Study on surface structure of plasma‐treated polydimethylsiloxane (PDMS) elastomer by slow positron beam

Abstract

In this paper, the variations in surface structure of polydimethylsiloxane elastomers before and after argon plasma treatments have been investigated by X‐ray photoelectron spectroscopy, slow positron beam, and scanning electron microscope. An inorganic silica‐like layer was probed by X‐ray photoelectron spectroscopy after 3 minutes or longer time of treatments, and the sample surface turned into totally hydrophilic. Short time (1 and 2 min) plasma exposure mainly removed preexisting low molecular weighted (LMW) siloxanes on sample surface. By using slow positron beam, the thicknesses of silica‐like layer for 3‐, 5‐, and 10‐minute–treated samples were estimated to be around 30, 66, and 91 nm, respectively. Beneath the silica‐like layer, a loose polymeric structure was also detected, which was ascribed to the accumulation of LMW siloxanes. Scanning electron microscope images showed that the silica‐like layer cracked after 10 minutes of plasma treatment, which provided direct diffusion pathways for LMW siloxanes. Hence, 10‐minute–treated sample showed rather low organic composition near surface. Slow positron beam provides valuable depth profile information for evaluating the surface aging condition of polydimethylsiloxane composite.

Investigation of the surface microstructure evolution of silicone rubber during corona discharge via slow positron beam and electrochemical impedance spectroscopy

“…We deduced that the cracks originate from the rupture of the silica‐like layer. Because this inorganic layer is brittle, it finally fractures after long‐term corona or plasma exposure . When the treatment time is longer (84 or 135 hr), pores cannot be found due to the massive generation of particle‐like species, as shown in Figure e–f.…”

Influenceof Vinyl Acetate Content on the Surface Hydrophobic Recovery of Ethylene Vinyl Acetate Copolymer after Plasma Modification

“…Generally, the polymer surface would be hydrophilic state immediately after plasma modification, but the surface would return to hydrophobic state after a few hours or days, which is called hydrophobic recovery . The hydrophobic recovery could be attributed to the diffusion of hydrophobic low molecular weight molecules or the relaxation of hydrophobic chain segments ,. In our previous study, it was found that the rheological property of EVA during the melt extrusion process is influenced by the vinyl acetate (VA) contents .…”

Barrier Diamond-like Carbon Coatings on Polydimethylsiloxane Substrate

“…Due to its properties, PDMS is a polymer material used in many applications, ranging from biomedicine to power engineering [ 1 , 2 , 3 , 4 , 5 ]. In addition, the properties of its surface can be changed via plasma modification, including corona plasma, DBD, and RF PACVD [ 1 , 4 ]. Laser treatment and UV radiation are also used for this purpose [ 1 , 6 , 7 , 8 , 9 ].…”