MOLECULAR AGGREGATION IN LIPID-WATER DISPERSION PHASES

Polar lipids from aqueous liquid-crystalline phases which are the basis for the understanding of their functionality in technical applications. The structural characteristics of these phases and the relation between chemical structure of lipid molecules and their phase properties are reviewed. Special attention is given to new results on cubic phases, the most complex of lipid-water phases. The lipid bilayer is curved in space so that there are no selfintersections. There are two water-channel systems separated by the bilayer. The characteristic feature of the cubic phases is that the lipid bilayer has zero average curvature in all points.     

THE PREPARATION AND STABILITY OF COLLOIDAL METAL DISPERSIONS PREPARED BY A TWO-PHASE NON-AQUEOUS ROUTE

Stable suspensions of small metal Au, Ru, PI, Pd, Rh, Co and Nl particles dispersed in n-heptane and n-dodecane have been prepared using a novel two-phase system, Involving the formation of the particles In a methanolic phase and subsequent phase transfer of the panicles to the alkane medium. The dispersions consisted of small particles having diameters In the range of 8-30 nm (the gold sols were very polydlsperse having average diameters of ca.34 nm). The phase transfer of the particles and their subsequent colloid stability were effected by the presence of dissolved dispersant in the hydrocarbon phase (either Oloa 1200 or Hypermer LP 8). In the case of Oloa 1200, a widely-used polylsobutylene succinimide automotive engine dispersant, It Is proposed that the amlne groups adsorb strongly to the acidic surface o1 the particles, and the 70-carbon polyisobutylene chains extend Into the hydrocarbon medium sufficiently to maintain the separation of adjacent particles by steric and possibly also by electrical repulsion.     

DLVO AND NON-DLVO SURFACE FORCES AND INTERACTIONS IN COLLOIDAL DISPERSIONS

Some aspects of DLVO and non-DLVO forces in colloidal systems are over-viewed. The influence of long range interactions on some kinetic properties of dispersions, as Brownian diffusion, is discussed. It is shown, both theoretically and experimentally, that the electrostatic repulsion increases the collective diffusivity. The film stratification and oscillatory structure forces in colloidal suspensions are considered within the framework of an uniform approach The presence of small colloidal species (e. g. micelles or polymer molecules) may lead to several maxima and minima in the disjoining pressure isotherm. The particular case of interacting emulsion droplets is examined accounting for the interfacial deformability. The droplet deformation acts as a soft repulsion but affects also the remaining contributions to the interaction energy due to changes of the droplet shape. A general procedure for calculating the inter-droplet interaction energy, as well as the equilibrium film radius and thickness in a doublet of droplets, is suggested. The energy of interaction between charged colloidal particles, due to correlations of the density fluctuations in the electric double layer is also studied. It is found that this effect may lead to attraction greater than the van der Waals contribution, especially when multivale counter ions are present.     

THE INFLUENCE OF SMECTIC PHASES OF PERFLUORODECYL DECANE ON THE PHOTOREACTIONS OF PERFLUOROHEPTYL OCTYL KETONE. AN EXAMPLE OF MICROSCOPIC DISORDER IN HIGHLY ORDERED LAYERED PHASES*

The consequences of solvent order, imposed by the two smectic phases of 1,1,1,2,2,3,3,4, 4,5,5,6,6,7,7,8,8,9,9,10,10-heneicosylfluoroeicosane (F10H10, a “diblock” molecule) on the photochemistry of 1,1,1,2,2,3,3,4,4,5,5.6,6,7,7-pentadecylfluoro-8-hexadecanone (F7COH8) were investigated. Results from irradiations of F7COH8 in smectic F10H10 are compared to those obtained in hexane, perfluorohexane, and the isotropic phase of F10H10. They are complemented by ²H-NMR experiments on F10H10 solutions of F7COH8 deuterated at the methylene alpha to the carbonyl, and differential scanning calorimetry thermograms. More than 85% of the photoproducts are derived from carbonyl reduction and Norrish II processes. Based upon the ²H-NMR spectra and Norrish II photoproduct ratios, the microscopic environment experienced by the locus of reaction of F7COH8 in smectic F10H10 is not very restrictive towards the solute shape changes that must occur. This conclusion was not anticipated because the macroscopic order of the smectic phases of F10H10 is high.     

聚(苯乙烯-co-甲基丙烯酸)胶体晶体原位反转制备孔阵列研究

利用甲苯浸泡法,将聚(苯乙烯-co-甲基丙烯酸)(P(Sc-o-MAA))胶体晶体转变成孔阵列,利用扫描电镜和原子力显微镜详细研究了胶体球在向孔转变过程中结构的变化细节,同时利用表面元素分析法检测其反转前后元素含量的变化.结果表明,在选择性溶剂作用下,胶体球经历了溶胀—粘连—破裂—溶解—成孔—扩张等一系列变化,处于内核的聚苯乙烯被溶出胶体球后不仅填充到球与球之间的空隙中而且扩散到了溶剂中,而胶体球表面富集的聚甲基丙烯酸链段与溶出的聚苯乙烯混合物则主要对孔结构起固定和支撑作用,但长时间的甲苯浸泡最终会破坏孔的结构和阵列的完整性.     

