Vacuum‐UV Irradiation‐Based Formation of Methyl‐Si‐O‐Si Networks from Poly(1,1‐Dimethylsilazane‐co‐1‐methylsilazane)

Abstract

The vacuum-UV (VUV)-induced conversion of commercially available poly(1,1-dimethylsilazane-co-1-methylsilazane) into methyl-Si-O-Si networks was studied using UV sources at wavelengths around 172, 185, and 222 nm, respectively. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), X-ray photo electron spectroscopy (XPS), and Fourier transform infrared (FTIR) measurements, as well as kinetic investigations, were carried out to elucidate the degradation process. First-order kinetics were found for the photolytically induced decomposition of the Si-NH-Si network, the subsequent formation of the methyl-Si-O-Si network and the concomitant degradation of the Si-CH(3) bond, which were additionally independent of the photon energy above a threshold of about 5.5 eV (225 nm). The kinetics of these processes were, however, dependent on the dose actually absorbed by the layer and, in the case of Si-O-Si formation, additionally on the oxygen concentration. The release of ammonia and methane accompanied the conversion process. Quantum-chemical calculations on methyl substituted cyclotetrasilazanes as model compounds substantiate the suggested reaction scheme. Layers <100 nm in thickness based on mixtures of poly(1,1-dimethylsilazane-co-1-methylsilazane) and perhydropolysilazane (PHPS) were coated onto polyethylene terephthalate (PET) foils by a continuous roll to roll process and cured by VUV irradiation by using wavelengths <200 nm and investigated for their O(2) and water vapor-barrier properties. It was found that the resulting layers displayed oxygen and water vapor transmission rates (OTR and WVTR, respectively) of <1 cm(3) m(-2) d(-1) bar(-1) and <4 g m(-2) d(-1), respectively.

Method of Low-Temperature Conversion of Pehydropolysilazane into Amorphous SiOx in Aqueous Solutions

“…Moreover, the dissociation energies of these bonds (0.377 -0.420 kJ mol À1 ) in inorganic PHPS are greater than that of Si-CH 3 (0.315 kJ mol À1 ) 6) bonds of the organosilazanes. The absorption peaks from Si-N, Si-H, and N-H bonds all disappeared in the case of H 2 O 2 (30% in aqueous solution) curing with and without UV irradiation even after a 10-min curing time.…”

Conducting and stretchable nanometer-thin gold/thiol-functionalized polydimethylsiloxane films

“…At irradiation wavelengths below 190 nm, methyl groups become sensitive to radicalization, so C─H or even Si─C bonds are radicalized and methyl side groups are separated from the Si-O backbone of the PDMS chain. 9,26,27 The growth of the metal and elastomer films was controlled using the spectroscopic ellipsometer SE801 (Sentech Instruments GmbH, Berlin, Germany) and cross checked via atomic force microscopy surface scans along intentionally induced scratches. To examine in situ the optical properties of the forming nanostructures, SpectraRay3 software was utilized.…”

Perhydropolysilazane derived silica for flexible transparent barrier foils using a reel-to-reel wet coating technique: Single- and multilayer structures

“…In [26] Prager and Buchmeiser et al demonstrate R2R-coating by using PHPS and give values for OTR 1 cm 3 /m 2 /d/bar and WVTR b 4 g/m 2 /d of R2R-coated samples (36 μm PET, b 100 nm SiO x ; VUV curing) for a single layer from a mixture of PHPS and a methyl-substituted derivative of it. To our knowledge R2R produced multilayer-stacks are not described in the literature presently.…”

“…An alternative route is the conversion by UV [22,23], especially at short wave lengths (vacuum-UV VUV, λ = 172 nm). The current focus in the research to PHPS lies on VUV as well as on lowtemperature conversion [24,25] and on R2R-processing (from singlelayers to laminates) respectively, as Prager et al report [26,27].…”