Photooxidation of Siloxane Polymers Under Vacuum Ultraviolet Irradiation

Abstract

Vacuum ultraviolet(VUV) irradiation (wavelength 147 nm) of siloxane polymers in the presence of air was studied using ATR FTIR and XPS spectroscopy. The ATR FTIR study revealed the formation of CO and OH groups in the surface layer depending on irradiation time and air pressure. The concentrations of CO and OH groups level off with the increase of irradiation time and pass through the maximum value with the increase of pressure in the range of 0.1-100 torr. The XPS study of irradiated polysiloxane films demonstrated that intermolecular crosslinking via oxygen atoms also takes place on the polymer surface. The concentrations of the most important oxygen species 0 and 03, produced by VUV photolysis of air and coming to the polymer surface were calculated for the air pressure range 0 .1-100torr. The photooxidation mechanism for siloxane polymers under VUV irradiation in air has been proposed.

A Comparative Mass‐Spectrometric Study of Plasma‐ and Vacuum Ultraviolet Ablation of Selected Polymers

“…Thus, for example, the bulk can be rendered more rigid, less susceptible to plastic deformation, by crosslinking with γ radiation,1–4 while polymer surfaces can be functionalised (rendered wettable, more amenable to adhesive bonding, bio‐compatible, etc.) by exposing them to ultraviolet (UV) light5–18 or to (low‐ or atmospheric‐pressure) plasmas 19–25. Indeed, most plasmas are emitters of photons in the UV portion of the spectrum, even in the vacuum ultraviolet (VUV, λ ≤ 200 nm), so that many plasma treatments automatically include a UV‐induced contribution to the final outcome.…”

The hydrophilization of polystyrene substrates by 172-nm vacuum ultraviolet light

“…Such radicals successively react with activated oxygen species simultaneously generated through the photoexcitation of atmospheric oxygen molecules. Consequently, the oxidation and etching of polymer surfaces proceed efficiently under VUV irradiation [25,26]. Indeed, VUV light has been demonstrated to play an important role in promoting surface modification in the plasma treatment of polymeric materials [27].…”

Sandwich Structure Containing Liquid Crystal Polymer Grafted on Polymer Support

“…The samples of PTFE and FEP, 10-130 pm thickness and 16 mm in diameter, were irradiated with vacuum ultraviolet ( W V ) in the vacuum chamber (3.3 X 10' Pa air pressure, 20 cm3 (standard temperature and pressure, STP)/minimum air flow rate) at room temperature. These conditions result in the maximum rate of surface oxidation under the simultaneous action of W V and atomic oxygen for a W V source intensity of 3 X 1015 quants/s at 147 nm and lamp-sample distance equal to 30 mm [6]. The radiation intensity at 147 nm was measured and controlled with a "sun blind" vacuum photodiode.…”