CONTROLLED MODIFICATION OF POLY(HYDROXYBUTYRATE) SURFACES BY A PERFLUOROHEXANE PLASMA - ESCA AND CONTACT-ANGLE STUDIES

Poly(hydroxybutyrate) films and inorganic glass slides were treated by cold plasma. The composition of the gas mixture of perfluorohexane an d hydrogen was varied to obtain controlled surface coatings of differe nt hydrophobicities. The analysis by weight variation, scanning electr on microscopy (SEM), electron spectroscopy for chemical analysis (ESCA ), and contact angle measurements were used to evaluate the influence of the flow rate, composition, and the plasma power on the surface str ucture after the plasma deposition. High-resolution ESCA spectra were used to determine quantitatively the amount of different fluorine-cont aining species present in the plasma-deposited layers. Molecular struc tures and surface energies of deposited layers on polymer substrates w ere compared with those on inorganic substrates. In both cases a stron g correlation was found between the surface free energy and the fluori ne/carbon ratio as well as the oxygen/carbon ratio. Furthermore, sampl es with high carbon/fluorine ratios showed a high content of CF2 and C F3 groups.