Chain expended or branched copolymers of vinylidene aromatic monomer and unsaturated compounds with electrophilic groups

A composition comprising one or more chain extended and/or branched copolymers which is the product of

• one or more first copolymers of one or more vinylidene aromatic monomers and one or more unsaturated compounds containing on average about 0.02 to about 3.0 percent by weight of nucleophilic groups pendant from the first copolymer, and
• one or more second copolymers of one or more vinylidene aromatic monomers and one or more unsaturated compounds having electrophilic groups,
• wherein the one or more first copolymers of one or more vinylidene aromatic monomers and one or more unsaturated compounds containing nucleophilic groups are chain extended and/or branched by the one or more second copolymers of one or more vinylidene aromatic monomers and one or more unsaturated compounds having electrophilic groups as a result of formation of bonds by all or a portion of the nucleophilic groups of the first copolymer with all or a portion of the electrophilic groups of the second copolymer,
• wherein the one or more chain extended and/or branched copolymers are soluble in methylene chloride at 23° C. and exhibit a polydispersity of 2.5 or greater.