回旋半径。较强的离子强度不但导致体系中聚电解质和带相反电荷表面活性剂之间的相互作用存在"假饱和"现象,而且也造成体系中表面活性剂在聚电解质周围聚集数显著提高。     

胶束催化2-氯乙基苯的氯甲基化

采用胶束催化,在油水两相体系中,进行了2-氯乙基苯的氯甲基化反应．通过比较阴离子、阳离子和非离子三种类型表面活性剂的催化效果,探索了2-氯乙基苯氯甲基化反应的机理及胶束催化的作用机理．研究结果表明,胶束催化是实现2-氯乙基苯氯甲基化的有效途径,且阳离子表面活性剂胶束催化的效果最为显著,阳离子表面活性剂的疏水链越长,其催化性能越好;在水相中加入无机电解质,能显著促进胶束催化作用．     

表面活性剂对污泥脱水性能影响的机理研究:Gemini表面活性剂与聚电解质相互作用的分子动力学模拟

表面活性剂可以与污泥表面的胞外聚合物(EPS)吸附形成胶束,释放出自由水和结合水,从而达到改善污泥脱水性能的目的.本文采用粗粒化的分子动力学模拟方法,研究了Gemini表面活性剂与EPS形成复合物的过程和结构.聚电解质链的亲疏水性对吸附过程有显著影响,亲水聚电解质链与Gemini表面活性剂吸附的主要驱动力为静电吸引,Gemini表面活性剂头基吸附在链上,尾链朝向溶剂;疏水聚电解质链与Gemini表面活性剂吸附过程由静电作用与疏水作用共同促进,Gemini表面活性剂以平行于聚电解质链的构型存在.Gemini表面活性剂联结基团长度对吸附过程的影响甚微;聚电解质链的电荷密度对亲水聚电解质链的吸附产生协同作用,对疏水聚电解质链的吸附不产生作用.     

水溶性聚电解质—表面活性剂复合物的聚集行为

聚电解质在溶液中与相反电荷的表面活性剂通过解电作用与疏水作用可形成聚电解质－表面活性剂复合物，依据反应条件生成的复事物可以是水溶性也可以是非水溶性的。水溶性的聚电解质－表面活性剂复合物由于有许多工业应用，因此近几十上来水溶性聚电解质－表面活性剂复合物的形成和结构已爱到人们的广泛重视。本文对水溶性聚电解质－表面活性剂复合物的聚集过程、聚集结构作了简要概述，此外对荧光光谱在这一领域的应用进行了重点介绍     

有机电解质在胶束催化聚苯乙烯氯甲基化反应中的作用

在实施聚苯乙烯氯甲基化反应的胶束催化体系中加入四丁基溴化铵 ((Bu)₄NBr, TBAB), 研究了有机电解质TBAB对胶束催化反应的影响规律. 实验结果表明, 在非离子表面活性剂NP-10及阴离子表面活性剂SDS的胶束催化体系中, TBAB的加入使聚苯乙烯氯甲基化反应的速率明显增大, 前者尤为突出；而在阳离子表面活性剂CTAB的胶束催化体系中, TBAB的加入几乎对反应速率无促进作用. 这种结果一方面归因于加入电解质TBAB会降低SDS的临界胶束浓度, 从而增强对聚苯乙烯四氯化碳溶液的增溶能力；更主要的原因是TBAB的丁基与表面活性剂碳氢链间的疏水相互作用会使季铵离子(Bu)₄N⁺嵌入SDS的胶束之中, 结合到NP-10的胶束表面, 使SDS胶束的阴离子头基对亲核取代反应(控制步骤)的禁阻作用得以减缓, 使NP-10的胶束表面携带了正电荷, 显著促进亲核取代反应的进行, 而对于CTAB的胶束, 由于静电排斥作用, 季铵离子(Bu)₄N⁺不能接近CTAB的胶束, 故TBAB的加入对聚苯乙烯氯甲基化反应不产生作用.     

电解质和pH值对毒死蜱微乳液透明温度范围的影响

研究了电解质和pH值对毒死蜱微乳剂透明温度范围的影响,表面活性剂采用特殊苯乙基酚甲醛树脂聚氧乙烯醚和十二烷基苯磺酸钙(DBSCa)(质量比为3:7)复合物,质量分数75%毒死蜱二甲苯溶液为油相。研究结果表明,电解质的加入对表面活性剂作用的微乳剂透明温度范围均有显著影响,使上限温度明显下降;随阳离子电解质质量分数增加,上限温度下降;随阴离子电解质价数增加,上限温度先略增加后下降。电解质及其价数对下限温度影响均不大。弱酸性介质有利于扩大体系的透明温度范围,使上限温度达到最大值;而强酸性和强碱性介质,均使体系的上限温度下降。体系下限温度随pH值的增加缓慢升高。     

