Abstract
Intrinsically recyclable polymers represent a circular economy approach to address plastics problems. However, the design of such circular polymers is challenged by unyielding trade-offs between the monomer’s polymerizability and the polymer’s depolymerizability and performance properties. Here, we introduce a hybrid monomer design strategy that synergistically couples a high ceiling temperature (HCT) sub-structure for high polymerizability and performance properties with a low ceiling temperature (LCT) sub-structure for high depolymerizability and recyclability within the same monomer structure. Thus, structural hybridization between HCT ε-caprolactone and LCT γ-butyrolactone led to an offspring [3.2.1]bicyclic lactone, which exhibits both high polymerizability and depolymerizability, otherwise conflicting properties in a typical monomer. The resulting polymer becomes a high-performance material, and thermal transition temperatures are ∼200°C higher and tensile modulus 10× higher than its parent polymers. These results demonstrate that the HCT/LCT hybrid monomer strategy is a powerful approach for designing circular polymers where conflicting properties must be exploited and unified.
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•Circular plastics can be designed with high-performance properties•Hybrid monomer design radically alters properties of the resulting recyclable polymers•Property trade-offs can be overcome by hybridizing low/high ceiling temperature monomers
Synthetic polymers have become indispensable for modern life and the global economy. However, the manufacturing and disposal of most of today’s polymers follow a linear economy model, which has caused accelerated depletion of finite natural resources, severe worldwide plastics pollution, and enormous materials value loss. The design of future circular polymers considers closed-loop lifecycles toward a circular economy. A key challenge of this promising design includes innovation in monomer structure that could enable not only efficient polymerization to polymers with properties comparable to today’s polymers but also selective depolymerization to recover the monomers with high yield and purity. However, these contrasting properties are conflicting in a single monomer structure. This work introduces a hybrid monomer design concept that hybridizes contrasting parent monomer structures to an offspring monomer that can unify conflicting (de)polymerizability and performance properties.
Hybrid monomer design is shown to be a powerful approach to develop robust circular plastics without yielding to common property trade-offs by hybridizing parent monomer structures to an offspring monomer that can unify conflicting (de)polymerizability and performance properties.