Effect of inorganic salts on the micellar behaviour of ethylene oxide-propylene oxide block copolymers in aqueous solution

The aggregation behaviour of two ethylene oxide-propylene oxide block copolymers (PEO-PPO-PEO) in aqueous solution has been investigated in the presence of added salts (KCNS, KI, KBr, KCl and KF) by viscosity, cloud point, light scattering, pulse gradient spin echo NMR, and solubilization measurements. The salts have a strong effect on the cloud points of the pluronics. Both P-85 and L-64 form micelles which increase in size and change into elongated shapes when the cloud point is approached. The changes of size and shape of the micelles, revealed by the intrinsic viscosity and rheological properties, seem to occur at the same temperature relative to the cloud point, independent of the nature of the salt. The onset of micelle formation is also shifted in the same direction as the cloud point by the salts, but by a much smaller amount.     

Surface activity and micellar properties of anionic gemini surfactants and their analogues

The properties of didodecyldiphenylether disulfonate gemini-type surfactants have been studied and compared to mono-alkylated and monosulfonated analogous surfactants. Dynamic and equilibrium surface tension measurements indicate that the gemini surfactants have a higher surface activity compared to that of the monoalkyl analogues. The gemini-type surfactants have much larger surface area per molecule, opposite effect of carbon number on CMC and considerable swelling of the micelles upon increasing surfactant concentration. Determination of aggregation numbers by fluorescence measurements reveals that the longer chain gemini surfactants form micelles having less than 10 molecules per micelle.     

Process of destruction of large unilamellar vesicles by a nonionic detergent,octylglucoside, and size growth factor in vesicle formation from phospholipid–detergent mixed micelles

The process of vesicle solubilization and size growth by detergents, especially by octylglucoside, was examined in detail in order to elucidate the phenomena observed in the vesicle-to-micelle transition and to clarify the size-determining factor of vesicles prepared by removing detergent from phospholipid–detergent mixed micelles. In the vesicle solubilization process, when the detergent concentration in the vesicle membrane reached a critical value, the collapse of large unilamellar vesicles (LUV) into small unilamellar vesicles (SUV) was observed. This newly appeared SUV were named SUV*. The SUV* could be produced by adding an appropriate amount of detergent to the SUV prepared by an ultrasonication method so as to increase the concentration to a little over the critical value, such as, in the case of adding octylglucoside, a molar ratio of 1.0–1.1 to phospholipid in the membrane phase. The SUV* containing octylglucoside were fusible and grow time-dependently, but those containing sodium cholate were not fusible. On the basis of the SUV* data, the following problems were solved: the variety of the size of the vesicles prepared by detergent removal from mixed micelles composed of a phospholipid and different detergents, or by different removal methods; the complex appearance of turbidity or vesicle size observed in vesicle destruction and formation; the conflict between LUV and SUV in the partition behavior of detergent and the size change with addition of detergent.     

Spectrophotometric Flow Injection Analysis of Sulfite and Formaldehyde In Aqueous Micellar Medium Using 5,5′-Dithiobis(2-Nitrobenzoic Acid)

Abstract

Aqueous sulfite and formaldehyde were quantitated in the nanomole range using the reaction of 5,5′-dithiobis(2-nitrobenzoic acid), DTNB, with sulfite. Cationic micelles were used and found to greatly increase the sensitivity, bathochromically shifting the absorption spectra as well as lowering the pK of the reaction. the method was adapted to flow injection analysis, allowing more than 100 samples to be analyzed per hour with a relative standard deviation of less than 1.5% in all cases studied. the method is simple, fast and more sensitive than any available methods. the great flexibility of the choice of pH, surfactant concentration and buffer concentration contributes much to the high precision that could be achieved.     

The size of sodium dodecyl sulfate micelles in the presence ofn-alcohols as determined by fluorescence quenching measurements

The steady-state fluorescence quenching technique was used to investigate the effect of the presence of a series of alcohol homologues of mid-sized straight chain on the size of mixed micelles of sodium dodecyl sulfate (SDS). We used pyrene at concentration of ca. 10^–6M, where only its monomer exhibits any fluorescence, as fluorescent probe, and cetylpiridinium chloride at concentrations in the range (1–9)×10^–5 M as quencher. This technique allows one to determine the micellar aggregation number. The number of alcohol molecules per micelle was calculated from reported values for the micelle-water partition coefficient. On the assumption of spherical micelles, their hydrophobic radii was then calculated. The hypothesis that micelle size is determined by the available surface area per charged headgroup is discussed in the light of the results obtained.     

