Multi-layer coated materials and methods of making them are disclosed. In a specific embodiment, a porous polymeric substrate is pre-activated and immersed in a polyelectrolyte solution to form a first layer having an electric charge and at least one functional group. The coated material is next immersed in a second solution of a material having an electric charge opposite of that of the first layer to provide a bi-layer coating. This process can be repeated to form multi-layer coatings on porous substrates.