Heteroatom Substitution Strategy Modulates Thermodynamics Towards Chemically Recyclable Polyesters and Monomeric Unit Sequence by Temperature Switching
Da Zhang, Xin Wang*（王鑫）, Zhengbiao Zhang*（张正彪）, Nikos Hadjichristidis
State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, Suzhou Key Laboratory of Macromolecula Design and Precision Synthesis, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123,China
Angew. Chem.Int. Ed.,2024, 63, e202402233
Abstract: In this paper, we proposed a heteroatom substitution strategy (HSS) in the δ-valerolactone (VL) system to modulate thermodynamics toward chemically recyclable polyesters. Three VL-based monomers containing different heteroatoms (M1 (N), M2 (S), and M3 (O)), instead of C-5 carbon, were designed and synthesized to verify our proposed HSS. All three monomers undergo organocatalytic living/controlled ROP and controllable depolymerization. Impressively, the resulting P(M1) achieved over 99 % monomer recovery under both mild solution depolymerization and high vacuum pyrolysis conditions without any side reactions, and the recycled monomers can be polymerized again forming new polymers. The systematic study of the relationship between heteroatom substitution and recyclability shows that introducing heteroatoms does change the thermodynamics of the monomers (ΔHpo, ΔSpo and Tc values), thereby adjusting the polymerizability and depolymerizability. DFT calculations found that the introduction of heteroatoms adjusts the ring strain by changing the angular strain of the monomers, and the order of their angular strain (M2>M1>M3) is consistent with the order of the experimentally obtained enthalpy change. Notably, the one-pot/one-step copolymerization of two of each of the three monomers enables the synthesis of sequence-controlled copolymers from gradient to random to block structures, by simply switching the copolymerization temperature.
链接：//onlinelibrary.wiley.com/doi/10.1002/anie.202402233
