Direct Coupling
of Biobased Bifunctional Hydroxy-Aldehyde
Monomers to Chemically Recyclable Alipharomatic Polyesters via Dehydrogenative Polycondensation
posted on 2024-02-11, 16:04authored byHui-Du Xu, Hui-Jia Deng, Hui-Mei Zeng, Weiran Yang, Changguang Yao
A series of biobased alipharomatic
polyesters using vanillin-derived
bifunctional hydroxy-aldehyde monomers (M1)s as the starting
materials are synthesized through direct dehydrogenative polycondensation
with commercially available Milstein catalyst. The thermal properties
of the resulting P(M1)s can be precisely tuned by altering
the alkylene length of the monomers, with a maximum Tg value reaching 37.9 °C. Compared to the reported
vanillic acid-based polyesters, the synthesis of M1 is
less labor-intensive, and the polymerization conditions are milder
than those of conventional polycondensation. Additionally, experimental
results and mechanism elucidations revealed four different types of
ester linkages in the P(M1) chain. The ruthenium dihydride
complex has been identified as the true active species required for
promoting the polymerization of hydroxy-aldehyde monomers into polyesters.
Moreover, this catalytic system also exhibits depolymerization capability
toward resulting polyester back into vanillin-derived diol (M2), which can then be repolymerized into a polyester P(M2) with an identical structure to that of P(M1), thus demonstrating a rare example where two different monomers
yield the same polymer product. This study presents a green and economical
approach to the preparation and recycling of widely used alipharomatic
polyesters.