Surface fluorination of polystyrene particles via CF4 plasma irradiation using a barrel-plasma-treatment system

In this study, polystyrene powder was subjected to CF4 plasma-treatment using a polygonal barrel-plasma-treatment system to enhance the hydrophobicity of the particles. The characterization of the treated samples showed that the orange-peel-like surface of the particles was changed into rugged structures by the CF4 plasma-treatment. The plasma-treatment using our system also resulted in the fluorination of the particle surfaces. The contact angle of a water droplet loaded on the sample treated at a radio frequency (RF) power of 150 W for 10 min (149.1°) was significantly larger than that on the untreated sample (123.6°): both the contact angle value and the fluorine content of sample depended on the RF power. These results indicate that the hydrophobicity of the polystyrene powder was improved by our system, allowing preparation of stable liquid marbles, including CuCl2 solutions, which can be used as NH3 gas sensors.