Data for: Low temperature thermal RAFT depolymerization: the effect of Z-group substituents on molecular weight control and yield

The labile end-groups inherent to many controlled radical polymerization methodologies, including atom transfer radical polymerization (ATRP) and reversible addition–fragmentation chain-transfer (RAFT) polymerization, can trigger the efficient chemical recycling of polymethacrylates yielding high percentages of pristine monomer. Yet, current thermal solution ATRP and RAFT depolymerization strategies require relatively high temperatures (i.e. 120–170 °C) to proceed, with slower depolymerization rates, and moderate yields often reported under milder reaction conditions (i.e. lower temperatures). In this work, we seek to promote the low temperature RAFT depolymerization of polymethacrylates via regulating the Z-group substitution of dithiobenzoate. While electron-withdrawing meta and para substituents, including trifluoromethyl (CF3) and trifluoromethoxy (OCF3), compromised the percentage of monomer recovery at 90 °C (e.g. 18% of conversion), instead the incorporation of electron-donating groups in the benzene ring, such as methoxy (OMe) and tertiary butoxy (OtBu), had a remarkable effect leading to up to four times higher conversions (e.g. 75%). Notably, electron-withdrawing Z-groups imposed control over depolymerization, reflected in the gradual decrease of the molecular weight during the reaction, as opposed to electron-donating groups which underwent a more uncontrolled depolymerization pathway. Density Functional Theory (DFT) calculations revealed accelerated bond fragmentation for electron-donating Z-groups, further supporting our findings. Taken altogether, this work highlights the importance of RAFT agent selection to either lower the reaction's temperature while maintaining high conversions, or induce control over the depolymerization.诸多可控自由基聚合方法（包括原子转移自由基聚合（atom transfer radical polymerization, ATRP）与可逆加成-断裂链转移（reversible addition-fragmentation chain-transfer, RAFT）聚合）所固有的活性端基，可引发聚甲基丙烯酸酯的高效化学回收，得到高比例的原始单体。但现有热溶液相ATRP与RAFT解聚策略通常需依托120~170 ℃的较高反应温度方可进行，且解聚速率较慢；在更温和的低温反应条件下，单体回收率往往仅处于中等水平。本研究通过调控二硫代苯甲酸酯的Z基团取代，旨在实现聚甲基丙烯酸酯的低温RAFT解聚。研究发现，90 ℃下，带有三氟甲基（CF3）、三氟甲氧基（OCF3）等吸电子间位/对位取代基团的体系会降低单体回收率（如转化率仅18%）；而在苯环上引入甲氧基（OMe）、叔丁氧基（OtBu）等给电子基团则可产生显著效果，使转化率最高提升4倍（如达75%）。值得注意的是，吸电子Z基团可对解聚过程实现精准调控，表现为反应过程中聚合物分子量逐步降低；与之相对，带有给电子Z基团的体系则呈现出更难控的解聚路径。密度泛函理论（Density Functional Theory, DFT）计算结果显示，给电子Z基团可加速化学键断裂过程，进一步佐证了本研究的实验发现。综上，本研究凸显了RAFT试剂选择的关键意义：既可在维持高单体转化率的前提下降低反应温度，也可实现对解聚过程的有效调控。