【作者】 李国宝；

【导师】 郝京诚；

【作者基本信息】 山东大学 ， 胶体与界面化学， 2011， 博士

【摘要】 表面活性剂混合体系的研究中,检测表面活性剂浓度的动态连续变化或平衡状态下稀溶液浓度的估算是研究者比较关心的一个问题。溶液中表面活性剂单体的浓度可以通过平衡渗析、超过滤、微量热滴定和表面活性剂离子选择性电极等手段来测定。以表面活性剂离子选择性电极为基础的电动势法,具有测定设备简单廉价、所需样品量少且不需要预处理、不易受其它加入物的干扰,良好的灵敏度和重现性等优点而受到不少研究者的青睐。最近十多年来,该方法已被成功应用到两亲分子溶液化学的研究中。有关表面活性剂离子选择性电极的研究报道,国内的文献主要集中于环境水体中表面活性剂的检测,国外的文献多集中于表面活性剂与高聚物的相互作用的研究。到目前为止,关于表面活性剂离子选择性电极在阴/阳离子表面活性剂复配体系研究中的应用,国内外均未见文献报道。这可能与阴/阳离子表面活性剂溶液的配制方法有关,因为只有维持恒定的离子强度时,测得的一系列电动势数据才具有可比性。论文主要利用电化学方法,并结合表面张力和流变学等手段研究了具有恒定离子强度的阴/阳离子表面活性剂复配体系的相行为,阳离子表面活性剂(CnTAB)与非离子三嵌段共聚物PluronicF127(PEO97-PPO69-PEO97)在不同盐度、高聚物浓度及温度下的相互作用等,具体内容分为五章：第一章概述了离子选择性电极的研究背景和表面活性剂离子选择性电极在表面活性剂混合体系中的研究进展,及其在表面活性剂复配体系、表面活性剂与聚合物相互作用研究领域的重要意义。结合实验工作,总结了表面活性剂离子选择性电极在使用过程中遇到的一些问题及相应处理措施等。第二章利用四苯硼钠(NaBQ4)、十二烷基硫酸钠(SDS)与长链烷基三甲基溴化铵(CnTAB)生成的中性离子对(CnTA-BQ4、CnTA-DS)作为电活性物质,以邻苯二甲酸二辛酯(DOP)为增塑剂、低分子量的聚氯乙烯粉(PVC)为成膜载体,以电动势和表面张力为主要测试手段,筛选制备具有最佳性能的表面活性剂离子选择性电极。实验结果表明：以BQ4-为反离子制备的中性离子对作为电活性剂物质,DOP含量为112.5 mg/mL, PVC含量为75mg/mL,电活性物质浓度为0.63mmol/L时制得的表面活性剂离子选择性电极性能最佳。通过对表面活性剂离子选择性电极稳定性、重现性的测试,发现制得的表面活性剂离子选择性电极的稳定性较好,在2 h的连续测定中数据偏差不超过1 mV。另外通过十六烷基三甲基溴化铵(CTAB)和十一酸钠(SU)、月桂酸钠(SL)得到的中性离子对CTA-U、CTA-L作为电活性物质,分别制得了对十一酸钠和月桂酸钠有响应的阴离子表面活性剂选择性电极,但遗憾的是这类电极的电动势测试结果并不能与表面张力测试结果完全吻合,Nernst响应斜率偏低,这可能与所用电活性物质的溶解性有关。尽管存在Nernst响应斜率低、电位漂移、膜电极的记忆效应等影响因素,但每次测试前只要充分清洗膜表面,都可获得较为满意的结果。可以应用于随后的表面活性剂混合体系的单体组分测定中。第三章采用电动势测定、电导率测定、偏光显微镜观察和流变学研究等方法考察了十四烷基三甲基溴化铵(TTAB)、十六烷基三甲基溴化铵(CTAB)分别和10-十一烯酸钠(10-SU)、十一酸钠(SU)所形成的复配体系TTAB/10-SU,TTAB/SU, CTAB/10-SU的相行为,将TTAB、CTAB、SU等表面活性剂离子选择性电极应用于该复配体系中,分别测得了总浓度不同时体系中游离表面活性剂的浓度,得出了游离表面活性剂浓度随体系组成的变化关系。研究结果表明：在恒定总浓度的混合体系中,随阳离子表活性剂组成Xn的增加,溶液经历了L1相、Lα相、Lαv相及粘稠L1相的转变过程。在聚集态转变过程中测得相应表面活性剂单体的浓度逐渐增加,在由L1相向Lα及粘稠的L1相等转变的区域,游离的表面活性剂浓度变化最明显,整个测定范围内其浓度曲线呈S型变化。对于TTAB/10-SU和TTAB/SU复配体系而言,其Xn(TTAB)为0.3,0.4,0.5,0.7时所对应的典型样品的流变学数据表明,在不同摩尔比例下得到的L1相体现出粘性特征,而对于CTAB/10-SU复配体系,其Xn(CTAB)为0.3,0.4,0.5,0.7时的样品也同样以粘性为主；随总浓度的增大,粘性增大,当Xn(CTAB)在0.7附近时体系表现出明显的弹性行为。第四章采用电化学法研究了非离子三嵌段共聚物Pluronic F127溶液的临界胶束温度(CMT)及其与阳离子表面活性剂CnTAB的相互作用。提出了利用循环伏安法测定非离子型聚合物溶液CMT的实验方法,借助具有疏水性能的电化学探针2,2,6,6-四甲基-1-哌啶氧自由基(TEMPO)在混合溶液中扩散系数的测定,比较了达饱和吸附浓度乃时CnTAB/F127混合溶液的疏水性能。采用表面活性剂离子选择性电极,测定了不同浓度的NaBr存在时CnTAB和F127相互作用的电动势曲线,结果发现随烷基链长的增加,与F127发生协同作用的程度增强,而且发生协同结合作用时的浓度T1基本与F127浓度无关；F127溶液浓度越高,协同结合作用结束时的浓度T2越大。而增加盐浓度和升高温度,对CnTAB和F127间的协同结合作用有不利影响。同时还发现在较低盐浓度下(1 mmol/L NaBr),或在较低的F127浓度(0.5 g/L)下,CTAB、TTAB与F127发生协同结合作用之前存在非协同结合现象。第五章采用循环伏安法研究了维生素K3(VK3)包覆在酸处理过的多壁碳纳米管(MWNTs)、壳聚糖(CHIT)所形成的单一膜以及混合膜中时,在磷酸盐缓冲溶液中的电化学性质及对多巴胺(DA)的电催化氧化。结果表明由于CHIT和MWNTs的存在,VK3在玻碳电极表面上的吸附大大增强,循环伏安响应明显增强,VK3的耐碱蚀能力得到极大提高,即使在pH=12的强碱性环境下,也存在氧化还原响应。通过改变溶液pH值以及改变扫描速率时的循环伏安测试,提出了吸附在固体表面上的VK3的氧化还原机理,计算出了电极表面与固定VK3的MWNTs/CHIT混合膜之间,以及电极表面与固定VK3的MWNTs膜之间的表观电荷转移速率常数ks和电子转移系数α分别为21.4s-1,0.49和3.2s-1,0.47。采用循环伏安法对DA的电催化氧化进行实验,结果表明VK3-MWNTs-CHIT混合膜修饰电极对DA具有较好的电催化性质。运用微分脉冲方法对溶液中的DA进行测定,在2-100μmol/L浓度范围内,稳态氧化峰电流和DA的浓度成线性关系,检测限为0.18μmol/L。更多还原

