Response of Plasma-Polymerized Hexamethyldisiloxane
Films to Aqueous Environments
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Abstract
Thin
plasma polymer films were deposited in hexamethyldisiloxane
(HMDSO) and HMDSO/O<sub>2</sub> low-pressure discharges and their
chemical structures analyzed using infrared (IR) spectroscopy and
neutron reflectometry (NR). The (plasma-polymerized) ppHMDSO film
exhibits hydrophobic, poly(dimethylsiloxane)-like properties, while
the retention of carbon groups is reduced by O<sub>2</sub> addition,
yielding a more inorganic, hydrophilic ppSiO<sub><i>x</i></sub> film. Both films show a minor (vertical) density gradient
perpendicular to the substrate, where the exposed film surface seems
to be more oxidized, indicating oxidative aging reactions upon contact
with air. The hydration and water uptake abilities of the films in
aqueous environments were investigated in humid environments using
ellipsometry, NR in D<sub>2</sub>O, and multiple transmission-reflection
IR measurements after equilibration of the films in water