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 the density functional theory (DFT) calculations to present a comprehensive understanding of water-zwitterionic polymer interaction at the atomic and electronic levels. We further explore ice nucleation and adhesion on the studied polymers using different sizes of ice clusters to examine possible ice structures during the nucleation process. Our study reveals distinct hydration behaviors across the studied four representative zwitterionic polymers—poly(sulfobetaine methacrylate) (polySB), its structural isomer (polySBi), poly(2-methacryloxyloxyethyl phosphorylcholine) (polyMPC), and poly(carboxybetaine acrylamide) (polyCBAA) which unveil the molecular origin of their anti-icing performance. Our calculations demonstrate that polySB and polyMPC form strong hydrogen bonds with water molecules and significantly deform ice clusters and promote surface lubrication, making ice formation energetically unfavorable in their hydration layers. Conversely, polySBi exhibits the lowest ice adhesion but weaker anti-icing properties, while polyCBAA has moderate ice-binding strength. 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.