A comparative study between inductively and capacitively coupled plasma deposited polystyrene films: Chemical and morphological characterizations

Thin polystyrene films were deposited on stainless steel substrates by capacitively and inductively coupled radio frequency glow discharge plasma, in order to compare their chemical and morphological properties. The films were characterized by Fourier-transform infrared spectroscopy (FTIR), X-Ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic force microscopy (AFM) and scanning electron microscope (SEM). Wettability properties were also determined by contact angle measurements. Ageing effect was studied by analysing films aged for 15 min and for 1 week. Results from both capacitively and inductively plasma polymerized polystyrene (pPS) films aged for 15 min showed that the chemical structure of the bulk, chemical composition of the surface (depth <10 nm) and wettability properties were rather similar. Only their microstructures were very different: the pPS film's microstructure showed homogeneous distribution of spherical particles of about 100 nm in diameter but the pPS film's microstructure seemed to be mainly influenced by the surface of the metallic substrate: orientated 'lamellae-like layers' of polymers were observed on each metallic grain. Ageing for 1 week in ambient air induced low oxygen uptake in the surface of both pPS films. The pPS topmost surface (depth <3 nm) was more oxidized than that of pPS but no modification of the chemical structure of the bulk or of the morphology was noticed after ageing.