两亲无规聚合物的聚集行为及其与非离子表面活性剂的相互作用

以2-丙烯酰胺基-十二烷基磺酸(AMC12S)与2-丙烯酰胺基-2-甲基丙磺酸(AMPS)进行无规共聚,合成了含AMC12S摩尔分数(X)较高(X=0.1,0.3,0.5)的一系列两亲聚合物.采用稳态荧光及动态光散射技术对聚合物在水溶液中的聚集行为及其与三种非离子表面活性剂(HO(CH2CH2O)10C12H25(C12E10)、HO(CH2CH2O)20C12H25(C12E20)和HO(CH2CH2O)40C12H25(C12E40))的相互作用进行了研究,并考察了X对聚集行为的影响以及表面活性剂亲水基团长度对相互作用的影响.随着X的增大,聚合物的临界聚集浓度(CAC)明显减小,X=0.5时聚合物的CAC低达0.0039g·L-1.聚集体的流体力学半径(Rh)都大于26nm,并随着聚合物浓度的升高而增大,说明聚合物分子主要以分子间的聚集方式聚集,形成多分子聚集体.随X的增大,聚集体Rh减小,同时Rh随聚合物浓度升高而增大的幅度减小,说明聚集体结构变得更加紧实.表面活性剂与聚合物之间存在很强的相互作用,在混合溶液中表面活性剂浓度达到临界胶束浓度(CMC)左右时聚合物聚集体开始解离,形成混合聚集体.亲水基团长度增长,表面活性剂对聚合物聚集体的解离能力随之增强.C12E40与X=0.5的聚合物形成的混合聚集体Rh为6.8nm,与C12E40自身形成的聚集体尺寸相当.     

聚共轭亚油酸基网状纳米金的制备及表面增强拉曼散射和催化性能

以天然不饱和脂肪酸共轭亚油酸(CLA)为绿色单体, 通过简单的分子自组装和可控自交联反应制备聚共轭亚油酸(PCLA)聚集体. 透射电子显微镜(TEM)结果显示, PCLA聚集体的形貌呈现独特网状结构, 其联结单元为来自于CLA胶束的膨大颗粒. 采用氯金酸在极性聚合物表面原位还原, 2 d后在网状PCLA基底上制备得到以CLA胶束为核(20 nm)的网状纳米金结构, 而且网状PCLA的原位还原作用与模板作用相结合是获得PCLA基网状纳米金的充分必要条件. 与普通球形胶态金纳米颗粒[(5±1) nm]相比, PCLA基网状纳米金对苯硫酚具有更好的表面增强拉曼散射(SERS)效应, 对对硝基苯酚具有更好的催化还原效果.     

含环状原酸酯侧基的两亲性嵌段共聚物及其酸敏感胶束状聚集体

合成了含有环状原酸酯基团的单体,甲基丙烯酸5-(5-甲基-2-乙氧基-1,3-二氧六环)甲酯(EDMM),以PEO大分子引发剂引发,通过原子转移自由基聚合方法制备了两个疏水链段(PEDMM)长度不同的酸敏感两亲性嵌段共聚物,PEO-b-PEDMM17和PEO-b-PEDMM34.两个聚合物在水溶液中形成粒径约为60～200nm的球型聚集体,通过动态光散射、透射电镜、荧光探针等手段表征了所得聚集体.结果显示,疏水链段较短的共聚物的临界聚集浓度较高,形成的聚集体尺寸较小.核磁和荧光探针结果表明,胶束状聚集体在中性(pH7.4)水溶液中比较稳定,在酸性水溶液中其疏水核的极性因原酸酯的水解而增加.该类酸敏感胶束状聚集体有望用于肿瘤、细胞内给药等药物传递体系.     

尾链长度高度不对称的阴/阳离子表面活性剂自组织

通过引进新的溶液制备方法,以光散射、流变、电镜等方法研究了烷烃链长度不对称的阴/阳离子表面活性剂等摩尔混合体系,其中阳离子为二十二烷基三甲基溴化铵(C₂₂TABr),阴离子是烷基羧酸钠(C_n-1COONa, n = 4, 6, 8, 10, 12, 14, 16).结果表明,烷烃链长度高度不对称时(C22/n4)生成了球状胶束,随着降低不对称度,聚集体向棒状、蠕虫状直至囊泡转变.在构成囊泡的体系中,随着降低链长不对称度,聚集体尺寸明显增大.机理分析表明,阴/阳离子对的几何形状决定了聚集体的形貌以及它们的转变.     