COALESCENCE OF SECONDARY DISPERSIONS IN COMPOSITE PACKED BEDS

Oil water dispersions have been separated efficiently using composite beds made up of several materials. Selection of these materials was based on their wetting properties and fibre size. A bed composed of three layers: two fibre glass layers of different sizes followed by woven layer of polypropylene and stainless steel was found to give the best results.     

CROSS-FLOW MICROFILTRATION OF BKNTOMTE-IN-WATER DISPERSIONS: EFFECTS OF SUSPENSIONRHEOLOGY

Cross-How filtration of bentonite-in-water suspensions is studied experimentally in a small laboratory device. The Theological behaviour and the filtration resistance in batch filtration are independently established. Both transient and steady-state data indicate channel constriction by a dense cake layer. Quantitative estimates based on measured parameters show that steady-state conditions can be ensured by tangential flow of the dense pseudoplastic bentonite cake. Steady-state is possible when the shear stress at the moving boundary feed suspension/dense cake exceeds appr.l Pa (at lower values of the shear stress the cross-flow microfiltration channel gets plugged). The material characteristics of the dense cake, which determine cross-flow filtration behaviour, are the viscosity and the specific filtration resistance. Indirect estimates of these quantities from measured cross-flow filtration parameters are consistent with results from direct measurements. The data support the convective model of cross-flow microfiltration.     

RHEOLOGICAL BEHAVIOR OF EPOXY RESIN WATERBORNE DISPERSIONS

The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that theconcentrated dispersions were highly viscoelatic and pseudoplastic, which was attributed to the formation of a physicalnetwor among tbe waterborne particles via hydrogen bond. The dilutc dispersions were Newtonian fluids. The discreteclusters composed of small waterborne particles were found in diluted dispersions. With increasing solid content, thereexisted a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network, whichwas qualitatively evidenced by the TEM morphologies.     

PHOTOREDUCTION OF NAD TO NADH IN SEMICONDUCTOR DISPERSIONS

Abstract— Band gap illumination of TiO₂ (anatase) dispersions in weakly alkaline solutions of nicotinamide-adenine-dinucleotide (NAD⁺) leads in the presence of rhodium trisbipyridyl complex [Rh(bipy)³⁺₃], to continuous generation of biologically active cofactor NADH. Effects of pH, NAD⁺ and Rh(bipy)³⁺₃ concentration on the efficiency of this photoconversion process are investigated. The reaction proceeds already in aqueous solution in the absence of external electron donors but it is enhanced significantly in the presence of 10% methanol.     

ELECTRO-OPTICAL STUDY OF OXIDE DISPERSIONS AND THEIR STABILIT

Oxide/solution interface is with the clear origin of the surface charge, obtained through ionization of surface hydroxyl groups. The oxide particles produced by flame hydrolysis present fractal aggregates built from nearly spherical particles with constant diameter (AI₂O₃, SiO₂). In the process of acid hydrolysis particles with well defined form (spheres, rods, ellipsoids) and high monodispersity could be obtained (α-Fe₂O₃, α-β-FeOOH). Different types of oxides are investigated by the means of electric light scattering. An information on the electric surface properties of oxide/solution interface as well as in presence of various additives, particles dimensions and fractal structure is obtained. The process of slow coagulation in presence of bivalent electrolyte and surface active substance is studied electrooptically. The change of dynamic electric behaviour (induced dipole moment) in the processes of interaction is followed. Some considerations are made on the nonequillbium electric properties of the interface and the connection with suspension stability.     

氨力农在胶束溶液中的极谱特性

在pH值为4.1的Hac-NaAc缓冲溶液中,氨力农于-1.37 V处产生一灵敏的示波极谱峰,当有0.0010%Tween-60存在时,峰电流显著增大,在5.5×10-2～2.8×10-5 mol/L范围内,峰高与浓度呈良好的线性关系,检测下限为6.0×10-9 mol/L,相关系数r=0.9980.利用此峰测定了血清中的氨力农,加标回收率为97.5%～103.0%,测定结果的相对标准偏差RSD不大于5%.利用电毛细管曲线、换液实验以及循环伏安法对氨力农的机理进行了探讨.     

