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Isoselective Ring‐Opening Polymerization of rac ‐Lactide Catalyzed by Sodium/potassium Tetradentate Aminobisphenolate Ion‐paired Complexes
Author(s) -
Li Xinlei,
Jia Zhaowei,
Pan Xiaobo,
Wu Jincai
Publication year - 2019
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201801834
Subject(s) - chemistry , polymerization , potassium , polymer chemistry , sodium , monomer , catalysis , ligand (biochemistry) , lactide , crown ether , inorganic chemistry , ion , organic chemistry , polymer , receptor , biochemistry
Two sodium/potassium tetradentate aminobisphenolate ion‐paired complexes were synthesized and structurally characterized. These ion‐paired complexes are efficient catalysts for the ring‐opening polymerization of rac ‐lactide ( rac ‐LA) in the presence of 5 equivalents BnOH as an initiator and the side reaction of epimerization can be suppressed well at low temperatures. The polymerizations are controllable, affording polylactides with desirable molecular weights and narrow molecular weight distributions; the highest molecular weight can reach 50.1 kg mol −1 in this system, and a best isoselectivity of P m =0.82 was achieved. Such polymerizations have rarely been reported for isoselective sodium/potassium complexes without crown ether as an auxiliary ligand. The solid structures suggest that BnOH can be activated by an interaction with the anion of sodium/potassium complex via a hydrogen bond and that the monomer is activated by coordination to sodium/potassium ion.