A highly efficient catalyst for the "living" and "immortal" polymerization of epsilon-caprolactone and L-lactide

Abstract

A novel ligand, 2,2'-methylenebis(4,6-di(1-methyl-1-phenylethyl)phenol) (MMPEP-H(2)) (1), has been prepared by the reaction of 2,4-bis(alpha,alpha -dimethylbenzyl)phenol with formaldehyde in the presence of a catalytic amount of benzenesulfonic acid. Further reaction of compound I with Me(3)Al in diethyl ether produces a four-coordinated monomeric aluminum complex [(MMPEP)AlMe(OEt(2))] (2). [(MMPEP)-Al(mu -OBn)](2) (3) can then be synthesized from the reaction of 2 with 1 molar equiv of benzyl alcohol at ambient temperature. 3 has demonstrated highly efficient catalytic activities in the ROP of epsilon -caprolactone and the ROP Of L-lactide. The "living" character of complex 3 enable us to prepare PCL-b-PLA copolymer, and the "immortal" character of 3 has paved a way to synthesize as much as 160-fold polymer chains of poly(caprolactone) with very narrow PDI in the presence of a small amount of initiator.