Noncovalently connected polymeric micelles in aqueous medium

Differing from the conventional micelles made of block or graft copolymers, in which the core and corona are connected by covalent bonding, the micell es reported in this paper are composed of a polymer pair and the core and c orona are connected by hydrogen bonding. Poly(styrene-co-methacrylic acid) (SMAA) and poly(vinylpyrrolidone) (PVPo) self-assembled into spherical mice lles with hydrodynamic radii around 100 nm in aqueous medium. These stable micelles are composed of the core of collapsed SMAA chains and the corona o f solvated PVPo chains. The hydrogen bonding between methacrylic acid and P V-Po units and the difference in the solubility in water between SMAA and P V-Po are the main factors responsible for the micelle formation. Using dyna mic light scattering, it was found that the hydrodynamic radius of the mice lles significantly increases with increasing initial concentrations of both SMAA and PVPo. The micelle size dose not depend on the MAA content (3.55-1 3.1 mol %) in SMAA monotonically, which can be rationalized by the coexiste nce of different stabilization mechanisms. Transmission electronic microsco py (TEM) was used to observe morphologies of the micelles. The core-shell s tructure of the micelles became visualized only when adequate staining of t he TEM specimens was employed.