The invention is based on the discovery that a remarkable improvement in the performance of maleimide thermosets can be achieved by incorporating amide-extended maleimides into an adhesive formulation. Amide-extended maleimides described herein can be used to toughen bismaleimide thermosetting materials without sacrificing any thermal stability. Amide-extended maleimides are readily prepared by reacting a bismaleimide with an appropriate amine via the well-known Michael addition reaction. Acylation of the resulting secondary amines provides the amide-extended maleimide. The acylating agent can also be used to introduce polymerizable functional groups into the backbones of these thermoset monomers. Amide-extended acrylate and methacrylate monomers can also be prepared.