Measurement of Solubilization Location in Micelles Using Anchored Aggregation-Induced Emission Donors

Solubilization locations play a critical role in developing advanced surfactants and improving solubilization power in micelle-based applications. However, the current polarity-based techniques for measuring solubilization locations could come to conflicting conclusions. The key challenge is the unpredictable polarities in the micellar microenvironment. Now, an approach that is independent of micellar polarities is used to measure solubilization locations by covalently linking tetraphenylethylene (TPE) to the alkyl chain end of cationic surfactants. The solubilization locations of solubilized acceptors in the TPE-cored spherical micelles were accurately measured by calculating the Förster resonance energy transfer distance between anchored TPE donors and solubilized acceptors. Solubilization locations of solubilized substances in the micellar interior and at the micellar surface depend on their size and hydrophobicity, respectively.     

Measurement of Solubilization Location in Micelles Using Anchored Aggregation‐Induced Emission Donors

Solubilization locations play a critical role in developing advanced surfactants and improving solubilization power in micelle‐based applications. However, the current polarity‐based techniques for measuring solubilization locations could come to conflicting conclusions. The key challenge is the unpredictable polarities in the micellar microenvironment. Now, an approach that is independent of micellar polarities is used to measure solubilization locations by covalently linking tetraphenylethylene (TPE) to the alkyl chain end of cationic surfactants. The solubilization locations of solubilized acceptors in the TPE‐cored spherical micelles were accurately measured by calculating the Förster resonance energy transfer distance between anchored TPE donors and solubilized acceptors. Solubilization locations of solubilized substances in the micellar interior and at the micellar surface depend on their size and hydrophobicity, respectively.     

Micellization,Solubilization and Microemulsions

Ohne Zusammenfassung

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Micellization, Solubilization and Microemulsions

     

The Solubilization of Isophorone in Ionic Surfactant Solutions

Solubilization of isophorone was studied in an anionic and a cationic surfactant solution of SDS and BKC respectively. Solubility of isophorone increases with increase in the surfactant concentrations due to solubilization in micelles. FT NMR spectroscopy was used to understand the location and orientation of isophorone at the micellar interface.     

Microemulsions as delivery systems

Solubilization capacity, dissolution efficiency, rate and extent of solute delivery are dependent on the microemulsion microstructure.     

Microemulsion Phase Behavior of Aerosol-OT Combined with a Cationic Hydrotrope in the Dilute Region

The phase behavior of systems containing minimum amounts of sodium bis (2-ethylhexyl) sulfosuccinate with equimolar ratio of tetra ethyl ammonium chloride were studied as a function of salt concentration and alkane carbon number at ambient temperature. Visual inspection as well as cross polarizers were used to detect anisotropy. Solubilization ratios for oil and brine in the middle phases were measured and used to calculate the interfacial tension. Ultra-low interfacial tension values were predicted for the systems containing heptane, octane and nonane as model oil. Different phase behavior was observed for systems with higher alkane number.     

Application of nonionic amphiphiles for increasing solubility in water of alkylated bibenzimidazole derivatives

Solubilization capacity of a number of nonionic micelle-forming compounds toward 2,2´-bibenzimidazole and its alkylated derivatives was determined by spectrophotometry. It was found that as the hydrophilic lipophilic balance of the studied amphiphiles grows, their solubilization effect toward 2,2´-bibenzimidazoles increases and reaches the highest value in the case of pluronic F127. The conversion of bibenzimidazoles to the cationic form induced by lowering the medium pH improves efficiency of the solubilizers.     

Improved solubilization of carbamazepine and structural transitions in nonionic microemulsions upon aqueous phase dilution

Solubilization capacity and structural transformations in nonionic microemulsions characterized by a large continuous isotropic region forming dilutable self-assembled nanodroplets containing solubilized carbamazepine, were studied along dilution lines 73 and 82 (70 and 80 wt% surfactant and 30 and 20 wt% of oil phase, respectively). The preparations were based on pharma-grade ingredients, water, R-(+)-limonene, ethanol, propylene glycol, and Tween 60. Solubilization capacity (SC) of the drug was dependent on the microstructure of the microemulsion and on the surfactant-to-oil phase weight ratio. The SC in the concentrate (reversed micelles) was 15 times higher than its solubility in the oil. Transition of the W/O microemulsion to a bicontinuous phase and to O/W droplets were indentified by electrical conductivity, viscosity, SAXS, and SD-NMR measurements. Once the system is diluted to 90 wt% aqueous phase, the SC is 10 and 16-fold higher, along dilution lines 73 and 82, respectively, than in pure water. Being solubilized, carbamazepine serves as a cosurfactant therefore it affects the curvatures of the microstructures and consequently the boundaries of the structural regions and the transition points between the different phases. Dilutable microemulsions are promising new carbamazepine vehicles for oral intake.     

