Stimuli-response of microsphere having poly(N-isopropylacrylamide) shell

Several kinds of submicron-sized microspheres having environment-sensitive shells were prepared and the effect of shell structure on the properties of microspheres was studied. The shell was composed of crosslinked or hairy poly(N-isopropyl acrylamide) (PNIPAM) whose lower critical solution temperature was about 32 °C but depended on the architecture of the shell. The resposivity of the shell to the change in environmental condition was sluggish when the shell was crosslinked. The decrease in the crosslink density of the shell was slightly effective in sharpening the response. But even non-crosslinked, hairy PNIPAM shell did not exhibit discontinuous transition at the critical condition. The response of hairy PNIPAM shell to environmental change was drastically sharpened by incorporating a slight amount of acrylic acid (AAc) in the hair.