AVS 50th International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS-WeP

Paper AS-WeP2
Wettability Control of Polymer Surface through 126 nm Vacuum Ultraviolet Light Irradiation

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: Y. Nakanishi, Waseda University, Japan
Authors: Y. Nakanishi, Waseda University, Japan
A. Hozumi, National Institute of Advanced Industrial Science and Technology, Japan
N. Shirahata, National Institute of Advanced Industrial Science and Technology, Japan
S. Asakura, Waseda University, Japan
A. Fuwa, Waseda University, Japan
Correspondent: Click to Email
The surface modification of polymeric materials through vacuum ultraviolet (VUV) light irradiation has attracted much attention due to its wide variety of applications, including improvement of the wettability, biocompatibility and coating adhesion of such surfaces. In this study, we report on the surface modification of poly (methyl methacrylate) (PMMA) using VUV light of 126 nm radiated from an Ar@sub 2@@super *@ excimer lamp. We have particularly focused on the effects of atmospheric pressure during VUV-irradiation on the surface wettability, chemical structure and morphology of the PMMA surfaces, since atmospheric oxygen plays a crucial role in the photocleavage of polymeric chains and subsequent photooxidation. Each of the samples was exposed to VUV light for 1~50 min under various pressures of 3x10@super -4@, 10, 10@super 3@ or 10@super 5@ Pa. Hydrophobic PMMA surface became hydrophilic during VUV irradiation conducted over the pressure range of 10~10@super 5@ Pa. However, the degree of hydrophilicity of the modified surface was primarily determined by the atmospheric pressure. The minimum water-contact angles of the samples treated at 10, 10@super 3@ and 10@super 5@ Pa were about 49, 31 and 64°, respectively. On the contrary, in the case of 3x10@super -4@ Pa, PMMA surface became highly hydrophobic with its contact angle changing from 80 to about 100°. As confirmed by X-ray photoelectron spectroscopy, at 3x10@super -4@ Pa the C concentration and the intensity of the C-C groups in the C1s spectra increased. This was probably due to crosslinking reactions including the formation of new C-C bonds. Since the oxidation reactions did not proceed efficiently under such high vacuum condition, the free radicals may have recombined and crosslinked with each other, resulting in the increase of C-C groups. These results indicate that surface wettability of the PMMA substrates might be controllable by selecting the atmospheric pressure during 126 nm VUV irradiation.