Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, SE-10044, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden.
Department of Fiber and Polymer Technology, KTH Royal Institute of Technology, SE-10044, Sweden; Wallenberg Wood Science Center, KTH Royal Institute of Technology, SE-10044, Sweden.
J Colloid Interface Sci. 2021 Apr 15;588:485-493. doi: 10.1016/j.jcis.2020.12.113. Epub 2020 Dec 31.
The adsorption of nonionic polymers to cellulose is of large importance both in the plant cell wall during synthesis and for the development of sustainable materials from wood. Here, the thermodynamics of adsorption of the polysaccharide xyloglucan (XG) to both native and chemically modified cellulose with carboxyl groups was investigated using molecular dynamics simulations. The free energy of adsorption was calculated as the potential of mean force between an XG oligomer and model cellulose surfaces in a range of temperatures from 298 K to 360 K. It was found that the adsorption near room temperature is an endothermic process dominated by the entropy of released interfacial water molecules. This was corroborated by quantitative assessment of the absolute entropy per water molecule both at the interface and in the bulk. In the case of native cellulose, the adsorption became exothermic at higher temperatures, while the relatively strong interactions between water and the charged groups of the oxidized cellulose impede such a transition. The results also indicate that the extraction of strongly associated hemicelluloses would be facilitated by low temperature.
非离子聚合物在植物细胞壁的合成过程中以及从木材中开发可持续材料方面对纤维素的吸附具有重要意义。在这里，使用分子动力学模拟研究了多糖木葡聚糖 (XG) 对带有羧基的天然和化学改性纤维素的吸附热力学。通过在从 298 K 到 360 K 的一系列温度下计算 XG 低聚物和模型纤维素表面之间的平均力势能，计算了吸附自由能。结果表明，吸附在室温附近是一个吸热过程，主要由释放的界面水分子的熵控制。这通过在界面和本体中每个水分子的绝对熵的定量评估得到了证实。在天然纤维素的情况下，随着温度的升高，吸附变为放热，而水与氧化纤维素的带电基团之间的相对强相互作用阻碍了这种转变。结果还表明，低温有利于提取强缔合的半纤维素。
