Preparation and Characterization of a Polymeric Dielectric Film with a Low Surface Free Energy

A polymeric nanofilm with a low surface free energy and high dielectric constant on the surface of a Mg-Mn-Ce magnesium alloy was prepared by a self-developed technique which was designed as polymer plating.The reaction mechanism during polymer plating was analyzed by X-ray photoelectron spectroscopy(XPS).The film formed on the magnesium alloy surface as determined by Fourier transform infrared(FT-IR) spectroscopy.The contact angle of distilled water and the surface free energy of the polymeric film were determined using a contact angle meter.The film thickness was characterized by spectroscopic ellipsometry.The dielectric property of the film was evaluated using a precision impedance analyzer.The experimental results show that the nanoscale polymeric film was successfully formed on the magnesium alloy surface after polymer plating.The contact angle of distilled water for the polymer-plated magnesium alloy increased to 150.5°compared with 70.8°for the substrate and the surface free energy of the polymer-plated magnesium alloy decreased to 1.57 mJ·m~(-2) from 37.96 mJ·m~(-2) for the substrate. Therefore,the functional performance changed from hydrophilic to hydrophobic.The film mass and thickness increased with the polymer-plating time before 20 min and then decreased slightly.The film mass and thickness after polymer-plating for 20 min increased to 23.5μg·cm~(-2) and 147.48 nm,respectively.The polymer-plated nanofilm at 20 min possesses a high relative dielectric constant of 24.922 at a frequency of 1 kHz.