Neutron Reflectometry and Spectroscopic Ellipsometry Studies of Cross-Linked Poly(dimethylsiloxane) after Irradiation at 172 nm

Abstract

Poly(dimethylsiloxane) (PDMS) was irradiated under ambient conditions in air with a Xe2-excimer lamp. The formation of atomic oxygen and ozone during irradiation in air by V-UV photons results in the transformation of PDMS to silicon oxide. The irradiated surfaces were studied by spectroscopic ellipsometry and neutron reflectometry. The measurements revealed the formation of a rough, i.e., between 11 and 20 nm, oxidized surface layer and a decrease of the total layer thickness. The thickness of the oxidized layer decreased for a given PDMS thickness when the polymer was irradiated for longer times and/or higher intensities. The composition of the oxidized layer after irradiation was not uniform through the layer and consisted of a mixture of original polymer and silicon bonded to three or four oxygen atoms (SiOx). The refractive index n determined by ellipsometry reaches a value similar to values reported for SiO2.

Dyeing of woven polyester fabric with curcumin: effect of dye concentrations and surface pre‐activation using air atmospheric plasma and ultraviolet excimer treatment

“…Just like air atmospheric plasma treatment, UV excimer irradiation uses the dielectric barrier discharge principle [8], but, contrary to plasma, the excimer lamp emits intense monochromatic light in the UV region of the spectrum. The Xe2-excimer lamp irradiation (172 nm) is absorbed by air and forms excited oxygen and ozone, which activate the surface of the irradiated substrate [13]. These lamps are available up to a length of 2.35 m, and hence they can be used to treat the entire width of a textile fabric.…”

Basic dyeable polyester: a new approach using a VUV excimer lamp

“…There is a second reaction also occurring concurrently. It is caused by the strong absorption of 172 nm radiation by atmospheric gases like oxygen, carbon dioxide and water vapour [10]. The oxygen in air absorbs the high energy photon and forms highly reactive excited oxygen O ( 1 D) either directly or first forming O 3 (ozone) and then dissociating into O ( 1 D) and O 2 .…”

“…Organic materials with multiple bonds or with atoms, which have non‐bonding electron pairs such as oxygen or nitrogen absorb light with a wavelength shorter than 200 nm very strongly [9]. For example, the Xe 2 *‐excimer lamp (172 nm) lamp irradiation is absorbed by air and forms excited oxygen and ozone [10]. This property limits the penetration depth of the photons to about 50–100 nm in the substrate (90% of the light is absorbed within a surface layer of this thickness) [9].…”

Effects of the morphology of sulfobetaine zwitterionic layers grafted onto a silicone surface on improving the hydrophilic stability, anti‐bacterial adhesion properties, and biocompatibility

“…From this viewpoint, vacuum ultraviolet (VUV) irradiation might be an effective and promising means for achieving uniform large‐area treatment under a short exposure time due to the high intensity and high photon energy provided by the excimer lamp. Graubner et al . and Schnyder et al .…”

“…However, the “hydrophobic recovery” of silicone should not be neglected in the applications of silicone materials . This property is mainly attributed to the diffusion of the linear and/or low molecular weight species produced in the activation or modification process, the reorientation of the polar groups on the surface and the nonpolar groups in the bulk, and the condensation of the surface hydroxyl groups . The “hydrophobic recovery” was evaluated by measuring the water contact angle(WCA), which increased with increasing storage time.…”