Patent ID: 7279542
Filing Date: 2007-10-09
Classification: C08F

Abstract:
1. A method of preparing solid micro- or nano-particles comprising a cross-linked hydrophobic polymer which has been chemically modified to comprise hydrophilic moieties at its surface and optionally in its core, which comprises: a) dispersing under stirring a hydrophobic monomer in a medium wherein the corresponding polymer is not soluble, said medium further comprising an initiator, a cross-linking agent and at least one stabiliser, thus providing a suspension, dispersion or miniemulsion; b) heating the suspension, dispersion or miniemulsion at a temperature of between 50 and 90° C., thus inducing polymerization and providing polymeric hydrophobic particles, c) optionally using an excess of an organic solvent to remove un-reacted monomers; and d) adding a chemical agent for chemically modifying the polymeric particles, so as to transform hydrophobic moieties of the polymer formed in step b) into hydrophilic moieties at the surface of the particles and optionally in part of the core of the particles, with the chemical agent being either an acid for transforming ester moieties into carboxylic acid moieties or a quaternisation agent for quaternising amino-moieties into quaternary ammonium moieties, thus forming the solid particles.