Sorption Hysteresis Modeling: a New Step toward the Understanding of Cell Wall Architecture

吸附滞后建模：理解细胞壁结构的新一步

• 批准号: RGPIN-2016-04325
• 负责人: Avramidis, Stavros
• 金额: $ 2.04万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=644339
• 关键词: Sorption; Hysteresis; Modeling; New; Step

We aim to elucidate the nanoscale wood cell-wall architecture by studying the hysteresis phenomenon. Explaining the hysteresis phenomenon in water sorption is a long-standing problem in biopolymer and in particular, wood science. Recent studies cast a lot of doubts on ability of classical theories to explain hysteresis in terms of accessible hydroxyls. Inspired by emerging nanoporous materials and sorption science, and our preliminary investigation on hysteresis patterns, we propose that the hysteresis is caused by the existence of metastable states taking place in water phase transitions (capillary condensation and evaporation in cell-walls) during the sorption process. Because the phase transition is highly affected by cell-wall pore sizes, by physically modeling or simulating hysteresis, we may reveal the cell-wall pore size distribution under different moisture contents. **We will conduct this research in four phases: experimental, mathematical modeling, Monte Carlo molecular simulation, and cell-wall structure investigation. The experimental phase includes systematic hysteresis patterns observations and material characterization. Our proposed hysteresis mechanism will be examined by observed hysteresis patterns. Then, in phase two, a mathematical model will be developed to describe and predict the scanning curves quantitatively. Furthermore, discussion of the properties and limit of the model will also help reveal physical origin of hysteresis. The third phase involves simulation of water adsorbed in cell-wall pores. In this phase, cell-walls will be considered as solid substances with uniformly distributed cylinder nanopores, and simple potential models will be used for both cell-walls and water molecules. In the last phase, we will use the simulation tool developed in phase three to explore cell-wall structures such as pore distribution, energy heterogeneous of cell-walls, adsorbed water structure and interaction of cell-wall and water. **We expect that this work will bring us toward a better understanding of cell-wall pore structures, and interaction between cell-wall biopolymers and water, e.g. evolution of hydrogen bounding networks, and clustering of water on cell-walls etc. We also expect the elucidated nanoscale cell-wall structure to provide new insights into cell-wall formation, deformation and degradation with possible applications in property and service prediction and optimization.*This research will be another brick towards our ultimate goal, the building of a universal wood model that will allow the simulation of its properties based on its anatomy, chemistry and ultrastructure.********

我们的目的是阐明纳米木材细胞壁结构通过研究滞后现象。对吸水滞后现象的解释是生物高分子，特别是木材科学中一个长期存在的问题。最近的研究对经典理论用可及羟基来解释滞后现象的能力提出了很多质疑。受新兴的纳米多孔材料和吸附科学的启发，以及我们对滞后模式的初步调查，我们提出滞后是由吸附过程中水相变（毛细管冷凝和细胞壁蒸发）中存在的亚稳态引起的。由于细胞壁孔径对相变过程有很大的影响，通过物理建模或模拟滞后现象，可以揭示不同含水率下细胞壁孔径的分布。** 我们将分四个阶段进行这项研究：实验，数学建模，Monte Carlo分子模拟和细胞壁结构研究。实验阶段包括系统的滞后模式观察和材料表征。我们提出的滞后机制将通过观察到的滞后模式进行检查。然后，在第二阶段，将开发一个数学模型来定量地描述和预测扫描曲线。此外，对该模型的性质和局限性的讨论也有助于揭示滞后现象的物理根源。第三阶段涉及模拟细胞壁孔隙中吸附的水。在这一阶段，细胞壁将被视为具有均匀分布的圆柱形纳米孔的固体物质，并且简单的势模型将用于细胞壁和水分子。在第三阶段，我们将使用第三阶段开发的模拟工具来探索细胞壁结构，如孔隙分布，细胞壁的能量不均匀性，吸附水结构和细胞壁与水的相互作用。** 我们期望这项工作将使我们更好地理解细胞壁孔结构，以及细胞壁生物聚合物和水之间的相互作用，例如氢结合网络的演变，以及水在细胞壁上的聚集等。我们还期望阐明的纳米级细胞壁结构为细胞壁形成提供新的见解，变形和退化，可能应用于性能和服务预测和优化。这项研究将是实现我们最终目标的另一块砖，即建立一个通用的木材模型，可以根据其解剖学，化学和超微结构模拟其特性。