Synergistic modification of short‐chain fluoro‐alcohol and siloxane end‐capping agents endowing an enhanced superhydrophobic waterborne polyurethane coating

Abstract Waterborne polyurethane (WPU) is an environmentally friendly product that can replace organic solvents with water. Still, its linear molecular chain structure and the presence of hydrophilic groups greatly affect water resistance and mechanical properties, limiting its wide application in the field of coatings. Herein, a series of fluorosilicone modified waterborne polyurethanes (FSiWPUs) were prepared by introducing tridecafluoro‐nonanol (TFN) and (3‐aminopropyl) triethoxysilane (APTES) into the ends of molecular chains of WPUs. These chains were constituted by different soft segments, including polybutylene adipate glycol, polycarbonate diol, or polytetramethylene ether glycol. Then fluorine element in TFN migrates and aggregates onto the surface during FSiWPU film‐forming to reduce the surface energy. Meanwhile, the hydrolytic condensation of APTES forms a Si–O–Si micro‐crosslinking structure. As a result, the two capping agents enable the modified FSiWPU to have better hydrophobicity, water resistance, and mechanical properties. The research results show that when the TFN:APTES molar ratio of capping agents introduced is 8:2, the static water contact angles of FSiWPUs with different soft sections reach 161.4°–165.3° and the maximum water absorption rate reduce to 8.9%–13.78%. Due to the simultaneous improvement of hydrophobic, water resistance, and mechanical properties, the modified FSiWPUs become the most promising candidates for superhydrophobic coatings.