Lewis acid-assisted anionic polymerization of methyl cyclobutene-1-carboxylate

A cyclobutene monomer, methyl cyclobutene-1-carboxylate (MHCB), has been polymerized by anionic addition polymerization. Although MHCB may be regarded as a member of α,β-disubstituted acrylate derivatives which are reluctant to undergo anionic addition polymerization, anionic polymerization of MHCB with tert-butyllithium (t-BuLi) in combination with bis(2,6-di-tert-butylphenoxy)ethylaluminum [EtAl(ODBP)2] in toluene at −78 °C gives a polymer consisting of 1,2-linked cyclobutane ring in the main chain with narrow molecular weight distribution. Copolymerization of MHCB and methyl methacrylate with t-BuLi/EtAl(ODBP)2 proceeds in a monomer-selective and living manner to form a block-like copolymer. Poly(MHCB) undergoes unique thermal reaction through ring opening of the cyclobutane units to form CC bonds between successive monomer units.