School of Chemical Engineering, The University of Queensland, Brisbane, Australia.
School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, Australia.
J Colloid Interface Sci. 2017 Jun 15;496:130-140. doi: 10.1016/j.jcis.2017.02.020. Epub 2017 Feb 12.
Nanocrystalline cellulose (NCC) is a negatively charged rod-like colloid obtained from the hydrolysis of plant material. It is thus expected that NCC suspensions display a rich set of phase behaviour with salt and pH because of its anisotropic shape and electrical double layer that gives rise to liquid crystallinity and self-assembly respectively. It should thus be possible to tune the rheological properties of NCC suspensions for a wide variety of end-use applications.
Rheology and structural analysis techniques are used to characterise surface-sulphated NCC suspensions as a function of pH, salinity (NaCl) and NCC concentration. Structural techniques include atomic force microscopy, Zeta potential, dynamic light scattering, and scanning electron microscopy.
A phase diagram is developed based on the structure-rheology measurements showing various states of NCC that form as a function of salt and NCC concentration, which go well beyond those previously reported. This extended range of conditions reveals regions where the suspension is a viscous fluid and viscoelastic soft solid, as well as regions of instability that is suggested to arise when there is sufficient salt to reduce the electrical double layer (as explained qualitatively using DLVO theory) but insufficient NCC to form a load bearing network.
纳米纤维素（NCC）是一种带负电荷的棒状胶体，由植物材料水解得到。由于其各向异性的形状和双电层分别赋予了液晶性和自组装性，因此预计 NCC 悬浮液会在盐和 pH 值的影响下表现出丰富的相行为。因此，应该可以调整 NCC 悬浮液的流变性能，以适应各种最终用途的应用。
使用流变学和结构分析技术来表征表面硫酸化的 NCC 悬浮液的 pH 值、盐度（NaCl）和 NCC 浓度的函数关系。结构技术包括原子力显微镜、Zeta 电位、动态光散射和扫描电子显微镜。
根据结构-流变学测量结果开发了一个相图，显示了 NCC 的各种状态，这些状态是盐和 NCC 浓度的函数，远远超出了以前报道的范围。这种扩展的条件范围揭示了悬浮液是粘性流体和粘弹性软固体的区域，以及当存在足够的盐来减小双电层（如使用 DLVO 理论定性解释）但 NCC 不足以为承载网络形成时出现的不稳定区域。
