Search for: All records

Chemically recyclable polymers offer a promising solution to address the issues associated with the unsustainable use of plastics by converting the traditional linear plastic economy into a circular one. Central to developing chemically recyclable polymers is to identify the appropriate monomers that enable practical conditions for polymerization and depolymerization and ensure useful stability and material properties. Our group has recently demonstrated thattrans‐cyclobutane‐fused cyclooctene (tCBCO) meets the abovementioned requirements and is a promising candidate for developing chemically recyclable polymers. Herein, encouraged by the success withtCBCO, we investigate the thermodynamics of polymerization of a relevant system,trans‐benzocyclobutene‐fused‐cyclooctene, which can be viewed astCBCO with an additional benzene ring. The study shows that introducing an additional benzene ring favors polymerization and disfavors depolymerization, and the effect is predominantly entropic. The benzo‐effect can be leveraged to fine‐tune the thermodynamics of polymerization and depolymerization to facilitate the chemical recycling of polymers.

 

Chemical recycling to monomer (CRM) is a promising route for transitioning to a circular polymer economy. To develop new CRM systems with useful properties, it is important to understand the effects of monomer structure on polymerization/depolymerization behavior. In earlier work, this group demonstrated chemically recyclable polymers prepared by ring‐opening metathesis polymerization oftrans‐cyclobutane fused cyclooctenes (tCBCO). Here, it is investigated how different substituents on cyclobutane impact the thermodynamics and thermal properties oftCBCO polymers. Introducing additional substituents to acis‐diester functionalizedtCBCO is found to favor the conversion of polymerization; increased polymerization conversion is also observed when thecis‐diester is isomerized into itstranscounterpart. The effects of these structural features on the thermal properties are also studied. These findings can provide important insights into designing next‐generation CRM polymers.

 

While depolymerizable polymers have been intensely pursued as a potential solution to address the challenges in polymer sustainability, most depolymerization systems are characterized by a low driving force in polymerization, which poses difficulties for accessing diverse functionalities and architectures of polymers. Here, we address this challenge by using a cyclooctene‐based depolymerization system, in which thecis‐to‐transalkene isomerization significantly increases the ring strain energy to enable living ring‐opening metathesis polymerization at monomer concentrations ≥0.025 M. An additionaltrans‐cyclobutane fused at the 5,6‐position of the cyclooctene reduces the ring strain energy of cyclooctene, enabling the corresponding polymers to depolymerize into thecis‐cyclooctene monomers. The use of excess triphenylphosphine was found to be essential to suppress secondary metathesis and depolymerization. The high‐driving‐force living polymerization of thetrans‐cyclobutane fusedtrans‐cyclooctene system holds promise for developing chemically recyclable polymers of a wide variety of polymer architectures.

 

Fluorinated polymers are important functional materials for a broad range of applications, but the recycling of current fluorinated polymers is challenging. We present the first example of semi-fluorinated polymers that can undergo chemical recycling to form the corresponding monomers under ambient conditions. Prepared through ring-opening metathesis polymerization of functionalized trans -cyclobutane fused cyclooctene ( t CBCO) monomers, these polymers show tunable glass transition temperatures (−2 °C to 88 °C), excellent thermal stability (decomposition onset temperatures >280 °C) and hydrophobicity (water contact angles >90°). The hydrophobicity of the semi-fluorinated polymers was further utilized in an amphiphilic diblock copolymer, which forms self-assembled micelles with a size of ∼88 nm in an aqueous solution. Finally, through an efficient, regioselective para -fluoro-thiol substitution reaction, post-polymerization functionalization of a polymer with a pentafluorophenyl imide substituent was achieved. The ease of preparation, functionalization, and recycling, along with the diverse thermomechanical properties and demonstrated hydrophobicity make the t CBCO-based depolymerizable semi-fluorinated polymers promising candidates for sustainable functional materials that can offer a solution to a circular economy.