层状液晶凝胶对微泡沫的稳定作用

以非离子表面活性剂单硬脂酸甘油酯(GMS)制备出稳定的微泡沫. 采用偏光显微镜、冷冻断裂蚀刻透射电子显微镜(FF-TEM)、差示扫描量热仪(DSC)和流变仪对其表面活性剂溶液相态、泡沫体系的微观结构、相变行为和流变性进行研究以探索微泡沫的稳定机理. 实验结果表明, 表面活性剂分子吸附在气泡界面, 发生晶化形成有序、紧密排列的层状液晶凝胶相液膜, 该液膜具有较强的刚性, 能抵抗由Laplace附加压力驱使的气泡溶解和聚并行为. 微泡沫可稳定10个月, 无明显的相分离和气泡破裂现象. 其稳定作用机理是通过影响泡沫排液过程, 增强Gibbs-Marangoni效应, 从而提高了气泡液膜强度, 减缓了气相扩散速率.     

正、负离子表面活性剂混合体系溶致液晶生成的相行为

研究了烷基(C8,C12,C14)三甲基溴化铵、烷基(C12,C14)溴化吡啶与烷基(C8,C12)硫酸钠混合体系溶致液晶形成的条件与结构的变化.在高浓度的水溶液中,随着正、负离子表面活性剂摩尔比接近于1,液晶结构由六角相过渡为层状相.表面活性剂非极性链长改变,对相行为影响显著,短碳链的正、负离子表面活性剂混合体系,在等摩尔比时,体系为层状液晶或立方液晶为主,夹杂少许沉淀.随碳链增长,两类表面活性剂间的静电吸引效果表现为生成沉淀的摩尔比例范围变宽,沉淀量增多,共存的液晶相减少,甚至消失.若只改变正离子的极性头基,季胺盐比吡啶盐与烷基硫酸盐的作用要强,形成不溶物的混合摩尔比例范围更宽.     

小角X射线散射表征AOT/水层状溶致液晶的有序性

用小角X射线散射研究了AOT/水层状溶致液晶的有序性. 通过对散射曲线的解析, 讨论了表面活性剂浓度、温度和助表面活性剂等三个方面对溶致液晶层状相结构有序性的影响. 在一定的范围内, 提高温度, 改变表面活性剂浓度和加入少量助表面活性剂可使碳氢链排列由稀疏转变为密实, 层状相也相应地由“柔性双层”过渡到更加有序化的“平面双层”. 基于形状因子和体系内分子间作用力, 提出了层状相形成与有序化的机理, 同时采用分子模拟的方法展现了不同浓度下的液晶结构.     

阴离子表面活性剂为模板合成双重介孔结构二氧化硅

本文报道以阴离子表面活性剂十二烷基肌氨酸钠为模板,合成具有层状结构和蠕虫状介观结构的双重介孔二氧化硅颗粒．这些颗粒的尺度在300～50011111,氮气吸附表明其比表面为536m^2/g,孔体积为0．83cm^3／g,具有3nm和12nm的双重介孔分布．层状结构形成可归因于表面活性剂形成的层状液晶相模板,而无序蠕虫相是由表面活性剂柱状液晶相模板诱导形成的．层状液晶相的产生可归因于部分质子化的羧酸表面活性剂诱导的柱状相到层状相的转化．     

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.     

直链醇链长对层状液晶结构与稳定性的影响

作为助表面活性剂,直链醇在层状溶致液晶的制备中是非常重要的。本文以层状液晶的相行为和小角度X射线衍射测量,研究了直链醇链长对层状液晶结构与稳定的影响。     

液晶模板法制备Au纳米线

利用非离子表面活性剂C₁₂E₄的层状液晶作为模板,以氯金酸(HAuCl₄)水溶液作为体系的水相和反应物,并利用C₁₂E₄中EO基团的还原性制备了Au的纳米线.研究表明,反应物的浓度、液晶体系的组成和反应时间都将影响产物的形貌.在适当条件下,可以得到直径约为20nm,长度达到几微米的均匀金纳米线,并探讨了纳米线形成过程中层状液晶的模板作用.     

