2 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
Kinetics of Light-Induced Concentration Patterns in Transparent Polymer Solutions
When
exposed to weak visible laser light, solutions of common polymers
like polyÂ(isoprene) and polyÂ(butadiene) respond by local concentration
variations, which in turn lead to refractive index changes. Various
micropatterns have been recently reported, depending mostly on the
solvent environment and the irradiation conditions. Here, we focused
on the simpler case of single polymer-rich filaments and we employed
phase contrast microscopy to systematically investigate the influence
of laser illumination and material parameters on the kinetics of the
optically induced local concentration increase in the polydiene solutions.
The refractive index contrast of the formed filaments increased exponentially
with the laser illumination time. The growth rate exhibited linear
dependence on the laser power and increased with polymer chain length
in semidilute solutions in good solvents. On the contrary, the kinetics
of the formed filaments appeared to be rather insensitive to the polymer
concentration. Albeit the origin of the peculiar light field-polymer
concentration coupling remains yet elusive, the new phenomenology
is considered necessary for the elucidation of its mechanism