单烷基乙二胺稀水溶液头基相互作用自组装形成 双分子膜

提出普通表面活性剂(单链两亲分子)亲水头基相互作用诱导疏水尾链平行聚集形成双分子膜的新机制。设计和合成了系列单烷基取代乙二胺C~nH~2~n~+~1NHC~2H~4NH~2(n=8,12,14,16,18)。通过电镜形态,分散液凝胶/液晶相变和对应铸膜的二维双层结构,表明单链两亲分子头基相互作用和脂链引入刚性片断一样,两者形成的双分子膜具有类似的结构和性能;展示了各体系取代乙二胺双层结构和性能的密切联系。指出了广泛认同的单链两亲分子形成双分子膜必须引入刚性片断的单一成膜机制的片面性,为组装新一类功能头基表面活性剂双分子膜独辟蹊径。     

Gemini表面活性剂分子结构对其水溶液中聚集行为的影响

Gemini表面活性剂是通过联接基团将两个具有亲水亲油性质的两亲结构单元在其亲水头基上或靠近亲水头基处以共价键方式连接而成的一类表面活性剂。这类表面活性剂由于联接基团的引入具有比传统单链表面活性剂更高的表面活性,同时分子结构中更多的可调控因素使其在水溶液中表现出更为丰富的自聚集行为,而且分子不同部位结构的改变对分子内或分子间相互作用产生不同的影响,可实现通过分子结构的设计有效调控其自聚集能力和聚集体结构。本综述将从联接基团、烷基链、亲水头基、反离子和其它功能性基团这五个方面概述近些年Gemini表面活性剂水溶液中聚集行为方面的研究进展,总结人们对Gemini表面活性剂分子间相互作用规律的认识,期望对于进一步发展这类高效的表面活性剂体系提供有益的帮助。     

10-十一烯酸衍生物混合体系有序溶液与聚集体研究

对三甲基－[2-(10-十一烯酰氧乙基）]碘化铵CH2＝CH（CH2）8COOCH2CH2N（CH3）3I和N，N－[2-(10-十一烯酰甲基牛磺酸钠）]CH2＝CH（CH2）8CON（CH3）CH2CH2SO3Na的表面及聚集行为进行了研究。混合体系溶解度良好，在40cmc时仍为稳定胶团溶液。结合正规溶液理论计算了混合体系表面吸附层、胶团的组成及分子间作用参数。基于两亲分子几何结构及分子间相互作用原理对上述现象进行了合理解释，发现了少量长链脂肪醇促使正负离子表面活性剂混合胶团转化为囊泡的新现象。     

疏水相互作用引起Gemini表面活性剂柔性联接链的弯曲

为了理解gemini表面活性剂柔性烷基联接链在自组织过程中的特殊作用,我们合成了三种gemini表面活性剂烷基-a,w-二（二-十二烷基甲基溴化铵）（记为2C12-s-2C12×2Br (s=3, 6, 8)）。2C12-s-2C12×2Br在水表面构成铺展膜后,由于每个分子带有4根烷烃链,它们形成了稠密的烷烃尾链层。增强的烷烃尾链与联接链间的疏水相互作用促使联接链弯曲朝向空气一端,可发生弯曲的联接链长度要小于吸附在水溶液表面上的gemini表面活性剂C12-s-C12×2Br,后者每个分子只有2根烷烃链。由此可见,增强的烷烃尾链与联接链间的疏水相互作用可以有效地促进联接链的弯曲。     