掺杂聚合物对溶致液晶结构的影响

利用聚合物大分子作构建组分,将其掺杂到不同类型表面活性剂构成的溶致液晶中,考察对液晶相结构的影响．利用小角X射线散射及偏光显微镜对聚合物掺杂前后液晶的结构进行表征,并讨论了聚合物与液晶模板间的相互作用．对阴离子型表面活性剂琥珀酸二异辛酯磺酸钠(AOT)／水液晶体系,聚合物的嵌入使层间距d增大;而对非离子表面活性剂十二烷基聚氧乙烯醚(C12EO4)／水体系,除小分子量的聚乙二醇PEG400外,其它聚合物嵌入使d减小,表明聚合物分子类型、大小及浓度对溶致液晶的结构参数甚至组装方式有不同的影响机制．     

层状溶致液晶中电沉积铂纳米线

以非离子表面活性剂四氧乙烯基正十二烷基醚与氯铂酸水溶液构建层状溶致液晶, 通过电沉积技术制备了金属铂纳米线. 分别采用偏光显微镜、小角X射线散射对液晶进行结构分析, 通过透射电镜和能量弥散X射线谱分析观测产物形貌并确定其组成. 结果表明, 相对于饱和甘汞电极, 沉积电势在0.05～0.20 V范围内, 金属铂沿表面活性剂双分子层膜生长, 反应前后液晶相的长程周期性结构无明显变化; 在0.10 V沉积电势下, 随反应时间从960 s延长至3840 s, 去除表面活性剂后沉积产物分别为层状纳米粒子、层状纳米线以及长度达十几微米且致密的纳米线. 讨论了层状液晶对沉积产物的结构导向作用.     

非水层状液晶的稳定性与相行为

水体系层状液晶已研究较久,非水层状液晶则是近十年来才得到发展。本文以层状液晶的相行为和~2H NMR测量,研究并比较了非水层状液晶十二烷基硫酸钠/正癸醇溶剂以甘油或甲酰胺为溶剂时体系的结构与稳定性。 表面活性剂十二烷基硫酸钠(BDH,简写SDS)经无水乙醇重结晶两次提纯。用铂环法测     

Phase behavior of a mixture of poly(isoprene)-poly(oxyethylene) diblock copolymer and poly(oxyethylene) surfactant in water

The phase behavior of a mixture of poly(isoprene)-poly(oxyethylene) diblock copolymer (PI-PEO or C250EO70) and poly(oxyethylene) surfactant (C12EO3, C12EO5, C12EO6, C12EO7, and C12EO9) in water was investigated by phase study, small-angle X-ray scattering, and dynamic light scattering (DLS). The copolymer is not soluble in surfactant micellar cubic (I1), hexagonal (H1), and lamellar (Lalpha) liquid crystals, whereas an isotropic copolymer fluid phase coexists with these liquid crystals. Although the PI-PEO is relatively lipophilic, it increases the cloud temperatures of C12EO3-9 aqueous solutions at a relatively high PI-PEO content in the mixture. Most probably, in the copolymer-rich region, PI-PEO and C12EOn form a spherical composite micelle in which surfactant molecules are located at the interface and the PI chains form an oil pool inside. In the C12EO5/ and C12EO6/PI-PEO systems, one kind of micelles is produced in the wide range of mixing fraction, although macroscopic phase separation was observed within a few days after the sample preparation. On the other hand, small surfactant micelles coexist with copolymer giant micelles in C12EO7/ and C12EO9/PI-PEO aqueous solutions in the surfactant-rich region. The micellar shape and size are calculated using simple geometrical relations and compared with DLS data. Consequently, a large PI-PEO molecule is not soluble in surfactant bilayers (Lalpha phase), infinitely long rod micelles (H1 phase), and spherical micelles (I1 phase or hydrophilic spherical micelles) as a result of the packing constraint of the large PI chain. However, the copolymer is soluble in surfactant rod micelles (C12EO5 and C12EO6) because a rod-sphere transition of the surfactant micelles takes place and the long PI chains are incorporated inside the large spherical micelles.     

