Immortal depolymerization of chemical recycling of CO2-Sourced poly (cyclohexene carbonate) to monomers: An overlooked effect of molecular weight

Poly(cyclohexene carbonate) (PCHC), produced via copolymerization of cyclohexene oxide (CHO) and CO 2 , is the most representative CO 2 -sourced polymer with desirable thermomechanical performance. Another important property of PCHC is its ability to be chemically recycled to monomers , which has made significant progress in the past decade. Even though, systematic studies on the effect of PCHC molecular weight on the degradation process have not been reported. The aim of this study was to investigate the correlation between the depolymerization effectiveness and the molecular weight of PCHC using two classical catalytic systems. A total of five PCHC samples with varying molecular weights were subjected to systematic investigation, including 14.5 kg mol −1 , 21.0 kg mol −1 , 56.0 kg mol −1 , 82.0 kg mol −1 , and 93.4 kg mol −1 . For the first time, we found that molecular weight significantly influences its degradation, and the degradation rate increases with an increase in the molecular weight. The PCHC sample with a higher molecular weight ( M n = 93.4 kg mol −1 ) exhibits a degradation TOF value of 1665 h −1 , which is over four times higher than that of the PCHC sample with a lower molecular weight ( M n = 14.5 kg mol −1 , TOF = 402 h −1 ) in the presence of cobalt catalyst. This interesting phenomenon is further corroborated by the use of the Cr III -Salen/PPN-Cl system. This phenomenon can be attributed to the so-called "immortal depolymerization", which occurs via two different chain-end catalyzed pathways: chain transfer depolymerization and transesterification . • The influence of molecular weight on the chemical recycling of poly(cyclohexene carbonate) (PCHC) was systematically studied. • PCHC with higher molecular weights facilitates a notable increase in the degradation rate. • "Immortal depolymerization" is elucidated through chain transfer depolymerization and transesterification .