Patent ID: 7056901

Claim:
An acid hydrolyzable microgel composition, comprising: (a) a polymer backbone crosslinked by an acid hydrolyzable crosslinker, wherein said crosslinker hydrolyzes at pH 4.5 to pH 7.4; (b) the crosslinker having the formula R 2 CH(OR 1 ) 2 , wherein R 1 is an acryloyl group; and R 2 is Ar—X where X is a water solubilizing group selected from hydrogen, methoxy, —O—(CH 2 —CH 2 —O) n —CH 3 wherein n is from 1 to 10, —O—CH 2 —CH 2 —O—C(O)—O—Ph—NO 2 and —O—CH 2 —CH 2 —CH 2 —NH—CO-(dextran polysaccharide), said dextran polysaccharide having a molecular weight from 300 to 100,000 daltons; and Ar is an aryl group; (c) a particle size of the microgel composition between 0.1–10 microns; and (d) cross linkages between 1 and 20 mole percent.