Patent ID: 8889603

Claim:
A composition comprising highly cross linked expandable polymeric microparticles comprising labile and non-labile crosslinkers having unexpanded volume average particle size diameters of about 0.05 to about 5,000 microns and a cross linking agent content of from 0 to about 300 ppm of non-labile cross linking agents and from about 100 to about 200,000 ppm oflabile crosslinking agents, wherein said labile crosslinking agents comprise one or more hydrolytically labile silyl ether or silyl ester crosslinkers and wherein said particle size is constrained by cross-linking with said labile and non-labile crosslinkers wherein said labile cross links begin to break upon exposure to pre-selected conditions of temperature and/or pH, thereby permitting the microparticles to expand in a controlled fashion.