【作者】 陈瑜；

【导师】 刘庆林；

【作者基本信息】 厦门大学 ， 化学工程， 2009， 硕士

【摘要】 本文主要采用分子动力学（MD）法和巨正则蒙特卡洛（GCMC）法,以COMPASS力场为势能模型,利用Material Studio软件分别对气体分子在聚酰胺酰亚胺体系中的溶解和扩散行为进行了分子模拟。首先从聚酰胺酰亚胺结构与性质的关系出发,对主链结构相似仅苯环取代位置不同的两种聚酰胺酰亚胺体系进行分子模拟。计算得到的体系的玻璃化转变温度和实验值较接近表明了模型的真实度。巨正则蒙特卡洛法计算得到的溶解度系数和实验值相差两倍以内,动力学计算得到的扩散选择性和实验值吻合较好。从分子层次对已有实验结果做出合理解释和其他性质模拟。研究了几何构象、单键旋转能垒、玻璃化转变温度、自由体积以及主链的活动性对CO₂/CH₄在该聚合物种中溶解和扩散的影响。结果表明,苯环对位取代结构可以破坏聚合物封装,有较大的自由体积,可以同时获得较好的渗透性和选择性。在分子模拟结构与性能关系的基础上,研究了五种二胺部分含有不同个数四氟乙烯片段的聚酰胺酰亚胺,利用分子动力学法和GCMC法对CO₂在聚酰胺酰亚胺体系中的溶解和扩散进行模拟。通过对比聚合物玻璃化转变温度的计算值和实验值、模拟得到的红外光谱峰强数据和文献数据,可以证实模型和真实体系吻合。计算得到的扩散系数比值和溶解度与实验得到的数值在误差的范围内,通过对模拟结果进行分析,从微观的角度了解影响气体分子扩散的几个因素。发现随着聚合物中四氟乙烯片段的增长,体系的玻璃化转变温度下降,二氧化碳在聚酰胺酰亚胺体系中的扩散系数增大。更多还原

【Abstract】 Grand Canonical Monte Carlo(GCMC) and Molecular dynamics(MD) simulation were used and COMPASS force field was adopted to discuss the sorption and diffusion properties of the polyamide-imides.First,we focused on the relationship between the chemical structure and the chemical-physical properties of polyamide-imides and the establishment of molecular simulation approach for two polyamide-imides.The only difference between the two systems is the substitution pattern of the phenyl ring in the diamine moiety.The calculated glass transition temperature is in good agreement with the experimental results.The solubility coefficients are within one to two times of the literature results,while diffusion selectivity is close to the reported experimental data.Various properties such as chain conformation,pair correlation function,T_g as well as X-ray and mechanical properties of the polyamide-imides were considered to investigate the microstructure of the polyamide-imides and structure dependence of diffusion properties of gas pair.It has been found that the para-substitution polyamide-imide offered better permeability/permselectivity combinations than its meta-isomer.With the above established molecular simulation analysis for the study of structure-permeability property,we designed five polyamide-imides with different length of oligo(tetrafluoroethene) segments.The sorption and diffusion properties of carbon dioxide have been studied using GCMC and MD methods,respectively.The calculated ratio of diffusion coefficients and solubility coefficients were also consistent with experiment data. With increasing F content in the polyamide-imides,the glass transition temperature of the system decreased and the diffusivity of carbon dioxide increased.更多还原