Ab initio investigations of zwitterionic polymers and their interactions with water and ice

Abstract

Preventing ice formation and accumulation on solid surfaces remains a great challenge across a wide range of applications. The application of anti-icing coatings has emerged as an effective strategy to reduce both ice formation and adhesion. Among those, zwitterionic polymeric coatings have recently demonstrated promising anti-icing performance; however, their interactions with water and ice at a fundamental level are not yet fully understood. In this work, we present an attempt to address this knowledge gap by employing density functional theory (DFT) calculations to present a comprehensive understanding of water-zwitterionic polymer interaction at the atomic and electronic levels. We further explored ice interactions and adhesion with the studied polymers using different sizes of ice clusters and the ice surface. Our study reveals distinct hydration behaviors across the studied four representative zwitterionic polymers – poly(sulfobetaine methacrylate) (polySB), its structural isomer (polySBi), poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC), and poly(carboxybetaine acrylamide) (polyCBAA) which unveil the molecular origin of their anti-icing performance. Our calculations show that polyMPC forms strong hydrogen bonds with water molecules, while polyCBAA develops a thicker hydration layer. Both polySB and polyMPC significantly deform ice clusters and promote surface lubrication, making ice formation energetically unfavorable within their hydration layers. PolyCBAA shows moderate binding with ice clusters, but substantially deforms the ice surface, promoting a lubricating water-like interfacial layer. In contrast, polySBi exhibits the lowest water adsorption and the weakest anti-icing performance. These molecular-level insights highlight the critical role of charged group arrangements in polymer–water–ice interactions, paving the way for the design of next-generation anti-icing materials.