A composition includes a plurality of particles. At least some of the plurality of particles include cross-linked polyvinyl alcohol and have a diameter of about 500 microns or less. The particles have a first average pore size in an interior region, and a second average pore size at a surface region....http://www.google.es/patents/US7842377?utm_source=gb-gplus-sharePatente US7842377 - Porous polymeric particle comprising polyvinyl alcohol and having interior to surface porosity-gradient
Porous polymeric particle comprising polyvinyl alcohol and having interior ...
