Additive-controlled Switching from Abnormal to Normal Unstoichiometric Suzuki–Miyaura Polycondensation for Poly(biphenylenevinylene)

Suzuki–Miyaura polycondensation of substituted 4,4′-stilbenediboronic acid ester with an excess of substituted 4,4′-dibromostilbene in the presence of 5 mol % of t-Bu3P-ligated palladium (Pd) precatalyst afforded high-molecular-weight poly(biphenylenevinylene) (PBPV) with boronic acid ester moieties at both ends, but the same polymerization in the presence of unsubstituted stilbene gave low-molecular-weight PBPV with bromines at both ends.