Acyclic diene metathesis (ADMET) polymerization of an
α,ω-diene
monomer of bis(undec-10-enoate) with isosorbide (M1)
using a RuCl2(IMesH2)(CH-2-O
i
Pr-C6H4) (HG2, IMesH2 = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) catalyst
and conducted at 50 °C (in vacuo) in ionic liquids (ILs) afforded
higher-molecular-weight polymers (P1, M
n = 32 200–39 200) than those reported
previously (M
n = 5600–14700). 1-n-Butyl-3-methyl imidazolium hexafluorophosphate ([Bmim]PF6) and 1-n-hexyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)imide
([Hmim]TFSI) were suitable as effective solvents among a series of
imidazolium salts and the pyridinium salts. The polymerization of
α,ω-diene monomers of bis(undec-10-enoate) with isomannide
(M2), 1,4-cyclohexanedimethanol (M3), and
1,4-butanediol (M4) in [Bmim]PF6 and [Hmim]TFSI
also afforded the higher-molecular-weight polymers. The M
n values in the resultant polymers did not decrease even
under the scale-up conditions (300 mg to 1.0 g scale, M1, M2, and M4) in the polymerizations in
[Hmim]TFSI; the subsequent reaction of P1 with ethylene
(0.8 MPa, 50 °C, and 5 h) gave oligomers (proceeded via depolymerization).
Tandem hydrogenation of the resultant unsaturated polymers (P1) in a [Bmim]PF6–toluene biphasic system
upon the addition of Al2O3 (1.0 MPa H2 at 50 °C) gave the corresponding saturated polymers (HP1), which waswere isolated by a phase separation in the
toluene layer. The [Bmim]PF6 layer containing the ruthenium
catalyst could be recycled without a decrease in the activity/selectivity
of the olefin hydrogenation at least eight times.
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