Self-assembly of stearic acid into nano flowers induces the tunable surface wettability of polyimide film

Polyimide (PI) films with special wettability have received great attention for their potential applications. However, it is still a challenge to fabricate PI film with tunable wettability from hydrophobic to superhydrophobic and tensile strength > 140 MPa. Herein, PI films with tunable surface wettability induced by the nano flowers of SA through the self-assembly. Flower-like ZnO was grown on PI film without seed layer or morphology controlling agents via a simple hydrothermal method, which promoted to the self-assembly of SA into nano-flowers. Morphologies of ZnO crystals change from open-flower to sphere-bud just by tuning the synthetic concentration of zinc solution. SA can assemble into nano flower-like structures on all ZnO modified films resulting in water contact angles changing from 124.0 degrees to 155.5 degrees. The self-assembly mechanism was also investigated. The superhydrophobic PI exhibits stable superhydrophobicity under dynamic water pressure, which is a crucial parameter for potential self-cleaning employment. Thermal stability of superhydrophobic film are comparable to the pristine PI film. Tensile strength of superhydrophobic PI film is higher than 140 MPa. (C) 2017 Published by Elsevier Ltd.