Monomer-Selective Living Copolymerization of t-Butyl Acrylate and Ethyl Methacrylate with t-Butyllithium/Bis(2,6-di-t-butylphenoxy)methylaluminum

Anionic polymerizations of t-butyl acrylate(t-BuA) were carried out in toluene with a combination of t-butyllithium(t-BuLi) and bis(2,6-di-t-butylphenoxy)methylaluminum [MeAl(ODBP)2] at low temperatures. The polymerization of t-BuA in the temperature range from −60°C to −20°C gave polymers with narrow molecular weight distribution(MWD). Anionic copolymerization of t-BuA and ethyl methacrylate(EMA) with t-BuLi/MeAl(ODBP)2 in toluene at −60°C proceeded in a monomer-selective manner. The propagating anions react selectively with t-BuA which may be activated through the preferential coordination with MeAl(ODBP)2. The copolymer showed a bimodal MWD, on-line SEC-NMR analysis of which revealed the formation of poly(t-BuA) as a lower molecular weight fraction and block-like copolymer as a higher molecular weight fraction. Increase in the polymerization temperature resulted in higher block efficiency, and the copolymers with narrow MWDs were formed at −40°C and −30°C. The 13C NMR spectra of the copolymers formed at and below −30°C indicated that the copolymers consisted of poly(t-BuA) block and poly(EMA) block. The copolymer formed at −20°C had narrow MWD and the random comonomer sequence.