Systematic study of the growth and morphology of vapor deposited porous polymer membranes

Abstract

In this paper, the authors systematically study the growth and morphology of porous polymer membranes fabricated via initiated chemical vapor deposition. The porous polymer membranes are formed by simultaneous solid monomer deposition and polymerization. The authors demonstrate that the solid monomer serves as both a porogen and a template for the polymerization, and therefore, the final structure of the membrane can be tuned by controlling the physical deposition of the monomer. The results show that the mass of the deposited monomer has a large dependence on the monomer flow rate and a small dependence on the substrate temperature, whereas the thickness has a large dependence on both parameters. The large dependence of the monomer thickness on the substrate temperature is due to significant differences in the morphologies, ranging from three-dimensional growth of pillared microstructures at low substrate temperatures to two-dimensional and weblike growth as the substrate temperature is increased. The authors also demonstrate that the location of membrane formation can be controlled by patterning the surface energy of the underlying substrate. These results can be used to fabricate polymer membranes of controllable morphology and thickness for a variety of applications in filtration, tissue scaffolding, and catalytic supports. In addition, the principles of the technique can be extended to other vapor phase polymerization and chemical vapor deposition processes.