We propose a new method for the determination of reactivity ratios based on a nonterminal model of copolymerization kinetics. Within the context of this model, we derive simple, reactivity-ratio-dependent expressions whose solution relies solely on monomer consumption information spanning the full range of conversion. Utilizing this method, reactivity ratios are obtained for the aluminum chelatecatalyzed copolymerization of phenyl glycidyl ether and allyl glycidyl ether (r PGE = 1.56 ± 0.01 and r AGE = 0.66 ± 0.03) with monomer consumption monitored by in situ 1 H NMR spectroscopy. Additionally, this approach is applied to experimental data extracted from the literature for other copolymerization systems encompassing a range of monomer types (styrenics, isoprene, lactones, lactide, and other cyclic ethers) and polymerization type (anionic, coordination, and zwitterionic) to obtain reactivity ratios under the mechanistic assumption of nonterminal model copolymerization kinetics. We present the nonterminal model of copolymerization as the first method that should be utilized before more complex frameworks (e.g., terminal or penultimate model of chain copolymerization) are used to understand copolymerization kinetics.

Decoupling bulk mechanics and ion conduction in conventional ion conducting polymers is challenging due to their mutual dependence on segmental chain dynamics. Polymers based on dynamic metal−ligand coordination are promising materials toward this aim. This work examines the effect of the nature and concentration of metal bis-(trifluoromethylsulfonyl)imide (MTFSI) salts on the mechanical properties and ionic conductivity of poly[(ethylene oxide)stat-(allyl glycidyl ether)] functionalized with tethered imidazole ligands (PIGE). Varying the cation identity of metal salts mixed in PIGE enables dramatic tunability of the zero-frequency viscosity from 0.3 to 100 kPa s. The ionic conductivity remains comparable at approximately 16 μS cm −1 among mono-, di-, and trivalent salts at constant metal-to-ligand molar ratios due to negligible changes in glass transition temperatures at low ion concentrations. Thus, polymers based on metal−ligand coordination enable decoupling of polymer zero-frequency viscosity from ion conduction. Pulsed-field-gradient NMR on PIGE containing Li + or Zn 2+ salts complement electrochemical impedance spectroscopy to demonstrate that both the anion and cation contribute to ionic conductivity.