Effect of the Backbone Tether on the Electrochemical Properties of Soluble Cyclopropenium Redox-Active Polymers

All measurements in 0.1 M TBAPF6, acetonitrile. Polymer solubilities up to 1.8 M in acetonitrile.

Scientific Achievement

A series of cyclopropenium polymers were synthesized and evaluated as high potential active material for size-exclusion flow batteries.

Significance and Impact

Increasing tether length between the polymer backbone and the charge-storing pendant group improved chemical reversibility and capacity retention, providing insight into materials design for stable redox-active polymers.

Research Details

  • Theoretical simulations of varied tether lengths predicted electronic isolation of the cyclopropenium redox group when the backbone was greater than x = 5 methylene groups away.
  • Polymers of tethers x = 1, 5, 7 were synthesized and displayed similar redox potentials and low degrees of electrode filming.
  • Chemical reversibility and capacity retention of the polymers increased with increasing tethers while cycling at Coulombic efficiencies near 100%.
  • Long-term charged state stability also increased with tether length as demonstrated by tracking the absorbance of charged cyclopropenium over an eight-day period.

DOI: 10.1021/acs.macromol.8b00574

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