Solvent-Free Graft-From Polymerization of Polyvinylpyrrolidone Imparting Ultralow Bacterial Fouling and Improved Biocompatibility

Polymer grafting has been a powerful tool in the surface modification of biomaterials. Traditional solvent-based grafting, however, often requires laborious procedures taken under harsh conditions, which seriously hinders its practical applications. Here, we report a facile solvent-free graft-from method that is able to achieve a superior surface functionality as compared to most reported results from traditional solvent-based grafting. The grafting was proceeded by conformally coating a cross-linked polyvinylpyrrolidone (PVP) prime layer in the vacuum, immediately followed by in situ grafting of PVP homopolymer chains from the propagating sites on the coating surface. The resultant coating exhibited enriched surface pyrrolidone content compared to the single-layer cross-linked counterpart and a water contact angle of 22°, lower than most reported PVP-grafted surfaces. Medical catheters grafted with PVP achieved a more than 99.9% bacterial antifouling enhancement compared to the pristine catheter, and significantly improved biocompatibility during a 4 week in vivo test in mice. The achieved surface functionality is attributed to the synergistic effect from the functional groups distributed both on the grafted chains and on the cross-linked primer. The effectiveness and simplicity of the vapor grafting method thus suggest a promising surface modification route for biomaterials and beyond.