A theory of micellization of AB diblock copolymer molecules in a selective solvent S is developed here. The micelles are assumed to have a completely segregated core region consisting only of the A block and a shell region consisting of the solvent S and the solvent compatible B block. The theory allows one to predict the critical micelle concentration, the micelle size distribution, the average aggregation number, as well as the core radius and the shell thickness of the micelle. The novel outcome of the present theory, in contrast to the treatments of micellization pioneered by de Gennes, Leibler, Orland, and Wheeler, and Noolandi and Hong, is its prediction that the solvent compatible B block plays an important role in determining the micellization behavior. The influence of the B block becomes relatively more prominent in systems where the solvent S constitutes a very good solvent for the B block. Further, scaling relations that are not system specific have been developed relating explicitly the micellar size parameters to the characteristics of the block copolymer and the solvent.

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Several extrinsic optical probes that have been used to monitor the extent of water penetration in micelles are aromatic in nature. We have studied the ring current-induced alterations in the NMR spectral signals of the various protons of the surfactant chains of micelles brought about by solubilizing some of these probes. The results indicate that such aromatic solubilizates are located near the headgroup region of the micelles. These probes would thus be expected to monitor the polarity and water content of the headgroup region and not the micellar interior.

We develop a theory of solubilization of low molecular weight species in block copolymer micelles, employing the scaling approach and building on the analogy between micelles and star polymers. Specifically, we consider spherical micelles of AB-diblock copolymers formed in selective solvents, in which the core and the shell regions are assumed to have radial concentration variations similar to those occurring in the solution state of a star polymer. Invoking the results for the conformation of a star polymer derived by Daoud and Cotton, expressions are developed for the free energy per molecule of the micelle AG, the core radius R, the shell thickness D, and the overall volume fraction of the polymer within the core #A as functions of the micellar aggregation number g. From the minimization of the free energy of an isolated micelle, the equilibrium values for all the micellar structural parameters and for the extent of solubilization are obtained. The results expressed as scaling relations for g, R, D, and +A are derived for various situations of interest including those of the solvent S being a good or theta solvent for the shell block B, and the solubilizate J being a good or theta solvent for the core block A.