“Total” analysis of the growing species in living cationic polymerizations by in‐situ multinucleate NMR spectroscopy

The nature of the growing species in living cationic polymerizations of vinyl ethers was discussed on the basis of in‐situ direct analysis of model growing ends [CH3Cδ+H(OiBu)… Bδ…MXn] by multinuclear NMR spectroscopy. The model reactions were to mimic the polymerizations initiated with protonic acid/metal halide systems [HB/MXn; HB = HCl, CF3CO2H, (C6H5O)2PO2 H; MXn = ZnCl2, SnCl4], where all of the three components of the growing end [carbocation (∼∼C+), counter‐anion (B−), and activator (MXn)] were analyzed by monitoring such nuclei as 1H, 13C, 19F, 31P, and 119Sn incorporated therein. The results demonstrated: (i) the MXn‐assisted formation of sp2‐type carbocations from the precursor CH3CH(OiBu)‐B; (ii) the interaction of MXn with the counteranion B−; and (iii) the suppression of dissociated carbocationic intermediates under the living polymerization conditions.