Hong Shiyao, Bean Ashley, Fang Yuan, Lavoine Nathalie, Lucia Lucian
Department of Forest Biomaterials, College of Natural Resources, North Carolina State University Raleigh NC 27695 USA
Department of Chemistry, College of Sciences, North Carolina State University Raleigh NC 27695 USA.
Nanoscale Adv. 2025 Apr 28;7(11):3476-3484. doi: 10.1039/d5na00069f. eCollection 2025 May 27.
This study attempts to quantify a relatively unexplored and very important subject: cellulose nanocrystal (CNC) bundles and their effective dimensions on phase separation and subsequent chiral resolution in CNC suspensions. Currently, there is little data discussing how effective bundle dimensions affect the onset of chiral nematic phase formation despite the fact that theory and experimental data indicate they are important factors. The effect of the extent of hydrolysis on the phase behavior of CNC suspensions was analyzed by correlating it with the critical weight concentration ( ), which is the CNC weight corresponding to the onset of the chiral nematic phase. From Onsager theory and its extension, is primarily a function of CNC size while surface charge exerts a non-negligible effect. CNCs were produced from never-dried bleached softwood pulp under varying acid hydrolysis times to systematically alter sizes and surface charges. Concentration-dependent phase diagrams were mapped to ascertain the of the produced suspensions. The data revealed a clear decrease in when the hydrolysis time increased from 25 to 90 minutes, despite similar individual CNC size and increasing surface charges. This latter discovery following shape and size distribution indicated an increased area-equivalent (AE) diameter from extended hydrolysis, suggesting particle aggregation/bundling. This result was corroborated by elevated particle surface charges from enhanced lateral adherence between CNCs. In contrast to our findings that higher surface charge reduces the effective diameter, the observed decrease in suggests that an earlier onset of the anisotropic phase is driven by CNC bundles, which were more prevalent in samples with elevated surface charge. These observations indicate that CNC bundles play a significant role in promoting the anisotropic phase, counteracting the effect of surface charge on . This work therefore provides invaluable insights into the complex interplay of CNC surface charge, shape, and size by shedding light on the importance of hydrolysis time on particle aggregation and phase behavior in CNC suspensions.
纤维素纳米晶体（CNC）束及其在CNC悬浮液中的相分离和后续手性拆分方面的有效尺寸。目前，尽管理论和实验数据表明它们是重要因素，但关于有效束尺寸如何影响手性向列相形成起始的讨论数据很少。通过将水解程度与临界重量浓度（ ）相关联，分析了水解程度对CNC悬浮液相行为的影响，临界重量浓度是指对应手性向列相起始的CNC重量。根据昂萨格理论及其扩展， 主要是CNC尺寸的函数，而表面电荷也有不可忽视的影响。在不同的酸水解时间下，从不干燥的漂白软木浆中制备CNC，以系统地改变其尺寸和表面电荷。绘制浓度依赖性相图以确定所制备悬浮液的 。数据显示，当水解时间从25分钟增加到90分钟时， 明显降低，尽管单个CNC尺寸相似且表面电荷增加。根据形状和尺寸分布的这一最新发现表明，延长水解会增加面积等效（AE）直径，表明颗粒聚集/成束。CNC之间横向附着力增强导致颗粒表面电荷升高，这一结果得到了证实。与我们发现的较高表面电荷会降低有效直径相反，观察到的 降低表明，各向异性相的较早起始是由CNC束驱动的，CNC束在表面电荷升高的样品中更为普遍。这些观察结果表明，CNC束在促进各向异性相方面发挥着重要作用，抵消了表面电荷对 的影响。因此，这项工作通过揭示水解时间对CNC悬浮液中颗粒聚集和相行为的重要性，为CNC表面电荷、形状和尺寸之间的复杂相互作用提供了宝贵的见解。
