Ion conduction in a semicrystalline polyviologen and its polyether mixtures

Polyviologen (PV) with C₆ spacers and bis(trifluoromethylsulfonyl)imide (Tf₂N-) anions is a semicrystalline polymer. Its semicrystalline mixtures with 18-crown-6 (18C6), 30-crown-10 (30C10), dibenzo-30-crown-10 (DB30C10), and poly(ethylene glycol) dimethyl ether 1000 (PEGDME) are prepared by evaporation of solutions. The ionic conductivities, measured by dielectric relaxation spectroscopy, of all of the mixtures are 10-100× higher than that of PV itself in spite of the fact that the ionic contents are reduced by ≈25%. The room temperature (RT) ionic conductivity of PV is 1.1 × 10-⁹ S cm ^-1, and that of its mixture with DB30C10 is over 100-fold higher even though its T_g is slightly above that of PV. The mixtures with 30C10 and PEGDME have similar RT conductivities. However, the 18C6 mixture, in spite of a 9 °C drop in T_g, displays a room temperature (RT) conductivity 10× lower than the other mixtures. Although plasticization probably plays a role, complexation of the polyethers with the viologen units plays a role in the higher conductivities, it is believed, because it increases the fraction of non-ion-paired mobile anions. With 30C10 and DB30C10, polypseudorotaxane formation is envisioned to play a significant role in conductivity enhancement.