title: Hydroxyl radical-induced crosslinking and radiation-initiated hydrogel formation in dilute aqueous solutions of carboxymethylcellulose.
abstract: Ionizing radiation causes chain scission of polysaccharides in the absence of crosslinking agents. It has been demonstrated before that degradation of carboxyalkylated polysaccharides may be prevented, despite presence of strong electrostatic repulsing forces between chains, at very high polymer concentration in water (paste-like state) when physical proximity promotes recombination of radiation-generated polymer radicals. In such conditions, crosslinking dominates over chain scission and covalent, macroscopic gels can be formed. In an approach proposed in this work, neutralizing the charges on carboxymethylcellulose (CMC) by lowering the pH results in retracting the electrostatic repulsion between chain segments and thus allows for substantial reduction of polymer concentration required to achieve gelation due to domination of crosslinking reactions. Electron-beam irradiation of aqueous solutions of low pH containing 0.5-2% CMC results in hydrogel formation with 70% yield, while both concentration and dose determine their swelling properties. Time-resolved studies by laser flash photolysis clearly indicate strong pH influence on decay kinetics of CMC radicals.
authors.affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland; Nuclear Professional School, School of Engineering, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Ibaraki 319-1188, Japan. Electronic address: wach@mitr.p.lodz.pl.
authors.forename: Radoslaw A
authors.initials: RA
authors.lastname: Wach
authors.affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
authors.forename: Bozena
authors.initials: B
authors.lastname: Rokita
authors.affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
authors.forename: Nina
authors.initials: N
authors.lastname: Bartoszek
authors.affiliation: Nuclear Professional School, School of Engineering, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Ibaraki 319-1188, Japan; Department of Nuclear Engineering and Management, School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Katsumura
authors.affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Ulanski
authors.affiliation: Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Wroblewskiego 15, 93-590 Lodz, Poland.
authors.forename: Janusz M
authors.initials: JM
authors.lastname: Rosiak
mesh_terms: D002266:Carboxymethylcellulose Sodium / Q000737:chemistry* / Q000528:radiation effects; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D011839:Radiation, Ionizing; D012996:Solutions / Q000737:chemistry / Q000528:radiation effects; D055672:Static Electricity; D014867:Water
chemical_list: D020100:Hydrogels; D012996:Solutions; D014867:Water; D017665:Hydroxyl Radical; D002266:Carboxymethylcellulose Sodium
keywords: Carboxymethylcellulose; Crosslinking; Ionizing radiation; Polymer solution; Polysaccharide hydrogels