Solubilization of phenols in anionic polyelectrolyte gels with adsorbed cationic surfactant

Solubilization isotherms for various phenols in cetylpyridinium chloride (CPC)-polyelectrolyte gel aggregates have been determined in order to compare solubilization within these aggregates with that in free micelles and to examine the effects of gel chemistry and structure on solubilization. The isotherms describing solubilization are quite similar to those found for free surfactant in solution. Solutes that are more hydrophobic give rise to larger solubilization constants with trends similar to what is seen for hydrophobic effects in adsorption from aqueous solutions onto hydrophobic solids. The solubilization constants decrease as the fraction of solute in the aggregates increases, indicating that the solutes partition into the palisade region of the aggregates. Solubilization is found to be quite insensitive to changes in gel structure (cross-linker varying from 1% to 3%) and chemistry (poly(acrylic acid) versus poly(methacrylic acid) and neutralization from 50% to 100%). However, the switch from poly(acrylic acid) to poly(methacrylic acid) did give rise to a slight decrease in magnitude of the slope of the isotherm. The most significant factors appear to be the initial concentration of surfactant in solution and the ratio of surfactant solution to gel amount. A decrease in surfactant concentration (especially combined with an increase in solution volume) gives rise to a decrease in solubilization constants.     

Solubilization of fullerene into water with fluoroalkyl end-capped amphiphilic oligomers-novel fluorescence properties

Solubilization of fullerene into water was studied by the use of fluoroalkyl end-capped acryloylmorpholine oligomers, N,N-dimethylacrylamide oligomers, and acrylic acid oligomers. In these fluorinated oligomers, fluoroalkyl end-capped acryloylmorpholine oligomers were more effective in solubilizing fullerene into water. Interestingly, the aqueous solutions of fullerene were applicable to fluorescence analyses.     

NMR and photo-CIDNP investigations of the glycyrrhizinic acid micelles influence on solubilized molecules

It was found that photolysis of N-acyl anthranilic acid methyl ester is very sensitive to solvent nature. This sensitivity was connected with the equilibrium between intramolecular and intermolecular hydrogen bonding. Also it has been established the glycyrrhizinic acid micelle formation in water-methanol mixture with CMC about 0.5–1 mM. Solubilization of N-acyl anthranilic acid methyl ester in glycyrrhizinic acid micelles decreases photoreaction efficiency comparing with the homogeneous solvent.     

有机硅微乳液的研究进展

近年来大量研究表明,有机硅微乳液与有机硅乳液相比,具有许多优异的性能,如优异的热稳定性、渗透性等。本文主要阐述了有机硅微乳液的形成原理、制备方法及制备过程中的影响因素。在有机硅微乳液的形成原理里,详细介绍了增溶理论和界面张力理论;在有机硅微乳液的制备中,着重讨论了表面活性剂、助表面活性剂、催化剂等对有机硅微乳液形成的影响。     

两亲嵌段共聚物聚乙二醇-聚谷氨酸苄酯纳米粒药物载体的合成研究

用磺酸酯法制备单端氨基聚乙二醇引发剂,引发谷氨酸苄酯羧酸酐开环聚合,生成可生物降解的两亲嵌段共聚物聚乙二醇﹣聚谷氨酸苄酯(PEG-PBLG),用IR,NMR和GPC表征了共聚物。用超微透析法制备PEG-PBLG聚合物纳米粒,荧光芘探针法测定纳米粒的临界聚集浓度(cac)。紫外分光光度计考察纳米粒对疏水性药物的增溶作用,PEG-PBLG可作为亚微粒药物输送系统的载体。     

Protein partition and ion copartition in aqueous-apolar two-liquid-phase systems

A thermodynamic treatment of protein partitioning in an aqueous-organic two-phase system is presented. The phenomenological analysis interprets the copartitioning of electrolytes. The analysis is supported by experimental results. Solubilization of cytochrome c in trioctylmethylammonium chloride reverse micelles is accompanied by the expulsion and inclusion of electrolytes (HCl) for pH levels below, and respectively above the pH of maximal solubilization. Maximal solubilization occurs when no copartitioning is required. The observations are discussed in terms of the change in Donnan exclusion due to double-layer overlap.     

