Slippery hydrophilic surfaces have gained significant attention due to their hydrophilicity and ultralow liquid adhesion, offering excellent biofouling resistance as well as enhanced condensation efficiency. Although polyethylene glycol (PEG) is widely used for such surfaces, the detailed molecular-level mechanism by which PEG chain length governs surface slipperiness remains elusive. Herein, we present a systematic approach to address this challenge by grafting silane-terminated PEGs of different molecular weights (0.3k, 5k, and 20k) onto smooth, nontextured substrates to unveil the role of PEG chain mobility in slippery behavior. While surface energies and packing densities were comparable across chain lengths, only the PEG5k-modified surface exhibited ultralow contact angle hysteresis (CAH), efficient droplet removal during condensation, and strong resistance to both protein adsorption and bacterial adhesion. We attribute these trends to differences in chain mobility governed by molecular weight, which influence how polymer brushes rearrange under stress to minimize contact line pinning. Utilizing PEG5k uniquely balances flexibility and packing to enable optimal slippery behavior, unlike PEG0.3k and PEG20k, which are either sterically limited or suffer from chain entanglement. This study provides a chemically simple and scalable route to engineer robust surfaces with antifouling and condensation-efficient properties for biomedical and environmental applications.
Keywords: PEGylation; antibiofouling; dropwise condensation; hydrophilic; slippery.