均匀球形α-Fe_2O_3胶体粒子的形成机理

在有关均匀胶体粒子的研究中,人们大多关注的是均匀胶体粒子的制备方法和实验条件的控制,其中包括溶液的组成,陈化温度和时间以及起决定作用的特殊阴离子.然而涉及其形成机理的分析很少,因为均匀胶体粒子的形成是个微观过程:成核、成长、相转变和微粒子的聚集等过程瞬息完成,难于捕捉到各个过程发生的具体时机.Sugimoto和Matijevic将含一定比例的FeSO_4,KOH和KNO_3溶液经85℃陈化制备均匀球状Fe_3O_4的实验中发现,陈化液中最初生成的Fe(OH)_2在硝酸根离子作用下经相转化生成Fe_3O_4微粒子,     

ADSORPTION OF COLLOIDAL MATERIALS ON POLYMER SURFACES

Polypropylene surfaces were rendered cationic by hydrophobic implantation and by grafting a quaternized polyvinyl pyridine onto a plasma treated surface. The polypropylene surface with the grafted polymer showed a strong adsorption of an anionic surfactant, corresponding to about ten monomolecular layers. High concentration of electrolyte caused a reduction of the adsorption at low concentrations of surfactant.     

若干有机分子的二阶非线性光学极化系数色散关系

在INDO/CI方法基础上, 用自己编制的计算二阶非线性极化系数β_(ijk)程序, 计算了苯胺、硝基苯、对硝基苯胺和4-硝基-4′-胺基二苯乙烯的β_(ijk), 并研究了其对外部激光场频率的依赖关系。结果表明, 分子内的电荷转移是产生非线性光学现象的根本原因, 而作为外因的激光场对二阶非线性光学系数的大小和方向也有直接的重要作用。当激光场频率与分子的共振频率接近时, 二阶非线性极化系数变得非常大, 在共振频率附近, β_(ijk)改变符号且Kleinman对称性被打破。     

PHOTOELECTROCHEMICAL OXIDATION OF OXALATE ION IN AQUEOUS DISPERSIONS OF ZINC OXIDE

The photooxidation of oxalate ions in aqueous dispersions of ZnO under UV-illumination has been investigated in order to determine the efficiency of oxalate ions as hole scavangers. The process has been studied by measuring the quantity of oxalate ions photooxidized at different experimental conditions. It is observed that the number of moles of oxalate photodecomposed increases with irradiation time and with the mass of semiconductor in suspension, attaining in this case a limiting value. Also, the amount of oxalate ions photooxidized increases with both initial oxalate concentration and light intensity. These results are discussed in terms of the different redox processes that take place at the semiconductor particle-electrolyte interface.     

胆红素有序分子膜的行为研究

研究了不同亚相表面胆红素(BR)单分子膜和LB膜的性质,讨论了胆红素分子在有序分子膜中的堆积密度、分子伸展和金属离子配位。在气-水界面,BR与金属离子的配位导致BR单分子截面积、崩溃压和可见紫外光谱的变化。原子力显微镜表明BR-Cu单分子膜的厚渡为1.23 nm。     

SYNTHESIS AND CHARACTERIZATION OF AN ORDERED LADDER POLYESTER

An ordered ladder polyester （LPE） was first synthesized through the ladder superstructure （LS） constructed by concerted interactions of hydroxyl- and aramide-based H-bonding and p-terphenyl （TP）-based π-stacking by dehydrochlorination condensation using phosgene （COCl2） as coupling agent. LPE was characterized by GPC, FTIR, NMR, XRD, DSC and AFM. Among them, a distinct image of regularly linear alignment corresponding to the ladder main chain of LPE was first revealed by high-resolution AFM.     

磺化聚苯乙烯胶体晶的红外光谱分析

单分散乳胶体系可以通过自组装形成有序的胶体晶结构 ,在窄波段光过滤器[1] 、生物医学传感器[2 ] 、智能化学传感器[3] 等领域具有重要的应用价值 .最近 ,人们以此有序结构作为模板 ,制备了有序孔材料[4～ 7] .另外 ,此有序结构在仿生学如模拟蛋白石等有序结构等方面也具有重要意义[8] .但是 ,一般的单分散体系如聚苯乙烯体系所形成的有序结构都属于硬性材料 ,缺乏对外场的响应特性 .此外 ,微球表面没有功能性基团 ,很难与其它物质兼容 ,这使得其作为模板合成其它复合材料的潜力大大降低 .本实验室通过对聚合物胶体晶进行改性 ,使其成为功…     

CONCERTED H-BONDING TEMPLATE SYNTHESIS OF AN ORDERED LADDER POLYSILSESQUIOXANE

A novel soluble regular ladder poly（benzoyl-3-aminopropyl） silsesquioxane （LPBAS） was facilely prepared under effective assistance of concerted H-bonding self-assembly of amido groups of side chains and silanol groups, respectively, of a new template monomer [1,3-bis（benzoyl-3-aminopropyl）-1,1,3,3-tetraethoxydisiloxane] （M）. The ordered ladder structure of LPBAS is manifested in： （1） the presence of two Bragg peaks representing the ladder width （d） and ladder thickness （t） in X-ray diffraction （XRD） pattern; （2） narrow base-line width （w = 6） of resonance absorption for -CH2SiO3/2 moiety in 29Si-NMR and （3） high glass transition temperature Tg = 1 12℃ in differential scanning calorimetry （DSC） analysis.