Phase Separation Behavior in Aqueous Suspensions of Bacterial Cellulose Nanocrystals Prepared by Sulfuric Acid Treatment
Phase Separation Behavior in Aqueous Suspensions of Bacterial Cellulose Nanocrystals Prepared by Sulfuric Acid Treatment
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DOI：
10.1021/la802947m
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发表时间：
2009-01-06
期刊：
影响因子：
3.9
通讯作者：
Tsuji, Masaki
中科院分区：
文献类型：
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作者：
Hirai, Asako;Inui, Osamu;Tsuji, Masaki
研究了硫酸水解法制备细菌纤维素（BC）过程中纤维素纳米晶水悬浮液的相分离现象。浓度高于0.42wt%的悬浮液分离成各向同性相和具有清晰相边界的手性双相。通过透射电子显微镜（TEM）和原子力显微镜（AFM）对两相中BC纳米晶的形状和尺寸分布进行了表征。用电导滴定法测定表面电荷密度。对于固定的总纤维素浓度，研究了添加的NaCl（0-5.0 mM）对水性悬浮液的相分离行为的影响。当NaCl浓度约为0.05时，手性相的Me体积分数最小。1.0在NaCl浓度范围为2.0至5.0mM时，悬浮液不分离成两相，而是完全变成液晶。在各向异性相的有序域的大小随NaCl浓度从0到2.75 mM的增加而减小。在2.75 mM时，在整个区域中仅观察到类晶。在5.0 mM时，不再观察到手性结构域。随着加入的NaCl浓度的增加，手性的手性的手性螺距降低，在约0.75 mM时达到最小值，然后随着NaCl浓度高达2.0 mM而急剧增加。
Phase separation phenomena of aqueous suspensions of cellulose nanocrystals have been studied for bacterial cellulose (BC) prepared by sulfuric acid hydrolysis. Suspensions at concentrations above 0.42 wt % separated into the isotropic and chiral nematic phases with a clear phase boundary. The shape and size distribution of BC nanocrystals in both the phases were determined by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The surface charge density was determined by conductometric titration. The effects of added NaCl (0-5.0 mM) on the phase separation behavior of the aqueous Suspensions were investigated for a fixed total cellulose concentration. Me volume fraction of the chiral nematic phase had a minimum value at a NaCl concentration of ca. 1.0 mM. At NaCl concentrations ranging from 2.0 to 5.0 mM, the suspensions did not separate into two phases, but became entirely liquid crystalline. The size of the ordered domains in the anisotropic phase decreased with an increase in the NaCl concentration from 0 to 2.75 mM. At 2.75 mM, only tactoids were observed in the entire region. At 5.0 mM, chiral nematic domains were no longer observed. The chiral nematic pitch decreased with increasing concentration of added NaCl, reached a minimum value at approximately 0.75 mM, and then increased sharply with the NaCl concentration up to 2.0 mM.