Figure 1. Workflow of Kendrick mass-analysis. Left: Traditional mass spectrometric characterization of polymers (i.e., MALDI-MS) provides a one-dimensional spectrum. Identification and assignment of all species in an ensemble of polymers with a distribution of molecular weights, chain-end types, and number of end groups per chain is challenging. Right: Application of a second-dimension resolves species with identical nonconstitutional repeating units (CRU; e.g., chain-ends, adducting ions, comonomers). The diameter of each circle in the Kendrick plot is proportional to the intensity of the corresponding MALDI peak. aOligomers were generated by frontal ring-opening metathesis oligomerization (FROMO). Conditions. (A/B) FROMO of 5-ethylidene-2-norbornene (A) and DCPD (B) catalyzed by G2 with styrene as the CTA. (C) FROMO of DCPD catalyzed by G2 with 3-bromostyrene as the CTA. Trace 3-chlorostyrene impurities existed in the CTA, as reflected in this detectable species. (D) FROMO of norbornene catalyzed by G2 with styrene as the CTA. Trace DCPD impurities in the monomer source resulted in detectable quantities of this co-oligomer. (E) FROMO of DCPD catalyzed by G2 and terminated with either 3-bromostyrene or ethyl vinyl ether. This species is likely the first oligomer generated and contains a precatalyst derived end-group. Figure reprinted and adapted ref (9). Copyright 2022 American Chemical Society. Figure 2. Fractional masses of stable nuclides derived from different Kendrick mass scales (≈ 350, m/z reported by the National Institute of Standards and Technology (11)). Kendrick masses were determined using eq 2, and the corresponding reference isotope is provided next to each curve. Fractional masses were calculated with eq 3. Inset: Common, low-mass nuclides most relevant for polymer chemistry (i.e., 1H through 37Cl). Dr. Diego Alzate-Sanchez, Dr. Julian Cooper, Dr. Oleg Davydovich, Dr. Jacob Lessard, Dr. Katherine Stawiasz, Henry Wang, and Christina Yu are thanked for insightful discussions. B.A.S. and J.S.M. acknowledge the Department of Energy (Office of Basic Energy Sciences, Energy Frontier Research Center) under Award number DE-SC0023457, titled Regenerative Energy-Efficient Manufacturing of Thermoset Polymeric Materials (REMAT). This article references 29 other publications. N denotes the set of natural numbers. N0 is the set of natural numbers including 0. This article has not yet been cited by other publications. Figure 1. Workflow of Kendrick mass-analysis. Left: Traditional mass spectrometric characterization of polymers (i.e., MALDI-MS) provides a one-dimensional spectrum. Identification and assignment of all species in an ensemble of polymers with a distribution of molecular weights, chain-end types, and number of end groups per chain is challenging. Right: Application of a second-dimension resolves species with identical nonconstitutional repeating units (CRU; e.g., chain-ends, adducting ions, comonomers). The diameter of each circle in the Kendrick plot is proportional to the intensity of the corresponding MALDI peak. aOligomers were generated by frontal ring-opening metathesis oligomerization (FROMO). Conditions. (A/B) FROMO of 5-ethylidene-2-norbornene (A) and DCPD (B) catalyzed by G2 with styrene as the CTA. (C) FROMO of DCPD catalyzed by G2 with 3-bromostyrene as the CTA. Trace 3-chlorostyrene impurities existed in the CTA, as reflected in this detectable species. (D) FROMO of norbornene catalyzed by G2 with styrene as the CTA. Trace DCPD impurities in the monomer source resulted in detectable quantities of this co-oligomer. (E) FROMO of DCPD catalyzed by G2 and terminated with either 3-bromostyrene or ethyl vinyl ether. This species is likely the first oligomer generated and contains a precatalyst derived end-group. Figure reprinted and adapted ref (9). Copyright 2022 American Chemical Society. Figure 2. Fractional masses of stable nuclides derived from different Kendrick mass scales (≈ 350, m/z reported by the National Institute of Standards and Technology (11)). Kendrick masses were determined using eq 2, and the corresponding reference isotope is provided next to each curve. Fractional masses were calculated with eq 3. Inset: Common, low-mass nuclides most relevant for polymer chemistry (i.e., 1H through 37Cl). This article references 29 other publications. N denotes the set of natural numbers. N0 is the set of natural numbers including 0.