Department of Chemical and Petroleum Engineering, University of Calgary, Alberta T2N 1N4, Canada.
Biomacromolecules. 2022 Apr 11;23(4):1592-1600. doi: 10.1021/acs.biomac.1c01392. Epub 2022 Mar 28.
The influence of shear flow on the nanomechanical properties of cellulose nanocrystal (CNC)/polyethylene glycol (PEG) composite films and the distribution of anisotropic phases are investigated at various CNC/PEG ratios. Here, the drying process of CNC/PEG mixed suspensions is systematically traced by rheology, followed by the spatial mapping of local mechanical properties of CNC/PEG films by nanoindentation. The detailed study of the morphology of CNC/PEG films by polarized optical microscopy (POM) and image analysis revealed the link between the mechanical properties and the influence of shear flow. A comparison of the data obtained for shear-dried films with nonsheared films showed the improved reduced Young's modulus () and hardness (), and suppression of microphase separation in the shear-dried films. Based on this experimental evidence, a mechanism is proposed to explain the microstructural transition during the shear-drying process leading to the generation of the anisotropic domains containing the shear-induced assembled structure of CNC particles coexisting with the elongated PEG microphases.
研究了在不同纤维素纳米晶体（CNC）/聚乙二醇（PEG）比例下，剪切流对纤维素纳米晶体（CNC）/聚乙二醇（PEG）复合薄膜的纳米力学性能和各向异性相分布的影响。在这里，通过流变学系统地跟踪了 CNC/PEG 混合悬浮液的干燥过程，然后通过纳米压痕对 CNC/PEG 薄膜的局部力学性能进行空间映射。通过偏光显微镜（POM）和图像分析对 CNC/PEG 薄膜的形态进行详细研究，揭示了力学性能与剪切流影响之间的联系。将剪切干燥薄膜与未剪切薄膜的数据进行比较，结果表明剪切干燥薄膜的杨氏模量（）和硬度（）降低，微相分离得到抑制。基于这一实验证据，提出了一种机制来解释在剪切干燥过程中导致各向异性区域产生的微观结构转变，该区域包含剪切诱导组装结构的 CNC 颗粒与伸长的 PEG 微相共存。
