Enabling Tunable Hydrophilicity of PDMS via Metal-ligand Coordinated Dynamic Networks

Polydimethylsiloxane (PDMS) has been widely used in various fields due to its appealing physical and chemical properties. However, its high hydrophobicity not only yields poor adhesion to substrates but also facilitates undesired adsorption of substances such as proteins, biofoulers, etc., which limits the performance and lifetime of PDMS. Moreover, traditional surface modification techniques are often not efficient on PDMS surfaces because of the surface reconstruction. Although new methods involving chemical modification have been developed, most of them require complicated procedures and equipment. To overcome this challenge, we incorporate metal-ligand coordination, a non-covalent interaction bearing polar functionality, into PDMS, which exposes the hydrophilicity progressively upon dynamic bond breakage and reformation. We demonstrate that the hydrophilicity of coordinated PDMS can be tailored by the choice of network structure, counter anions, and metal cations, which yield distinct network dynamics. The wetting mechanism is discussed in the context of chain reconfiguration and surface reconstruction. We also show that a properly designed metal-ligand coordinated PDMS has potential as a superior marine fouling release coating by weakening diatom attachment. Through this paper, we introduce a new concept for tuning material hydrophilicity via dynamic polar functionalities, which is applicable to a wide range of polymers.