Construction of PS/PNIPAM core-shell particles and hollow spheres by using hydrophobic interaction and thermosensitive phase separation

This paper reports an easy and effective way to fabricate polystyrene/poly(N-isopropylacrylamide)(PS/PNIPAM)core-shell particles and PNIPAM hollow spheres.The main point of the method is to take advantage of the hydrophobic interaction between initiator and PS particles.The hydrophobic azodiisobutyronitriles automatically concentrate around the PS particles and initiate polymerization of N-isopropylacrylamide(NIPAM)and the crosslinkermethylene bisacrylamide(MBA),which dissolve in the aqueous phase,at the surface of the PS nanoparticles.Then,PNIPAM adheres to the PS particles to form a coreshell structure as a result of their hydrophobic interaction.This interaction is due to the unique property of PNIPAM,namely,its ability to transition from hydrophilic to hydrophobic when the temperature rises to 32℃.Furthermore,the hollow PNIPAM spheres were obtained by etching the PS core with chloroform.