A polyester containing electron deficient internal alkyne units derived from acetylene dicarboxylic acid in the main backbone was employed as a polymeric platform in copper free cycloaddition reactions.
This
study describes a straightforward post-polymerization modification
(PPM) methodology from polyketone via chlorodimethylsilane (CDMS)-mediated
reductive etherification reaction (RER). The polyketone platform was
prepared via acyclic diene metathesis (ADMET) polymerization and reacted
with a variety of alcohols in the presence of CDMS to create a wide
range of polymers possessing pendant functional-alkoxy structures
under mild conditions. The effect of parameters such as solvents and
the amount of reactants on RER were studied. We have also explored
the effect of other silane compounds on RER, none of which provided
as high efficiency as the CDMS-mediated one. It has been found that
the primary alcohols yielded corresponding alkoxy structures in high
efficiencies, high isolated yields, and a wide range of functional
group tolerance. It was also found that the formation of polyalcohol
was inevitable, to some extent, during the RERs in addition to the
alkoxy-functional polymers. All the polymers obtained were characterized
in detail by various spectroscopic measurements, and a mechanistic
aspect was also presented to evaluate the product distributions. Since
operationally simple chemical methods, with a high yield and functional
group tolerance, that can be easily adapted to the macromolecular
level are always desired in synthetic polymer chemistry, this study
promises remarkable opportunities for synthesizing functional polymers
and may pave a way for the development of a novel metal-free PPM method.
Polyethers
have always been privileged compounds in polymer chemistry
and have found extensive applications in both academic research and
industry. However, the currently employed strategies for their synthesis
require harsh conditions such as ionic polymerizations together with
limited precursor monomer options. In this study, a chlorodimethylsilane
(CDMS)-mediated reductive etherification reaction was introduced as
a versatile strategy for polyether synthesis. Accordingly, terephthalaldehyde
(TPA) and 1,4-butanediol were first reacted at room temperature in
the presence of CDMS using nitromethane as the polymerization solvent
to reveal the optimum conditions for the proposed system. Subsequently,
a variety of diols ranging from linear to sterically congested diols
were reacted with TPA (and its isomers) under the optimized conditions
to create a polyether library. Meanwhile, in addition to polyether
having the expected alternating units, the formation of polyether
stem from the self-condensation of TPA was found to be inevitable
in all cases. From the proposed strategy, polyethers with a molecular
weight of up to 110.4 kDa and a high alternating unit of up to 93%
were obtained. The versatile and robust character of the presented
strategy was supported by a model end-group study, and the polymerization
behavior was examined mechanistically. It is anticipated that the
presented method might be a strong candidate for polyether synthesis
with different backbones, given the unlimited sources of diols.
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