%0 Generic
%A Wang, Yang
%A Zhao, Wei
%A Liu, Xinli
%A Cui, Dongmei
%A Chen, Eugene Y.-X.
%D 2016
%T Ligand-Free Magnesium
Catalyst System: Immortal Polymerization of l‑Lactide
with High Catalyst Efficiency and Structure of Active Intermediates
%U https://acs.figshare.com/articles/dataset/Ligand_Free_Magnesium_Catalyst_System_Immortal_Polymerization_of_l_Lactide_with_High_Catalyst_Efficiency_and_Structure_of_Active_Intermediates/2488438
%R 10.1021/ma3007625.s002
%2 https://ndownloader.figshare.com/files/4131226
%K PhCH 2OH diphenylmethanol
%K 3COH
%K Ph 2CHOH
%K 2 D DOSY
%K Ph 2CHOH loading
%K MgnBu
%K Mg
%K catalyst system
%K polymerization
%K PDI
%K PLA
%K High Catalyst Efficiency
%X A simple, inexpensive, and convenient catalyst system
consisting of supporting ligand-free MgnBu2 in combination with an alcohol, isopropanol (iPrOH), benzyl methanol (PhCH2OH),
diphenylmethanol (Ph2CHOH), or triphenylmethanol (Ph3COH), generates a convenient catalyst system to promote the
polymerization of l-LA. In particular, the binary system
MgnBu2/Ph2CHOH demonstrates
an unprecedentedly high activity in the presence of a large excess
amount of Ph2CHOH with the [OH]0/[Mg]0 ratio varying from 2 to 500, producing up to 500 polylactide (PLA)
chains per Mg center and thus showing a typical nature of immortal
polymerization. The molecular weights of the obtained PLAs with a
broad range of monomer-to-metal ratios ([l-LA]0/[Mg]0 = 200–5000) are rather accurately controlled
by the Ph2CHOH loading, relative to [Mg]0, while
the molecular weight distributions remain nearly constant with polydispersity
index (PDI) = 1.08–1.18. Moreover, the active polymerization
intermediate has been isolated from the stoichiometric reaction between
MgnBu2 and Ph2CHOH
and structurally characterized as a tetranuclear complex, Mg4(Ph2CHO)8(THF)2 (1).
Complex 1 remains the tetranuclear structure in solution
or in the presence of excess Ph2CHOH as determined by 2D
DOSY. On the basis of structural information about the active intermediates
and polymerization kinetics, a coordination–insertion polymerization
mechanism is proposed.
%I ACS Publications