The physical properties of cyclic polymers can be perturbed by the presence of architectural impurities, even in trace amounts. As a result, it is important to develop techniques for quantifying and improving the purity of cyclic polymer samples. The zwitterionic ring-expansion polymerization (ZREP) of glycidyl phenyl ether (GPE) with B(C₆F₅)₃ is a convenient, one-step method to generate cyclic polyethers in large amounts. However, the obtained cyclic samples are inherently contaminated by architectural impurities, which in this study are detected, identified, quantified, and successfully removed by a “click-scavenging” approach. The analytical techniques employed included matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS), quantitative Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography/multiangle light scattering (GPC–MALS). The end-group functionalization of the architectural impurities was a particularly useful method in the identification of tadpole and linear polymers in cyclic poly(glycidyl phenyl ether) samples of M_n = 1.1 and 11.7 kg/mol. Moreover, differential scanning calorimetry (DSC) measurements demonstrated that the presence of architectural impurities cause only a small reduction (1.4–2.0 °C) of the glass transition temperature (T_g) of the cyclic polyether; an effect that is corroborated in this investigation by means of dielectric spectroscopy. The segmental and local dynamics of cyclic samples are shown to be only slightly modified by the presence of a small percentage of architectural impurities.