A polymer blend for use in a biomedical application comprising: (A) a polymer A, bearing zwitterionic pendant groups; and (B) a hydrophobic addition polymer B, selected from the group consisting silyl(alk)acrylates, alkyl(alk)acrylamides, dialkyl(alk)acrylamides, and alkyl(alk)acrylate polymers, wherein the structure of the blend exhibits phase separation forming a micro-phase segregated structure at a surface. Articles, methods of production and liquid blend compositions are also disclosed. Preferably A is a copolymer of 15 to 30 mole % 2-methacryloyloxyethyl-2'-trimethylammonium ethyl phosphate inner salt and 85 to 70 mole % of a C6-18 alkyl methacrylate, and B is a homopolymer of a C4-18 alkyl(meth)acrylate, blended in weight proportions of 1:1 to 1:50.