Multiscale composite membrane with carbon nanofibers with tunable characteristics from superhydrophilic to superhydrophobic

Porous composite membranes with carbon nanofibers were successfully developed and were shown to show controlled wetting characteristics ranging from superhydrophilic all the way to superhydrophobic. The tunability of the surface morphology and the wetting properties was accomplished by adjusting the CNF characteristics post-processing. First, carbon nanofibers (CNF) with 150 nm dia., and length ∼100 µm were functionalized by a solution process method. They were then dispersed by sonication in deionized water. The dispersion was then vacuum-filtered in the membrane. Second, CNF-based composite films were obtained from dispersing as-received CNF in different solvent systems using sonication processing, then filtered into a membrane architecture separately. The optimum film obtained was found to be a CNF-trifluorotoluene composite. The former CNF-based film displays superhydrophilic wetting characteristics, with a contact angle of ∼0°. The latter coating shows superhydrophobic behavior with a contact angle of as high as 154° and negligible hysteresis.