含酰胺结构的巯基自组装膜的设计与结构表征

提出了一种简便通用的合成巯基化合物的途径，以分子中的羧基CO2H为起始基团，与2-流基乙胺的氨基选择性缩合；合成了一系列具有RC（O）NHCH2CH2SH（R分别为偶氯苯衍生物，双炔衍生物及直链烷基）结构的化合物，并用接触角测量，电化学和掠角反射红外光谱（GIR-IR）等手段对这些化合物在金表面形成的自组装单分子膜进行了表征。发现4-（N－（2‘-巯基已基））酰胺偶氮苯的自组装膜表现出良好的电活性，电化学测定表面浓度为4．21×10(－10)mol·cm(-2)．当R为烷基链时，随烷基链的增长，膜的致密度与有序度增加GIR-IR证明在自组装腹中CH3（CH2）6C（O）NHCH2CH2SH的C＝O和N－H键与Au表面平行，分子轴线与Au表面近似垂直．     

含Gemini表面活性剂结构单元的新型两亲聚电解质的合成及聚集行为

分别将Gemini型单体1,3-双(二甲基十四烷基溴化铵)-2-丙烯酰氧基丙烷(14G)或1,3-双(二甲基十六烷基溴化铵)-2-丙烯酰氧基丙烷(16G)与丙烯酰氧乙基三甲基氯化铵(DAC, D)共聚合反应, 合成了新型含Gemini表面活性剂结构单元的两亲性阳离子聚电解质(D14G和D16G). 采用稳态荧光、电导、动态光散射及透射电镜等手段研究了这些聚电解质在水溶液中的聚集行为. 结果表明, 临界聚集浓度(CAC)随着Gemini型表面活性剂单元含量的增加而减小, 同时随着Gemini型表面活性剂单元中疏水碳链长度的增加而降低. 这些聚电解质在水溶液中同时存在分子内和分子间两种类型的聚集体, 而且碳链越长, 形成分子内聚集体的倾向越强. 随着Gemini表面活性剂单元含量的增加, D14G溶液中聚集体的流体动力学半径(Rh)也有所增大, 而D16G溶液中的聚集体的流体动力学半径(Rh) 却略有减小.     

两亲聚合物表面的反相气相色谱分析

采用反相气相色谱探针技术研究了苯乙烯－氧乙烯－苯乙烯三嵌段两亲聚合物的表面物理化学性质。包括表面吸附热力学函数,表面能的色散分量以及表面分子链与探针的分子间相互作用,。探讨了共聚物中亲油性链段聚苯乙烯（PS）和亲水性链段聚氧乙烯（PEO）的组成比例与其表面性质的关系。结果表明共聚物表面组成中随PEO含量的增加,其表面能增大,表面分子链与探针分子的相互作用增强,表面吸附能力也增强。     

合成双分子膜的研究（Ⅱ）：HBBTAB的合成及其在水溶液中的自组织行为

1977年Kunitake等首次报道了双十二烷基二甲基溴化铵在水溶液中自组织成类似于卵磷脂双层结构的囊泡,泡壁即为双分子膜。该发现表明可以用人工合成方法建造仿生组织,开辟了合成双分子膜研究的新领域。单链两亲性成膜物质,一般由亲水基团、间链、刚性生色基和尾链4部分组成。本文报道4-(4′-十六烷氧基-4-联苯氧基)丁基三甲基溴化铵     

4-(5-癸氧基-1-萘氧基)丁基三甲基溴化铵的自组织作用

生物膜的基质是脂类双分子膜。脂类分子,特别是磷脂,在稀溶液中自组织成的双分子膜,是构成生物膜的基本骨架结构。就分子结构而言,磷脂是具有两个烷基链的双亲性分子,而普通表面活性剂则是只有单烷基链的双亲性分     

不同添加物对表面活性剂溶液预胶束形成的影响

关于表面活性剂溶液中预胶束的形成问题已有不少报道［’－‘］．预胶束是表面活性剂溶液在浓度很稀时（远小于其临界胶束浓度（CMC》、表面活性分子所形成的一种集合体·由于一般的物理化学方法对其难于捡出，因此常被研究者忽略．文献间曾指出：预胶束形成的驱动力与胶束一样，也是疏水作用所致．因此表面活性分子的链长、头部极性、溶剂性质以及添加物的引入等因素必然会影响预胶束的形成．本工作是对添加物的引入问题所作的初步研究·。作中所研究的阴离子表面活性剂有十二烷基硫酸钠（sss）·＋”烷基；Iv酸钠（5％）和十六烷基硫酸…     

