Micellar inversion process

The solubility and release of naproxen from Pluronic PF-127 micelles were studied as a function of temperature and pH by Suh and Jun (1996). The solubility of the drug at pH 2 was signiLcantly increased as a linear function of PF-127 concentrations for three temperatures. Naproxen was highly entrapped by the micelles as indicated by large partition coefLcient. The micellar solubilization was a spontaneous (AG 0) and exothermic (AH< 0) process that resulted in a less ordered state (AS > 0). In the presence of PF-127, the release of naproxen was sustained at pH 2 and inversely proportional to the surfactant concentration. In contrast, at pH 7, PF-127 had little effect on the membrane transport of naproxen. The release of naproxen from the PF-127 gel into isopropanol myristate was also found to be dependent on the medium pH with the highest release observed at pH 6.3. 

A hydrophobically modified polybetaine proved to be an efficient pour point depressant (PPD), to inhibit the deposition of wax, and to improve the viscosity of waxy crude oil from the Kumkol-Akshabulak oil field (western Kazakhstan) [282]. The inhibition of wax deposits in the presence of the hydrophobic polybetaine was interpreted in terms of its interference with the wax crystalhzation process, due to the formation of inverse micellar structures. While the zwitterionic parts on the polymer backbone stabilize the... 

The ultrasonification process is connected with the rapidly increased oil-water interfacial area as well as the significant re-organization of the droplet clusters or droplet surface layer. This may lead to the formation of additional water-oil interface (inverse micelles) and, thereby, decrease the amount of free emulsifier in the reaction medium. This is supposed to be more pronounced in the systems with non-ionic emulsifier. Furthermore, the high-oil solubility of non-ionic emulsifier and the continuous release of non-micellar emulsifier during polymerization influence the particle nucleation and polymerization kinetics by a complex way. For example, the hairy particles stabilized by non-ionic emulsifier (electrosteric or steric stabilization) enhance the barrier for entering radicals and differ from the polymer particles stabilized by ionic emulsifier. The hydro-phobic non-ionic emulsifier (at high temperature) can act as hydrophobe. 

Abstract Faradaic electron transfer in reverse microemulsions of water, AOT, and toluene is strongly influenced by cosurfactants such as primary amides. Cosurfactant concentration, as a field variable, drives redox electron transfer processes from a low-flux to a high-flux state. Thresholds in this electron-transport phenomenon correlate with percolation thresholds in electrical conductivity in the same microemulsions and are inversely proportional to the interfacial activity of the cosurfactants. The critical exponents derived from the scaling analyses of low-frequency conductivity and dielectric spectra suggest that this percolation is close to static percolation limits, implying that percolative transport is along the extended fractal clusters of swollen micellar droplets. and NMR spectra show that surfactant packing... 

The computer modeling [150] shows that exhibits two exponential (kinetic) regimes, AB and CD, and two inverse-square-root (diffusion) regimes, BC and DE, see Figure 4.8. In particular, the point C corresponds to the moment Xq = (Dilhj)tc where is the characteristic time of the slow micellar process see Ref. [149]. x also serves as a characteristic relaxation... 

Amphiphilic diblock copolymers undergo a self-assembly micellar process in solvents that are selective for one of the blocks [100]. By choosing selective conditions for each block, conventional micelles and so-called inverse micelles can be formed. Examples of the so-called schizophrenic micelles were reported [101]. In this case hydrophilic AB diblock copolymers can form micelles in an aqueous solution, in which the A block forms the inner core and inverted micelles (with the B block forming the iimer core) [102]. A diblock copolymer with two weak polybases, (poly-[2-(N-morphoUno)ethyl methacrylate-i)Iock-2- and (diethyl amino)ethyl methacrylate) (PMEMA-block-DEAEMA), forms stable micelles with DEAEMA cores by adjusting the pH value of the solution. The formation of inverted micelles (MEMA core) was achieved by a salting out effect by adding electrolytes to the aqueous solution. 

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