Disclosed are adhesive compositions comprising nonfunctionalized base resins and functionalized ethylene copolymers such as ethylene/maleic anhydride (E/MAH) or ethylene/ethyl hydrogen maleate (E/MAME) copolymer, which are synthesized directly in a high pressure autoclave. These adhesive compositions can be applied as self-supporting films or can be co-extruded or extrusion coated onto a substrate. Also disclosed are multilayer structures, films, pipe coatings and building panels comprising these compositions.