This invention relates to a general method to surface modify porous membranes with a free radical polymerized polymer coating in a layer which is less than the thickness of the membrane. Another object of this invention relates to a general method to surface modify porous membranes with a free radical polymerized polymer coating to a predetermined and controlled depth from a first facial surface. Another object of this invention is to provide a general method to surface modify porous membranes with a free radical polymerized polymer coating into a pattern on one or both facial surfaces, the pattern maintaining its form to a controlled depth into the membrane. Membrane modification is spatially controlled through the use of a polymerization preventing agent (PPA), which prevents modification from occurring in defined spatially volumes of the membrane. The invention relates to porous membranes surface modified by the methods described.