Characterization of the micellar ring opening metathesis polymerization in water of a norbornene derivative initiated by Hoveyda‐Grubbs' catalyst

Solubilization of the hydrophobic Hoveyda‐Grubbs' catalyst in micellar aqueous phase has been achieved using dodecyl and cetyl ammonium chloride as surfactants. The domain of solubilization has been estimated before carrying out ring‐opening metathesis polymerization in these micellar solutions with a hydrophilic monomer. Kinetics orders have been determined relative to monomer, initiator, and surfactant. A good control of the molecular weight has been obtained for ratios [micelles]/[initiator] over 1. The better control of the polymerization obtained in micellar solution has been explained by a difference of reactivity leading to a more efficient initiation step in the presence of the micelles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2833–2844, 2008     

The solubilization of fatty acids in systems based on block copolymers and nonionic surfactants

The solubilizing action of micellar, microemulsion, and polymer-colloid systems formed on the basis of biologically compatible amphiphilic polymers and nonionic surfactants on capric, lauric, palmitic, and stearic acids was characterized quantitatively. Systems based on micelle forming oxyethyl compounds increased the solubility of fatty acids by more than an order of magnitude. Acid molecules incorporated into micelles increased their size and caused structural changes. Solubilization was accompanied by complete or partial destruction of intrinsic acid associates and an increase in their pK _a by 1.5–2 units compared with water.     

SOLUBILIZATION IN LYOTROPIC LIQUID CRYSTALS

Solubilization in non-aqeuous lyotropic liquid crystals was investigated by determination of the stability region of a lamellar liquid crystal in systems of triethanolamine (TEA), dodecylbenzenesulfonic acid (DBSA) and a series of solvents.

The solubilization maximum was moved towards higher OBSA/TEA ratios for polar solvents and the reverse for non-polar ones. The solvents caused the maximum increase of interlayer spacing when added.     

Influence of trans-cis photoisomerizations of solubilized compounds on transition temperatures in the system cetyltrimethylammonium bromide-water: Light-induced phase transitions

Transition temperatures (TN1) from the nematic lyotropic liquid-crystalline phase to the isotropic phase were measured for the system cetyltrimethylammonium bromide (CTAB) water in the presence of small amounts of 3-stilbene carboxylic acid (3SC), 4-stilbene carboxylic acid (4SC) and Δ2/2'-bi-(2H-l,4-benzothiazine) (BT). TNI, increases as a function of trans-3SC or trans-4SC concentration, ranging from 01 to 08 wt %, by up to 12°C. A further increase in TNI between 2 and 5°C can be achieved by photochemically converting the solubilized trans stilbene derivatives to the cis isomers. Irradiation of a trans-3SC containing sample at a temperature just above TNl leads to a light-induced phase transition to the lyotropic liquid-crystalline phase. Solubilization of trans-BT causes a slight decrease of TNI while photoisomerization to cis-BT increases T_NI by 1°C.     

Room temperature luminescence of a retinal complex of cyclodextrin

Retinal, which is normally insoluble in an aqueous medium and not fluorescent in solution at room temperature, emits a luminescence in the region of 450 nm, even in air-saturated aqueous solutions, when complexed to β or γ-cyclodextrin. The intensity decreases in the order β> γ and the quantum yields of luminescence are in the range 10^?3–10^?4. Further, retinal molecules in the inclusion complexes are subject to a bleaching process. Solubilization in micellar sodium dodecyl sulphate solutions also allows emission, albeit in smaller yield.     

Diameter-selective solubilization of single-walled carbon nanotubes by reversible cyclic peptides

We have utilized reversible cyclic peptides (RCPs)-peptides containing alternating l- and d-amino acids with N- and C-termini derivatized with thiol-containing groups allowing reversible peptide cyclization-to solubilize and noncovalently functionalize carbon single-walled nanotubes (SWNTs) in aqueous solution. Solubilization occurs through wrapping of RCPs around the circumference of a SWNT, followed by the formation of head-to-tail covalent bonds, yielding closed rings on the nanotubes. By controlling the length of the RCPs, we have demonstrated limited diameter-selective solubilization of the SWNTs as revealed by UV/vis/NIR and Raman spectroscopies, as well as atomic force microscopy.