Bifunctional and recyclable polyesters by chemoselective ring-opening polymerization of a δ-lactone derived from CO2 and butadiene
When aiming at the direct use of CO 2 for the preparation of advanced/value-added materials, the synthesis of CO 2 /olefin copolymers is very appealing but challenging. The δ-lactone 3-ethylidene-6-vinyltetrahydro-2 H -pyran-2-one (EVP), synthesized by telomerization of CO 2 with 1,3-butadiene, is a promising monomer. However, its chemoselective ring-opening polymerization (ROP) is hampered by unfavorable thermodynamics and the competitive polymerization of highly reactive C=C double bonds under usual conditions. Herein, we report the chemoselective ROP of EVP using a phosphazene/urea binary catalyst, affording exclusively a linear unsaturated polyester poly(EVP) ROP , with a molar mass ( M n ) up to 16.1 kg·mol −1 and a narrow distribution ( Ð < 1.6), which can be fully recycled back to the pristine monomer, thus establishing a monomer-polymer-monomer closed-loop life cycle. In these polyesters, the CO 2 content reaches 33 mol% (29 wt%). The reasons for the unexpected chemoselectivity were investigated by Density-functional theory (DFT) calculations. The poly(EVP) ROP features two pendent C=C double bonds per repeating unit, which show distinct reactivity and thus can be properly engaged in sequential functionalizations towards the synthesis of bifunctional polyesters. We disclose here a methodology providing a facile access to bifunctional and recyclable polyesters from readily available feedstocks.
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