Striegel André M
Chemical Sciences Division, National Institute of Standards and Technology (NIST), 100 Bureau Drive, MS 8390, Gaithersburg, MD 20899-8390, USA.
Chromatographia. 2024 Feb;87(2). doi: 10.1007/s10337-023-04306-8.
Worldwide polystyrene (PS) production in 2020 was approximately 27 million metric tons, distributed among many nations, making it one of the most heavily imported and exported chemicals. Commercially produced PS usually possesses a broad molar mass distribution, often with a substantial oligomeric component. The latter can significantly affect processing and end-use, in addition to having potentially hazardous health effects and to impacting the polymer's export classification by regulatory agencies. Quantitation of the oligomeric region of polymers by size-exclusion chromatography with concentration-sensitive and/or static light scattering detection is complicated by the non-constancy of the specific refractive index increment in this region, which affects the calculated amount (mass fraction) of oligomer in a polymer, molar mass averages, and related conclusions regarding macromolecular properties. Here, a multi-detector SEC approach including differential refractometry, multi-angle static light scattering, and differential viscometry has been applied to determining the of -butyl terminated styrene oligomers at each degree of polymerization from monomer to hexamer, and also of a hexadecamer. Large changes in this parameter from one degree of polymerization to the next are observed, including but not restricted to the fact that the of the monomer is less than half that of PS polymer at identical experimental conditions. As part of this study, the individual effects of injection volume, flow rate, and temperature on chromatographic resolution were examined. Incorporation of the on-line viscometer allowed for accurate determination of the intrinsic viscosity and viscometric radius of the monomer and oligomers.
2020年全球聚苯乙烯（PS）产量约为2700万吨，分布于许多国家，使其成为进出口量最大的化学品之一。商业生产的PS通常具有较宽的摩尔质量分布，且往往含有大量的低聚物成分。除了可能对健康产生有害影响以及影响聚合物在监管机构的出口分类外，后者还会显著影响加工过程和最终用途。通过尺寸排阻色谱结合浓度敏感和/或静态光散射检测对聚合物低聚物区域进行定量分析时，由于该区域的比折光指数增量不恒定，这会影响聚合物中低聚物的计算量（质量分数）、摩尔质量平均值以及有关大分子性质的相关结论，从而使分析变得复杂。在此，一种包括示差折光法、多角度静态光散射和示差粘度法的多检测器尺寸排阻色谱方法已被用于测定从单体到六聚体以及十六聚体的每种聚合度下的叔丁基封端苯乙烯低聚物的[具体内容缺失]。观察到该参数从一个聚合度到下一个聚合度有很大变化，包括但不限于在相同实验条件下，单体的[具体内容缺失]小于PS聚合物的一半这一事实。作为本研究的一部分，还考察了进样体积、流速和温度对色谱分辨率的各自影响。在线粘度计的加入使得能够准确测定单体和低聚物的特性粘度和粘度半径。
