1-Methoxy-2-methylpropylene
oxide (MOMPO), an alkoxyoxirane that
can generate a carbocation adjacent to an alkoxy group via ring-opening,
was demonstrated to polymerize in a controlled manner with the use
of a metal chloride as a Lewis acid catalyst. The choice of the initiating
system is critical for the successful controlled homopolymerization
of this alkoxyoxirane; a GaCl3/THF system was observed
to be the best combination for the initiating system. Furthermore,
the copolymerization of MOMPO with isopropyl vinyl ether (IPVE) generated
long-lived species when CF3SO3H/nBu4NI was used as the initiating system. Surprisingly,
the reaction proceeded via the transfer of the alkoxy group in the
IPVE unit. More specifically, the isopropoxy group at the penultimate
IPVE unit transferred to the MOMPO-derived propagating cation after
the crossover reaction from the IPVE-derived carbocation to MOMPO.
This type of reaction creates a side group that possesses the ring-opened
MOMPO structure with the isopropoxy group. The generation of copolymers
via the “alkoxy-group transfer” mechanism is unique
to the copolymerization in this study and was confirmed by 1H, 13C, and 2D NMR analyses and by the acid hydrolysis
and subsequent reacetalization reactions of the products.
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