Department of Chemistry, McGill University, 801 Sherbrooke St. West, Montreal, Quebec H3A 0B8, Canada.
Department of Bioengineering, McGill University, 3480 University St. #350, Montreal, Quebec H3A 0E9, Canada.
Biomacromolecules. 2023 Sep 11;24(9):4180-4189. doi: 10.1021/acs.biomac.3c00513. Epub 2023 Aug 22.
Chitin nanocrystals (ChNCs) are unique to all other bio-derived nanomaterials in one aspect: the inherent presence of a nitrogen moiety. By tuning the chemical functionality of this nanomaterial, and thus its charge and hydrogen bonding capacity, one can heavily impact its macroscopic properties such as its rheological and self-assembly characteristics. In this study, two types of ChNCs are made using acid hydrolysis (AH-ChNCs) and oxidative (OX-ChNCs) pathways, unto which deacetylation using a solvent-free procedure is utilized to create chitosan nanocrystals (ChsNCs) of varying degree of deacetylation (DDA). These nanocrystals were then studied for their rheological behavior and liquid crystalline ordering. It was found that with both deacetylation and carboxylation of ChNCs, viscosity continually increased with increasing concentrations from 2 to 8 wt %, contrary to AH-ChNC dispersions in the same range. Interestingly, increasing the amine content of ChNCs was not proportional to the storage modulus, where a peak saturation of amines provided the most stiffness. Conversely, while the introduction of carboxylation increased the elastic modulus of OX-ChNCs by an order of magnitude from that of AH-ChNCs, it was decreased by increasing DDA. Deacetylation and carboxylation both inhibited the formation of a chiral nematic phase. Finally, these series of nanocrystals were incorporated into biodegradable pectin-alginate films as a physical reinforcement, which showed increased tensile strength and Young's modulus values for the films incorporated with ChsNCs. Overall, this study is the first to investigate how surface functionalization of chitin-derived nanocrystals can affect their rheological and liquid crystalline properties and how it augments pectin/alginate films as a physical reinforcement nanofiller.
壳聚糖纳米晶（ChNCs）在一个方面与所有其他生物衍生的纳米材料不同：其固有存在含氮部分。通过调整这种纳米材料的化学功能，从而改变其电荷和氢键能力，可以极大地影响其宏观性质，如流变学和自组装特性。在本研究中，使用酸水解（AH-ChNCs）和氧化（OX-ChNCs）两种途径制备壳聚糖纳米晶（ChNCs），然后使用无溶剂程序进行脱乙酰化，制备不同脱乙酰度（DDA）的壳聚糖纳米晶（ChsNCs）。然后研究这些纳米晶的流变行为和液晶有序性。结果发现，随着 ChNCs 的脱乙酰化和羧化，粘度在 2 至 8wt%的范围内连续增加，与相同范围内的 AH-ChNC 分散体相反。有趣的是，随着 ChNCs 中胺含量的增加，存储模量并没有成比例增加，其中胺的峰值饱和提供了最大的刚性。相反，虽然羧化的引入使 OX-ChNCs 的弹性模量比 AH-ChNCs 增加了一个数量级，但随着 DDA 的增加而降低。脱乙酰化和羧化都抑制了手性向列相的形成。最后，将这些纳米晶系列掺入可生物降解的果胶-藻酸盐薄膜中作为物理增强剂，发现掺入 ChsNCs 的薄膜的拉伸强度和杨氏模量值均有所提高。总的来说，这项研究首次调查了壳聚糖衍生纳米晶的表面功能化如何影响其流变学和液晶性质，以及如何增强果胶/藻酸盐薄膜作为物理增强纳米填料。
