Micelle-water Partition Coefficient Research Articles

Molecular modeling of micelle formation and solubilization in block copolymer micelles. 2. Lattice theory for monomers with internal degrees of freedom

A self-consistent mean-field lattice theory of the micellization and solubilization properties of poly(ethylene oxide)-poly(propylene oxide) block copolymers is described. The polymer segments are allowed to assume both polar and nonpolar conformations (corresponding to the gauche and trans rotations of the C-C and C-O bonds), which permits the dependence of the segment-segment interactions on temperature and composition to be accounted for in a physically realistic manner. The phase diagrams of poly(ethylene oxide) and poly(propylene oxide) in water, both of which exhibit lower critical solution temperatures, can be reproduced semiquantitatively. The predictions of the theory compare favorably with published light scattering results on the aggregation behavior of block copolymers and with the authors experimental results for the solubilization of naphthalene in these micelles as a function of polymer composition and molecular weight. The dependence of the micelle-water partition coefficient on polymer composition is not simply related to the proportion of the hydrophobic constituent but depends on the detailed micelle structure. The strong effect of the molecular weight and PPO content of the polymer on the amount of naphthalene solubilized observed experimentally was interpreted in terms of the model results.

Some factors in solute partitioning between water and micelles or polymeric micelle analogues

Micelle—water partition coefficients of p-nitroaniline and p-nitrophenol have been determined for several alkyltrimethylammonium salts including a polymer of undecenltrimethylammonium bromide. Solubilization depends upon the “concentration” of micellizedd alkyl carbon atoms regardless of micelle size. Counterion effects are an important aspect of the process. Micelle-like polymers may be useful in theoretical studies by eliminating some of the interactive variables which complicate pseudophase liquid chromatography with ordinary micelles.

Connection of electro-magnetic rotation with uni-polar induction

We present results on the effects of various hydrophobic drugs and additives on the micellar structure of Pluronic F127 solutions. Small-angle neutron scattering experiments on 5 wt% F127 solutions were used to measure micelle core size (R1), micelle corona size (R2), intermicellar interaction distance (Rint), polydispersity (σ), and aggregation number (Nagg); dynamic light scattering was used to measure critical micelle concentration (CMC); and ultraviolet spectroscopy was used to measure drug solubility and apparent micelle–water partition coefficient (Kmw). The core and corona size were found to generally increase in the presence of the drugs, as did Rint. Both σ and Nagg were found to decrease in the presence of most of the drugs, and the CMC was found to vary considerably with no clear correlation. A design of experiments (DOE) approach was used to analyze the results and build empirical correlations. All of the parameters from the SANS experiments were found to depend strongly on drug solubility, with a weak dependence on Kmw in most cases. The aggregation number, however, was found to depend strongly on both Kmw and solubility. The correlations can be used to roughly predict the structural parameters of F127 micelles for other hydrophobic drugs.