【Abstract】 In the research of surfactant mixtures solutions, monitoring of the continued change in surfactant concentration or its estimation in a dilute solution under equilibrium condition is a matter of concern to researchers. The isolated surfactant concentration can be determined by some methods such as the equilibrium dialysis, ultrafiltration, isothermal titration calorimetry (ITC) and surfactant ion-selective electrodes (SISEs). Compared to the other determination methods, the electromotive force method based on SISEs is favored by many researchers because of its advantages of low cost, high sensitivity, reproducibility, without disturbing by additions and need little amount of sample with almost no pretreatment. In the past decades, this method was applied successfully to the research of amphiphilic molecules systems in solution. Domestic papers involved in SISEs mainly focused on analytic determination environmental waste water samples, and external papers mainly focused on the research domain of interaction between surfactants and polymers. So far, no papers have been published about SISEs in the research of cationic/anionic surfactant system, the reason may be the preparation of cationic/anionic binary systems where ionic strength was usually inconsistent. Only when the samples maintain the same ionic strength, have the electromotive force (EMF) data comparability.The focus of this thesis have been on the following aspects:Construction of a series of cationic/anionic surfactant systems with almost the same ionic strength, i.e. TTAB/SU. TTAB/10-SU and CTAB/10-SU system, whose phase behaviors were studied in detail by conductivity, polarized light, EMF and rheology techniques, some important evidence for these binary systems were obtained. Detailed study on the interaction between long-chain alkyltrimethylammonium bromide CnTAB (n=16, CTAB;n=14, TTAB;n=12, DTAB) and nonionic triblocked copolymer Pluronic F127 (PEO97-PPO69-PEO97) under various NaBr salinity, different polymer concentration and different temperature were performed using EMF measurement based on SISEs and cyclic voltammetry (CV) measurement. The present dissertation includes five chapters.In chapter I, the research background about ion selective electrodes (ISEs), the study progress and the importance on SISEs applying to study of compounded system composed of cationic/anionic surfactants, polymers or biomacromolecules are summarized, including some problems about SISEs and corresponding settlement encountered during the testing procedure in our own research work.In chapter II, sodium tetraphenylborate (NaBQ4) and sodium dodecyl sulfate (SDS) respectively interact with n-cetyl-N, N, N-trimethylammonium bromide (CTAB) cationic surfactant by electrostatic force, which forms a series of neutral ion-pair complexes (CTA-BQ4, CTA-DS) as electroactive substance. Then, combining with bis-(2-ethylhexyl) phthalate (DOP) as plasticiser and polyvinyl chloride (PVC) with low molecular weight as film materials, SISEs were fabricated. The performance of SISEs was compared through EMF and surface