Solvent‐Free Synthesis of Selectively Wetting Multilayer and Janus Membranes

In this work, the deposition of hydrophobic coatings onto porous materials is systematically studied for the fabrication of membranes with asymmetric and symmetric wetting properties. Initiated plasma-enhanced chemical vapor deposition is used to deposit an organosilicon polymer coating onto chromatography paper of different thicknesses. The hydrophobic organosilicon polymer serves as an environmentally friendly alternative to fluorinated polymers and the all-dry coating process does not use solvents. The deposition time, thickness of the paper, and orientation of the paper relative to the stage are shown to affect the symmetry of the wettability. The chemical functionality of the deposited polymer is characterized via Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hydrophobicity and wetting behavior of the coated paper are characterized with contact angle goniometry and wicking studies. Scale-up of the process is also demonstrated by using a roll-to-roll module. The ability to systematically tune the wettability of materials allows for the fabrication of multilayer and Janus membranes for potential applications including filtration, smart textiles, flexible sensors, and wound dressings.