Weak interactions at the photoexcited states of partially oriented aromatic chromophores in man-made bilayer membranes

Monoalkyl and dialkyl quarternary ammonium salt-type cationic surfactants containing a phenoxy group as aromatic chromophores at different positions of alkyl chains were synthesized. Monoalkyl-type surfactants formed micelles in aqueous solutions. The bilayer structure similar to that found in phospholipid liposomes was obtained in the aqueous dispersions of dialkyl-type surfactants. The phenoxy groups were partially oriented and aligned in these molecular assemblies. The interactions of aligned phenoxy groups in micelles or bilayers resulted in luminescence with lower energy than that of the monomer fluorescence or in a radiationless deactivation of excited states. Such interactions could be effectively prevented in bilayer structures composed of surfactant molecules containing a “spacer chain” between aligned chromophores. Evidence was obtained supporting energy migrations between aligned chromophores that were separated by a dodecyl chain in the bilayer structure.     

Structure of nonionic surfactant micelles in the ionic liquid ethylammonium nitrate

The structure of micelles formed by nonionic polyoxyethylene alkyl ether nonionic surfactants, C n E m , in the room-temperature ionic liquid, ethylammonium nitrate (EAN), has been determined by small-angle neutron scattering (SANS) as a function of alkyl and ethoxy chain length, concentration, and temperature. Micelles are found to form for all alkyl chains from dodecyl through to octadecyl. Dodecyl-chained surfactants have high critical micelle concentrations, around 1 wt%, and form weakly structured micelles. Surfactants with longer alkyl chains readily form micelles in EAN. The observed micelle structure changes systematically with alkyl and ethoxy chain length, in parallel with observations in aqueous solutions. Decreasing ethoxy chain length at constant alkyl chain length leads to a sphere to rod transition. These micelles also grow into rods with increasing temperature as their cloud point is approached in EAN.     

Self-assembly of different single-chain bolaphospholipids and their miscibility with phospholipids or classical amphiphiles

A variety of bolalipids with a single long alkyl chain and two identical headgroups self-assemble in aqueous solutions into helical entangled nanofibers leading to the formation of a hydrogel. An increase in temperature usually leads to the break-up of the fiber structure into micellar aggregates. In this paper the question is addressed whether bolalipids of different lengths or different headgroup structures can form mixed fibers. Also, the stability of the fiber aggregation of bolalipids in mixtures with phospholipids forming lamellar bilayers is discussed. Here, the question whether single-chain bolalipids can be incorporated into phospholipid bilayers to stabilize bilayer membranes is important, as possibly lipid vesicles used for drug delivery can be improved. Finally, the stability of the fiber aggregate against solubilisation by common surfactants was studied. The paper addresses the question which type of aggregate structure dominates the self-assembly of bipolar and monopolar amphiphiles in aqueous suspension.     

单链2,7-取代萘刚性生色基双亲化合物的合成及其在稀溶液中的自组织

合成了系列单链含2,7-取代萘刚性生色基的双亲化合物C_nNaph(2,7)C₆N⁺(n=4,7,10,12,16),分别用透射电镜、¹HNMR和DSC观测了该系列双亲物在稀溶液中的聚集形态,研究了聚集体内的分子运动和凝胶态到液晶态的相变.结果表明,当尾链n≥7时,该系列化合物在稀溶液中自组织成双分子层排列的囊泡,当n=4时聚集体无确定形态.     

