Uniform Macromolecules: Performance of Common Analytic Instruments in Detecting Impurities

Inspired by the highly defined structure of biomacromolecules, e.g. deoxyribonuleic acid (DNA) and proteins, the preparation and characterization of sequence-defined and uniform macromolecules gained interest in polymer chemistry. With the development of various synthetic approaches, the challenge of analyzing and confirming the uniform structures emerged. Here, the investigation on the performance of common analytical instruments for the characterization of uniform macromolecules regarding impurities of ±1 in degree of oligomerization is presented. Thus, different mixtures containing oligomers differing in one repeating unit of oligo(ethylene glycol)s (OEG)s, oligo(phenylene ethynylene)s (OPE)s, and Passerini oligomers, respectively, are synthesized, and analyzed by proton nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC), and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). These results demonstrate the indispensability of a careful characterization using more than one technique for determining uniformity. In particular, the obtained SEC results show that it is a powerful tool for purity determination of low molecular weight oligomers.