Hydrophobic Coating of Solid Materials by Plasma-Polymerized Thin Film using Tetrafluoroethylene

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Abstract
Highly hydrophobic coating of solid materials by plasma polymerization of tetrafluoroethylene (TFE) in a cylindrical flow-through chamber under a glow discharge condition is described. Growth rate of the coating film depositing on a glass slide was raised with increasing high-frequency input power under plasma condition of relatively low electric field strength, while it was reduced under that of high field strength, presumably because intense fragmentation of the monomer to smaller molecules, useless for polymer formation, took place. Transparency of the coated film having 2000 .ANG. thickness was practically 100% throughout the visible light range and gradually decreased with shorter UV wave length. Effective transparency was observed in IR spectrum with the same film thickness except .nu.C-F vibration at 1400-1000 cm-1. Hydrophobic coating was further applied to ashed biological specimens which have very hydroscopic nature forming droplets in ambient air. Specimens of animal tissues and bacterial spores on glass slides were ashed by low-temperature plasma oxidation and subsequently coated with TFE. The treatment successfully altered the ashed specimens to the non-hygroscopic and at the same time strongly fixed the fine ash structures on the glass slides to make permanent preparations.