Carbon‐13 NMR spectra and reactivities of vinyl compounds in ionic and radical polymerizations

The 13 C‐chemical shift of β‐carbon in the vinyl group of monomers was correlated with the relative reactivity of the monomer in the cationic copolymerizations of substituted styrenes, benzyl vinyl ethers, and phenyl vinyl ethers and also in the copolymerization of substituted styrenes by Ziegler catalysts. It was found that the β‐carbon resonates at the higher field, the higher the reactivity of the monomer is. The reverse was the case in the anionic addition reaction of substituted styrene to living polystyrene. The relations were also studied between the 13 C‐chemical shift and the e ‐value of the monomer and some direct evidence was obtained for the validity of the Q–e scheme. From these results it was revealed that the 13 C‐chemical shift of vinyl compounds is an important tool for the examination of the mechanism of polymerization reaction.