Salt-induced micelle behavior of poly(sodium acrylate)-block-poly(N-isopropylacrylamide) by ATRP

Temperature- and pH-sensitive diblock copolymers PAANa(75)-b-PNIPAM(m) are prepared by a combination of reverse and normal ATRP in aqueous solution at room temperature. The block copolymer is also stimuli-sensitive with respect to salt in the aqueous solution, and forms spherical star-like micelles with a PNIPAM core and an expanded PAANa shell for PAANa(75)-b-PNIPAM(76) as well as spherical crew-out micelles with a PNIPAM core for PAANa(75)-b-PNIPAM(5110), as indicated by a fluorescence probe technique and TEM. A three-stage model mechanism of phase transition driven by small molecule salt is proposed.