Synthesis of ring-opening metathesis polymers containing pendant diglycolamide or CyMe4 – BTPhen ligands for the separation of actinides from lanthanides
The expansion of nuclear energy as a replacement for fossil fuels for electricity production has been impeded by the presence of minor actinides such as americium and curium in the liquid waste generated by nuclear reactors. These species are responsible for the high radiotoxicity of the spent fuel, which may last for millennia. Thus, actinide removal from nuclear waste would reduce the lifetime of the waste as well as the cost associated with storing it. Unfortunately, the co-existence of the chemically similar lanthanides in nuclear waste renders this task challenging. Multi-dentate ligands such as carbamoylmethylphosphineoxides (CMPOs), diglycolamide (DGAs), and N-heterocycles have been studied comprehensively, and have shown to be capable of performing this arduous separation. Among these, CyMe4-BTPhen developed by Lewis et al. has shown great promise as an effective actinide extractant. Numerous research efforts have also shown that preorganizing these ligands onto various platforms such as calixarenes, cavitands, trityls, and tripods greatly enhance extraction efficiency and selectivity while simultaneously reducing the required ligand concentrations. The Holliday group has studied various polymeric matrices containing CMPO ligands and found that these CMPOs-tethered scaffolds outperformed the free ligands. These polymer matrices may also be suitable for DGAs as well as the bulky CyMe4-BTPhen ligand. Herein, two new monomer-containing pendant N,N-dimethyl diglycolamide (DMDGA) and N,N-dioctyl diglycolamide (DODGA) ligands have been synthesized. A new ROM-type polymer with varying molecular weights and high thermal stability was also obtained from the DMDGA ligands. CyMe4-BrBTPhen was also synthesized and efforts to form a monomer and subsequent polymers are being investigated.