Thermosensitive noncovalently bonded block copolymerlike micelles from interpolymer complexes

Interpolymer complexes between polystyrene-b-poly(2-vinylpyridine), (PS-P2VP), and poly(methacrylic acid) (PMAA), have been studied in dioxane. Dioxane is a good solvent for PS-P2VP copolymers but it is a nonsolvent for PMAA at room temperature. In this way noncovalent bonded micelles are formed after mixing the solutions of the polymers at 60 degreesC and then allowing them to cool at room temperature. Static and dynamic light scattering as well as viscosity measurements have been used to study the dependence of aggregate mass and size as a function of the molar ratio of functional groups in PS-P2VP/PMAA mixtures, as well as temperature. Plots of apparent average molecular weight and hydrodynamic radius of the aggregates versus amine to carboxyl group ratio show a maximum at a ratio close to one. The size of the aggregates decreases at higher ratios because of the formation of more stable micelles with smaller cores. In all cases rather compact structures were formed, as evidenced by viscometry. The mass of the aggregates was found to decrease by an increase in temperature while hydrodynamic radii were increased. This was attributed to the increase of the thermodynamic quality of the solvent toward PMAA as temperature increases. (C) 2004 Wiley Periodicals, Inc.