1,3,5-三甲氧基苯的绿色合成工艺

以间苯三酚(PG)为原料,碳酸二甲酯(DMC)为甲基化试剂,在K2CO3/(Bu)4NBr催化下合成了1,3,5-三甲氧基苯,其结构经1H NMR,13C NMR和HR-ESI-MS确证。最佳工艺条件为:PG 10 mmol,n(DMC)∶n[(Bu)4NBr]∶n(K2CO3)∶n(PG)=12∶0.15∶1.5∶1,于160℃反应24 h,收率76.0%。     

PLA-b-PEO-b-PLA三嵌段共聚物分子聚集体性质的研究

采用开环聚合的方法 ,合成了组成不同的PLA b PEO b PLA三嵌段共聚物 .滴加选择性溶剂水于共聚物的良溶剂溶液中 ,制备了共聚物以水为介质的“平头”聚集体胶束溶液 .把聚集体胶束溶液浇铸在云母片上 ,采用扫描探针显微镜 (SPM)表征了其形貌和表面微粘弹性 .发现脱离了极性介质水的聚集体的表面性质发生了不均一化 ,聚集体的顶部比相连接的部分具有较高的储能模量 .聚集体环境的改变使聚集体中不同嵌段的迁移导致了这种表面粘弹性的不均一 .另外 ,采用动态光散射的方法测量了体系溶液中聚集体胶束的尺寸 .实验发现光散射所得到的聚集体的尺寸远远大于SPM所得到尺寸 .增加聚合物的起始浓度使聚集体胶束的尺寸以及多分散性都在不同程度上增大 .然而聚合物的不同 ,这种增加的程度会有比较大的差别     

水溶液中Pluronic嵌段共聚物聚集行为的介观模拟

通过介观动力学方法(MesoDyn)研究了低浓度下的三嵌段共聚物PEO27PPO61PEO27 (P104)水溶液的聚集行为, 讨论了聚合物浓度、模拟时间对P104水溶液相行为的影响. 在聚合物浓度较低(φ<35%)的情况下, 可以形成三种不同的胶束聚集体：球形胶束(spherical micelle)、胶束簇(micellar cluster)和盘状胶束(disk-like micelle). (1) 球形胶束(5%-10%, φ), 模拟的胶束结构表明疏水的PPO嵌段形成球形内核(micellar core), 而亲水的PEO嵌段形成核壳(micellar corona), 并有水分子存在内核和核壳之中；(2) 胶束簇(11%-15%, φ), 由于球形胶束之间的缔合, 形成直径明显高于球形胶束的聚集体, 其半径比球形胶束大1 nm左右；(3) 盘状胶束(16%-25%, φ), 胶束簇核壳PEO嵌段之间的相互缠绕, 形成了成串的类似盘状的胶束. 模拟中有序参数随浓度的变化证明了这种结构划分的合理性.     

C12EO4与氨丙基三乙氧基硅烷水溶液自组装和流变性研究（英文）

研究了3-氨丙基三乙氧基硅烷(APTES)和非离子表面活性剂十二烷基聚氧乙烯(C12EO4)水溶液的相行为、溶液自聚集作用和流变性,小角度X-射线散射(SAXS)、低温透射电子显微镜(cryo-TEM)和氘谱核磁共振(2H NMR)测定确定了溶液中聚集体结构,测定了聚集体混合物溶液的流变性质.结果表明:随着溶液混合物组分的变化,溶液聚集体结构发生了改变,在Lα相区内,恒定C12EO4浓度,随着APTES浓度增加聚集体结构由高曲率聚集体转变为低曲率的层状结构;而在恒定APTES浓度时,随着C12EO4增加,Lα相由低粘弹性的囊泡溶液转变为粘弹性极高的密堆积囊泡和平面层状结构共存的类凝胶相,溶液聚集体结构和结构转变是由于APTES水解产物插入至C12EO4胶束引起的.非离子表面活性剂和氨基硅烷混合物溶液相结构及结构转变的新结果对于完全理解该类混合物的实际应用,特别是作为模板合成硅材料的应用具有重要理论意义.     

