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Ion-Induced Hydrogel Formation and Nematic Ordering of Nanocrystalline Cellulose Suspensions
Biomacromolecules ( IF 5.5 ) Pub Date : 2017-10-20 00:00:00 , DOI: 10.1021/acs.biomac.7b01119 Pascal Bertsch 1 , Stéphane Isabettini 1 , Peter Fischer 1
Biomacromolecules ( IF 5.5 ) Pub Date : 2017-10-20 00:00:00 , DOI: 10.1021/acs.biomac.7b01119 Pascal Bertsch 1 , Stéphane Isabettini 1 , Peter Fischer 1
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Nanocrystalline cellulose (NCC) is a promising material for formation of hydrogels and nematic liquid crystals. While salt addition is known to facilitate hydrogel formation, it remains unclear whether this originates from cationic bridging or charge screening effects. Herein, we demonstrate the effect of mono- and divalent salts on NCC gelation and nematic ordering. A strong correlation of NCC suspension zeta-potential and rheological behavior was found. Lower concentrations of divalent cations were needed to decrease NCC zeta-potential and form hydrogels. The same zeta-potentials and gel strengths were achieved at higher concentrations of monovalent salts. Salt-induced NCC aggregation is thus caused by intermolecular attractive forces rather than cationic bridging. Against excluded volume argumentation, salt addition was found to promote NCC nematic phase formation. Increased nematic ordering was observed in a transition regime of moderate salt addition before complete aggregation occurs. This regime is governed by an equilibrium of repulsive and attractive forces. Small angle neutron scattering suggests lateral orientation of NCC. Hence, NCC gelation and nematic ordering can be modulated via its zeta-potential by targeted salt addition.
中文翻译：
离子诱导水凝胶的形成和纳米晶纤维素悬浮液的向列有序性
纳米晶纤维素（NCC）是用于形成水凝胶和向列液晶的有前途的材料。尽管已知添加盐有助于水凝胶的形成，但尚不清楚这是否源于阳离子桥联或电荷屏蔽作用。在本文中，我们证明了一价盐和二价盐对NCC凝胶化和向列有序性的影响。发现NCC悬浮液的Zeta电位与流变行为密切相关。需要较低浓度的二价阳离子以降低NCCζ电位并形成水凝胶。在更高浓度的一价盐下，可以获得相同的ζ电位和凝胶强度。因此，盐诱导的NCC聚集是由分子间吸引力而不是阳离子桥连引起的。反对排除量论证，发现添加盐可以促进NCC向列相的形成。在完全聚集发生之前，在适度添加盐的过渡过程中观察到向列顺序增加。这种制度受排斥力和吸引力的平衡支配。小角度中子散射表明NCC的横向取向。因此，NCC凝胶化和向列顺序可以通过其zeta电位通过靶向盐的添加来调节。
更新日期：2017-10-21
中文翻译：
离子诱导水凝胶的形成和纳米晶纤维素悬浮液的向列有序性
纳米晶纤维素（NCC）是用于形成水凝胶和向列液晶的有前途的材料。尽管已知添加盐有助于水凝胶的形成，但尚不清楚这是否源于阳离子桥联或电荷屏蔽作用。在本文中，我们证明了一价盐和二价盐对NCC凝胶化和向列有序性的影响。发现NCC悬浮液的Zeta电位与流变行为密切相关。需要较低浓度的二价阳离子以降低NCCζ电位并形成水凝胶。在更高浓度的一价盐下，可以获得相同的ζ电位和凝胶强度。因此，盐诱导的NCC聚集是由分子间吸引力而不是阳离子桥连引起的。反对排除量论证，发现添加盐可以促进NCC向列相的形成。在完全聚集发生之前，在适度添加盐的过渡过程中观察到向列顺序增加。这种制度受排斥力和吸引力的平衡支配。小角度中子散射表明NCC的横向取向。因此，NCC凝胶化和向列顺序可以通过其zeta电位通过靶向盐的添加来调节。
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