Chemical and electrical properties of HMDSO plasma coated polyimide

In this work, surface properties of polyimide (PI) films coated by thin layers deposited from pure hexamethyldisiloxane (HMDSO) vapours in low frequency powered plasma reactor have been investigated. The polymer thin layers were elaborated at different plasma treatment times. The surface characterization of the coated PI film is performed using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), refractive index, scanning electron microscopy (SEM), water droplet contact angle measurements and surface potential decay. The high carbon content revealed by ATR-FTIR analysis makes the coated surface PI films more hydrophobic. The water contact angle increased from 63° for untreated film to 115° after 10 min of HMDSO plasma coating. The coated PI surfaces were found to stay practically unchanged following storage of the samples in ambient conditions, indicating stable hydrophobic surface treatments. The increase of the refractive index indicates less porous structure. Scanning electron microscopy images showed a homogenous coating without crack. Surface potential evolution after corona charge deposition showed the retention of deposited charges at the surface of coated PI film. Correlation between these different analysis techniques results has been discussed.

► Plasma polymer thin layers were deposited from HMDSO on PI substrates.
► The percentage of the organic groups (ATR-FTIR) increases with increasing treatment time.
► The water contact angle increase with increasing treatment time.
► The hydrophobicity of the thin layers films was correlated to the surface potential decay.