Bridging the Monomer to Polymer Gap in Radical Polymer Design

Radical polymers bearing open-shell moieties at pendantsites exhibitunique redox and optoelectronic properties that are promising formany organic electronic applications. Nevertheless, gaps remain inrelating the electronic properties of repeat units, which can be easilycalculated, to the condensed-phase charge transport behaviors of thesematerials. To address this gap, we have performed the first quantumchemical study on a broad swathe of radical polymer design space thatexplicitly includes the coupling between polymer constraints and radical-mediatedintramolecular charge transfer. For this purpose, a chemical spaceof 64 radical polymer chemistries was constructed based on varyingbackbone units, open-shell chemistries, and spacer units between thebackbone and the radical groups. For each combination of backbone,radical, and spacer, comprehensive conformational sampling was usedto calculate expected values of intrachain charge transport usingseveral complementary metrics, including the end-to-end thermal Green'sfunction, Delta-Wye transformed inverse resistance, and theKirchhoff transport index. We observe that charge transport in radicalpolymers is primarily driven by the choice radical chemistry, whichinfluences the optimal choice of backbone chemistry and spacer groupthat mediate radical alignment and avoid the formation of undesiredtrap states. Given the limited exploration of radical chemistriesbeyond the TEMPO radical for this class of materials, these findingssuggest tremendous opportunities exist for synthetic exploration inradical polymers.