NMR Studies of Dynamics and Structure of Penetrants and Polymers in High Permeability Membrane Materials and Barrier Materials

将研究高渗透性聚合物系统的动力学和结构，以发展从分子到形态水平的运输理解。 高渗透系统中的输运将通过使用重复单元的结构修饰、混合、结晶、样品制备和样品历史来定制。 裁剪程序将用于使材料不均匀，以产生快速扩散，通过不良包装，低密度和高自由体积的区域。 无序的高渗透率玻璃将通过增加高自由体积区域的比例来生产，例如通过具有在玻璃形成时无法良好填充的庞大、缓慢重排的骨架单元。 在共混物中，高自由体积区域将通过将低玻璃化转变聚合物与高玻璃化转变聚合物组合来产生。 将确定缺陷或高自由体积区域的分子水平特征，并且将表征区域的较长长度尺度组织。 核磁共振（NMR）光谱将被用作主要的实验方法，因为NMR已被公认为是研究分子结构长度尺度材料的工具。 将使用氙-129 NMR检查吸收剂的吸附位点，并且将观察到平移运动的短程方面作为氙-129光谱中位点之间的交换。 在高自由体积区域的共混物中的局部链段运动将使用自旋-晶格弛豫和固体州线形状进行研究。 这些实验将着眼于纳米尺度上的性质，而更长的长度尺度，100纳米至微米尺度上的形态学性质将通过脉冲场梯度（PFG）扩散实验进行研究。 这种方法将被示出检测与纳米尺寸的缺陷区域的较长范围的组织或连接性相关联的结构。 我们将试图表明，这些地区导致快速扩散在高渗透率系统和观察的签名曲折和限制扩散在高渗透率系统中的表观扩散常数减缓的时间尺度上观察到的扩散增加的PFG实验。 计算机模拟将被用来帮助理解这种行为，并阐明样品制备，样品历史和老化在高渗透性聚合物中的作用。 PFG NMR实验将用于提供与缺陷组织相关的长尺度上的老化和调节效应的独特视图。 当侧链将主链锁定为刚性但堆积不良的状态时，NMR将用于量化结晶时侧链结晶系统的变化。 研究人员将联合收割机的NMR实验结果与传统的渗透性和溶解性实验，机械实验，散射实验和介电实验的信息相结合，通过与合作者网络的相互作用，这些聚合物系统是根本的兴趣，但也作为分离膜，控制输送系统和电池中的固体电解质的基础。 膜分离系统是分离永久气体如氮气和氧气的能量有效形式。 分离膜可用于环境应用中，以收集有机气体，同时释放水和二氧化碳。 侧链结晶聚合物用作受控递送系统，其将允许高于侧链熔点的小分子通过并将含有高于熔点的小分子。 在两种共混物中的低玻璃化转变组分是聚环氧乙烷，其在电池应用中用作锂盐的溶剂。 从拟议的研究中发展出来的理解将有助于改进这些应用。

The dynamics and structure of high permeability polymeric systems will be studied to develop a molecular to morphological level of understanding of transport. Transport in high permeability systems will be tailored through the use of structural modification of repeat units, blending, crystallization, sample preparation and sample history. The tailoring procedures will be used to make the materials inhomogeneous to produce rapid diffusion through regions of poor packing, low density, and high free volume. Disordered high permeability glasses will be produced by increasing the fraction of high free volume regions by for instance having bulky, slowly rearranging backbone units that are unable to pack well as the glass is formed. In blends, high free volume regions will be produced by combining a low glass transition polymer with a high glass transition polymer. The molecular level characteristics of the defect or high free volume regions will be determined and the longer length scale organization of the regions will be characterized. Nuclear magnetic resonance (NMR) spectroscopy will be used as the primary experimental method since NMR is well established as a tool for the study of materials on the length scale of molecular structure. Sorption sites of penetrants will be examined using xenon-129 NMR and the short range aspects of translational motion will be observed as exchange between sites in xenon-129 spectra. Local segmental motion in high free volume regions in a blend will be studied using spin-lattice relaxation and solid state line shapes. These experiments will look at properties on the nanometer scale while longer length scale, morphological properties on a scale of 100's nanometers to microns will be studied by pulse field gradient (PFG) diffusion experiments. This method will be shown to detect structure associated with the longer range organization or connectivity of the nanometer sized defect regions. We will attempt to show that these regions lead to rapid diffusion in high permeability systems and to the observation of the signature of tortuous and restricted diffusion in high permeability systems where the apparent diffusion constant slows as the time scale over which diffusion is observed increases in the PFG experiment. Computer simulation will be used to aid in understanding such behavior and to clarify the role of sample preparation, sample history and aging in high permeability polymers. PFG NMR experiments will be used to provide a unique view of aging and conditioning effects on the long length scale associated with the organization of defects. NMR will be used to quantify the changes in side chain crystalline systems upon crystallization when the side chains lock the backbone into a rigid though poorly packed state. The investigators will combine the results of the NMR experiments with information from traditional permeability and solubility experiments, mechanical experiments, scattering experiments and dielectric experiments through interaction with a network of collaborators.These polymer systems are of fundamental interest but also serve as the basis for separation membranes, controlled delivery systems and solid electrolytes in batteries. Membrane separation systems are an energy efficient form of separation of permanent gases such as nitrogen and oxygen. Separation membranes can be used in environmental applications to collect organic gases while releasing water and carbon dioxide. The side chain crystalline polymers are used as controlled delivery systems which will allow the passage of small molecules above the melting point of the side chain and will contain the small molecules above the melting point. The low glass transition component in two of the blends to be studied is polyethylene oxide which acts as a solvent for lithium salts in battery applications. The understanding developed from the proposed research will aid in improving such applications.