Water-In-Water Emulsion Gels Stabilized by Cellulose Nanocrystals
Water-In-Water Emulsion Gels Stabilized by Cellulose Nanocrystals
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DOI：
10.1021/acs.langmuir.8b01239
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发表时间：
2018-06-12
期刊：
影响因子：
3.9
通讯作者：
Benyahia, Lazhar
中科院分区：
文献类型：
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作者：
Ben Ayed, Emna;Cochereau, Remy;Benyahia, Lazhar
通过在水中混合葡聚糖和聚（环氧乙烷）（PEO）并添加纤维素纳米晶体（CNC）来制备颗粒稳定的水包水乳液。CNC在由富PEO相形成的分散液滴的表面处形成层。过量的CNC分配到连续葡聚糖相中。通过加入10和100 mM之间的NaCl诱导CNC以不同的速率聚集。在超过2 g/L CNC的存在下，快速聚集导致形成乳液凝胶，没有显示出乳状液分层的迹象。共聚焦激光扫描显微镜显示，乳胶是由CNC的连续网络形成的，其中随机分布的液滴嵌入其中。用振荡剪切流变学测量凝胶刚度，并且发现随着CNC浓度的增加而强烈增加（C）。分散液滴具有弹性活性，并在低C下增加凝胶刚度。然而，当C = 10 g/L时，屈服应力太小而不能抑制凝胶倾斜时的流动。在C <2g/L时，观察到乳状液分层，直到连接的液滴的网络变得足够致密以足够强以抵抗浮力。
Particle-stabilized water-in-water emulsions were prepared by mixing dextran and poly(ethylene oxide) (PEO) in water and adding cellulose nanocrystals (CNC). The CNC formed a layer at the surface of the dispersed droplets formed by the PEO-rich phase. Excess CNC partitioned to the continuous dextran phase. Aggregation of CNC at different rates was induced by adding NaCl between 10 and 100 mM. In the presence of more than 2 g/L CNC, fast aggregation led to the formation of an emulsion gel showing no signs of creaming. Confocal laser scanning microscopy showed that the emulgels were formed by a continuous network of CNC in which the randomly distributed droplets were embedded. The gel stiffness was measured with oscillatory shear rheology and found to increase strongly with increasing CNC concentration (C). The dispersed droplets were elastically active and increased the gel stiffness at low C. However, up to C = 10 g/L, the yield stress was too small to inhibit the flow when the gels were tilted. At C < 2 g/L, creaming was observed until the network of connected droplets became sufficiently dense to be strong enough to resist buoyancy.