Stimulus-Responsive Biopolymeric Surface: Molecular Switches for Oil/Water Separation

In this work, we fabricated a stimulus-responsive biopolymeric material and demonstrated the reversible character of a hydrophilic/hydrophobic interface upon exposure to UV light. Importantly, this stimulus-responsive material exhibited excellent features in an oil/water separation system. Cellulose was functionalized on both sides of the surface with a dopamine polymer and further modified with an azobenzene-fluorosilane material. Azobenzene can alter the properties of a material via an isomerization effect (trans-cis) upon exposure to UV light. Initially, the azobenzene-fluorosilane material was in a hydrophobic state; the contact angle was over 130°; and absorption performance with various organic solvents showed there to be high levels of extractive activity and outstanding reusability. When we exposed the material to UV light, the surface changed to that of a hydrophilic nature, and this phenomenon was influenced by the azobenzene chemistry of folding and unfolding of an azobenzene-fluorosilane molecule. Significantly, this phenomenon is a reversible, reusable, and eco-friendly material. Furthermore, dopamine polymers could block organic material, bacteria, and fungi, and this surface can be used for wastewater purification. Therefore, we foresee that the stimulus-responsive surface of biopolymeric material could result in a different direction in the oil/water purification fields.