Plasma Polymerization of n-hexane in a Modular Reactor

The plasma polymer films were prepared in the Typical Modular Reactor (TMR). Two modules of this reactor with different geometry were used – parallel plate electrode arrangement and tubular arrangement. The homogeneity in thickness and the same chemical structure were found in the former case in the area of the substrate plane, corresponding to the size of the excitation electrode. In the latter case the same was observed in about 100 mm long region near the centre of the tubular module. Introduction The most widely used types of reactors for plasma polymerization can be divided into two main groups the parallel plate electrode reactor and the tubular reactor (more detailed description of these systems is in [1]). These reactors were used since 70. of the 20 century. It has been shown ( [2], [3]) that the exact geometry of the experiment influences the properties and the structure of the resulting films. The comparison of the experimental results between individual labs is then very difficult. Therefore it has been decided ( [4]) to develop and present a new variable system, which will include both types of reactors (with possibility to mount other types of reactors). A new so-called Typical modular reactor (TMR) was developed by J.Vyskocil, P. Hedbavny and H. Biederman. It has been decided to test the TMR performance with mixture of argon and n-hexane. The first set of experiments was done with the parallel plate electrode configuration. The second set of experiments was done in the tubular part with the same type of working gas. Experimental The stainless steel chamber was pumped by diffusion pump Edwards Diffstak MK2 with rotary backing pump. Two main sets of experiments were done to test the capabilities of the modular system. As mentioned before, properties of the resulting layers depend strongly on the geometry of the experiment. The thickness of the layers was measured as a function of the distance in the substrate plane to gain information on the homogeneity of the deposition process. For the thickness measurement the Surfometer SF 200 Planner Industrial was used. FTIR spectra were measured to examine chemical composition and homogeneity of the produced layers. FTIR reflection absorption spectra on silver-coated glass by means of the Bruker Equinox 55 were measured. Water contact angle (droplet method at water/air interface) measurement provided us with additional information on plasma polymer wettability. The water contact angles of droplets (about 2 mm in diameter) were measured by the self-built angle meter in static contact mode when the constant time (1 min) passed after dropping of water. Accuracy of the contact measurement is approx. 5° for angles close to 90°. Parallel plate electrode reactor module The reactor was made as a stainless steel chamber (300 mm in diameter, 300 mm in height). A water-cooled excitation copper electrode (81 mm in diameter) was mounted from the top (E1 in Fig.1). An aluminium counter-electrode was placed below. Distance of the counter-electrode was adjustable from 6 to 8.5 cm. Samples were placed directly on the counter-electrode (S2) or inserted via load-lock (S1). The RF generator Dressler Cesar 136 with a matching unit was used. Argon gas was introduced through a needle valve. As a monomer we used n-hexane in a glass container, that was connected to the chamber through another needle valve. Gas inlets (Ar and nH1 in Fig.1) were placed symmetrically with respect to the excitation electrode axis. WDS'06 Proceedings of Contributed Papers, Part III, 82–85, 2006. ISBN 80-86732-86-X © MATFYZPRESS