MIL-53填充PEBA混合基质膜界面相容性的分子模拟

Understanding the interface compatibility of MIL-53 filled PEBA mixed matrix membrane using molecular simulation

混合基质与高分子间界面相容性的优劣,是决定混合基质膜分离性能的关键因素之一.现有实验手段,无法在分子水平空间尺度下可视化表征混合基质与高分子间的界面相互作用.因此,本研究采用分子动力学的手段,首先模拟了不同相对分子质量聚醚嵌段聚酰胺(PEBA)基质的结构性质,如密度、XRD等,并与文献的相关数据进行比较,结果显示计算值与实验值接近,表明了力场参数的合理性.随后,计算了PEBA基质的分子模型在良溶剂糠醛及不良溶剂水中的溶胀,计算结果与实验结果具有一致性,说明了模型和方法的合理性.进而,模拟计算了PEBA基质与金属有机框架MIL-53的界面相容性.结果表明,不同孔尺寸的MIL-53与PEBA接触时,通过无机-有机界面的可视化分析,得知PEBA与宽孔MIL-53及窄孔MIL-53皆不会形成界面缺陷,表明两者具有良好的界面相容性.此外,宽孔MIL-53与PEBA接触时,PEBA分子链会进入MIL-53的孔道中;而窄孔的MIL-53与PEBA接触时,PEBA仅停留在MIL-53表面而无法进入MIL-53的孔道中,提示MIL-53的呼吸效应会影响混合基质膜的分离性能.

The interfacial compatibility of the mixed matrix is one of the key factors determining the separation performance of the mixed matrix membrane. Existing experimental methods cannot visualize the interfacial interactions between mixed matrices and polymer at the molecular level. This work using molecular dynamics study the effect of molecular weight on the structure of PEBA matrix, such as density and XRD. Those results were similar with the relevant data in the reference, indicating the suitable of the force field parameters. Subsequently, the swelling of PEBA in furfural, water and furfural/water mixed solution was calculated. The swelling results of the PEBA matrix molecular model in different solutions are consistent with the experimental results, indicating the suitable of the model and method. Finally, interface compatibility between PEBA matrix and MIL-53 was studied. Through the visual analysis of the interface between MIL-53 with different pore sizes and PEBA, the results show that PEBA does not form interface defects with either large-pore or narrow-hole MIL-53, indicating good interface compatibility between MIL-53 and PEBA. In addition, when the large pore MIL-53 is in contact with PEBA, the PEBA molecular chain will enter the pores of MIL-53. When MIL-53 with narrow pores is in contact with PEBA, PEBA only stays on the surface of MIL-53 and can not enter the pores of MIL-53, suggesting that the respiration effect of MIL-53 will affect the separation performance of the mixed matrix membrane.