Temperature-responsive polymer microspheres prepared with a macroinitiator

A macroinitiator was prepared by coupling of the disuccinimidyl ester of 4,4'-azobis(cyanovaleric acid) with poly(N-isopropylacrylamide) (PIPA) with terminal amino group. Styrene and divinylbenzene were copolymerized with the initiator in the presence of sodium dodecylsulfate. The polymer microspheres obtained have PIPA chains on their surfaces, and the stability of a suspension of the microspheres in the presence of electrolyte is largely influenced by the temperature, whereas that of microspheres without PIPA chains is not. The usefulness of macroinitiators to prepare various polymer materials which are responsive to external stimuli was strongly emphasized.