不同寡聚度磺酸盐表面活性剂与支化羧酸盐混合体系的聚集行为

采用表面张力、Zeta电位和小角中子散射技术,研究了pH 11条件下2-己基癸酸、异硬脂酸对具有单头单链十二烷基磺酸钠（SDoS）和星状四聚磺酸盐表面活性剂EDA-（C₁₂SO₃Na）₄的气液界面性质、胶束化行为和乳化性能的影响.结果表明,在气液界面和胶束中支化羧酸盐分子与磺酸盐表面活性剂间有不同程度的相互吸引作用,而且在降低表面张力效率方面具有协同作用,但胶束中分子间相互吸引作用更强的四聚磺酸盐表面活性剂混合体系在聚集体形成方面却未表现出协同作用.同时,随着羧酸盐的加入,SDoS和EDA-（C₁₂SO₃Na）₄呈现出不同的聚集体转变规律,羧酸盐与SDoS的混合聚集体随着浓度增大逐渐由球形胶束转变为棒状胶束,而羧酸盐与EDA-（C₁₂SO₃Na）₄的棒状胶束随着羧酸盐摩尔分数的增大而增长,随着总浓度的增大而减小.此外,在同等乳化烷烃的效果下,支化羧酸盐分子的加入可以大幅减少寡聚磺酸盐表面活性剂的使用量.     

含偶氮苯侧链分子刷聚合物的合成及其光响应自组装

分子刷聚合物伸展的高分子主链、高密度的侧链和较低的侧链空间缠结,使其展现出独特的流变学、力学性能和特殊的分子聚集状态,在纳米技术、表面科学等领域有着广泛的应用前景.基于同时含有2-羰基溴与炔基基团的大分子试剂聚2-((2-溴代丙酰氧基)甲基)丙烯酸丙炔酯,引发偶氮苯丙烯酸酯单体的原子转移自由基聚合(ATRP)与叠氮功能化的巴比妥酸衍生物的点击反应,合成了新型含偶氮苯侧链的分子刷聚合物聚丙烯酸酯-g-聚(6-(4-丁基-4′-氧偶氮苯)正己基丙烯酸酯)/巴比妥酸(PA-g-PAzo/Bar),研究了其在溶液中的自组装和光响应性行为.随着分子刷聚合物浓度的增加,聚集体由柱状胶束向复合胶束转变.由于光响应性偶氮苯侧链的存在,在紫外光的照射下偶氮苯生色团发生trans-cis异构化转变,促使柱状胶束融合形成多孔网状聚集体,同时球形复合胶束融合形成珍珠项链状聚集体.     

Influences of Micelle Formation and Added Salts on the Hydrolysis Reaction Rate of p‐Nitrophenyl Benzoate in Aqueous Buffered Media

The hydrolysis reaction rate of p‐nitrophenyl benzoate (p‐NPB) has been examined in aqueous buffer media of pH 9.18, containing surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), or sodium dodecyl sulfate (SDS) at 35°C. Although the rate constant [log (k /s⁻¹)] of p‐NPB hydrolysis has once decreased slightly below the critical micelle concentration (CMC) value for CTAB and CTAC, it has begun to increase drastically with micellar formation. With increasing concentrations larger than the CMC value, the log (k /s⁻¹) value has reached the optimal value, i.e., a 140‐ and 200‐fold rate acceleration for CTAB and CTAC, respectively, compared to that without a surfactant. Whereas the anionic surfactant, SDS, has caused only a gradual rate deceleration in the whole concentration range (up to 0.03 mol dm⁻³). Increases in pH of the buffer have resulted in increases of the hydrolysis rate. In the CTAB micellar solution, the remarkably enhanced rate has been retarded significantly by the addition of only 0.10 mol dm⁻³ bromide salts. The effects of rate retardation caused by the added salts follows in the order of NaBr > Me₄NBr > Et₄NBr > Pr₄NBr > n‐Bu₄NBr. In the absence of surfactant, however, the addition of the bromide salts has accelerated the hydrolysis rate, except for the metallic salt of NaBr, with the order of Me₄NBr < Et₄NBr < Pr₄NBr < n‐Bu₄NBr. In the CTAC micellar solution, similar rate retardation effects have been observed in the presence of chloride salts (NaCl, Et₄NCl, and n‐Bu₄NCl). The effects of added salts have been interpreted from the viewpoints of the changes in activity of the OH⁻ ion and/or the nucleophilicities of the anions from the added salts.     

