氨分子对纤维素Iβ性能影响的分子动力学模拟

Studies on Influence of Ammonia on Properties of Cellulose Iβ Based on Molecular Dynamics Simulation

以纤维素Iβ为研究对象,通过分子模拟的方法,分别对其在有氨环境和无氨环境下的性能变化进行了仿真分析,主要包括对纤维素末端距、氨分子的扩散运动及氨分子与纤维素的氢键作用的研究.结果表明:氨分子的加入使得纤维素链的末端距增大,改善了纤维素链的柔顺性,合理的解释了"液氨整理可以用来改善棉麻纤维的柔顺性"的普遍共识;氨分子在纤维素中的均方位移和扩散系数随着温度的提高而变大,温度从298 K升高到398 K,氨分子的扩散系数增大87.8%,所以液氨整理过程中相应升高温度可以减少浸泡时间,提高生产效率;氨分子与纤维素形成的氢键,使得系统内的氢键总数增加,纤维素链内氢键数基本不变,但削弱了纤维素链间的氢键作用,加剧了纤维素链的运动,体现出良好的溶胀性能.

The performance changes of cellulose Iβ in the ammonia environment and non-ammonia environment were studied based on molecular dynamics simulation. The end-to-end distance of one cellulose chain, the diffusion behavior of ammonia in cellulose and hydrogen bonds between cellulose and ammonia were investigated. The results indicated that the end-to-end distance of the cellulose chain in ammonia environment got longer than that in non-ammonia condition with improving the flexibility of cellulose chain, which could reasonably interpret the common sense that ＂The treatment of liquid ammonia can be used to improve fiber flexibility＂. The mean square displacements （MSDs） and diffusion coefficients of ammonia rose with increasing temperatures. When the temperature rose from 298 K to 398 K, the diffusion coefficients of ammonia increased by 87.8%. So the appropriate elevated temperature could reduce the soak time and thus the production efficiency in treatment of liquid ammonia could be improved. The total number of hydrogen bonds in ammonia environment increased due to the forming of hydrogen bonds between ammonia and cellulose I13. By adding ammonia, the number of intrachain hydrogen bonds in a cellulose chain remained unchanged, but interchain hydrogen bonds among cellulose chains were weakened, contributing to the stronger movement of cellulose chains and showing a good swelling property of cellulose.