AVS 49th International Symposium
    Biomaterials Wednesday Sessions
       Session BI-WeP

Paper BI-WeP19
Poly(ethylene oxide)-Terminated Monolayer Formed at Solid/Vapor Interface

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Biointerfaces and Surfaces II
Presenter: A. Hozumi, National Institute of Advanced Industrial Science and Technology, Japan
Authors: A. Hozumi, National Institute of Advanced Industrial Science and Technology, Japan
Y. Yokogawa, National Institute of Advanced Industrial Science and Technology, Japan
T. Kameyama, National Institute of Advanced Industrial Science and Technology, Japan
Correspondent: Click to Email
Poly(ethylene oxide) (PEO) has been widely applied to the fabrication of protein or cell repellent surfaces in biotechnical and biomedical applications. Although extensive research on PEO-coating techniques has been reported in the literature, there have been few reports on preparing PEO-terminated monolayers from the vapor phase. Here, we report on the formation of a PEO-terminated monolayer on SiO@sub 2@/Si sample substrates through a chemical vapor deposition (CVD) method. Si substrates covered with na tive oxide (SiO@sub 2@/Si) were first cleaned by UV/ozone treatment. The cleaned samples were then exposed to vapor of organosilane, that is, 2-[methoxy (polyethyleneoxy) propyl] trimethoxysilane (MPEOPS) for 1~7 hours at 150 @degree@C. We have investigated in detail chemical and electokinetic properties of this PEO-terminated monolayer. The SiO@sub 2@/Si surface after CVD became relatively hydrophobic showing a water-contact angle of ca. 67±2. Thickness of the MPEOPS-monolayer was ca. 0.8±0.1 nm as estimated by ellipsomrtry. As confirmed by AFM, the surface was very smooth and homogeneous with almost identical to that of the SiO@sub 2@/Si substrate. Zeta-potentials of the MPEOPS-monolayer covered SiO@sub 2@/Si substrates were measu red as a fun ction of pH by means of an electrophoretic light scattering spectrophotometer. Isoelectric point of the MPEOPS-monolayer covered surface was observed at around pH 5 which was higher than that of SiO@sub 2@/Si (~pH 2.0). These results are att r ibutable to a reduction in the density of surface silanol (Si-OH) groups on the SiO@sub 2@/Si substrate. Si-OH groups were consumed due to the formation of siloxane bondings with the MPEOPS. Furthermore, we demonstrated micropatterning of this MPEOPS-mo no layer based o n the photolithography using an excimer lamp radiating vacuum ultra violet light of 172 nm in wavelength.