tension measurements, and the results indicate that, when the ion pairs containing BQ4- as counter ion are selected as electroactive species, and the concentrations of DOP, PVC and the electroactive specie are respectively 112.5 mg/mL,75 mg/mL and 0.63 mmol/L, the SISEs perform best. Correspondingly, the SISEs show good stability and reproducibility, and the inaccuracy is less than 1 mV in 2 h continuous testing. In addition, the SISEs which are sensitive to anionic surfactant such as sodium undecanoate (SU) and sodium laurate (SL), were also fabricated by using the netural ion-pairs complexes (CTA-U and CTA-L) formed by CTAB interacting with SU and SL, respectively, as electroactive species, respectively. However, the EMF data of these electrodes can not completely coincide with the results of the surface tension. The response slope of Nernst is somewhat low, which may be relevent with the solubility of the ion-pairs complexes and the properties of the aqueous fatty acid sodium solution. Though largely influenced by low response slope of Nernst, potential drift and memory effect of membrane electrode, after carefully cleaning of the film surface, the SISEs can still be well applied in the monomer composition measurement of the surfactant mixtures.In chapter III, the phase behavior of catanionic surfactant mixtures, composed of alkyltrimethylammonium bromide (TTAB, CTAB) and fatty acid sodium salts (10-SU, SU), was researched by EMF and electrical conductivity measurements, observation through polarizing microscope, and rheological study. Then the SISEs sensitive to TTAB, CTAB and SU were used to determine the surfactant monomer concentration, in order to confirm a correlation between surfactant mole fraction in whole solution and its isolated monomer concentration. The results indicate that, with the increase of cationic surfactants at fixed concentration of mixtures, a series of phase changes were observed in sequence:a clear dilute micellar solution (L1-phase), a micellar/vesicular two-phase region (L1/La-phase), a single vesicle phase (Lav-phase), and a viscous micellar solution (L1-phase). Accompanied with the ordinal phase transitions, the concentration of the surfactant monomer gradually increases, especially for the transitions from L1-phase to Lav-phase to viscous L1-phase. For TTAB/10-SU and TTAB/SU mixed systems, the rheology behavior was studied when the molar fraction of TTAB (Xn(TTAB)) is 0.3,0.4,0.5, and 0.7, respectively, which reveals that the L1-phases all show viscosity at different Xn(TTAB)-For CTAB/10-SU mixture, the solution also obviously shows viscous characteristic at Xn(CTAB)=0.3,0.4,0.5, and 0.7. Furthermore, the viscosity increases with the increase of the total concentration, and the mixed solution exhibits elastic behavior when Xn(CTAB) is near 0.7.In chapter IV part, potentiometric method based on SISEs and CV method have been used to study the interactions between a homologous series