pH-dependent micellization of poly(2-vinylpyridine)-block-poly((dimethylamino)ethyl methacrylate) diblock copolymers

A series of poly(2-vinylpyridine)-block-poly (dimethylamino)ethyl methaeryl ate) diblock copolymers (P2VP-b-PDMAEKA) have been synthesized by living an ionic polymerization of the comonomers. Dynamic light scattering (DLS) has been used to study the associative behavior of these copolymers in water as a function of copolymer composition, pH, ionic strength, and temperature. Three association regimes are observed. At low pH, loose aggregates are for med, although both the P2VP and PDMAEMA blocks are protonated. At intermedi ate pH, micelles are observed that consist of an uncharged hydrophobic P2VP core surrounded by a protonated PDMAEMA corona. At higher pH, the PDMAEDA corona is essentially uncharged and collapses at temperatures higher than 4 0 degreesC, which results in unstable micelles. The micelles observed by tr ansmission electron microscopy are spherical.