10.1021/acs.macromol.8b00924.s001
Jianwen Hu
Jianwen
Hu
Chao Kan
Chao
Kan
Haobing Wang
Haobing
Wang
Haiyan Ma
Haiyan
Ma
Highly Active Chiral Oxazolinyl Aminophenolate Magnesium
Initiators for Isoselective Ring-Opening Polymerization of <i>rac</i>-Lactide: Dinuclearity Induced Enantiomorphic Site Control
American Chemical Society
2018
chiral magnesium complexes
Active Chiral Oxazolinyl Aminophenolate Magnesium Initiators
enantiomorphic site control
racemic magnesium initiators
investigation
ROP
Dinuclearity Induced Enantiomorphic Site Control
enantiomorphic site control mechanism
challenge
isoselective magnesium complexes
isotactic PLAs
isotactic stereoblock PLA
Isoselective Ring-Opening Polymerization
chiral oxazolinyl aminophenolate ligands
TOF
magnesium lactate model complexes
2018-07-11 18:34:01
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Highly_Active_Chiral_Oxazolinyl_Aminophenolate_Magnesium_Initiators_for_Isoselective_Ring-Opening_Polymerization_of_i_rac_i_-Lactide_Dinuclearity_Induced_Enantiomorphic_Site_Control/6807020
The most important challenge in ring-opening
polymerization of <i>rac</i>-lactide today is to obtain
isotactic PLAs with high
molecular weights. The goal of our work is to address this important
challenge by developing novel catalysts that enable precise control
over stereoselectivity and produce high molecular weight PLAs at the
same time. Here we report some rare examples of isoselective magnesium
complexes toward the ROP of <i>rac</i>-LA, which are supported
by chiral oxazolinyl aminophenolate ligands. Preliminary kinetic investigations
confirmed that isotactic PLAs could be achieved via an enantiomorphic
site control mechanism by using these chiral magnesium complexes.
A pair of racemic magnesium initiators proved to integrate hyperactivity
(TOF up to 54 000 h<sup>–1</sup> at 25 °C) with
sufficient isoselectivity (<i>P</i><sub>m</sub> = 0.80)
toward the ROP of <i>rac</i>-LA, leading to the formation
of isotactic stereoblock PLA with high molecular weight (<i>M</i><sub>n</sub> = 461 kg mol<sup>–1</sup>) and a semicrystalline
property (<i>T</i><sub>m</sub> = 164 °C). Detailed
structural investigation on the magnesium lactate model complexes
suggested that the high degree of enantiomorphic site control is derived
from both the ligand chirality and the dinuclear feature of the magnesium
active species.