Institute for Frontier Materials, Deakin University, Geelong, VIC 3216, Australia.
Research and Innovation Center, Ford Motor Company, Dearborn, Michigan 48124, United States.
Biomacromolecules. 2021 Sep 13;22(9):3884-3891. doi: 10.1021/acs.biomac.1c00690. Epub 2021 Aug 1.
The use of cellulose has considerable promise in a wide range of industrial applications but is hampered by degradation in mechanical properties due to ambient moisture uptake. Existing models of equilibrium moisture content can predict the impact of these effects, but at present, the dynamical, atomic-scale picture of water ingress into cellulose is lacking. The present work reports nonequilibrium molecular simulations of the interface between cellulose and water aimed at capturing the initial stages of two simultaneous dynamical processes, water ingress into cellulose and cellulose dissolution into water. These simulations demonstrate that the process depends on the temperature and chain length in the amorphous region, where high temperatures can induce more mass exchange and short chains can easily detach from amorphous cellulose. A cooperative mechanism that involves both chemical and physical aspects, namely, hydrogen bonding and chain intertwining, respectively, is proposed to interpret the incipient dual ingress/dissolution process. Outcomes of this work will provide a foundation for cellulose functionalization strategies to impede moisture uptake and preserve the mechanical properties of nanocellulose in applications.
纤维素在广泛的工业应用中具有相当大的应用前景，但由于环境湿度的吸收，其机械性能会退化，从而受到阻碍。现有的平衡水分含量模型可以预测这些影响，但目前，纤维素中水分进入的动态、原子尺度的情况还不清楚。本工作报告了纤维素和水之间界面的非平衡分子模拟，旨在捕捉两个同时发生的动态过程的初始阶段，即水进入纤维素和纤维素溶解在水中。这些模拟表明，这个过程取决于非晶区的温度和链长，其中高温可以诱导更多的质量交换，短链可以很容易地从无定形纤维素中脱离。提出了一种协同机制，分别涉及氢键和链交织等化学和物理方面，以解释初始的双重进入/溶解过程。这项工作的结果将为纤维素功能化策略提供基础，以阻止水分吸收并在应用中保持纳米纤维素的机械性能。
