Modelling for effects of surface chemical composition on contact angle and applications in membrane flux control

Abstract

Surface wettability is related to the chemical composition of the surfaces; however, their mathematical connections are not well understood. An accurate and concise equation was derived to relate the contact angle and chemical composition of a composite surface, and subsequently verified by measuring the apparent water contact angle (WCA) on a special uniform surface with an increasing modification ratio. This surface was fabricated using the layer-by-layer method and modified using the ion exchange method. Excellent correlation (R2 = 0.9985) of the linear fit between the WCA cosine value and modification ratio verified the theoretical correlation. This conclusion was further applied to the study of membrane separation performance. The water flux of two cellulose membranes modified by chlorosulfonic acid had a good linear relationship (R2 = 0.9875) with the modification ratio. This result provides insight into precise wettability control, which is significant for the study of surfaces, membranes, and other fields.