Carbon tetrafluoride plasma modification of polyimide: A method of in-situ formed hydrophilic and hydrophobic surfaces

This study demonstrates that carbon tetrafluoride (CF4) plasma can result in relatively hydrophobic and hydrophilic surfaces formed in-situ on polyimide (PI) films using a mask and controlling the distance of the mask to the substrate. The surface properties of plasma-treated PI films are characterized by contact angle measurement, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). Under specific modification conditions, contact angles for hydrophobic and hydrophilic surfaces reach values of 108.3 +/- 0.6 degrees and below 5 degrees, respectively. The XPS analyses indicate that the "unshielded" surfaces contained a high proportion of the CF2-CF2 group and therefore decreased the wettability of the surface. On the other hand, the "shielded" surface contained hydrophilic groups such as carbonyl or carboxyl with few fluorinated groups, resulting in increased wettability of the surface. (C) 2009 Elsevier B.V. All rights reserved.