*Xuan-Xuan Chang, Ping-Yen Hsieh, Ju-Liang He, Feng Chia University, Taichung City, Taiwan
With the versatile properties of biocompatibility, flexibility, low friction coefficient, anti-sticking, and chemical stability, parylene film has been applied commercially as a surface treatment for biomedical materials. Although parylene film fulfils its clinical requirement, the preparation route involves the high temperature pyrolysis of powdery di-para-xylene dimmer, which leads to the drawbacks of expensive starting material, low deposition rate, and high thermal energy consumption. In this study, a growth technique for obtaining parylene-like film on silicone rubber was developed by using para-xylene as the starting monomer. With the implementation of a pulsed power supply, featuring very low duty cycle and very short output pulse (in few micro second), it efficiently initiate the free-radical polymerization and greatly reduce the chance of fragmentation of the monomers. Thus, the pulsed plasma polymerized film remain largely the monomer structure than any other plasma technique. As a result of the pulsed plasma polymerization, the chemical structure of the obtained plasma polymer film strongly depends on the pulse on/off ratio. Under the optimal duty cycle condition, the film exhibit its structure and composition close to parylene, as opposed to the film obtained by using conventional pulsed-DC plasma polymerization, where aromatic rings are largely fragmented. Such pulsed plasma polymerized parylene film also reveal hydrophobic surface characteristic and a film adhesion grade of 5B determined using Scotch-tape test. These results imply that the pulsed plasma polymerization is a possible alternative to the conventional parylene preparation route for biomedical surface modification.