Monodisperse core-shell
microspheres, composed of
poly(N-isopropylacrylamide) (
PNIPAM) core with thermo-responsive swelling/shrinking function and biocompatible poly(2-hydroxyethyl methacrylate) (
PHEMA) shell with "open/close" switching function, have been successfully prepared by microfluidic emulsification,
free-radical polymerization and atom transfer radical polymerization (ATRP). The effects of grafting time for the ATRP and
polyvinyl alcohol (PVA) concentration inside the core on the thermo-responsive behavior of core-shell
microspheres are investigated. For the core-shell
microspheres prepared with PVA concentration of 2% (w/v) and grafting time of 2 h, the
PNIPAM core is in the shrunken state and the solid
PHEMA shell protect the whole
PNIPAM core at temperatures above the volume phase transition temperature (VPTT); as environmental temperature decreases below the VPTT, the
PNIPAM core swells dramatically and the
PHEMA shell
ruptures a large area. The thermo-responsive function of the core-shell
microspheres is reversible and the appearance/recovery of
PHEMA shell crack exhibits an "open/close" switching function. Such core-shell
microspheres are highly attractive for developing drug delivery systems with both biocompatible and thermo-responsive characteristics.