Poly(styrene-methacrylic acid) block copolymers in aqueous media

Solution properties of block copolymer micelles formed by diblock and triblock copolymers of styrene and methacrylic acid were studied by classic and quasi-elastic light scattering, sedimentation velocity, and viscometry. The results show that the micelles are spherical in shape and have a narrow distribution of sizes. The aggregation number of micelles depends on copolymer molar mass and composition. Hydrodynamically, micelles behave like impermeable spherical particles. The critical micelle concentration is too low to be measured experimentally. Three independent methods used for obtaining molar mass of micelles agreed well with each other.; When two different types of micelles are mixed together, they have a tendency to hybridize. The kinetics of block copolymer micellar hybridization was studied by sedimentation velocity. The rate of hybridization was found to be very sensitive to the structure of block copolymers and thermodynamic properties of the solvent. Its time scale varied from a few minutes to several months. In many instances, it was imperceptibly slow and totally frozen when the solvent was very poor with respect to the micellar core.; Block copolymer micelles can selectively take up organic molecules in aqueous media. Both gas chromatography and light scattering experimental results show that the extent of solubilization of organic molecular by copolymer micelles depends on the chemical nature of organic molecules, specifically, on the interactions between the solvents and micellar cores. Molecules that have stronger interaction with polystyrene are substantially solubilized by micelles while molecules that have weak interaction with polystyrene are solubilized to much lesser degree.; Block copolymer micelles are potential carriers for the release of hydrophobic substances. A fluorescence based technique was developed for following the release of model compounds from the cores of block copolymer micelles into aqueous media. The release curves were compatible with theoretical dependences for diffusion controlled release from spherical particles. The diffusion coefficient of phenanthrene within the micellar cores was found to be of order of 10{dollar}sp{lcub}-18{rcub}{dollar} cm{dollar}sp2{dollar}/s for the micelles in aqueous buffer. The partition coefficients are of the order of 10{dollar}sp5{dollar} and are comparable to the values obtained in uptaking experiments.; Finally, block copolymer micelles and polystyrene latex were immobilized in a polyacrylamide hydrogel. The structure of the colloidal particles was examined by light scattering. For polymer latex, both molar mass and size are unchanged during the embedding procedure. For block copolymer micelles, the size decreased after polymerization of the solvent while molar mass remained the same.