Photochemical Modification of Cross-Linked Poly(dimethylsiloxane) by Irradiation at 172 nm

Abstract

Cross-linked poly(dimethylsiloxane) (PDMS) was irradiated with a Xe2*-excimer lamp (172 nm) under ambient conditions. The irradiation in combination with the formed ozone results in an oxidation of PDMS to SiO2 at the polymer−air interface. The surface properties of the irradiated surfaces were studied by means of contact angle measurements, infrared spectroscopy, and X-ray photoelectron spectroscopy. The photochemical conversion of surface methylsilane groups to silanol groups is responsible for the large increase in surface free energy. Subsequent degradation of the polymer and formation of SiO x was monitored by infrared spectroscopy. As determined by X-ray photoelectron spectroscopy, the binding energy shifts reach values corresponding to SiO2. The atomic ratio concentration O:Si changes from about 1:1 (PDMS) to about 2:1 (SiO2). On the basis of the XPS and IR results, the photochemical reaction pathway from PDMS to silicon oxide via surface silanol groups is discussed. The strict linearity of the contact angle versus irradiation time and the clear dependence from irradiation intensity allows the tuning of the chemical surface functionalities.

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

“…Various approaches have been used to modify the surfaces of PDMS, including: chemical methods [9][10][11] and physical methods, such as ultraviolet ozone [12], and oxygen plasma [8,13]. In this paper, we used molding in order to reach the required roughness.…”

Silicones for Microfluidic Systems

“…Surface etching with plasma (oxygen [33,36,37], air [38], NH 3 [39] , argon [33], helium [33] or nitrogen [23]) consisting of high energy species such as electrons, ions and radicals, induces degradation of the polymer structure (siloxane bonds redistribution, removal of methyl groups from the polymer chain - Figure 24.2) and leads to formation of a thin, solid and hydrophilic surface layer (containing SiO x moieties and silanol groups [40,41]). Th e formation of functional groups as a result of plasma treatment is restricted to a depth of few hundred nanometers into the polymer bulk.…”

Hexagonal Network Organization of Dye-Loaded Zeolite L Crystals by Surface-Tension Driven Autoassembly

“…Oxidation of this type of film has two consequences: first, the overall film surface exhibits a higher wettability, thus avoiding removal of all zeolites during the sucking of the excess suspension. Second, the presence of two different materials results in specific oxidation processes and chemical functions [24][25][26] on the surface, allowing the creation of a surface-tension contrast between the PDMS protuberances and the PS network. Zeolite L crystals feature a distinct chemistry associated with the presence of silanol groups on the external crystal surfaces.…”