Temperature-Induced Ordering and Gelation of Star Micelles Based on ABA Triblocks Synthesized Via Aqueous RAFT Polymerization

The reversible formation of ordered physical gels from stimuli-responsive ABA [A poly(N,N-dimethylacrylamide) (PDMA), B = poly(N-isopropylacrylamide) (PNIPAM)] triblock copolymers is investigated utilizing dynamic light scattering, small angle X-ray scattering, and low-shear rheometry. As the temperature is increased above the phase transition temperature of the PNIPAM segment, triblock copolymers under a critical molecular weight are capable of packing into body-centered cubic arrays. Rheometric tests indicate that the storage moduli of the gels at 50 degrees C are inversely related to the molecular weight of the polymer