Surface Morphologies and Wettability Studies of pH‐Sensitive Nanofibrillated Membranes

Abstract

AbstractThe pH‐sensitive membranes have been extensively used in various fields. Through the incorporation of specific functional groups on pH‐sensitive molecules, diverse surface energies and degrees of wettability can be achieved at different pH values. In this study, we transformed pH‐sensitive copolymers into nanofibrillated membranes to increase their sensitivity to pH in terms of the contact angle formed by liquid droplets on their surface. Because N,N‐dimethylaminoethyl methacrylate (DMAEMA) contains an amino group, it is sensitive to acidic and alkaline environments. Moreover, to enhance the functionality, we selected styrene and methyl methacrylate (MMA) for random copolymerization with DMAEMA. We then used anodized aluminum oxide (AAO) templates to process the two copolymers into biomimetic fibrillated membranes. The contact angles between various‐pH aqueous droplets and different membranes were measured. Our results indicated that when the droplets were alkaline, the contact angle on the nanofibrillated membranes was large. When the pH of the droplets was decreased, the contact angle also decreased. In addition, the membranes were found to be reusable after being tested, washed, and dried. The surface free energy of nanofibrillated membranes with different molar feed ratios was also investigated in this study by using the model of Owens, Wendt, Rabel and Kaelble.