(714b) Janus Membranes Via Physicochemical Area Selective Initiated Chemical Vapor Deposition

Development of scalable methods for fabrication of flexible, porous, and chemically heterogeneous thin films are of high interest, especially in membrane-based separation and purification technologies. Here, we introduce a simple method to fabricate thin film composite membranes through area-selective initiated chemical vapor deposition (iCVD). Using iCVD, we gained exceptional control over thickness, pore size, and porosity of the produced flexible films. Our method uses physicochemical templating of the surface to allow for area-selective deposition of polymers. We studied different conditions to identify the effective time constant during which the film growth can be suppressed. We used both free radical scavenger and monomer diffusivity in the templated domain, as the controlling parameters, and inhibited radical chain polymerization. We achieved control over spacing between the pores, pore diameter, and thickness of the films at the submicron resolution and on the planar surfaces (e.g., Si wafer). The chemical and physical properties of the porous films were analyzed through scanning electron microscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, we extended this approach to the 3-Dimensional (3D) substrates and created composite membranes by selective deposition of fluoropolymers on porous hydrophilic supports. We evaluated the performance of these membranes in seawater desalination through direct contact membrane distillation and recorded a stable permeate flux of 24±3 kg m^-2 h^-1 and a 100% rejection for the solute.