Supramolecular Cocrystals Built Through Redox-Triggered ion Intercalation in π-Conjugated Polymers
Abstract Self-organization in π-conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicrystalline polymers results not only in effective charge transport, but also allows the inclusion of various functional molecules and ions. In particular, redox-triggered ion-intercalation in a polymer's lamellae is an ideal system for molecular doping, for which extremely high charge carrier density, corresponding to one carrier per monomer unit, has been achieved. We conducted a detailed structural analysis and electron density simulation to pinpoint exactly where the guest dopants are located periodically in the restricted void space in a polymer's lamellae. Our findings are indicative of an intercalation compound of layered polymers and a guest intercalant. In addition, we show that a homogeneous cocrystal structure can be realized throughout the host polymer medium, which is proved unambiguously by the observation of coherent carrier transport across microscopic-scale films. Also, the intercalation cocrystal nature gives the best achievable doping level in semicrystalline conjugated polymers and excellent environmental stability. These findings should open up new possibilities for tuning the collective dynamics of functional molecules and ions through intercalation phenomena.
