Reversible Modulation of Conductivity in Azobenzene Polyelectrolytes Using Light

Incorporatinglight-responsive azobenzene into polyelectrolytescouples photoinduced changes in steric interactions and polarity toionic conductivity. The reversible isomerization of an azobenzenemoiety yields a 2-7 times change in the ion conductivity (sigma(trans) > sigma(cis)) depending on the polymercomposition.These trends cannot be explained by differences in the glass-transitiontemperatures of the polymers. Instead, UV-vis spectroscopyreveals a bathochromic shift in the pi -> pi*transition of cis-poly(azobenzene) upon adding lithiumbis(trifluoromethane)sulfonimide (LiTFSI) salt, suggesting that coordinationof the cis isomer with Li+ is responsiblefor its lower conductivity. In summary, azobenzene is a simple andconvenient functional unit to control the conductivity of polymericmaterials using light.