Photoresponsive Polymer Coatings with Regulated Molecular Organization for Switchable Wettability and Oil/Water Separation

Abstract

Photoresponsive polymer coatings capable of dynamically regulating surface wettability are promising for smart interfaces and oil/water separation, yet their performance is often limited by the crystallization and phase separation of fluorinated photoresponsive molecules during film formation. Herein, we present a supramolecular strategy to regulate molecular organization in photoresponsive polymer coatings by employing a thymine-functionalized copolymer, P(MMA-co-MAT), as the host matrix and an adenine-terminated fluorinated azobenzene (A-AZO-OCF3) as the photoresponsive guest molecule. Complementary thymine–adenine hydrogen bonding effectively suppresses fluorinated azobenzene crystallization, improves polymer–guest compatibility, and enables the formation of homogeneous amorphous coatings without requiring complex covalent modification. Differential scanning calorimetry, variable-temperature FTIR spectroscopy, and optical microscopy collectively demonstrate that supramolecular interactions dynamically regulate molecular organization while preserving sufficient molecular mobility for efficient photoisomerization. Consequently, the optimized T/A = 9/1 coating exhibits the largest light-induced wettability switching (ΔCA = 10.8°). Furthermore, the homogeneous coating is successfully transferred onto a three-dimensional melamine sponge to construct a photoresponsive porous interface with excellent hydrophobicity, strong interfacial adhesion, and efficient gravity-driven oil/water separation, achieving separation efficiencies of 95%, 90%, and 86% for dichloromethane, petroleum ether, and diesel, respectively. Reversible azobenzene photoisomerization further enables light-controlled fluid transport, allowing the porous interface to function as a photoresponsive fluidic gate. This work demonstrates that supramolecular regulation of molecular organization provides a simple and versatile strategy for constructing homogeneous photoresponsive polymer coatings with switchable wettability and controllable oil/water separation, offering opportunities for smart coatings and stimuli-responsive porous materials.