Preparation of poly(vinyl alcohol)/poly(acrylic acid) microcapsules and microspheres and their pH-responsive release behavior

The pH-responsive poly(vinyl alcohol)/poly(acrylic acid) hydrogel microparticles containing vitamin B-12 were prepared with emulsion polymerization. Both microcapsule and microsphere were easily produced by simply changing the sequence of ingredient addition during the emulsion polymerization. The microparticles showed the faster and larger release of vitamin B-12 due to the higher swelling of hydrogel by electrostatic repulsion of carboxylate groups in poly(acrylic acid) as the pH was changed into more basic condition. The microcapsules showed a faster release than the microspheres did due to the less hindered passage through the thinner shell of microcapsules. The poly(vinyl alcohol)/poly(acrylic acid) hydrogel microparticles either protected or released the vitamin B-12 effectively depending on pH. (C) 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.