Self-assembling and Chiral Nematic Properties of Organophilic Cellulose Nanocrystals
Self-assembling and Chiral Nematic Properties of Organophilic Cellulose Nanocrystals
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DOI：
10.1021/jp900122t
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发表时间：
2009-08-13
影响因子：
3.3
通讯作者：
Heux, Laurent
中科院分区：
文献类型：
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作者：
Elazzouzi-Hafraoui, Samira;Putaux, Jean-Luc;Heux, Laurent
以环己烷为模型溶剂，用表面活性剂分散了不同长径比的棉纤维纳米晶。在高于临界浓度的条件下，悬浮液自发相分离为手性向列相。根据Onsager的理论，相分离受长宽比控制，而受多分散性的影响。具有最大长径比的样品没有出现任何相分离，而是在高浓度下出现了各向异性的凝胶相。实验发现临界浓度远低于预测值，表明棒与棒之间存在吸引人的相互作用。由于非极介质中的手性相互作用较强，小到2微米的手性向列相间距比在水中测得的要小得多。
Cotton cellulose nanocrystals with different aspect ratios have been dispersed in cyclohexane as a model apolar solvent, using surfactants. Above a critical concentration, which was higher than that in water, the suspensions spontaneously phase separated into a chiral nematic mesophase. According to Onsager's theory, the phase separation is controlled by the aspect ratio, while being influenced by the polydispersity. The sample with the highest aspect ratio did not show any phase separation but instead shows an anisotropic gel phase at high concentration. Experimental critical concentrations were found to be much lower than the predicted ones, revealing an attractive interaction between the rods. Chiral nematic pitches as small as 2 mu m were found to be much lower than those measured in water, due to stronger chiral interactions in the apolar medium.