Within this project, our primary focus was on achieving low-temperature depolymerization of RAFT polymers by altering the electronic properties of the RAFT agents and achieving higher depolymerization conversions with longer polymer chains. The latter was accomplished through the preparation of bifunctional polymers.
In WP1, we synthesized RAFT agents with various substitutions to control their activities. The enhancement of electron density of these RAFT agents enabled the polymers to depolymerize at lower temperatures (90 °C) than reported in the literature (120 °C). Five different substitutions were employed to study both the enhancement and decrement effects on depolymerization. Polymers containing the RAFT agent with the lowest electron density exhibited a slower depolymerization at lower temperatures and a lower yield (~20%) of depolymerization. Conversely, the enhancement of electron density of the RAFT agent facilitated a higher rate of depolymerization, with yields closer to 80%. These substitutions highlight the fact that depolymerization can be facilitated without using any catalyst by simply altering the electron densities of the RAFT agents. Furthermore, calculations demonstrated that the enhanced electron density of the RAFT agents facilitated faster C-S bond scission between the RAFT agent and the polymer, ultimately resulting in faster and higher yield depolymerization. To date, the project results have been shared in conferences, and the main manuscript is nearing completion for publication.
In WP2, our aim was to address the enhancement of depolymerization yields in RAFT polymers and introduce the depolymerization of bifunctional polymers. Bifunctional polymers, as described in literature, have been utilized in various applications such as material preparation and polymer self-assembly. This research underscores the importance of having multiple RAFT active sites in RAFT polymers and the use of different bifunctional RAFT agents to achieve higher depolymerization yields. Within this work package, we synthesized two different bifunctional RAFT agents with active sites located at the ends and in the middle of the chains. Having multiple active sites facilitated multiple activations of the depolymerization process, thus enhancing depolymerization yields. Furthermore, we highlighted that the positioning of the RAFT agent (whether at the end or in the middle) also affects the final conversion of the depolymerization. Having RAFT agents in the middle of the polymer chains further enhances depolymerization and yields better monomer recovery at the end of the depolymerization process. Moreover, we delved into the mechanisms of depolymerization of these polymers and analyzed the depolymerization processes of bifunctional polymers in detail. The outcomes of this project are currently undergoing preparation for publication, and we anticipate their publication in the near future.
