Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter St, Columbia, South Carolina 29203, United States.
Anal Chem. 2023 May 23;95(20):7849-7854. doi: 10.1021/acs.analchem.2c05531. Epub 2023 May 5.
Diffusion-ordered spectroscopy (DOSY) H nuclear magnetic resonance (H NMR) has become a powerful tool to characterize the molecular weights of polymers. Compared to common characterization techniques, such as size exclusion chromatography (SEC), DOSY is faster, uses less solvent, and does not require a purified polymer sample. Poly(methyl methacrylate) (PMMA), polystyrene (PS), and polybutadiene (PB) molecular weights were determined by the linear correlation between the logarithm of their diffusion coefficients (D) and the logarithm of their molecular weights based on SEC molecular weights. Here, we emphasize the importance of the preparation needed to generate the calibration curves, which includes choosing the correct pulse sequence, optimizing parameters, and sample preparation. The limitation of the PMMA calibration curve was investigated by increasing the dispersity of PMMA. Additionally, by accounting for viscosity in the Stokes-Einstein equation, a variety of solvents were used to produce a "universal" calibration curve for PMMA to determine molecular weight. Furthermore, we place a spotlight on the increasing importance of DOSY NMR being incorporated into the polymer chemist's toolbox.
扩散排序光谱（DOSY）氢核磁共振（H NMR）已成为一种强大的工具，用于表征聚合物的分子量。与常见的表征技术，如尺寸排阻色谱（SEC）相比，DOSY 更快、使用的溶剂更少，并且不需要纯化的聚合物样品。通过基于 SEC 分子量的扩散系数（D）的对数与分子量的对数之间的线性相关关系，确定聚甲基丙烯酸甲酯（PMMA）、聚苯乙烯（PS）和聚丁二烯（PB）的分子量。在这里，我们强调了生成校准曲线所需的准备工作的重要性，包括选择正确的脉冲序列、优化参数和样品制备。通过增加 PMMA 的分散度，研究了 PMMA 校准曲线的局限性。此外，通过在斯托克斯-爱因斯坦方程中考虑粘度，使用各种溶剂生成 PMMA 的“通用”校准曲线，以确定分子量。此外，我们还强调了 DOSY NMR 被纳入聚合物化学家工具包的重要性日益增加。
