Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Chem Phys. 2012 Jan 7;136(1):014510. doi: 10.1063/1.3669449.
Nuclear magnetic resonance spectroscopy has been utilized to investigate the dynamics of poly(ethylene oxide)-based lithium sulfonate ionomer samples that have low glass transition temperatures. (1)H and (7)Li spin-lattice relaxation times (T(1)) of the bulk polymer and lithium ions, respectively, were measured and analyzed in samples with a range of ion contents. The temperature dependence of T(1) values along with the presence of minima in T(1) as a function of temperature enabled correlation times and activation energies to be obtained for both the segmental motion of the polymer backbone and the hopping motion of lithium cations. Similar activation energies for motion of both the polymer and lithium ions in the samples with lower ion content indicate that the polymer segmental motion and lithium ion hopping motion are correlated in these samples, even though lithium hopping is about ten times slower than the segmental motion. A divergent trend is observed for correlation times and activation energies of the highest ion content sample with 100% lithium sulfonation due to the presence of ionic aggregation. Details of the polymer and cation dynamics on the nanosecond timescale are discussed and complement the findings of X-ray scattering and quasi-elastic neutron scattering experiments.
核磁共振波谱已被用于研究具有低玻璃化转变温度的基于聚环氧乙烷的锂磺酸盐离聚物样品的动力学。（1）H 和（7）Li 核自旋晶格弛豫时间（T（1））分别测量并分析了一系列离子含量的样品中的聚合物本体和锂离子。T（1）值随温度的变化以及 T（1）随温度的最小值的存在，使得聚合物主链的段运动和锂离子的跳跃运动的相关时间和活化能得以获得。在离子含量较低的样品中，聚合物和锂离子的运动具有相似的活化能，表明聚合物段运动和锂离子跳跃运动在这些样品中是相关的，尽管锂离子跳跃比段运动慢约十倍。对于 100%锂磺化的最高离子含量样品，由于存在离子聚集，相关时间和活化能呈现发散趋势。讨论了纳秒时间尺度上聚合物和阳离子动力学的细节，补充了 X 射线散射和准弹性中子散射实验的结果。
