Functionalization micelle incorporation

The description given here is confined to the method developed by Abuin and Lissi demonstrating the use of fluorescence as a method for determining partition coefficients for solutes that are not by themselves fluorescent. The method is based on the observation that an additive changes the characteristics of the fluorescence of a micelle-incorporated probe such as pyrene. It is assumed that the fluorescence intensity of micelle-incorporated pyrene is determined only by the mole fraction of solute in the micellar pseudophase. The probe fluorescence intensity ratio f/I in the absence and presence of a solute is measured as a function of the solute concentration at different surfactant concentrations. From plots of the intensity ratio vs. the solute concentration at different surfactant concentrations we obtain a set of additive concentrations c,o, that corresponds to the same f/I value and thereby the same and K. Ctot is related to the concentration of micellized surfactant, through the following equation ... 

One of the most comprehensive studies has been carried out by Bruice et al. [19] who studied the rate of solvolysis of neutral, positively and negatively charged esters when incorporated into non-functional and functional micelles of neutral, positive and negative charges. The second-order rate constants for alkaline hydrolysis, /cqh [0H ] were found to decrease with increasing concentration of surfactant for all cases studied. The association of the esters with non-nucleophilic micelles must either decrease the availability of the esters to OH attack or provide a less favourable medium for the hydrolysis reaction to occur. This is another circumvention of the simple electrostatic rules as the kinetic effect seems to have nothing to do with the concentration or restriction of access of the hydroxyl ions in the Stern layer of the micelles. Presumably the labile ester bond is not positioned near the surface of these micelles, but the molecules are oriented as shown in Fig. 11.2. 

Bruice, T.C., Katzhendler, J., Fedor, L.R. Nucleophilic micelles. II. Effect on the rate of solvolysis of neutral, positively, and negatively charged esters of varied chain length when incorporated into nonfunctional and functional micelles of neutral, positive, and negative charge. J. Am. Chem. Soc. 1968, 90(5), 1333-1348. 

The unimer micelles can be functionalized by incorporating various functional groups into the hydrophobic microdomains of the unimer micelles. The incorporation of functional groups can be effected by covalent bonding of functional groups onto the amphiphilic polymers that form unimer micelles. 

An effect similar to that of cetyltrimethylammonium bromide micelles can be realized through the use of microgels with trimethylamino side-chain function and this may then allow solid supported microgels to be used in a continuous reaction. Evans et al. (1995) have utilized microgels incorporating 2-tetradecyl dimethyl amino/ethyl methacrylate bromide, which solubilizes aryl laurate esters in an aquous solution and catalyses the alkaline hydrolysis. 

Micelles forming above the c.m.c. incorporate hydrophobic molecules in addition to those dissolved in the aqueous phase, which results in apparently increased aqueous concentrations. It has to be noted, however, that a micelle-solubilised chemical is not truly water-dissolved, and, as a consequence, is differently bioavailable than a water-dissolved chemical. The bioavailability of hydrophobic organic compounds was, for instance, reduced by the addition of surfactant micelles when no excess separate phase compound was present and water-dissolved molecules became solubilised by the micelles [69], In these experiments, bacterial uptake rates were a function of the truly water-dissolved substrate concentration. It seems therefore that micellar solubilisation increases bioavailability only when it transfers additional separate phase substrate into the aqueous phase, e.g. by increasing the rates of desorption or dissolution, and when micelle-solubilised substrate is efficiently transferred to the microorganisms. Theoretically, this transfer can occur exclusively via the water phase, involving release of substrate molecules from micelles, molecular diffusion through the aqueous phase and microbial uptake of water-dissolved molecules. This was obviously the case, when bacterial uptake rates of naphthalene and phenanthrene responded directly to micelle-mediated lowered truly water-dissolved concentrations of these chemicals [69]. These authors concluded from their experiments that micellar naphthalene and phenanthrene had to leave the micellar phase and diffuse through the water phase to become... 

In contrast to dendrimers built up from aliphatic chains, polyphenylene dendrimer micelles possess shape and size persistent cavities due to their rigid scaffold which strongly depends on the type of dendrimer. In this case a selective incorporation of guest molecules, e.g., fluorescent dyes, should be possible, dependent on the size of the guest molecule and the cavity of the host. The non-covalent uptake of dyes with an appropriate size thus allows the investigation of their interactions within the dendritic micelle. In our case we made the second-generation polyphenylene dendrimer 48, which bears 16 carboxy-functions at the periphery, by starting from a tetrahedral core and an appropriately... 

In a recent paper, the interaction of various simple flavonoids with an anionic surfactant, sodium dodecyl sulfate (SDS) in aqueous solution, has been studied through absorption spectroscopy as a function of the concentration of the surfactant above and below the critical micelle concentration.The approximate number of additive molecules (flavonoids) incorporated per micelle was estimated at a particular concentration of SDS. Incorporation of flavonoids in micelles shifted the UV absorption bands toward higher wavelengths, and the bathochromic shifts also depended upon the nature of the surfactant head group. 

Lipid micellization Vesicles for encapsulation, controlled release, functional incorporation of proteins and mimicking of biological membranes Singh et al., 1995 Taylor et al., 2005 Sagalowicz et al., 2006 Mozafari et al., 2006... 

Incorporation of large amounts of functionalized monomer in the growing polymer creates a polar micellar environment that discourages migration of gaseous ethylene to the micelles. 

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