Search results for " MICELLE"
showing 10 items of 179 documents
Quantitative description of temperature induced self-aggregation thermograms determined by differential scanning calorimetry
2012
A novel thermodynamic approach for the description of differential scanning calorimetry (DSC) experiments on self-aggregating systems is derived and presented. The method is based on a mass action model where temperature dependence of aggregation numbers is considered. The validity of the model was confirmed by describing the aggregation behavior of poly(ethylene oxide)-poly(propylene oxide) block copolymers, which are well-known to exhibit a strong temperature dependence. The quantitative description of the thermograms could be performed without any discrepancy between calorimetric and van 't Hoff enthalpies, and moreover, the aggregation numbers obtained from the best fit of the DSC exper…
Multicomponent polymeric micelles based on polyaspartamide as tunable fluorescent pH-window biosensors
2010
Abstract PHEA-PEG 5000 -C 16 is a polyaspartamide polymer with appended hydrophilic PEG 5000 functions and hydrophobic n-C 16 units forming biocompatible micelles with a CAC as low as 1.8 × 10 −7 M. The protonation and acidity constants of the polymer's amino and carboxylic groups have been determined by potentiometric titrations at five different concentrations higher than CAC, finding concentration-independent values. Viscosity and polarity of the micellar core have been investigated by means of fluorescent probes, finding local values comparable to those of pure toluene and to the core of sodium dodecyl sulphate micelles, independently on the protonation degree of the polymer. The fluor…
A fluorescent molecular sensor for pH windows in traditional and polymeric biocompatible micelles: comicellization of anionic species to shift and re…
2011
A new approach is presented to obtain fluorescent sensors for pH windows that work in water and under biomimetic conditions. A single molecule that features all-covalently linked components is used, thus making it capable of working as a fluorescent sensor with an OFF/ON/OFF response to pH value. The components are a tertiary amine, a pyridine, and a fluorophore (pyrene). The forms with both protonated bases or both neutral bases quench the pyrene fluorescence, whereas the form with the neutral pyridine and protonated amine groups is fluorescent. The molecular sensor is also equipped with a long alkyl chain to make it highly hydrophobic in all its protonated and unprotonated forms, that is,…
Green Synthesis, Molecular Characterization and Associative Behavior of Some Gemini Surfactants without a Spacer Group.
2013
A series of new gemini surfactants without a spacer group, disodium 2,3-dialkyl-1,2,3,4-butanetetracarboxylates, were synthesized in a green chemistry context minimizing the use of organic solvents and applying microwaves (MW) when activation energy was required. Once the desired architecture was confirmed by means of the nuclear magnetic resonance technique (1H-NMR, 1H-1H COSY) for all the studied surfactants, the critical micellization concentration was determined by conductance measurements. The diffusion coefficient of micelles formed by the four compounds was characterized using pulsed field gradient (PFG)-NMR. Diffusion coefficients were found to be dependent on the concentration and …
Compatibility of surfactants with activated-persulfate for the selective oxidation of PAH in groundwater remediation
2017
Abstract Surfactants foam technology can improve the in situ remediation of hydrophobic organic contaminants by enhancing their solubility and the delivery of remediation chemicals. However, the presence of surfactants may impair the effectiveness of the selective oxidation of those contaminants. To tackle the issue, kinetics and selectivity of phenanthrene (PHE) oxidation in aqueous suspensions and its affecting factors including surfactant concentration (CS) and nature, temperature and persulfate (PS) concentration were studied. Significant differences in selectivity were observed between surfactants, reflecting Coulomb interactions with the anionic oxidizers. Lauryl Betaine (LB) stood ou…
New folate-functionalized biocompatible block copolymer micelles as potential anti-cancer drug delivery systems
2006
Abstract The main objective of this study was to synthesize novel folic acid-functionalized diblock copolymer micelles and evaluate their solubilization of two poorly water-soluble anti-tumor drugs, tamoxifen and paclitaxel, which suffer from low water solubility and/or poor hydrolytic stability. The diblock copolymer consisted of a permanently hydrophilic block comprising 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) residues and a pH-sensitive hydrophobic block comprising 2-(diisopropylamino)ethyl methacrylate (DPA) residues. Folic acid (FA) was conjugated to the end of the MPC block so that this group was located on the micelle periphery. Tamoxifen- and paclitaxel-loaded micelles were…
Alkaline titrations of poly(dG-dC).poly(dG-dC): microemulsion versus solution behaviour
2007
PolyGC was titrated with a strong base in the presence of increasing concentrations of NaCl (from 0.00 to 0.60M) either in water solution or with the polynucleotide solubilized in the aqueous core of reverse micelles, i.e., the cationic quaternary water-in-oil microemulsion CTAB/n-hexane/n-pentanol/water. The results for matched samples in the two media were compared. CD and UV spectroscopies and, for the solution experiments, pH measurements were used to follow the course of deprotonation. In both media the primary effect of the addition of base was denaturation of the polynucleotide, reversible by back-titration with a strong acid. In solution, the apparent pK(a) of the transition decreas…
NEW INSIGHTS ON SUPRAMOLECULAR AGGREGATES OF SODIUM DOCUSATE (AOTNa) BY ION MOBILITY MASS SPECTROMETRY
2013
Backgorund: The ability of some surfactants to form charged aggregates in gas phase has been proven experimentally by electrospray ionization (ESI) spectrometry [1- 5]. However, in the early investigations, interesting questions concerning the structural organization of these aggregates in gas phase and if they reflect their typical self-assembling in the starting liquid solutions were not addressed. Subsequently, independently of their aggregation motive in liquid phase and of the charge state in the gas phase, some hints suggesting that surfactant molecules are organized in gas phase as reverse micelle-like aggregates have been reported Objective: The supramolecular charged aggregates for…
New Insights and Recent Developments in Micellar Liquid Chromatography
2009
Abstract: Micellar liquid chromatography (MLC) is an efficient alternative to conventional reversed–phase liquid chromatography with hydro‐organic mobile phases. Almost three decades of experience have resulted in an increasing production of analytical applications. Current concern about the environment also reveals MLC as an interesting technique for “green” chemistry because it uses mobile phases containing 90% or more water. These micellar mobile phases have a low toxicity and are not producing hazardous wastes. After a rapid overview of the two first decades of the technique, this review focuses on the recent advances on fundamental aspects and analytical applications. Traditional and n…