Tailoring Surface Characteristics of Polyamide Thin‐Film Composite Membranes toward Pronounced Switchable Wettability

Abstract

AbstractThis work is the first attempt to imitate the well known, bio‐inspired, super‐hydrophilicity/‐hydrophobicity phenomena by polyamide (PA) thin‐film composite (TFC) reverse osmosis (RO) membranes, without impairing their high separation ability. Two interdisciplinary approaches, “surface micropatterning” and “double stimuli responsivity,” are successfully consolidated to obtain novel PA TFC membranes that are capable of reversibly switching between strong surface hydrophilicity and surface hydrophobicity, upon changing temperature and pH. Efficient micropatterned PA TFC membranes are developed using two techniques, namely phase separation micromolding and microimprinting lithography. Poly(N‐isopropylacrylamide) (PNIPAAm) homopolymer and random copolymers of PNIPAAm with poly(acrylic acid) are specifically coated on the micropatterned PA TFC membranes employing carbodiimide coupling. Contact angle measurements reveal that the dual surface responsivity, derived by the grafted polyacrylamide‐based polymer coatings, is successfully amplified by virtue of promoting the membranes' surface roughness via “surface micropatterning.” Interestingly, most of the new surface modified PA TFC membranes also exhibit an improvement in the separation performance compared to their precursors. This work emphasizes the successful combination of “surface micropatterning” and “double stimuli responsivity” to prepare new tailored micropatterned surface‐coated membranes, and their potential toward enhanced separation performance and innovative membrane‐based desalination applications.