Li J, Revol J F, Naranjo E, Marchessault R H
Department of Chemistry, McGill University, Montreal, PQ, Canada.
Int J Biol Macromol. 1996 Apr;18(3):177-87. doi: 10.1016/0141-8130(95)01066-1.
Optical and electron microscopy were used to observe the dynamics of the phase separation in aqueous chitin suspensions prepared by HCl hydrolysis of crab chitin. Freeze-fracture transmission electron microscopy reveals that chitin crystallites are partially aggregated in the suspension and have an average length of 200 nm and an average width of 8 nm. They exhibit a positive surface charge of approximately 0.5 e/nm2 when fully protonated. The liquid crystal-forming aqueous suspensions of such crystallites are investigated through phase diagrams and Zeta potential measurements for different ionic strength. Exposure of the suspension to a low concentration of univalent electrolyte has a negligible effect on phase separation because of the contribution of the charged crystallites themselves to the ionic strength. The thickness of the effective repulsive layer is estimated both from the phase diagrams according to Onsager's theory and from the computed interaction energy derived from the Poisson-Boltzmann equation using the experimental Zeta potential as surface potential. When the contribution of crystallites to the ionic strength is taken into account and an hypothetical linear charge density close to the Manning limit is assumed, there is good agreement with the Debye length.
利用光学显微镜和电子显微镜观察了通过盐酸水解蟹壳几丁质制备的几丁质水悬浮液中相分离的动力学过程。冷冻断裂透射电子显微镜显示，几丁质微晶在悬浮液中部分聚集，平均长度为200纳米，平均宽度为8纳米。当完全质子化时，它们表现出约0.5 e/nm² 的正表面电荷。通过相图和不同离子强度下的zeta电位测量，研究了此类微晶形成液晶的水悬浮液。由于带电微晶本身对离子强度的贡献，将悬浮液暴露于低浓度单价电解质对相分离的影响可忽略不计。根据昂萨格理论从相图以及使用实验zeta电位作为表面电位从泊松-玻尔兹曼方程导出的计算相互作用能来估计有效排斥层的厚度。当考虑微晶对离子强度的贡献并假设接近曼宁极限的假设线性电荷密度时，与德拜长度有良好的一致性。
