In the ground state, sp-hybridized carbon chains can exist in two forms: “polyyne” or “cumulene” (Fig. 1a). While alkyne-based conjugated polymers have been extensively studied, there have been very few reports on their cumulenic counterparts. Cumulene-based conjugated polymers are not only predicted to possess unique optoelectronic properties, but also hold promise as model molecules for studying "carbyne". However, due to their high instability and low solubility, to date, researchers have only been able to synthesize polymers with up to three cumulative double bonds (Fig. 1b). Higher cumulene-based conjugated polymers remain unknown.
Fig.1 Cumulenic conjugated polymers: challenges and strategies.
Prof. Rong Zhu’s group at the College of Chemistry and Molecular Engineering, Peking University has introduced a family of new polymerization reactions based on cumulenes, namely condensation polymerization of propargylic electrophiles, CPPE (see JACS, 2022, 144, 8807; JACS, 2022, 144, 4315; JACS, 2023, 145, 2045; Giant, 2023, 13,100139). Recently, they took a “Meet in the middle” strategy (Fig. 1c) and succeeded in developing a step-growth CPPE reaction (sg-C3-CPPE). This method enables unprecedented high-molecular-weight conjugated [5]cumulene polymers, setting a new record of the number of consecutive carbon-carbon double bonds in stable conjugated polymers.
This work was published online in the Journal of the American Chemical Society entitled “Conjugated [5]Cumulene Polymers Enabled by Condensation Polymerization of Propargylic Electrophiles”. It demonstrates the potential of CPPE in constructing stable and structurally tunable cumulenic conjugated polymers, providing a platform for studying the potential applications of these novel sp-carbon-rich materials.
Zi-Yuan Wang, a Ph.D. candidate in the Zhu group, is the first author of this paper. Prof. Rong Zhu is the corresponding author. This research was generously supported by the National Natural Science Foundation of China and the Beijing National Laboratory for Molecular Sciences.
Original link for the paper: https://pubs.acs.org/doi/full/10.1021/jacs.3c08290.