感光性聚电解质复合物与十二烷基硫酸钠的相互作用及聚电解质复合物的自组装研究

论文的第一部分研究二苯胺-4-重氮树脂(DR)与十二烷基硫酸钠(SDS)的相互作用,发现重氮树脂(DR)水溶液中加入SDS后,体系先产生重氮树脂-SDS复合物沉淀,继续加入SDS,该沉淀又会重新溶解.SDS与重氮树脂间的疏水相互作用对这一现象作了解释.另外,还发现SDS水溶液可以溶解难溶的聚电解质复合物,并通过比较溶解前后重氮基的热分解温度及红外振动吸收来判定其所对应的反离子,从而确定了该溶解的过程是SDS先将聚电解质复合物拆开,再通过疏水相互作用将带有相反电荷的聚电解质溶解.用SDS水溶液溶解的含有感光性重氮树脂的聚电解质复合物可用于阴图PS版感光液的制备,得到一种稳定好,污染小,成本低的感光液.     

水溶性高分子链中磺酸盐基团含量的电导滴定测定法

研究了N ,N ,N 三甲基十六烷基溴化铵 (CTAB)与丙烯酰胺 (AM) 2 丙烯酰胺基 2 甲基丙磺酸钠盐(NaAMPS)二元共聚物P(AM co NaAMPS)的复合作用 .在复合作用过程中 ,由于不断释放出高导电性的无机盐小离子 ,故随着表面活性剂的加入 ,聚电解质水溶液的电导率不断增大 .当采用较低浓度 (0 0 0 1mol·L- 1 )且使二者的离子等摩尔量发生复合作用时 ,体系的电导率会发生明显的转折 .利用电导率的这一转折性变化 ,建立起了复合作用电导滴定法测定共聚物P(AM co NaAMPS)分子链中磺酸盐单体NaAMPS含量的新方法 .与元素分析进行比较的结果表明 ,上述复合作用电导滴定法可作为测定水溶性大分子链中磺酸盐单体含量的方便而又准确的方法 ,而且预计还可用作为测定水溶性大分子链中其它离子性基团含量的简捷方法     

Nanocrystallite Titanium Dioxide Films Made by the Sol-Gel Method Using Reverse Micelles

Reverse micelles have been made by dissolving Triton X-100 in cyclohexane and adding water. Titanium isopropoxide was then introduced in the solution under vigorous stirring yielding a clear sol. If left at ambient temperature the sol gels in a time of a few hours. Gelation has been studied by fluorescence probing. When a glass slide was dipped in the sol at an early stage of gelation, a thin, photometrically uniform film formed, containing both TiO₂ and surfactant. The organic substances could then be burned out at 400–450°C. Heating secured total TiO₂ formation and permanent attachment to the glass substrate. The ensuing film was studied by electron and AFM microscopy. The film possessed a mesoporous structure characterized by uniformity and particle size monodispersity. It also possessed a high capacity for adsorption of a variety of inorganic particle and ionic species.     

Solubilization of an Ionic Liquid,l-Butyl-3-methylimidazolium Hexafluorophosphate,in a Surfactant-Water System

The amphiphilic association structures were determined in the system; water, Laureth 4 (approximately C₁₂(EO) ₄), and the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate ([bmim[PF₆]), using visual observation and small angle x-ray diffraction. The system showed a lamellar liquid crystal solubilizing the ionic liquid ([bmim[PF₆]) to a maximum of 15%, an isotropic surfactant solution dissolving the ionic liquid to a maximum of 39%, an isotropic ionic liquid solution with less than 0.5% of water and surfactant and finally, an aqueous solution with only traces of surfactant and ionic liquid. The small angle x-ray diffraction results showed the ionic liquid to be solubilized into the lamellar liquid crystal without changing the dimensions of the amphiphile layer or the interlayer spacing dependence on the water content.     

Modifying the thermosensitivity of copolymers of sodium styrene sulfonate and<Emphasis Type="Italic"> N</Emphasis>-isopropylacrylamide with dodecyltrimethylammonium chloride

The interactions between copolymers of sodium styrene sulfonate (SSS) and N-isopropylacrylamide (NIPAM), anionic polyelectrolytes, and dodecyltrimethylammonium chloride (DTAC), a cationic surfactant, were studied in aqueous solutions of various ionic strengths. The copolymers were found to be thermoresponsive, showing a lower critical solution temperature (LCST). The influence of the polymer composition, the surfactant concentration, and the ionic strength on the LCST was studied. The surfactant was found to interact strongly with the polymer, forming mixed polymer-surfactant micelles. The critical aggregation concentration (cac) of the polymer-surfactant system was found from fluorescence spectroscopy using pyrene as a fluorescent probe. A strong dependence of the anionic polyelectrolyte-cationic surfactant interactions on the structure of the ionic comonomer was observed.     

