Patent ID: 8382945

Claim:
An expandable microsphere comprising: a gas impermeable shell encapsulating at least one blowing agent, said gas impermeable shell including: a first polymeric layer surrounding said at least one blowing agent; and a second polymeric layer at least substantially encapsulating said first polymeric layer, wherein said second polymeric layer includes a homo- and/or co-polymer of at least one monomer selected from the group consisting of a monomer having a weight average Tg of at least 85° C. and a chemically reactive monomer; wherein said at least one monomer is selected from the group consisting of acrylonitrile, vinylidene chloride, methyl methacrylate, tetraethylene glycol dimethacrylate, 2,3-epoxypropyl acrylate, methacrylonitrile, glycidyl methacrylate, methacrylic acid, and vinyl benzyl chloride; and wherein said second polymeric layer has a weight average Tg that is greater than a weight average Tg of the first polymeric layer.