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Aluminium and rare earths alkoxides as initiators for the heterogeneous anionic coordinated polymerisation of propylene oxide. A 1 H NMR approach of the regioselectivity and transfer ability of the catalytic system
Author(s) -
JacquierGonod Véronique,
Llauro MarieFrance,
Hamaide Thierry
Publication year - 2000
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(20000101)201:1<12::aid-macp12>3.0.co;2-n
Subject(s) - regioselectivity , triethylamine , alkoxide , chemistry , monomer , polymerization , polymer chemistry , propylene oxide , aluminium , catalysis , organic chemistry , polymer , copolymer , ethylene oxide
In order to outline the placement of the monomer units during the heterogeneous anionic coordinated polymerization of propylene oxide, the regioselectivity of the first monomer insertion at the initiator was examined by 1 H NMR. To start, aluminium benzyl oxide chemically grafted onto a porous support was used as initiator. It was shown that the regioselectivity of the first insertion reflects the placement of the monomer units in the chain. Although there is no direct correlation between these two parameters, a knowledge of the regioselectivity of this first insertion allowed us to compare different catalytic systems. With aluminium alkoxides as initiators, both carbon atoms are attacked at random in the first insertion step. Adding triethylamine increases notably the regioselectivity. The replacement of aluminium by zirconium or a rare earth element gives about the same percentage of regular insertion as that obtained with the complex aluminium alkoxide‐NEt 3 . On the other hand, the allyl double bond content was measured and the values of the transfer constant were deduced. Adding triethylamine to aluminium alkoxides or using Zr and rare earth based systems causes a decrease of the transfer constant. The more regular the PO insertion is, the lower is the transfer constant.