Dept. of Chemical Engineering, Auburn University, Auburn, AL 36849, USA.
Analyst. 2019 Feb 25;144(5):1679-1686. doi: 10.1039/c8an01810c.
The accurate characterization of relative composition in multicomponent polymer systems such as statistical copolymers, block copolymers, and polymer blends is critical to understanding and predicting their behavior. Typically, polymer compositional analysis is performed using 1H Nuclear Magnetic Resonance (NMR) Spectroscopy which provides quantitative chemical group concentrations without prior calibration. This utility has led 1H NMR spectroscopy to become a routine method for the molecular characterization of polymers. Unfortunately, due to cost constraints, NMR spectroscopy is rarely used for routine materials verification such as quality control in industrial settings that commonly lack on-site advanced instrumentation facilities. Recently, low-field or so-called benchtop NMR spectrometers have been introduced commercially as a less expensive alternative to higher field, and costlier, NMR spectrometers. Here, we examine the capability of a low-field 1H NMR spectrometer (60 MHz) for the compositional analysis of select block copolymers and polymer blends by direct comparison with results obtained using a 400 MHz NMR spectrometer. In the analysis of high 1,4-content polyisoprene we find quantitative agreement between the 400 and 60 MHz spectrometers. Furthermore, quantitative agreement is demonstrated for compositional analysis of commercially available poly(styrene-b-isoprene-b-styrene) (SIS) and poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymers and polymer blends of polystyrene/polyisoprene (PS/PI) and polystyrene/poly(methyl methacrylate) (PS/PMMA) that also serve as proxies for statistical and block copolymer analysis. Overall, we find low-field 1H NMR spectroscopy to be an accessible, powerful and useful tool for polymer characterization.
准确描述多组分聚合物体系（如统计共聚物、嵌段共聚物和聚合物共混物）的相对组成对于理解和预测其行为至关重要。通常，使用 1H 核磁共振（NMR）光谱法对聚合物组成进行分析，该方法无需预先校准即可提供定量的化学基团浓度。这种实用性使得 1H NMR 光谱法成为聚合物分子特性分析的常规方法。不幸的是，由于成本限制，NMR 光谱法很少用于常规材料验证，例如工业环境中的质量控制，而这些环境通常缺乏现场先进的仪器设备。最近，低场或所谓的台式 NMR 光谱仪已作为更高场和更昂贵的 NMR 光谱仪的低成本替代品在商业上推出。在这里，我们通过与使用 400 MHz NMR 光谱仪获得的结果直接比较，检查了低场 1H NMR 光谱仪（60 MHz）用于选择嵌段共聚物和聚合物共混物组成分析的能力。在高 1,4-含量聚异戊二烯的分析中，我们发现 400 和 60 MHz 光谱仪之间存在定量一致性。此外，对于市售的聚苯乙烯-异戊二烯-苯乙烯（SIS）和聚苯乙烯-丁二烯-苯乙烯（SBS）嵌段共聚物以及聚苯乙烯/聚异戊二烯（PS/PI）和聚苯乙烯/聚（甲基丙烯酸甲酯）（PS/PMMA）的聚合物共混物的组成分析也证明了定量一致性，这些共混物也可作为统计和嵌段共聚物分析的替代品。总体而言，我们发现低场 1H NMR 光谱法是一种易于使用、功能强大且有用的聚合物特性分析工具。
