Two-component polymer composite structures are described, such as a composite structure that includes a first polymer structure and a second polymer structure adhered to one another through interfacial adhesion provided by a semicrystalline random copolymer with 70-88 mole % propylene units and alpha olefin units having 2 or from 4 to 10 carbon atoms, the semicrystalline random copolymer having a heat of fusion of from 2 to 90 J/g and a crystallinity of from 2% to 65% of the crystallinity of isotatic polypropylene.