Minkler Michael J, Kim Jung Min, Shinde Vinita V, Beckingham Bryan S
Department of Chemical Engineering, Auburn University, Auburn, Alabama, USA.
Magn Reson Chem. 2020 Dec;58(12):1168-1176. doi: 10.1002/mrc.5022. Epub 2020 Apr 7.
Low-cost, high-accuracy characterization of polymeric materials is critical for satisfying societal demand for high-quality materials with ultra-specific requirements. Low-field nuclear magnetic resonance (NMR) spectroscopy presents an opportunity to replace costlier or destructive methods while utilizing nondeuterated solvents. Many factors play key roles in the ability of low-field NMR spectroscopy to accurately analyze polymer systems. Sample characteristics such as polymer concentration, composition, and molecular weight all directly affect the capability of low-field spectrometers to accurately determine polymer microstructure compositions. In addition to inherent sample properties affecting instrumental accuracy, many choices concerning instrumental parameters (including number of scans, relaxation delay, spectral width, and points per scan) must be made that impact the quality of the resulting NMR spectra. In this work, we benchmark the capability of a 60-MHz low-field NMR spectrometer for analyzing polymer materials using mixed microstructure polyisoprenes as a model polymer system of interest. The aforementioned critical sample and instrumental variables are varied, and we report on the ability to quantitatively characterize polyisoprene microstructure to within 1-2% of a higher field NMR spectrometer (400 MHz). We anticipate our findings to be generally applicable to other low-field spectrometers of similar field strength and other polymer systems.
对聚合物材料进行低成本、高精度的表征对于满足社会对具有超特定要求的高质量材料的需求至关重要。低场核磁共振（NMR）光谱提供了一个机会，可以在使用非氘代溶剂的同时取代成本更高或具有破坏性的方法。许多因素在低场NMR光谱准确分析聚合物体系的能力中起着关键作用。诸如聚合物浓度、组成和分子量等样品特性都直接影响低场光谱仪准确测定聚合物微观结构组成的能力。除了影响仪器准确性的固有样品特性外，还必须做出许多关于仪器参数的选择（包括扫描次数、弛豫延迟、光谱宽度和每次扫描的点数），这些选择会影响所得NMR光谱的质量。在这项工作中，我们以60兆赫的低场NMR光谱仪分析聚合物材料的能力为基准，使用混合微观结构的聚异戊二烯作为感兴趣的模型聚合物体系。上述关键的样品和仪器变量是可变的，我们报告了将聚异戊二烯微观结构定量表征到比高场NMR光谱仪（400兆赫）的结果在1% - 2%以内的能力。我们预计我们的发现通常适用于其他具有类似场强的低场光谱仪和其他聚合物体系。
