Thermoresponsive micelles from well-defined block copolymers synthesized via reversible addition-fragmentation chain transfer polymerization

Poly(N-isopropylacrylamide) (PNIPAAm) homopolymers synthesized by reversible addition-fragmentation chain transfer polymerization were used as macro-chain-transfer agents to synthesize smart amphiphilic block Copolymers with a switchable hydrophilic-hydrophobic block of PNIPAAm and a hydrophilic block of poly(N-dimethylacrylamide). All polymers were characterized by gel permeation chromatography, H-1 NMR, and differential scanning calorimetry. The reversible micelles formed by the block copolymers of various compositions in aqueous solutions were characterized by 1H NMR, dynamic light scattering, and tensiornetry. Micelles were observed in the aqueous solutions when the temperature was increased to 40 degrees C because of the collapse of the PNIPAAm structure, which led to a PNIPAAm hydrophobic block. The drug loading capacity was illustrated with the use of the solvato-chromic Reichardt's dye and measured by ultraviolet-visible. (c) 2005 Wiley Periodicals, Inc.