This invention relates to compositions and methods for improving the impact properties of polymer-matrix composites and to improving the adhesion of resin compositions to substrate materials. More particularly, the invention relates to compositions and methods for improving the impact properties of ring opening metathesis polymerization (ROMP) polymer-matrix composites and to improving the adhesion of ROMP compositions to substrate materials using adhesion promoters containing at least two isocyanate groups and functional elastomers comprising a maleic anhydride grafted styrene-ethylene/butylene-styrene hydrogenated copolymer in a resin composition. The polymer products produced via ROMP reactions of the invention may be utilized for a wide range of materials and composite applications. The invention has utility in the fields of polymer and materials chemistry and manufacture.