Preparation of thermo-responsive core-shell microcapsules with a porous membrane and poly(N-isopropylacrylamide) gates

A thermo-responsive core-shell microcapsule with a porous membrane and poly(N-isopropylacrylamide) (PNIPAM) gates was prepared using interfacial polymerization to prepare polyamide core-shell microcapsules, and plasma-graft pore-filling polymerization to graft PNIPAM into the pores in the microcapsule wall. The proposed thermo-responsive microcapsule could be a positive thermo-response controlled-release one or a negative thermo-response one by changing the PNIPAM graft yield. When the graft yield is low, the release rate from the microcapsules is higher at temperatures above the lower critical solution temperature (LCST) than that below the LCST, due to the opened/closed pores in the microcapsule membranes controlled by the PNIPAM gates. In contrast, when the graft yield is high, the release rate is lower at temperatures above the LCST than that below the LCST, due to the hydrophilic/hydrophobic phase transition of the PNIPAM gates.