Anionic Ring-Opening Polymerization of Phenylsilacyclobutanes

Butyllithium-induced anionic ring-opening polymerization of phenyl-substituted silacyclobutanes was investigated. Polymerization of 1, 1-dimethyl-3-phenylsilacyclobutane in tetrahydrofuran

(THF) at −78°C proceeded in a living fashion. A linear relationship between ln[M]0/[M] and time ([M]0 is the initial concentration of the monomer and [M] is the concentration of monomer) and

a linear relationship between number-average molecular weight (Mn) and monomer conversion were observed. The molecular weight of the obtained polymer was very narrow (Mw/Mn = 1.09, Mw is

weight-average molecular weight). In contrast, neither 1,1-dimethyl-2-phenylsilacyclobutane nor 1-methyl-1-phenylsilacyclobutane showed a living nature under the same polymerization

conditions, which were confirmed by two-step monomer addition experiments. 13C NMR and 29Si NMR spectrum of the poly(1,1-dimethyl-2-phenylsilacyclobutane) indicated that polymerization of

1,1-dimethyl-2-phenylsilacyclobutane proceeded without regioselectivity. By differential scanning calorimetry (DSC) measurements, glass transition temperatures (Tg)s were determined at −5°C

for poly(1,1-dimethyl-3-phenylsilacyclobutane), 27°C for poly(1,1-dimethyl-2-phenylsilacyclobutane), and −29°C for poly(1-methyl-1-phenylsilacyclobutane).

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