title: Controlled Ring-Opening Polymerization of O-Carboxyanhydrides Using a β-Diiminate Zinc Catalyst.
abstract: Recently O-carboxyanhydrides (OCAs) have emerged as a class of viable monomers which can undergo ring-opening polymerization (ROP) to prepare poly(α-hydroxyalkanoic acid) with functional groups that are typically difficult to achieve by ROP of lactones. Organocatalysts for the ROP of OCAs, such as dimethylaminopyridine (DMAP), may induce undesired epimerization of the α-carbon atom in polyesters resulting in the loss of isotacticity. Herein, we report the use of (BDI-IE)Zn(OCH(CH3)COOCH3) ((BDI)Zn-1, (BDI-IE)=2-((2,6-diethylphenyl)amino)-4-((2,6-diisopropylphenyl)imino)-2-pentene), for the controlled ROP of various OCAs without epimerization. Both homopolymers and block copolymers with controlled molecular weights, narrow molecular weight distributions, and isotactic backbones can be readily synthesized. (BDI)Zn-1 also enables controlled copolymerization of OCAs and lactide, facilitating the synthesis of block copolymers potentially useful for various biomedical applications. Preliminary mechanistic studies suggest that the monomer/dimer equilibrium of the zinc catalyst influences the ROP of OCAs, with the monomeric (BDI)Zn-1 possessing superior catalytic activity for the initiation of ROP in comparison to the dimeric (BDI)Zn complex.
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL, 61801, USA.
authors.forename: Ruibo
authors.initials: R
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL, 61801, USA.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL, 61801, USA.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yin
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL, 61801, USA.
authors.forename: Yunxiang
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 W Green St., Urbana, IL, 61801, USA. jianjunc@illinois.edu.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Department of Chemical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Rd., Blacksburg, VA, 24061, USA. rtong@vt.edu.
authors.forename: Rong
authors.initials: R
authors.lastname: Tong
keywords: O-carboxyanhydrides; copolymerization; ring-opening polymerization; stereoregularity; zinc