Reactions of 2,2‘-(2-Methoxybenzylidene)bis(4-methyl-6-tert-butylphenol) with Trimethylaluminum:  Novel Efficient Catalysts for “Living” and “Immortal” Polymerization of ε-Caprolactone

A sterically hindered biphenol 2,2‘-(2-methoxybenzylidene)bis(4-methyl-6- tert -butylphenol) (MEBBP-H 2 ) ( 1 ) has been prepared by the reaction of o -anisaldehyde with 2- tert -butyl-4-methylphenol in the presence of a catalytic amount of benzenesulfonic acid. Further reaction of compound 1 with a stoichiometric amount of Me 3 Al in tetrahydrofuran produces a four-coordinated monomeric aluminum complex [(MEBBP)AlMe(THF)] ( 2 ). [(MEBBP)Al(μ-OBn)] 2 ( 3 ) can then be synthesized by the reaction of 2 with 1 mol equiv of benzyl alcohol at ambient temperature. Compound 3 has demonstrated highly efficient activities toward ring-opening polymerization of ε-caprolactone. The “living” and the “immortal” character of 3 has paved a way to synthesize as much as 256-fold polymer chains of poly(ε-caprolactone) with a very narrow polydispersity index in the presence of a small amount of initiator. In addition, the polystyrene- b -poly(ε-caprolactone) copolymer has also been prepared using polystyrene containing a hydroxy chain end as an initiator in the presence of 2 .