Effect of polymer characteristics on structure of polymer-liposome complexes

In the current study, we examined the effect of polymer characteristics on the structure of complexes formed between poly(methacrylic acid-co-n-alkyl methacrylate) and with phosphatidylcholine/cholesterol liposomes. We varied the polymer concentration in the vesicles, the preparation concentration of lipid and polymer components during preparation, the molecular weight of the polymer chain, the molecular weight of the polymer's hydrophobic side groups and their mole fraction. The vesicle behavior indicated polymer-free bilayers and bilayers complexed with polymer coexisted at low polymer concentrations. As the polymer concentration exceeds a critical level, however, the system became homogeneous, indicating bilayer uniformity of the bilayer. As the polymer content was raised, the vesicle size and fluidity increased, and the transition temperature decreased. We found that the vesicle size mostly affects the membrane fluidity. We also found that the thermal properties (transition temperature and the magnitude of heat capacity of the peak, DeltaCp) are governed by the effects of the polymer on the structure of bilayer. The length of the alkyl chain of the polymer is shown to significantly affect the structure of polymer-liposome complexes, as did the chain molecular weight and mole concentration of hydrophobic group in the polymer.     

Spectral characterization of self-assemblies of aldopyranoside amphiphilic gelators: what is the essential structural difference between simple amphiphiles and bolaamphiphiles?

An aldopyranoside-based gelators (dodecanoyl-p-aminophenyl-beta-D-aldopyranoside)s and [1,12-dodecanedicarboxylic-bis(p-aminophenyl-beta-D-aldopyranoside)]s 1-4 were synthesized, and their gelation ability was evaluated in organic solvents and water. Simple aldopyranoside amphiphiles 1 and 2 were found to gelate organic solvents as well as water in the presence of a small amount of alcoholic solvents. More interestingly, not only extremely dilute aqueous solutions (0.05 wt%) of the bolaamphiphiles 3 and 4, but solutions of 3 and 4 in several organic solvents could be gelatinized. These results indicate that 1-4 can act as versatile amphiphilic gelators. We characterized the superstructures of the aqueous gels and organogels prepared from 1-4 using SEM, TEM, NMR and IR spectroscopy, and XRD. The aqueous gels 1 and 2 formed a three-dimensional network of puckered fibrils diameters in the range 20-200 nm, whereas the aqueous gels 3 and 4 produced filmlike lamellar structures with 50-100 nm thickness at extremely low concentrations (0.05 wt%). Powder XRD experiments indicate that the aqueous gels 1 and 2 maintain an interdigitated bilayer structure with a 2.90 nm period with the alkyl chain tilted, while the organogels 1 and 2 take a loosely interdigitated bilayer structure with a 3.48 nm period. On the other hand, the aqueous- and the organogels 3 and 4 have 3.58 nm spacing, which corresponds to a monolayered structure. The XRD, 1H NMR and FT-IR results suggest that 1-4 are stabilized by a combination of the hydrogen-bonding, pi-pi interactions and hydrophobic forces.     

Aromatic molecules in restricted geometries: pyrene excimer formation in an anchored bilayer

The galleries of an anionic clay, Mg-Al Layered Double Hydroxide (Mg-Al LDH) have been functionalized by intercalating the anionic surfactant do-decyl sulfate. Within the galleries, the alkyl chains of the surfactant adopt a bilayer structure with the sulfate headgroup anchored to the inorganic sheet. Pyrene molecules have been solubilized in the anchored bilayer by partitioning from polar solvents. The presence of pyrene molecules induces conformational disorder in the alkyl chains of the bilayer and more importantly inhibits the rotational disordering motion of the sulfate headgroup. Pyrene fluorescence indicates formation of excimers whose intensity increases with concentration of solubilized pyrene indicating that they are mobile. Pyrene solubilized in the anchored bilayer exhibits unusual phenomena; on evacuation the excimer band disappear but reappears on releasing vacuum. It is shown that this behavior arises due to the loss of water of hydration of the headgroup on evacuation and as a consequence the pyrene moves into the less polar interior of the bilayer where it is immobile and can no longer diffuse and form excimers. The motion of pyrene into the interior of the bilayer creates free space near the surfactant chain termini, which manifests in the disappearance of the methyl-rocking mode of the ordered (-tt) end-chain conformer in the Raman spectra.     

