Polymer barrier materials have been increasingly used in many applications such as metal anti-corrosion, electronic packaging, and cultural relic protection, but they have poor resistance to water vapor compared to inorganic barrier materials. Herein, we demonstrate the first application of hyperthermal hydrogen induced cross-linking (HHIC) technology to improve dramatically the water vapor barrier properties of poly(chloro-p-xylylene) (PPXC) films by building a dense and intact surface cross-linking layer. With the HHIC treatment, a dense cross-linked layer is formed on the surface of the PPXC film, which serves as a dense barrier layer to water vapor diffusion. The water vapor transmission rate of the PPXC film sharply decreases from 8.4 × 10−16 to 2.1 × 10−16 g cm cm−2 s−1 Pa by 75% after 5 min HHIC treatment. Due to the advantage of selective cleavage of C–H bonds by HHIC treatment, the desired chloride groups and original physical properties (e.g. mechanical strength and light transmittance) were well preserved.
