(144d) Surface Modification of Membranes by Initiated Chemical Vapor Deposition

Initiated chemical vapor deposition (iCVD) is a low energy process that can be used to produce thin polymeric films in which the pendant chemical moities are kept intact. iCVD has been used to polymerize a wide variety of vinyl monomers such as glycidyl methacrylate, 2-hydroxyethyl methacrylate, and 2-(perfluoroalkyl)ethyl methacrylate. The proposed polymerization mechanism is the classical free radical polymerization mechanism of vinyl monomers.

iCVD has the environmental benefit of using no solvents and the process can be used to conformally coat substrates with complex geometries such as membranes. The goal of this study is to use the iCVD process to functionalize the surfaces of polymeric membranes. These membranes have monodisperse pore distributions and vary in porosity, length, and diameter. iCVD is being used to coat these membranes with a low surface energy (10 mN/m) fluoropolymer that renders the membranes both hydrophobic and oleophobic. Contact angle measurements have been used to show that the hydrophobicity of the coated membrane is much larger than the uncoated membrane and x-ray photoelectron spectroscopy has been used to verify the presence of fluorine in the coated membranes . Dynamic contact angle measurements show a low hysteresis indicating that the internal pore surfaces are coated with the fluoropolymer. We are currently studying the depth of penetration of the coating as a function of pore diameter, pore length, and coating thickness.