STIMULI-RESPONSIVE POLYMERS - CHEMICAL-INDUCED REVERSIBLE PHASE-SEPARATION OF AN AQUEOUS-SOLUTION OF POLY(N-ISOPROPYLACRYLAMIDE) WITH PENDENT CROWN-ETHER GROUPS

Benzo[18]crown-6 was incorporated into pendent groups of poly(N-isopropylacrylamide) to obtain chemical-responsive polymer systems. The aqueous solution of the polymer containing 11.6 mol % pendent benzo[18]crown-6 groups underwent a phase transition from the phase-separated to the homogeneous state at 32-degrees-C by the addition of K+ and Na+. The threshold ion concentration to induce the phase transition depended on the kind of metal ion. A very small amount of K+ was sufficient to induce the transition, while 6.0 x 10(-2) M Na+ was required. At 37-degrees-C only K+ could induce the phase transition.