*2.3. Characterizations of the Films*

The surface chemical structure of the film was identified by a FTIR Spectrometer (Thermo Nicolet 6700, Madison, WI, USA) with an ATR device. The spectra were collected at the following instrument parameters: scan range 400–4000 cm−<sup>1</sup> , resolution 4 cm−<sup>1</sup> , and scan times 16 [33]. The WCA of the surface was measured by a contact angle meter (Powereach JC 2000D, Shanghai, China). The surface morphology of the films was analyzed by AFM (Veeco DI3100, Plainview, NY, USA). The surface roughness of the films was the average roughness of three areas.
