A non-conjugated polymer with flexible backbones bearing spin-delocalized pendant radical groups

Radical polymer thin films have shown high electrical conductivity values when locally ordered domains form after thermal annealing. However, most efforts in the radical polymer studies have focused on polymers bearing spin-localized nitroxide radical groups, and macromolecules bearing spin-delocalized radical groups have received little attention. To open new insights into the solid-state charge transport mechanism in radical polymer thin films, a polysiloxane-based polymer bearing galvinoxyl radical groups has been synthesized. Density functional theory (DFT) calculations predicted that the spin delocalization behavior of the galvinoxyl group would result in a higher charge transfer rate compared with nitroxide radical systems. It is determined that the flexible backbone endowed the polymer with a glass transition temperature around 0 °C, and this feature allowed the molecules to pack into ordered structures after thermal annealing. Furthermore, the conductivity of this radical polymer was quantified after being cast into a thin film. Thus, these studies provide a strategy to direct molecular packing and facilitate charge transport in radical polymers with delocalized open-shell sites, which can aid in deciphering the charge transport mechanism in radical polymer thin films.