Poly(N-isopropylacrylamide)/chitosan microgel was synthesized by surfactant-free emulsion polymerization.The morphology and stimuli-responsive properties of the microgel were characterized with transmission electron microscope and dynamic light scattering.The results showed that the microgel particles presented a microsphere with core-shell morphology.The addition of chitosan had a significant effect on the volume phase transition temperature (VPTT) of PNIPAM microgel

and the VPTT shifted to a high temperature with increasing amount of chitosan.This result was consistent with measurements of differential scanning calorimeter.The diameter changes of the microgels at various pH solutions indicated that the size decreased gradually with increasing pH

and then increased after pH>7

implying obvious pH sensitivity of the particles.The relevant Zeta potential of the particles also decreased gradually

and changed to a negative value.This transition can explain reasonably the pH sensitivity of the microgel.