Surface modification of organic polymers, especially using ultraviolet ( UV ) excimer and Nd:YAG lasers, has been studied extensively. Since most of the organic polymers have very strong absorption bands only in the UV or vacuum-UV wavelength region, surface modification of polymeric materials by lasers in visible ranges is seldom reported....[ Read more ]

Surface modification of organic polymers, especially using ultraviolet ( UV ) excimer and Nd:YAG lasers, has been studied extensively. Since most of the organic polymers have very strong absorption bands only in the UV or vacuum-UV wavelength region, surface modification of polymeric materials by lasers in visible ranges is seldom reported.

Our research interest is to enhance the surface hydrophilicity of polyimide by Nd:YAG laser at 355nm and 533nm . Dyes, such as benzophenone, Disperse Yellow 9 and Rhodamine 6G, were used to dope the XU218 polyimide in order to achieve our goal.

The surface changes, after laser treatment, were analyzed by Contact Angles measurement, X-ray Photoelectron Spectroscopy ( XPS ), Scanning Electron Microscopy ( SEM ) and Time-of-flight Secordary Ion Mass Spectroscopy ( ToFSIMS ).

All the doped polyimides show an increase in surface hydrophilicity after laser treatment. XPS and ToF-SIMS proved surface hydrophilicity enhancement is mainly due to chemical changes on the polymer surface. Different dopants lead to the formation of different surface morphologies after laser treatment.

Wettability of polyimide doped with silicon dioxides was increased after laser treatment at 533nm although the doped polymer films are transparent at this wavelength. In order to investigate the reasons of such phenomenon, contact angle measurement, X-ray Photoelectron Spectroscopy and Quartz Crystal Microbalance ( QCM ) were applied to analyze the samples. The contact angles on SiO2 doped polyimides were changed slightly after laser treatment at 533nm but XPS results show there is no significant chemical change. From the QCM experiment, the increase in gas diffusion rate of the doped polyimides has been observed after laser exposure at 533nm. Results supported that the increase in surface wettability is mainly due to the formation of microporosity in the doped polyimides by laser pressure generated in the presence of silicon dioxides.