Designing effective underwater self-cleaning surfaces by investigating the oil dewetting ability of hydrophobic and underwater superoleophobic Poly(Diisobutyl Glycolide)-Silica composite surfaces

Abstract

This study introduces composite thin films of amphiphilic structures to fabricate underwater superoleophobic surfaces. The hydrophobic part of the structure is created by poly(diisobutyl glycolide) thanks to a side chain of isobutyl groups, while the hydrophilic component is formed with hydrophilic silica nanoparticles. Poly(diisobutyl glycolide), having a 77° water contact angle, was obtained through ring-opening polymerization of l-diisobutyl glycolide in a bulk medium, resulting in excellent conversion (97.9 %) and narrow polydispersity (1.47), while maintaining the chiral center. The investigation revealed a notable increment in the underwater hexadecane contact angle from 110° to 160° In contrast, the water contact angle exhibited partial constancy in the air environment because of the augmenting silica content. At a silica content reached up to 30 %, the self-cleaning underwater oil-repellent surface was accomplished, attributable to the phenomenon of the underwater Cassie state, which effectively trapped air within the hierarchical rough structure. Moreover, the surface free energy (SFE) of the composite films was evaluated using both the van Oss-Chaudary-Good and Owens-Wendt methods. Notably, the contact angle of underwater hexadecane decreased with the increase of polar interactions as determined by both methods, owing to the influence of the underwater Cassie state of the hierarchical composite surface.