Heat capacities of crystalline tetraalkylammonium salts

The behavior of crystalline tetraalkylammonium salts at 290–350 K was studied by differential scanning calorimetry. For tetraethyl- and tetrabutylammonium bromides (Et₄NBr and Bu₄NBr), the experimental heat capacities agreed well with the literature values. For tetrahexyl-, tetraheptyl-, and tetraoctylam-monium bromides (Hex₄NBr, Hep₄NBr, and Oct₄NBr), phase transitions were found between crystal modifications whose characteristic temperatures depended significantly on the size of the cation. Empirical equations for the temperature dependences of the heat capacities of the salts within the ranges of homogeneous equilibrium phases were derived.     

Isopiestic determination of the osmotic and activity coefficients of dilute aqueous solutions of symmetrical and unsymmetrical quaternary ammonium bromides with a new isopiestic cell at 298.15 K

The osmotic coefficients of Bu₄NBr, sec-Bu₄NBr, iso-Bu₄NBr, Bu₂Et₂NBr and Bu₃EtNBr were determined by isopiestic method at 298.15 K in dilute aqueous solutions. A branched isopiestic cell was used. The osmotic coefficients of tetra-alkyl-ammonium solutions were analyzed comparing these with the Debye–Hückel limiting law. The order of the osmotic coefficient variation is Bu²Et₂N⁺ > BuEt₃N⁺ > sec-Bu₄N⁺ > iso-Bu₄N⁺ > n-Bu₄N⁺. The results were fitted to the Pitzer equation and the parameters β₀ and β₁ were calculated. The results are discussed.     

Diisoamyldibutylammonium Bromide Clathrate Hydrates

In the system i-Am₂Bu₂NBr-H₂O, along with the known compound i-Am₂Bu₂NBr·38H₂O, three new clathrate hydrates were revealed: i-Am₂Bu₂NBr·32H₂O, i-Am₂Bu₂NBr·26H₂O, and i-Am₂Bu₂NBr·24H₂O. Crystals of all the hydrates were isolated, and their compositions and melting points were determined.     

Role of the hydrophobic properties of functional detergents on micellar effects in the dissociation of environmental toxicants

1-Alkyl-3-(2-oximinopropyl)imidazolium chlorides were prepared with different alkyl chain lengths (Alk = C₁₂H₂₅, C₁₄H₂₉). Some physicochemical indices (CMC and pK _a^app) were determined. The reactivity of these compounds was studied in the dissociation of 4-nitrophenyl esters of diethylphosphonic, diethylphosphoric, and toluenesulfonic acids. The times for 50% conversion of the substrates into reaction products decrease in the series: C₁₂H₂₅ > C₁₄H₂₉ >C₁₆H₃₃. In selecting the direction of modification of the supernucleophilic functional surfactants, we should take into account not only their hydrophobic properties but also the efficiency of substrate solubilization as well as the reactivity of the oximate group in the surfactant micelles.     

Protonation of the lithio derivatives of the 1,2,4-tri-phosphaferrocenes, [LiFe(η-P2C2Bu2PBu)(η-C5R5)] (R = H, Me): Crystal and molecular structure of [Fe(η-P3C2Bu2BuH)(η-C5Me5)]

A new synthetic route is described to generate the 4-centre-5 electron donor ring system (P₃C₂^tBu₂BuH), via protonation of the lithium salts [LiFe(η⁴-P₂C₂^tBu₂PBu)(η⁵-C₅R₅)] (R = H, Me). The molecular structure of [Fe(η⁴-P₃C₂^tBu₂BuH)(η⁵-C₅R₅)] (R = Me) has been determined by a single crystal X-ray study.     