of n-alkyl trimethyl ammonium bromides (CnTAB) and triblock copolymer pluronic F127. The CV method was firstly introduced to determine the critical micelle temperature (CMT) of nonionic polymer solution. The hydrohpobic behavior of CnTAB/F127 mixture solutions were discussed by comparing the variation of the diffusion coefficient of electroactive probe 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) in mixture solutions. Using SISEs, the EMF data of CnTAB/F127 systems were obtained under different salinity of NaBr. From these data, it is shown that the synergistic interactions between CnTAB and F127 were enhanced with the increase of surfactant chain-length, the concentration of CnTAB when the synergistic interact begin (noted as T1) were almost independent of the F127 concentration, the surfactant concentration where the polymer is saturated with surfactant (noted as T2) increases as the F127 concentration increases. But the increase of salinity and temperature has a negative influence on the synergistic interaction between CnTAB and F127. From the EMF data, uncooperative binding process of CTAB/F127 and TTAB/F127 systems was detected before the synergistic interactions in solutions with low salinity (lmmol/L NaBr) or with low F127 concentration (0.5 g/L).In chapter V, the electrochemical characteristics of vitamin K3 (denoted VK3) incorporated in acid-treated multiwalled carbon nanotubes (MWNTs) film, chitosan (CHIT) film and MWNTs-CHIT hybrid films in phosphate buffer solutions were studied respectively and the electrocatalytic oxidation of dopamine (DA) was investigated by cyclic voltammetry method. The results shown that the adsorbility of VK3 on the surface of a GC electrode was greatly enhanced by CHIT and MWNTs, and the redox peak currents of VK3 increased dramatically with the addition of MWNTs in cyclic voltammogram. Because of the existence of CHIT, the alkali resistance of VK3 get a great improvement, even if in pH=12 strong alkali solution, there are also redox response of VK3 in cyclic voltammogram. By changing pH of solutions and scan rate of cyclic voltmmetry measurements, the proton number and electron number involved in redox process were calculated, and the redox mechanism of VK3 incorporated in hybrid films was given. The apparent charge-transfer rate constant ks and transfer coefficient a for electron transfer between the electrode surface and immobilized VK3 in MWNTs-CHIT hybrid films and in MWNTs films were calculated as 21.4 s-1,0.49 and 3.2 s-1,0.47, respectively. The electrocatalytic oxidation of DA evaluated by cyclic voltammetric measurements indicates that VK3-MWNTs-CHIT hybrid film modified electrodes have good electrocatalytic property to DA. The differential pulse voltammograms were used to detect the DA concentration. A linear relationship between steady-state current and DA concentration was obtained over the range of 2-100μmol/L with a detection limit of 0.18μmol/L.更多还原