Effect of molecular weight on radiation chemical degradation yield of chain scission of 纬-irradiated chitosan in solid state and in aqueous solution

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• 作者：Djamel Tahtat ; ¹ ; ^{tahtatdja@yahoo.fr} ; Mohamed Mahlous ; Samah Benamer ; Assia Nacer Khodja ; Souad Larbi Youcef
• 关键词：Chitosan ; Gamma irradiation ; Degradation ; G-value ; Molecular weight
• 刊名：Radiation Physics and Chemistry
• 出版年：2012
• 期刊代码：68_0969806x
• 类别：ph
• 出版时间：June, 2012
• 卷：81
• 期：6
• 页码：659-665
• 文件大小：292 K

摘要

Chitosan A₁, A₂ and A₃ with molecular weight of 471, 207 and 100 kDa respectively, produced from squid pen chitin was degraded by gamma rays in the solid state and in aqueous solution with various doses in air at ambient temperature. Effect of molecular weight on radiation chemical degradation yield of chain scission and degradation rate constants of 纬-irradiated chitosan in solid state and in aqueous solution was investigated. The radiation chemical degradation yield G_(s) and degradation rate values were calculated. The molecular weight changes were monitored by capillary viscometry method and the chemical structure changes were followed by UV analysis. The results showed that, the degradation of chitosan was faster in solution, than in solid state. The values of G_(s) in solid state and in aqueous solution were respectively 1.1脳10^鈭? mol/J and 0.074脳10^鈭? mol/J for A₁, 4.42脳10^鈭? mol/J and 0.28脳10^鈭? mol/J for A₂ and 6.08脳10^鈭? mol/J and 0.38脳10^鈭? mol/J for A₃. Degradation rate constants values ranged from 0.41脳10^鈭? to 2.1脳10^鈭? kGy^鈭? in solid state, whereas in solution they ranged from 13脳10^鈭? to 68脳10^鈭? kGy^鈭?. The chitosan A₃ was more sensitive to radiolysis than A₁ and A₂. The chain scission yield, G_(s) and degradation rate constants seems to be greatly influenced by the initial molecular weight of the chitosan. Structural changes in irradiated chitosan are revealed by the apparition of absorption peaks at 261 and 295 nm, which could be attributed to the formation of carbonyl groups. In both conditions the peak intensity was higher in chitosan A₃ than in A₁ and A₂, the oxidative products decreased with increasing molecular weight of chitosan.