A composition is described comprising a styrene-isobutylene block copolymer; and at least one ethylenically unsaturated monomer. After curing the composition comprises polymerized units of the ethylenically unsaturated monomer. In some embodiments the ethylenically unsaturated groups are selected from (meth)acryl or vinyl ether. The composition is suitable for use as a (e.g. pressure sensitive) adhesive. Articles, methods of making an article, and methods of bonding are also described.