Solventborne thermosetting compositions containing copolymers of isobutylene type monomers

A curable, solventborne film-forming composition comprising:

• (a) a polymeric binder comprising a copolymer, said copolymer being a polymerization product of:
• (i) 10 to 30 percent by weight, based on the total weight of monomers used to prepare the copolymer, of a donor monomer having the following structure (I):
• wherein R1 comprises linear or branched C1 to C4 alkyl, and R2 comprises methyl, linear, cyclic or branched C1 to C20 alkyl or alkenyl;
• (ii) 5 to 25 percent by weight, based on the total weight of monomers used to prepare the copolymer, of a monomer having aromatic functionality;
• (iii) 0 to 60 percent by weight, based on the total weight of monomers used to prepare the copolymer, of an acceptor monomer comprising an ethylenically unsaturated monomer containing secondary hydroxyl groups;
• and
• (iv) 15 to 50 percent by weight, based on the total weight of monomers used to prepare the copolymer, of an acceptor monomer comprising an ethylenically unsaturated monomer containing primary hydroxyl groups;
• wherein at least 15 mol percent of the copolymer comprises residues having the following alternating structural units:
• -[DM-AM]-
• wherein DM represents a residue from a donor monomer, and AM represents a residue from an acceptor monomer;
• (b) an aminoplast curing agent;
• and
• (c) 3 to 5 percent by weight, based on the total weight of (a), (b), and (c), of a compound comprising a capped isocyanate-functional material.