%0 Journal Article
%A Zune, C.
%A Dubois, P.
%A Jérôme, R.
%A Kříž, J.
%A Dybal, J.
%A Lochmann, L.
%A Janata, M.
%A Vlček, P.
%A Werkhoven, T. M.
%A Lugtenburg, J.
%D 1998
%T Study of the Propagation Center in the Anionic Polymerization of
(Meth)acrylic Monomers: NMR and MO LCAO Study of the Interaction
of Di-tert-butyl 2-Lithio-2,4,4-trimethylglutarate and the Living
Poly(tert-butyl methacrylate) Oligomers with Lithium
2-(2-Methoxyethoxy)ethoxide in Tetrahydrofuran
%U https://acs.figshare.com/articles/journal_contribution/Study_of_the_Propagation_Center_in_the_Anionic_Polymerization_of_Meth_acrylic_Monomers_NMR_and_MO_LCAO_Study_of_the_Interaction_of_Di-_i_tert_i_-butyl_2-Lithio-2_4_4-trimethylglutarate_and_the_Living_Poly_i_tert_i_-butyl_methacrylate_Oligomers_with_Lithiu/3732555
%R 10.1021/ma971368s.s001
%2 https://acs.figshare.com/ndownloader/files/5824326
%K THF
%K form metastable systems
%K MNDO quantum chemical calculations
%K NMR
%K tert
%K butyl methacrylate
%K SCF
%K model dimer di
%K aggregates LiOEEM 1
%K MO LCAO Study
%X Interactions of lithium 2-(2-methoxyethoxy)ethoxide (LiOEEM)
with the model dimer di-tert-butyl 2-lithio-2,4,4-trimethylglutarate (A)
and the living poly(tert-butyl methacrylate) oligomers
(B)
were studied in tetrahydrofuran-d8 at 203−273
K using 1H, 13C, 7Li, and
6Li, 1D and 2D, NMR and ab
initio SCF 3-21G and MNDO quantum chemical calculations. LiOEEM is
shown to have a strong tendency
to self-aggregation, producing dimeric, trimeric, and tetrameric
aggregates and competing with its mixed
aggregation (or complexation) with A and, in particular,
B. When dissolved in THF, LiOEEM as well
as
its mixtures with A form metastable systems which relax in
several days at 258 K into equilibrium.
Interaction of LiOEEM with A leads to a system of mixed
aggregates
LiOEEM1A1,
LiOEEM3A1,
and
possibly
LiOEEM2A1
along with the original components, in relative populations depending
on the
LiOEEM/A molar ratio, temperature, time, and probably other
factors of preparation. Probable structures
of these complexes are proposed, and the nature of the prevalent
bonding is suggested. Experimental
results indicate that LiOEEM is unable to convert A
completely at moderate excess (up to 4/1 mol/mol).
Interaction of LiOEEM with B leads to quite analogous
complexes but with even lower yields. There
appear to be traces of uncomplexed B even at the LiOEEM/B
ratio of 10 mol/mol. This is suggested to
produce at least two different kinds of active growth centers in the
corresponding ligated anionic
polymerization of tert-butyl methacrylate and, consequently,
the observed bimodality of the polymeric
product. The difference with respect to methyl methacrylate, where
LiOEEM ensures an almost ideal
living polymerization, is suggested to be due to the steric hindrance
of efficient complexation exerted by
the tert-butyl group.
%I ACS Publications