Plasma polymerization in a microcapillary using an atmospheric pressure dielectric barrier discharge

Atmospheric pressure plasma deposition is a beneficial technology due to its low cost and flexibility in terms of its operation and integration for in-line processing. This paper presents the use of an atmospheric pressure dielectric barrier discharge (DBD) to deposit an amine functional polymer film onto the inner surface of a glass microcapillary. A micro discharge was generated in a DBD chip made from a rectangular borosilicate glass capillary using externally attached parallel plate electrodes. A new microplasma configuration which consists of a perforated high voltage electrode and a ground electrode with large surface area is implemented to sustain a stable glow discharge at atmospheric pressure and a temperature of 35 °C. Polymerization was performed using a laboratory made plasma source working at a frequency of 8 kHz with 50% duty ratio of the inverter. The monomer precursors allylamine and ethylenediamine were selected to optimize the polymerization conditions at atmospheric pressure. The hydrophobicity and philicity of the deposited surface were controlled as functions of plasma power. The atmospheric pressure plasma polymerized (APPP) films were characterized using Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), plasma emission spectroscopy, contact angle measurements and growth rate analysis. An average growth rate of 1.18 μg s− 1 for plasma polymerized ethylenediamine (PPEDA) and 1.91 μg s− 1 for plasma polymerized allylamine (PPAA) was obtained at a discharge power of 15 W and 10 sccm of monomer flow rate. The film thickness of 0.9 μm for PPEDA and 2.1 μm for PPAA was determined using AFM for deposition time of 10 min. Polymerization results showed that the properties of APPP films can be controlled through optimization of parameters such as discharge power, treatment time and flow rates of the main gas and monomer vapors.