Asymmetric articles with a porous substrate and a polymeric coating extending into the substrate and methods of making the same

A method of making an asymmetric composite article comprising:

• providing a porous substrate comprising a first major surface, a second major surface opposing the first major surface, and a porous structure extending therebetween, wherein the porous substrate comprises polypropylene membrane or an ethylene chlorotrifluoroethylene membrane;
• treating the porous substrate with a plasma treatment or a corona treatment, from the first major surface to a depth of the porous structure between the first major surface and the second major surface, wherein the depth comprises a depth of at least 0.5 μm from the first major surface and up to 30 μm from the first major surface;
• applying a coating solution to the treated porous substrate, wherein the coating solution comprises a polymer solution or a polymer emulsion in water or solvent or a water/solvent blend;
• and
• drying the coating solution to form a composite asymmetric composite article comprising a polymeric coating disposed on the first major surface or on the second major surface and extending into the porous structure to the depth of the treated porous structure.