11 research outputs found
Ionic Conductivity and Self-Assembly in Poly(isoprene‑<i>b</i>‑ethylene oxide) Electrolytes Doped with LiTf and EMITf
Diblock
copolymers of polyÂ(isoprene-<i>b</i>-ethylene oxide), PI-<i>b</i>-PEO (IEO), are employed as templates for the development
of nanostructured polymer electrolytes by salt-doping. For this purpose,
lithium triflate (CF<sub>3</sub>SO<sub>3</sub>Li, LiTf) and 1-ethyl-3-methylimidazolium
trifluoromethanesulfonate (CF<sub>3</sub>SO<sub>3</sub>–C<sub>6</sub>H<sub>11</sub>N<sub>2</sub>, EMITf) salts were separately
introduced at various [EO]:[salt] ratios. The local structure, nanodomain
morphology and ion dynamics of the resulted block copolymer electrolytes
were investigated by infrared spectroscopy, X-ray scattering, differential
scanning calorimetry and dielectric spectroscopy. The structural investigation
revealed strong effects of both LiTf and EMITf salt addition to the
copolymer nanodomain morphology. These include transitions between
different ordered nanophases and an increased domain spacing. The
latter was independent of the kind of salt providing the possibility
of studying ion transport under identical nanodomain sizes but in
the presence of different interactions. Ionic conductivity in the
two systems was fundamentally different. In IEO/EMITf ionic conductivity
was much higher and comparable to the PEO/EMITf case. However, in
IEO/LiTf, ion conductivity was reduced by a factor of a 100 relative
to the PEO/LiTf case. This reflects combined effects of increased
interaction parameter and of preferential wetting of electrodes. These
results suggest ways for manipulating ion transport in polymer electrolytes