Radiation-degraded chitosan

Tham, L. X., Nagasawa, N., Matsuhashi, S., Ishioka, N. S., Ito, T., Kume, T. 2001. Effect of radiation-degraded chitosan on plants stressed with vanadium. Radiation Physics and Chemistry 61 171-175. 

Radiation-degraded chitosan with molecular wdght of 45 kDa, DD > 80% was found to act as a plant-growth stimulator in orchid tissue cultivation. It was found that the optimal concentration of the chitosan oligomer of 50-75 ppm was the most effective for plant-growth promotion (Upathum 2002). 

FIGURE 31.7 Radiation and chemical-radiation degradation of chitosan (hydrogen peroxide is added before irradiated by electron beam). (From Chmielewski, A.G. et al., Radiat. Phys. Chem., 76, 1840, 2007. With permission.)... 

Upathum, C. S. 2002. Radiation degradation of chitosan and its application for young orchid plant growth promotion. In Advances in Chitin Science, Vol. V, K. Suchiva, S. Chandrkrachang, P. Methacanon, M. G. Peter (eds.), Bangkok, Thailand, pp. 475-478, ISBN 974-229-412-7. 

Philipchatina, O.A. and Sharpatyi, V.A. (2007) Free-radical mechanism of chitosan radiation degradation and problems of the chemical antiradiation... 

For the in vitro application of polymers and microgels, ionizing radiation is an efficient tool for their synthesis. Chitosan can be degraded in a controlled way and the target molecular weight can be reached by selection of the appropriate radiation dose. The irradiation of vinyl pyrrolidone is a convenient way to synthesize microgels that exhibit uniform sizes after grinding and fractionation. 

Czechowska-Biskup R, Rokita B, Ulanski P, Rosiak JM (2005) Radiation-induced and sono-chemical degradation of chitosan as a way to increase its fat-binding capacity. Nucl Instrum Methods Phys Res B 236 383-390... 

Naeem, M., Hassan, A, Ahmed, M., and El- Sayed, A., Radiation induced degradation of chitosan for possible use as a growth promoter in agricultural purposes, Cgrbohydr olym, 79 (2010), 555-562. 

Chitosan in the solid state could be degraded by y-irradiation, and usually a 100kGy dose is applied to obtain low-molecular-weight chitosan (Li et al. 2001). The mechanism may be ascribed to the direct action of radiation on the chitosan chain (reactions (31.1) and (31.2)) ... 

The radiation-induced degradation mechanism of chitosan in the aqueous HjOj solution is more complicated than that in solid state. Besides the reactions in solid state, the primary reactions might occur as follows (reactions (31.11) through (31.14)) ... 

Radiation-Induced Degradation of CM-Chitosan 31.2.2.1 Degradation in Solid State... 

The Gi of radiation-induced degradation of CM-chitosan in various conditions was listed in Table 31.1. 

In the CM-chitosan solutions that contained 0.02mol/L H2O2 (condition c) or 2.5 x 10" mol/L N2O (condition b), were 280% and 150% of that in condition a (Nj-saturated). In condition d, because 0.76 mol/L isopropanol was added into the CM-chitosan solution, G decreased to 5% of that in condition a. Similar to the degradation mechanism of chitosan in aqueous solution, the radiation energy of y-ray is absorbed mainly by water in dilute CM-chitosan aqueous solutions, and the direct effect of radiation on CM-chitosan can be neglected. The radiation chemical yield of reactive species released in the radiolysis of water are constant in the wide range of pH. In condition a, CM-chitosan aqueous solution was radiated with saturated N2. The active species that resulted in... 

The radiation effect of chitosan derivatives can be summarized as follows solid state and lowconcentrated solution state result in degradation, while high-concentrated solution state is favorable for cross-linking. The irradiation effect of chitosan derivatives in different conditions are proposed in Scheme 31.4. 

FIGURE 31.13 Radiation-induced degradation and cross-linking of DHP-chitosan in various conditions (irradiated at lOOkGy). (From Zhao, L. and Mitomo, H., Carbohydr. Polym., 76, 314, 2009. With permission.)... 

Huang, L., Zhai, M. L., Peng, J., Li, J. Q., Wei, G. S. 2007b. Radiation-induced degradation of carboxymethylated chitosan in aqueous solution. Carbohydrate Polymers 67 305-312. 

Kang, B., Dai, Y. D., Zhang, H. Q., Chen, D. 2007. Synergetic degradation of chitosan with gamma radiation and hydrogen peroxide. Polymer Degradation and Stability 92 359-362. 

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