Studies on ion-pair and triple-ion formation of some tetraalkylammonium salts in binary solvent mixtures of benzene and tetrahydrofuran at 298.15 K

Conductivities of some tetraalkylammonium halides, viz. tetrabutylammonium bromide (Bu₄NBr), tetrapentylammonium bromide (Pen₄NBr), tetrahexylammonium bromide (Hex₄NBr) and tetraheptylammonium bromide (Hep₄NBr) were measured at 298.15 K in THF + C₆H₆ mixtures with 10, 20, 30 and 40 mass% of C₆H₆. A minimum in the conductance values was observed as concentration increases, which dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M⁺ + X⁻ ↔ MX, K_P) and triple-ions (2 M⁺ + X⁻ ↔ M₂X⁺; M⁺ + 2X⁻ ↔ MX₂⁻, K_T). A linear relationship between the triple-ion formation constants [log(K_T/K_P)] and the salt concentrations at the minimum conductivity (log C_min) was given for all salts in C₆H₆ + THF mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R₄N⁺ X⁻).     

Salting-in of alcohols in aqueous solutions by tetraalkylammonium bromides at the freezing temperature

The freezing-point depression of the ternary systems tetraalkylammonium bromides-t-butanol-water for the first five homologs of R₄NBr was measured. In the case of Bu₄NBr, the effect of size of the alcohol (methahol ton-butanol) was also investigated. From the corresponding freezing-point data for the binary systems the apparent salting constants were calculated. The true salting constantsk _s were obtained by extrapolation to infinite dilution. These are all very close to zero at the freezing temperature. From the corresponding thermochemical data the temperature dependence ofk _s was calculated, and above 5°C all the R₄NBr salts int-butanol; the salting-in increases with temperature and with the size of the hydrophobic cations. The scaled-particle theory is at present the only one which can account semiquantitatively for the temperature dependence of the salting-in effect. On leave of absence from Chemistry Department, The University, Sheffield S3 7HF, England To whom correspondence should be addressed.     

Organotin wood preservatives: Their compatibility with synthetic pyrethroid insecticides

The stability of three synthetic pyrethroids (cypermethrin, deltamethrin and permethrin) to selected tributyltin compounds, Bu₃SnX [where X = OSnBu₃, Cl, O₂CC₆H₅, O₂C(naphthenyl), OSO₂C₂H₅], (Bu₃SnO)₃PO and (Bu₄N) (Bu₃SnCl₂), in toluene solution was investigated by infrared spectroscopy over a 24-week period. It was found that only (Bu₃Sn)₂O reacted with the pyrethroids and that their order of reactivity was cypermethrin>deltamethrin>permethrin. An attempt was made to elucidate the reaction mechanism(s) occurring between (Bu₃Sn)₂O and the pyrethroids by studying mixtures of this tributyltin fungicide with simple model compounds, R¹CO₂R² where R¹=CH₃; R²=CH₂C₆H₅ and R¹=cyclo-C₃H₅ and R²=CH₂C₆H₅.     

Thermochemistry of Bu<Subscript>4</Subscript>NBr solutions in binary solvents containing formamide

The heats of solution of tetrabutylammonium bromide have been measured in mixtures of formamide (FA) with methanol (MeOH) and ethylene glycol (EG) at 313.15 K by calorimetric method. The standard enthalpies of solution in binary mixtures have been extrapolated to infinite dilution by Redlich–Rosenfeld–Meyer type equation using the literary data at 298.15 K and the present paper data at 313.15 K. The Debye–Hückel limiting law slope A _H required for calculation of the ∆_sol H ⁰ value has been obtained with application the new additive scheme of determination of the physic-chemical characteristics of binaries. The scheme is tested on the example of Bu₄NBr solutions in FA–MeOH mixture at 298.15 K. Its application yields the ∆_sol H ⁰ value very closed on the ones determined with the real (non-additive) characteristics of binaries. The standard enthalpies of solution extrapolated by Redlich–Rosenfeld–Meyer type equation are in a good agreement with the ones computed in terms of the Debye–Hückel theory in the second approximation. The heat capacities characteristics of Bu₄NBr have been calculated in H₂O–FA, MeOH–FA and EG–FA mixtures using the literary and present data. The sequence of solvents H₂O > FA > EG > MeOH located on their ability to solvophobic solvation found by us earlier for enthalpic characteristics is confirmed by the ∆C _p ⁰ values. The comparison of thermochemical characteristics of Bu₄NBr solutions in aqueous and non-aqueous mixtures containing FA has been carried out. The own structure of water remains in the region of small additions of formamide to co-solvents. It considerably differs the H₂O–FA mixture from the investigated non-aqueous systems.