(277f) New Approaches to Synthesize Temperature-Senstitive Hollow Microspheres: in Situ Interfacial Polymerizations

In this study, novel one-step synthetic strategies for preparing hollow PNIPAM microspheres via an interfacial polymerization approach at the interface of an inverse W/O emulsion or a suspension polymerization is proposed and demonstrated. The results show that the PNIPAM microspheres prepared have real empty core and polymer shell structure, with a wall thickness ca. 100 nm, and a size range of 1-3 um in inverse emulsion polymerization case, and partcile size of ca. 3-5 um in suspension polymerization case respectively. The hollow microspheres experienced a reversible swelling and deswelling processes by mediating the temperature below and above the lower critical solution temperature (LCST) of the PNIPAM. The new approach provided not only a unique technical pathway to prepare hollow PNIPAM microspheres in situ under mild reaction conditions, extending easily to encapsulating bioactive guests, but also opened a platform in helping understanding of the mechanism of diffusion, migration of the PNIPAM at an oil/water interface above its LCST, and the polymer layer formation mechanism as well.