Anionic Polyaddition of Methyl‐Substituted Stilbene Through Unstable Anionic Species

Anionic polyaddition of methyl‐substituted stilbene, namely β‐tolylstyrene, was examined using proton abstraction by lithium diisopropylamide (LDA) in the presence of excess diisopropylamine (DIA) and amine ligands. Once the tolyl proton is abstracted by LDA, the resulting carbanion adds to the vinyl group of the monomer. The newly generated carbanion is intrinsically unstable and can be rapidly protonated by DIA before undergoing decomposition. Therefore, increasing the [DIA]/[LDA] ratio promotes immediate protonation of the unstable anionic species, thereby suppressing stilbene decomposition and facilitating homopolymerization. At a [DIA]/[LDA] ratio of 20, both the polymer yield and number‐average molecular weight ( M ₙ) increased with increasing reaction temperature and reaction time. The resulting poly(β‐tolylstyrene), synthesized via this anionic polyaddition mechanism, exhibited superior thermal properties compared with polystyrene, as demonstrated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements, which is attributed to the incorporation of phenyl groups into the polymer main chain.