Surface Oxidation of Cellulose Fibers by Vacuum Ultraviolet Irradiation KOICHI KATO, 1 VICTOR N. VASILETS, 2 MIKHAIL N. FURSA, 2 MASASHI MEGURO, 1 YOSHITO IKADA, 3 KATSUHIKO NAKAMAE 1 1 Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan 2 Institute of Energy Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast’ 142432, Russia 3 Institute for Frontier Medical Sciences, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan Received 10 February 1998; accepted 24 June 1998 ABSTRACT: The efficacy of vacuum ultraviolet irradiation for oxidizing the surface of cellulose fibers was compared to that of the conventional wet and dry processes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 357–361, 1999 Keywords: cellulose fiber; oxidation; vacuum ultraviolet; surface modification; car- boxylic acid; hemostatic agent INTRODUCTION Numerous studies have been made on the surface modification of conventional polymeric materials with a view to improve surface properties such as adhesion, wettability, friction, wear, fouling, bar- rier, insulation, dyeing, biocompatibility, etc. The modification techniques thus far developed in- clude physical dry treatments by gas discharge, corona, ozone, and UV radiation, in addition to chemical wet processes. Vacuum ultraviolet (VUV) irradiation is a rel- atively new physical technique, which uses wave- length shorter than 200 nm for irradiation of poly- mers. 1–5 Due to high absorption coefficients (10 4 – 10 5 cm -1 ) of VUV the characteristic depth of VUV penetration for polymers does not exceed a few hundreds nanometer. 4 The energy of VUV pho- tons is enough for scission of any chemical bond including COC, COH, COO, COSi, and COF to produce radicals in the irradiated polymer sur- face layer. Recombination of the radicals formed by VUV irradiation can result in formation of double bonds and crosslinks in the surface layer. In the presence of air the radicals react with O 2 molecules as well as with O * 2 ,O 3 , and O active species produced by VUV photolysis of O 2 in the reaction chamber. These processes can initiate effective oxidation of the polymer surface. Pho- tooxidation by 123.6 and 147.0 nm radiation in the presence of air was investigated earlier for poly- (methyl methacrylate) and a siloxane rubber. 3,4 Cellulose fibers have been widely utilized for many years as row materials in the production of textile, paper, membrane, and hygiene materials. The surface functionalization of cellulose fibers is also required in some specific applications. For example, oxidized cellulose is applied as a topical hemostatic agent in surgical operations. 6 In spite of the importance of cellulose oxida- tion, relatively few approaches are currently available. 7 Therefore, we examined the feasibility of VUV irradiation for oxidizing the surface of cellulose fibers. It should be stressed that, for most of the applications, oxidation needs to be Correspondence to: K. Nakamae (Tel: +81-78-803-1163. Fax: +81-78-803-1169. E-mail: nakamae@cx.kobe-u.ac.jp) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 37, 357–361 (1999) © 1999 John Wiley & Sons, Inc. CCC 0887-624X/99/030357-05 357