Surfaces with Switchable Wettability for Anti-Smudge and Antimicrobial Applications

Abstract

The increase in surface disinfectant usage has raised concerns regarding overexposure and environmental contamination, driving a growing interest in developing antimicrobial coatings. For long-lasting antimicrobial performance, coatings should incorporate contact-active, surface-attached biocides and exhibit durability. Surfaces equipped with immobilized biocides eliminate bacteria on contact without releasing harmful agents, addressing the limitations of conventional disinfectants that require frequent reapplication and contribute to environmental pollution. These coatings provide a more sustainable and long-lasting alternative to traditional surface disinfectants. In this work, we explore the synthesis, formulation, and functional properties of inorganic-organic hybrid coatings engineered to deliver dual functionalities: anti-smudge and antimicrobial performance, while achieving high hardness and flexibility. The coatings are based on a photocurable, double-grafted copolymer system, [L-(QAS)], where the graft copolymer AS consists of poly(dimethyl siloxane) (PDMS, S) grafted onto quaternized (Q) poly(dimethylaminoethyl methacrylate) (PDMAEMA, A), which is then grafted onto a ladder-like polysilsesquioxane (ELASQ, L) backbone. Formulated from 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, L-based coatings exhibit enhanced hardness combined with flexibility, characteristic of inorganic-organic hybrid materials. The double-grafted copolymer architecture enables controlled surface reconstruction upon exposure to moisture, allowing the coating’s surface properties to adapt in response to environmental conditions. In air, the coatings demonstrate effective anti-smudge properties, attributed to the presence of hydrophobic PDMS chains at the surface. Upon contact with droplets carrying bacterial E. coli cells, the surface undergoes reconstruction, exposing quaternary ammonium groups that disrupt bacterial membranes, providing potent antimicrobial activity. This work comprehensively examines the factors influencing the formulation, smudge resistance, surface reconstruction, and antimicrobial performance of these hybrid coatings, positioning them as promising candidates for durable, multifunctional surface protection in diverse applications.