Self-Alternating Polymerization of <i>m</i>-Vinyl-1,1-diphenylethylene and Cyclopolymerization of <i>o</i>-Vinyl-1,1-diphenylethylene

4-Vinyl-1,1-diphenylethylene (p-VDPE)─an AB-type difunctional monomer containing two reactive C═C bonds─undergoes anionic polymerization via intermolecular crossover propagation on styrene and 1,1-diphenylethylene frameworks in an alternating manner. In this study, the anionic polymerization behavior of the positional isomers of p-VDPE, 3-vinyl-1,1-diphenylethylene (m-VDPE), and 2-vinyl-1,1-diphenylethylene (o-VDPE) was investigated under various conditions in tetrahydrofuran. Their anionic polymerization produced soluble polymers with predictable molecular weights and relatively narrow molecular weight distributions (Mw/Mn = 1.14–1.44). The polymer of m-VDPE possessed a unique polymeric structure corresponding to the (AB)n-type sequence, indicating that the anionic self-alternating polymerization of m-VDPE proceeded similarly to that of p-VDPE. In contrast, the polymer of o-VDPE had an annular Indane-type main chain with a cyclization efficiency of 68–82%, suggesting that o-VDPE undergoes cyclopolymerization involving an intramolecular cyclization reaction. Thus, the substitution position of the vinyl group in VDPE framework strongly affects the polymerization behavior of the AB-type difunctional monomer.