Patent ID: 8557288

Claim:
A process for forming microparticles comprising a cross-linked water-soluble polymer or cross-linked water-soluble polymers; the process comprising: combining macromers comprising at least one water-soluble polymer and at least one cross-linking agent in an aqueous solvent, wherein at least one of the macromers comprises a functionality of greater than 2, wherein at least one of the water-soluble polymers comprises a lower critical solution temperature (LCST), wherein functional groups of the cross-linking agent and the macromers react to form covalent bonds, wherein the covalent bonds form the cross-linked water-soluble polymer; and coacervation polymerizing the macromers to form a solution, wherein the coacervation polymerization comprises cross-linking the macromers at a temperature that is above the lower critical solution temperature (LCST) of at least one of the macromers, wherein the coacervation polymerization is done in the absence of mixing or agitation, wherein polymer-rich phases of the cross-linked water-soluble polymers gel before the solution coarsens to form droplets less than about 1 mm in diameter, wherein the macromers comprises at least one water-soluble polymer selected from the group consisting of polyacrylate, polyacrylamide, poly(acrylamide sulphonic acid), polyacrylonitrile, polyamines, poly(ethylene glycol), poly(ethylene imine), poly(ethylene oxide), poly(ethyloxazoline), polyhydroxyethylacrylate, polymethacrylate, polymethacrylamide, poly(oxyalkylene oxide), poly(propylene oxide), polyurethane, poly(vinyl alcohol), and poly(vinyl pyrrolidone).