两亲聚合物胶束自组装包药研究进展

两亲聚合物胶束具有突出的理化性能和独特功能,能够在溶液中自组形成具有核壳结构的聚合物胶束,同时实现药物的负载。自组装包药技术能够缓解我国药物辅料缺乏的现状,符合目前药物辅料发展的新趋势。通过自组装形成的聚合物胶束在药物控释、药物靶向载体、药物制剂开发、新型药物辅料等方面具有广阔的应用前景。本文综述了两亲聚合物胶束自组装包载药物的原理以及方法,重点介绍了三类两亲聚合物在自组装包药方面的最新研究成果和发展趋势。本文还对载药胶束在药物释放方面的应用进行了概述。     

Use of cholate derivatives with submicellar concentration for controlling selectivity of proteins in hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) of proteins using a phenyl column has been performed in the presence of various surfactants with micellar and submicellar concentration ranges. Most surfactants were effective for a decrease in the retention of proteins in both concentration ranges. However, the use of anionic cholate derivatives increased the retention of the proteins with high isoelectric point, such as lysozyme, cytochrome c, and trypsin, in submicellar concentration range, and then decreased it above the critical micellar concentration, while the retention of the other proteins was monotonously decreased. The results of frontal chromatographic analysis of the surfactant and capillary electrophoresis for the proteins in the presence of surfactant show that in the submicellar concentration range, cholate derivatives allowed to be adsorbed on the stationary phase, while they exhibited no interactions with the proteins. Thus, it appeared that the increase in the retention of basic proteins was due to the electrostatic attraction between the proteins and cholate-modified stationary phase. We have applied the unique property of cholate to the separation of ovalbumin and lysozyme in egg white sample using hydrophobic chromatography.     

meso-四(4-磺基苯基)卟啉(TPPS)在水及胶束体系中的二聚行为研究

研究了meso-四（4-磺基苯基）卟啉（TPPS）在胶束（TritonX－100）、KCl水溶液中的电子吸收光谱变化,计算了TPPS的二聚常数KD,用分光光度法研究了TPPS在KCI水溶液中的二聚反应动力学,提出了与实验结果相吻合的二聚机理．根据温度对二聚平衡的影响,计算了二聚平衡的乙和     

Preparation of micelles with azobenzene at their coronas or cores from ‘nonamphiphilic’ diblock copolymers

Micelles with azobenzene at the coronas or the cores were prepared by the micellization of nonamphiphilic diblock copolymers through hydrogen bond cross-linking. We used 4-(phenylazophenoxymethyl)styrene (AS) as the azobenzene. A poly(vinylphenol)-block-poly(AS-co-styrene) diblock copolymer (PVPh-b-P(AS-co-St)) was prepared by combination of the nitroxide-mediated living radical polymerization and the hydrolysis. The copolymer contained ca. 1 mol% of the azobenzene units in the P(AS-co-St) blocks on the basis of ¹H NMR analysis. The PVPh-b-P(AS-co-St) copolymer showed no micellization in 1,4-dioxane, the nonselective solvent. Dynamic light scattering demonstrated that the copolymer formed micelles in the presence of 1,4-butanediamine (BDA) in this solvent. ¹H NMR analysis revealed that the azobenzene moieties were located at the coronas of the micelles, because the signals of the aromatic protons originating from the azobenzene had no changes in the shape and the intensity by the micellization. UV analysis supported the presence of the azobenzene at the micellar coronas. The size of the PVPh-b-P(AS-co-St) micelles was independent of the copolymer concentration. On the other hand, the aggregation number of the micelles was dependent not only on the copolymer concentration but also on the kind of the diamine. A poly(AS-co-vinylphenol)-block-polystyrene diblock copolymer (P(AS-co-VPh)-b-PSt) formed the micelles with the azobenzene at the cores of the micelles by BDA. UV analysis demonstrated that the azobenzene at the micellar cores still had the potential to function as photorefractive switching.     

Interfacially Cross‐Linked Reverse Micelles as Soluble Support for Palladium Nanoparticle Catalysts

Reverse micelles (RM) were formed in heptane/CHCl₃ with a surfactant carrying the triallylammonium (=triprop‐2‐en‐1‐ylammonium) head group (Scheme). Photo‐cross‐linking with dithiothreitol (=rel‐(2R,3R)‐1,4‐dimercaptobutane‐2,3‐diol; DTT) captured the RMs and afforded organic, soluble nanoparticles in a one‐step reaction. Similar to dendrimers, the cross‐linked reverse micelles could encapsulate palladium nanoparticles within their hydrophilic cores and protect them in catalytic reactions. Good to excellent yields were obtained in the Heck coupling of a range of alkyl acrylates (=alkyl prop‐2‐enoates) and iodobenzenes (Tables 1 and 2). The catalytic activity of the palladium nanoparticles was maintained in several repeated runs.