Comparative Reactivity of Me3Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerizationстатья
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Дата последнего поиска статьи во внешних источниках: 18 апреля 2017 г.
Аннотация:Silyl substituted norbornenes and their derivatives
are effective monomers in the synthesis of new
prospective polymer materials for gas separation membranes
by metathesis and addition polymerization. Comparative
activity of norbornenes (NB), norbornadienes
(NBD) and tricyclononenes (TCN) with different spatial
arrangement of one or two Me3Si substituents in
ring-opening metathesis polymerization (ROMP) in the
presence of Grubbs initiator Cl2(PCy3)2Ru=CHPh were
studied by NMR and GC. It was shown that the rate
of the initiation was lower than the propagation for
all monomers and the highest activity was inherent
to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-
trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN
turned out to be more active than NB having the same
number and position of the substituents. The latter were
more active than the corresponding NBD. It was found
that syn- and anti-isomers of 3-TCNSi polymerized with
close rates in contrast to exo- and endo-substituted 5-NBSi,
for which polymerization rates were substantially different.
Special behavior of monomers with bulky substituents in
the geminal position was observed: 5,5-NBSi2 was inactive
in the presence of the 1st generation Grubbs initiator,
whereas it was polymerized in the presence of the 2nd
generation one. Quantum-chemical calculations were in
agreement with experimental data and evidenced the influence
of energy, electronic and structural properties of the
norbornene-type monomers studied on their activity in
ROMP.