Radiation-chemical degradation of cellulose and other polysaccharides

Abstract

The state-selective dissociation dynamics for anionic and excited neutral fragments of gaseous SiCl 4 following Cl 2p and Si 2p core-level excitations were characterized by combining measurements of the photoninduced anionic dissociation, x-ray absorption and UV/visible dispersed fluorescence. The transitions of core electrons to high Rydberg states/doubly excited states in the vicinity of both Si 2p and Cl 2p ionization thresholds of gaseous SiCl 4 lead to a remarkably enhanced production of anionic, Si − and Cl − , fragments and excited neutral atomic, Si * , fragments. This enhancement via core-level excitation near the ionization threshold of gaseous SiCl 4 is explained in terms of the contributions from the Auger decay of doubly excited states, shake-modified resonant Auger decay, or/and post-collision interaction. These complementary results provide insight into the state-selective anionic and excited neutral fragmentation of gaseous molecules via core-level excitation.

Hydrogel of Radiation-Induced Cross-Linked Hydroxypropylcellulose

“…[22,23] It was postulated that polysaccharides like cellulose and its derivatives degrade by the rupture of glycosidic bond, which is the most prone to destruction in such macromolecules. [24,25] The yield of scission depends on the type of glycosidic bond. [26] For cellobiose, which similar to cellulose possesses b-1-4 linkages, the radicals placed on carbons next to the glycosidic bond i. e., C1 and C4 (and probably also that at C5) lead to scission.…”

Functional Properties of Some Non-Conventional Treated Starches

“…The descending change of solution pH after e-beam treatment of starchsimilar results on gamma-irradiated dry bean starch (Duarte & Rupnow, 1994) or e-beam treated sago starch (Pimpa et al, 2007) being previously reported by other research groupsindicates the formation of chemical groups with acidic character such as carboxyl, carbonyl or peroxide groups. This behavior is sustained also due to the fact that e-beam treatment was carried out in presence of oxygen determining thus the appearance of free radicals, compounds with carbonyl bonds (aldehydes/ketones), organic peroxides or other polysaccharide degradation products (Ershov, 1998) that can lead to the increase of starch acidity.…”

Hydrogels: Methods of Preparation, Characterisation and Applications

“…The hydroxyl radicals react with hyaluronan with a rate constant k 2 = 0.9 x 10 9 mol -1 dm 3 s -1 , whereas H atoms rate is a lower order of magnitude k 2 = 7 x 10 7 mol -1 dm 3 s -1 (Myint et al, 1987). Figure 11 shows the various hydrolysis, rearrangement, and fragmentation reactions during aqueous radiolysis of cellobiose to gives possible chain break (Sonntag, 1987 Fei et al, 2000;Liu et al, 2002b;Wach et al, 2003a;) (Fei et al, 2000;Liu et al, 2002b;Wach et al, 2001;Wach et al, 2003a;) Hydroxy ethyl cellulose (Fei et al, 2000;Wach et al, 2003a) (Fei et al, 2000;Wach et al, 2001) chitin, chitosan & derivatives (Ershov et al, 1993;Ershov, 1998;Jarry et al, 2001;Jarry et al, 2002;) (Wasikiewicz et al, 2005) Cellulose & derivatives (Ershov, 1998;Nakamura et al, 1985;Phillips, 1961;Phillips, 1963;Wach et al, 2002) (Phillips & Moody, 1959;Wach et al, 2002) Starch and derivatives (Ershov, 1998;Nagasawa et al, 2004;Phillips, 1961;Zhai et al, 2003) D-glucose (Phillips, 1963;Schiller et al, 1998) (Sharpatyi, 2003) Hyaluronan & hyaluronic acid (Al-Assaf et al, 1995;Al-Assaf et al, 2006a;Ershov, 1998;…”