Effect of added poly(oxyethylene)dodecyl ether on the phase and rheological behavior of wormlike micelles in aqueous SDS solutions

Upon the addition of a short EO chain nonionic surfactant, poly(oxyethylene) dodecyl ether (C12EOn), to dilute micellar solution of sodium dodecyl sulfate (SDS) above a particular concentration, a sharp increase in viscosity occurs and a highly viscoelastic micellar solution is formed. The oscillatory-shear rheological behavior of the viscoselastic solutions can be described by the Maxwell model at low shear frequency and combined Maxwell-Rouse model at high shear frequency. This property is typical of wormlike micelles entangled to form a transient network. It is found that when C12EO4 in the mixed system is replaced by C12EO3 the micellar growth occurs more effectively. However, with the further decrease in EO chain length, phase separation occurs before a viscoelastic solution is formed. As a result, the maximum zero-shear viscosity is observed at an appropriate mixing fraction of surfactant in the SDS-C12EO3 system. We also investigated the micellar growth in the mixed surfactant systems by means of small-angle X-ray scattering (SAXS). It was found from the SAXS data that the one-dimensional growth of micelles was obtained in all the SDS-C12EOn (n=0-4) aqueous solutions. In a short EO chain C12EOn system, the micelles grow faster at a low mixing fraction of nonionic surfactant.     

Solubilization and location of phenethylalcohol, benzaldehyde, and limonene in lamellar liquid crystal formed with block copolymer and water

Three fragrances, phenethylalcohol, benzaldehyde, and limonene (that differ in their polarity), were solubilized in lamellar liquid crystal using the polyethylene oxide-polypropylene oxide-polyethylene oxide, (EO27PO61EO27), P104 triblock copolymer, and water. The interlayer spacing of the lamellar liquid crystal were established using small angle X-ray scattering (SAXS). The SAXS data are used to calculate the interfacial area per polyethylene oxide (PEO) block and to determine the location of each fragrance in the association structure. The results show the presence of phenethylalcohol at the interface while part of benzaldehyde contributing to the interface and the other part being located inside the polar/apolar domains. The third fragrance, limonene, did not participate in the formation of the interface and is located inside the apolar domain.     

Vesicle formation with amphiphilic chitosan derivatives and a conventional cationic surfactant in mixed systems

In this study, molecular packing in lamellar liquid crystals in poly(oxyethylene) dodecyl ether(C(12)EO(n)) pure systems and the two surfactant mixtures of C(12)EO(8)/1-dodecanol(C(12)EO(0)), C(12)EO(8)/lipophilic sucrose laurate (L-595), hydrophilic sucrose laurate (L-1695)/C(12)EO(2) is investigated in terms of mean molecular area and partial molecular area (PMA). Lamellar liquid crystals formed in the C(12)EO(8)/C(12)EO(0) mixed system show higher melting temperatures than those in the C(12)EO(n) pure systems, even though the average number of EO units in the mixed surfactant system is the same as in the pure system. We compared the mean molecular area at the interface between hydrophilic and lipophilic moieties in the lamellar liquid crystals in each system. In the mixed system, the molecules are packed more tightly than in the pure system. Among the C(12)EO(n) and sucrose laurate mixtures, the L-1695/C(12)EO(2) mixed system showed a smaller mean molecular area per lipophilic chain than the C(12)EO(8)/L-595 mixed system. We investigated the effect of mixing two surfactants with different head group geometry on molecular packing by comparing the PMA of each surfactant.     

Phase polymorphism by mixing of poly(oxyethylene)-poly(dimethylsiloxane) copolymer and nonionic surfactant in water

