Template Polymerization to Fabricate Hydrogen-Bonded Poly(acrylic acid)/Poly(vinylpyrrolidone)Hollow Microcapsules with a pH-Mediated Swelling-Deswelling Property

摘要

Hydrogen-bonded hollow microcapsules with a lightly cross-linked shell structure were fabricated by polymerization of acrylic acid in a solution containing surface-modified silica particles and polyvinylpyrrolidone)and a subsequent core removal with HF;By further incorporating additional cross-linkers,a highly cross-linked shell structure was produced,which endows the microcapsules with better stability against large pH fluctuations;The hollow and intact microcapsules in both wet and dry states were characterized and confirmed by TEM,SEM,AFM,and CLSM;The chemical compositions of the microcapsules and hydrogen bonding in the shells were determined by elemental analysis and FTIR spectroscopy,respectively;The continuous shells of the lightly cross-linked microcapsules on the silica particles are composed of PVP and PAA with an equal molar ratio of AA to VP;Alkaline treatment cannot separate PVP from PAA,which demonstrates the strong interactions between PAA and PVP;The lightly cross-linked and highly cross-linked microcapsules could increase their sizes along with the pH increase,following a sigmoidal regime;The capsule swelling-shrinking process is completely reversible at high and low pH values,respectively.