Depth Profile Analysis of the Modified Layer of Poly(vinyltrimethylsilane) Films Treated by Direct-Current Discharge

Mikhail Piskarev,Alexander Kuznetsov,Boris Senatulin,Alla Gilman,Elena Skryleva,Alexander Zinoviev,Daria Syrtsova,Vladimir Teplyakov

doi:10.3390/coatings11111317

Abstract

Previously, we found that modification of the membrane surface from polyvinyltrimethylsilane (PVTMS) by treatment with low-temperature plasma induced by low pressure DC discharge leads to a significant increase in gas separation characteristics. To understand the mechanism of this phenomenon, in this article XPS combined with precision etching 10 keV beam of Ar2500+ clusters was used for depth profiling of PVTMS spin-coated films before and after DC discharge treatment. The etching craters depths were measured by stylus surface profiler. The average etching rate of the untreated PVTMS film by Ar2500+ clusters was defined (230 nm/min). It was found that the low temperature plasma treatment of PVTMS leads to a sharp increase in the oxygen concentration on a surface with a simultaneous decrease in the carbon content. The experimental data obtained indicate also that the treatment of PVTMS film by plasma leads not only to a change in the chemical structure of the surface, but also to the formation of a gradient subsurface layer with a thickness of about 50 nm.

Highlights

Low-temperature plasma is widely used to modify the surface properties of polymeric materials [1,2,3,4,5,6]
PVTMS films were treated by DC discharge-induced cold plasma in vacuum using a technique and installation that we described in detail in [18]
It can be assumed that during plasma-induced chemical reactions, the C atoms of the Si(CH3 )3 fragments on the surface pass into the composition reactions, the C atoms of the Si(CH3)3 fragments on the surface pass into the composition of volatile products and are removed from the sample, while Si atoms and C atoms of of volatile products and are removed from the sample, while Si atoms and C atoms of the the main chain enter into chemical reactions, but they mostly remain in the modified main chain enter into chemical reactions, but they mostly remain in the modified layer

Summary

Introduction

Low-temperature plasma is widely used to modify the surface properties of polymeric materials [1,2,3,4,5,6]. It is currently believed that the depth of a modified layer of polymers, treated by various kinds of discharges, is in the range from several nanometers to ≤1–2 μm. In 1991, Nakayama et al [7] reported the determination of the depth of modified layer of a poly(ethylene terephthalate) (PET) 20 μm film after treatment by argon RF-discharge, using XPS in combination with secondary ion mass spectrometry and transmission electron microscopy. We determined the depth of the modified layer of polytetrafluoroethylene (PTFE) μm film treated by DC discharge of air at the anode (pressure of 10 Pa; discharge current of 50 mA; processing time of 60 s) [8]. It was found that the depth of the modified layer was 40–50 nm in this case

Methods

Results

Discussion

Conclusion