The phase behavior of the water/poly(oxyethylene)-poly(dimethylsiloxane) copolymer (Si25C3EO51.6)/pentaoxyethylene dodecyl ether (C12EO5) ternary system has been studied. Both the silicone copolymer and the surfactant have equal volumes of hydrophilic and lipophilic parts; i.e., these are balanced amphiphiles. Although only a lamellar phase is observed in water-Si25C3EO51.6 and water-C12EO5 binary systems, a variety of liquid crystalline phases, including normal micellar cubic (I1), hexagonal (H1), bicontinuous cubic (V1), lamellar (L(alpha)), reverse bicontinuous cubic (V2), and reverse hexagonal (H2), are observed in the copolymer-rich region of the ternary phase diagram. The small C12EO5 molecules dissolve at the hydrophobic interface in the thick bilayer of the Si25C3EO51.6 L(alpha) phase occupying a large area of the total interface of the aggregates and modulate the curvature of the aggregates. Hence a variety of self-assembled structures are observed. In contrast, Si25C3EO51.6 is not dissolved in the thin bilayer of the C12EO5 lamellar phase (L'(alpha)). Hence, the C12EO5 L'(alpha) phase coexists with copolymer-rich L(alpha) and H2 phases. Consequently, small surfactant molecules are dissolved in a large silicone copolymer aggregate to induce a change in layer curvature, but a large copolymer molecule is hard to incorporate with surfactant aggregates.     

Poly(vinyl alcohol)-Amino Acid Hydrogels Fabricated into Tissue Engineering Scaffolds by Colloidal Gas Aphron Technology

A new class of hydrogels made from poly(vinyl alcohol) (PVA) and amino acid was formed into porous tissue engineering scaffolds by the colloidal gas aphron (CGA) method. CGA microfoams are formed using high speed stirring to generate uniform, micrometer scale bubbles. CGAs offer several advantages over conventional scaffold fabrication techniques including room temperature processing, aqueous conditions and utilization of air bubbles to create uniform pores. This technique eliminates the need for toxic solvents and salt templates. In addition, the novel poly(vinyl alcohol) hydrogels are inherently strong, eliminating the need for crosslinkers.     

Stabilization of nonaqueous foam with lamellar liquid crystal particles in diglycerol monolaurate/olive oil system

Nonaqueous foams stabilized by lamellar liquid crystal (L alpha) dispersion in diglycerol monolaurate (designated as C12G2)/olive oil systems are presented. Foamability and foam stability depending on composition and the effects of added water on the nonaqueous foaming behavior were systematically studied. It was found that the foamability increases with increasing C12G2 concentration from 1 to 3 wt% and then decreases with further increasing concentration, but the foam stability increases continuously with concentration. Depending on compositions, foams are stable for a few minutes to several hours. Foams produced by 10 wt% C12G2/olive oil system are stable for more than 6 h. In the study of effects of added water on the foaming properties of 5 wt% C12G2/olive oil system, it was found that the foamability and foam stability of 5 wt% C12G2/olive oil decreases upon addition of 1 wt% water, but with further increasing water, both the foamability and foam stability increase. Foams with 10% water added system are stable for approximately 4 h. Phase behavior study of the C12G2 in olive oil has shown the dispersion of L alpha particles in the dilute regions at 25 degrees C. Thus, stable foams in the C12G2/olive oil system can be attributed to L alpha particle, which adsorb at the gas-liquid interface as confirmed by surface tension measurements and optical microscopy. Laser diffraction particle size analyzer has shown that the average particle diameter decreases with increasing the C12G2 concentration and, hence, the foams are more stable at higher surfactant concentration. Judging from foaming test, optical micrographs, and particle size, it can be concluded that stable nonaqueous foams in the studied systems are mainly caused by the dispersion of L alpha particles and depending on the particle size the foam stability largely differs.     

Igepal CO系列表面活性剂溶致液晶的结构特性

对壬基酚聚氧乙烯醚（IgepalCO）系列表面活性剂,生成何种溶致液晶与其EO基团数n有关,而在何浓度范围内生成溶致液晶则与生成溶致液晶的最低水含量及最大水增溶量有关．EO基团数n小于10时,生成层状液晶,n大于10时则生成六角状液晶,层状液晶两亲双层内,水与表面活性剂的最低摩尔比rmin和最高摩尔比rmax随EO基团数n增加分别是非线型增加与线型增加,在IgepalCO520（n＝5）中加入IgepalCO710（n＝10．5）,对层状液晶的生成无显著影响,在IgepalCO710中加入IgepalCO520,则对六角状液晶的生成产生显著影响,出现了六角状液晶向层状液晶的转变。     

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.