Homogeneous and stable layers were deposited through allylamine plasma polymerization (75 W, 100 Pa, 15 min) onto poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] (91 : 9 wt.-%) (P(HB-co-9%HV)) film surfaces. XPS analysis using take-off angles of 20" and 70" and performed 10 days and 20 days after plasma treatment gives information on the composition (in atom %) of the modified surface: C, 62.74; N, 19.60; 0, 17.65. The unexpected oxygen percentage is weaker if argon plasma pretreatment (25 W, 40 Pa, 5 min) is applied. Then, a succinct mechanism is proposed. The study of changes in element ratios and binding energy values shows that the majority of incorporated functional groups seem to be amide and imine groups.
Poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)](91 : 9 mass-%) (P(HB-co-9% HV)) film surfaces were modified by an oxygen plasma treatment (75 W, 50 Pa, 5 min). The number of oxygen atoms increases about 12-13% and the polar component of the surface energy increases from 6.3 to 21 mN-m-'. However, the wettability is stable only after 60 days. Untreated and treated film surfaces are studied by means of X-ray photoelectron spectroscopy with two different depth analyses. With storage time, the oxygen contents of the modified film is constant at a take-off angle of 20" but decreases to the initial value at a take-off angle of 70". The superficial layer of the polymer film between the top of the film to a depth of 10 nm is divided into three superimposing zones. The interpretation is supported by motions of modified macromolecular chains and buried polar groups, chain cleavage and the formation of low-molecular-weight molecules which leads to a decrease of the glass transition temperature (plasticizer effect) and migration of short chains from the lowest modified zone toward the surface.
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