Laboratoire des Matériaux Polymères et des Biomatériaux, UMR CNRS 5223 IMP, Université de Lyon, F-69622 Villeurbanne Cedex, France.
Biomacromolecules. 2010 May 10;11(5):1376-86. doi: 10.1021/bm1001685.
The heterogeneous hydrolysis of fully deacetylated chitosan solid samples was carried out with concentrated HCl. The hydrolysis kinetics was studied at different temperatures and HCl concentrations. From 5 to 50 degrees C in the hydrolysis time range up to 50 h, a monomodal distribution of molecular weights was observed connected to the only degradation of amorphous domains. Between 70 and 90 degrees C and for the hydrolysis longest times, a multimodal distribution appeared with the additional hydrolysis of the crystalline phase. The crystallinity index increased from 57 to 73% with the elimination and partial recrystallization of amorphous regions. X-ray diffraction patterns revealed the presence of the anhydrous polymorph, absent in the starting materials only containing the hydrated polymorph. The apparent crystallite width (from the Scherrer equation) of both the anhydrous and hydrated allomorphs did not vary significantly with time despite the increase in the fraction of anhydrous allomorph. Therefore, the hydrolysis in the solid state was complex, revealing several regimes. The activation energy parameters were deduced, and the mechanisms were discussed.
采用浓盐酸对完全脱乙酰化壳聚糖固体样品进行不均匀水解。在不同温度和盐酸浓度下研究了水解动力学。在水解时间范围为 5 至 50°C，长达 50 小时内，观察到分子量呈单模态分布，这与非晶区的唯一降解有关。在 70 至 90°C 且水解时间最长时，出现了多模态分布，同时结晶相也发生了水解。结晶度指数从 57%增加到 73%，这是由于无定形区的消除和部分再结晶。X 射线衍射图谱表明，无水多晶型物的存在，而起始材料仅含有水合多晶型物时不存在无水多晶型物。尽管无水多晶型物的比例增加，但来自谢乐（Scherrer）方程的表观晶粒宽度（anhydrous allomorph）并未随时间发生显著变化。因此，固态水解很复杂，揭示了几个反应阶段。推断了活化能参数，并讨论了反应机制。
