Long-term stability of antifouling poly(carboxybetaine acrylamide) brush coatings

Abstract

A comprehensive understanding how storage conditions affect functional surface properties of antifouling organic coatings remains a persistent challenge across industry and research worldwide. This study investigates the long-term storage stability of state-of-art antifouling functionalizable zwitterionic poly(carboxybetaine acrylamide) (pCBAA) brushes using spectroscopic ellipsometry (SE), infrared reflection-absorption spectroscopy (IRRAS), surface plasmon resonance (SPR), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The pCBAA brushes, prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) on SPR substrates, were subjected to various storage conditions for 43 days: kept in dry state at room temperature or −20 °C, and immersed in water or phosphate-buffered saline (PBS) and kept at 6 °C or −20 °C. The IRRAS, SE and AFM data confirm only negligible release of pCBAA under these storage conditions. However, SE indicated a slightly lower brush swelling ratio depending on storage. The SPR was used to evaluate the resistance of unmodified pCBAA, pCBAA activated by EDC/NHS chemistry and deactivated with 2-(2-aminoethoxy)acetic acid (AEAA), and pCBAA functionalized with anti-E. coli antibodies against fouling from undiluted human blood plasma. The results confirm that pCBAA brushes maintain or may even improve their exceptional antifouling performance after prolonged storage, while displaying a slight deterioration in their binding capacity for anti-E. coli antibodies.