Effects of film thickness on moisture sorption, glass transition temperature and morphology of poly(chloro-p-xylylene) film

Moisture sorption, glass transition temperature (Tg) and morphology of ultra thin poly(chloro-p-xylylene) (parylene-C) are greatly influenced by geometrical confinement effects. For film <50 nm, the equilibrium moisture saturation is a decreasing function of film thickness. However, the Tg of film <50 nm is about 10 °C higher than thicker films. The above phenomena are attributed to the effect of geometrical confinement on the thermal properties and the morphology of parylene-C film. Surface confinement results in an increased in Tg, but a decreased in crystallinity for films <50 nm. In this study, we show that the increase in moisture sorption for parylene-C films <50 nm is dominated by the crystallinity variation.