Efficient Photoelectrochemical Reduction of Carbon Dioxide to Formic Acid: A Functionalized Ionic Liquid as an Absorbent and Electrolyte

Photoelectrochemical (PEC) reduction of carbon dioxide (CO₂) is a potential method for production of fuels and chemicals from a C1 feedstock accumulated in the atmosphere. However, the low solubility of CO₂ in water, and complicated processes associated with capture and conversion, render CO₂ conversion inefficient. A new concept is proposed in which a PEC system is used to capture and convert CO₂ into formic acid. The process is assisted by an ionic liquid (1‐aminopropyl‐3‐methylimidazolium bromide) aqueous solution, which functions as an absorbent and electrolyte at ambient temperature and pressure. Within this PEC reduction strategy, the ionic liquid plays a critical role in promoting the conversion of CO₂ to formic acid and suppressing the reduction of H₂O to H₂. At an applied voltage of 1.7 V, the Faradaic efficiency for formic acid production is as high as 94.1 % and the electro‐to‐chemical efficiency is 86.2 %.     

THEORETICAL MODELING OF IONIC SURFACTANT ADSORPTION ON MINERAL OXIDE SURFACES

A model for the adsorption of ionic surfactants on oppositely charged solid surfaces of uniform charge density is developed. The model is based on the assumption that, on the solid surface, adsorbed surfactant monomers, monolayered and bilayered surfactant aggregates of different sizes and specifically adsorbing ions of added electrolyte constitute a mixture of hard discs. It means that only excluded area interactions between the surface discs are taken into account. To avoid a rapid two-dimensional condensation of the adsorbed surfactant the potential energy per molecule in the surface aggregates, which is a sum of chemical and electrostatic interactions, is assumed to decrease linearly with the increasing aggregate size. The electrostatic interactions of ionic species with the charged solid surface are described in terms of the Guy-Chapman theory of the double layer formation. The appropriate equations for adsorption isotherms of surfactant and electrolyte ions are derived and used to predict the experimental adsorption isotherms of DTAB on the precipitated silica at two different salt concentrations in the aqueous solution, On the basis of the obtained results the evolution of the adsorbed phase structure and the charge of silica particles with an increasing surface coverage is discussed.     

Dynamic Surface Tension and Adsorption Mechanism of Surfactant Benzyltrimethylammonium Bromide at the Air/Water Interface

The air‐solution equilibrium tension, γ_c and dynamic surface tension, γ_t, of aqueous solutions of a novel ionic surfactant benzyltrimethylammonium bromide (BTAB) were measured by Wilhelmy method and Maximum bubble pressure method (MBPM), respectively. Adsorption equilibrium and mechanism of BTAB at the air‐solution interface were studied. The CMC was determined to be 0.11 mol/L. The results show that at the start, the adsorption process is controlled by a diffusion step. Toward the end, it changes to a mixed kinetic‐diffusion controlled mechanism with the adsorption activation energy of about 11.0 KJ/mol. Effects of temperature, inorganic salts, and alcohols on adsorption kinetics also are discussed.     

Viscosity-Temperature Behavior of Hydroxypropyl Cellulose Solution in Presence of an Electrolyte or a Surfactant: A Convenient Method to Determine the Cloud Point of Polymer Solutions

The viscosity of hydroxypropyl cellulose (HPC) solution with or without an additive has been measured continuously as a function of temperature with the help of a vibro-viscometer. The viscosity of the polymer solution showed a gradual decrease initially with increase in temperature until a particular point beyond which there was a sharp decrease in the viscosity, which coincided with the clouding of the solution. The cloud point temperature (CP) of the polymer solution was determined from the first derivative plot of viscosity vs. temperature. Effect of addition of an electrolyte or a surfactant on the CP of HPC solution has also been studied. While a decrease in CP of HPC solution in presence of fluoride, chloride, or bromide ions was observed, presence of iodide or thiocyanide ions led to an increase in the CP. However, presence of an ionic surfactant initially lowered the CP but beyond a particular surfactant concentration a sharp increase in cloud point was observed due to interaction of the surfactant with the polymer. The results suggest that surfactants with longer hydrophobic tail or more hydrophobic groups have more affinity for HPC.     

Adsorption of sodium dodecylsulfate on chrysotile

Adsorption of sodium dodecylsulfate (SDS) onto chrysotile from aqueous solutions was investigated along with varying temperature, ionic strength and surface treatments. Commercial chrysotile fibers were treated by sonication or extensive washings. The ratio of adsorbed SDS per gram of chrysotile is approximately constant with varying chrysotile masses. A steady state is reached after about 2 h of contact between SDS and chrysotile. In general, less surfactant is adsorbed on the sonicated chrysotile than on the extensively washed chrysotile. For the sonicated chrysotile, isotherms presented an adsorption maximum in the region of the surfactant critical micelle concentration, when the experiments were carried out without ionic strength control. The adsorption maximum is due to the presence of magnesium ions in the solution, which can form complexes with dodecylsulfate ions. For the extensively washed chrysotile, the isotherm behavior is similar to that obtained with sonicated chrysotile in the presence of an inert electrolyte. No significant difference in adsorption of SDS on the extensively washed chrysotile was observed when varying temperature or ionic strength. The adsorption of SDS was found to be dependent on the prior surface treatment.