Critical need for absolute molecular weight determination on size exclusion chromatography system

聚合物的大小或分子量是决定物理性能的最重要因素之一。粘度、结晶度、硬度、生物利用度、传导性和其他性质都与分子量密切相关。例如，对于给定的相同重复单元的乙烯，可以使用低相对分子质量的聚丙烯作为塑料袋，但可以使用超高相对分子质量的聚丙烯作为防刺背心。尺寸排阻色谱(SEC)是一种无处不在的测定分子量的仪器。根据聚合物从色谱柱洗脱出来所需的时间来估算分子量：聚合物越小，它与色谱柱的固定固相相互作用越多，洗脱时间就越长。值得注意的是，在聚合物研究界和UofT广泛使用的典型方法不能准确地确定分子量。大多数研究人员使用一组已知分子量的标准聚合物样品来创建校准曲线，以将聚合物洗脱所需的时间与其已知分子量相关联。然而，洗脱所需的时间与聚合物的特性密切相关。对于相同的相对分子质量，在选择的溶剂中紧密缠绕的聚合物与松散缠绕的聚合物的洗脱时间不同。因此，用于创建校准曲线的标准聚合物样品的特性必须与要表征的聚合物的特性相匹配。由于有有限的标准，通常使用聚苯乙烯或聚甲基丙烯酸甲酯作为标准。因此，如果未知聚合物的行为与标准相同，则根据标准校准SEC确定的分子量才是一个很好的估计。随着UofT正在开发新的聚合物，我们发现这种估计不再合适，那里存在非常大的差异。所要求的SEC系统与多角度光散射技术相结合，将使当地聚合物研究团体能够确定绝对分子量。此外，UofT中缺少选择的氯仿溶剂体系，而UofT是唯一能增溶一些UofT研究人员开发的新型共轭聚合物的溶剂。此外，它使用快速分析程序，每次运行比市场上任何可用的系统少85%的溶剂。这五个联合PI包括Tran、Khan、Seferos、Winnik和Bender，最初有50多名高素质的人员作为潜在用户。

The size, or molecular weight, of a polymer is one of the most important factors in determining physical properties. Viscosity, degree of crystallinity, stiffness, bioavailability, conductivity, and other properties are all intimately associated with molecular weight. For example, for a given identical repeat unit of ethylene, polypropylene with a low molecular weight may be used as a plastic bag but polypropylene with ultrahigh high molecular weight may be used as anti-stab vests. Size exclusion chromatography (SEC) is a ubiquitous equipment to determine the molecular weight. The molecular weight is estimated by the time it takes for the polymer to elute from the column: the smaller the polymer, the more it interacts with the stationary solid phase of the column, the longer it takes to elute. Notably, typical methods widespread in the polymer research community and also at UofT inaccurately determine the molecular weight. Most researchers use a set of standard polymer samples with known molecular weight to create a calibration curve to correlate the time it takes for a polymer to elute and its known molecular weight. However, the time it takes to elute is intimately related to the identity of the polymer. For the same molecular weight, a polymer that is tightly coiled in a select solvent will elute at a different time that a polymer that is loosely coiled. Thus, the identity of the standard polymer samples used to create the calibration curve must match the identity of the polymer to be characterized. Since there are limited standards, often poly(styrene) or poly(methyl methacrylate) is used as a standard. Thus, the molecular weights determined by SEC calibrated against a standard is only a good estimated if the unknown polymer behaves like the standards. As new polymers are being developed at UofT, we are discovering that this estimation is no longer appropriate, where there are very large discrepancies. The requested SEC system coupled with a multi-angle light scattering technique, the first of its type at UofT and surrounding institutions to our knowledge, will enable the local polymer research community to determine absolute molecular weight. Moreover, the selected solvent system of chloroform is missing from UofT, which is the only solvent which solubilizes the new conjugated polymers developed by some of the UofT researchers. Also, it uses a quick analysis procedure and 85% less solvent per run than any system that is available on the market. The five co-PIs include Tran, Khan, Seferos, Winnik, and Bender, with more than 50 highly qualified personnel as potential users at the onset.