Solubilization of dodac small unilamellar vesicles by sucrose esters: A fluorescence study

A fluorescence method was employed to study the solubilizing interactions of several sucrose esters with Dioctadecyldimethylammonium chloride small unilamellar vesicles. In this paper we studied four different alkyl esters of sucrose, saturation and solubilization concentrations (C_sat and C_sol), the ester–DODAC molar ratio (R_e) and bilayer/aqueous partition coefficients (K) were measured by monitoring changes in laurdan generalized polarization values. A new critical surfactant concentration at lower values than saturation concentration was observed. All critical concentrations showed linear dependence with DODAC concentration. The decrease in the length of surfactant alkyl chain (upper cmc) led to an increase in its ability to saturate and solubilize vesicles and to a decrease in its bilayer affinity. Consequently the shorter alkyl chain (lauryl sucrose ester), the higher ability to saturate and solubilize the vesicles, whereas the longer chain (stearyl sucrose ester), exhibited the highest degree of partitioning into the vesicles.     

Construction of higher-ordered monolayer membranes derived from archaeal membrane lipid-inspired cyclic lipids with longer alkyl chains

A series of artificial cyclic lipids that mimic archaeal membrane ones has been synthesized. The structural features of these molecules include a longer cyclic framework, in which the alkyl chain length ranges from 24 to 32 in carbon number, which is longer than our first analogous molecule with 20-carbon long alkyl chains [K. Miyawaki, T. Takagi, M. Shibakami, Synlett 8 (2002) 1326]. Microscopic observation reveals that these molecules have a self-assembling ability: hydration of the lipids yields multilamellar vesicles in aqueous solution and monolayer sheets on solid supports. High-sensitivity differential scanning calorimetry (24- and 28-carbon alkyl chain lipids) indicates that (i) the alkyl chain length affects their phase behavior and (ii) the enthalpies of endothermic peaks accompanied by phase transition were considerably lower than those of their monomeric phospholipid analogs. Fluorescence polarization measurements suggest that the membranes made from the 24-carbon alkyl chain lipid have a higher polarization factor than membranes composed of DMPC and DMPC plus cholesterol. These findings imply that the cyclic lipids containing 24- and 28-carbon alkyl chain construct well-organized monolayer membranes and, in particular, that the molecular order of the 24-carbon alkyl chain lipid is higher than that of bilayer membranes in the liquid-ordered phase.     

Structure and composition of cationic-nonionic surfactant mixed adsorbed layers on mica

The composition and morphology of mixed adsorbed layers comprising one of several poly(oxyethylene) alkyl ether nonionic surfactants, C(i)E(j), and two cationic surfactants-dodecyltrimethylammonium bromide (DTAB) and tetradecyltriethylammonium bromide (TTeAB)-at the mica/solution interface have been studied using depletion adsorption and atomic force microscopy. The nonionic surfactants do not themselves adsorb onto mica, but can coadsorb with a cationic surfactant. The extent of their hydrophobic association with the adsorbed cationic surfactant depends on alkyl chain length, while the adsorbed layer morphologies are sensitive to the number of ethoxy groups. Nonionic surfactants with headgroups containing less than eight ethylene oxide units decrease the adsorbed aggregate curvature, gradually transforming globular TTeAB or cylindrical DTAB adsorbed aggregates into a rod, mesh, or bilayer structure. Those with larger headgroups favor globular aggregates. The mechanism by which the nonionic surfactant modifies the adsorbed morphology is the formation of defects in the form of cylinder end-caps or branch-points, leading to adsorbed layer compositions that differ from ideal mixing predictions. All mixed adsorbed films become saturated with the nonionic component when the capacity of the aqueous side of the adsorbed layer is reached.