Abstract: The use of a block copolymer of the following structure. Wherein R and R1 may be the same or different and each independently represents an alkyl or aryl group, X may be hydrogen or C1 to C20 alkyl group which may be branched or linear and wherein the aromatic ring substituent joined to polymer B is positioned meta or para to the aromatic ring substituent joined to polymer A and, wherein polymer A is a polymer (or copolymer) of ethylene and polymer B is a polymer of monomers selected from vinyl acetate, C1-C9 acrylate esters, acrylic acid and mixtures thereof as an additive in polyethylene or polyethylene terephthalate to improve the adhesion between co-extruded layers of the polyethylene and the polyethylene terephthalate and laminated films derived from such use.