In this work, an in situ pressure-contact
Fourier transform infrared
attenuated total reflectance (FTIR-ATR) spectroscopy apparatus was
designed and developed for measuring liquid transport in free-standing
polymer films. This new technique allows time-resolved infrared data
of liquid transport in free-standing films to be collected accurately
without solution casting the film directly onto the ATR element. Liquid
water transport in free-standing films of a rubbery polymer (poly(isobutylene);
PIB), a glassy polymer (poly(methyl methacrylate); PMMA), and a cross-linked
polymer (epoxy/amine resin) was investigated using this technique.
The in situ pressure-contact FTIR-ATR spectroscopy apparatus showed
similar results to those obtained using the conventional solution-cast
FTIR-ATR apparatus for PIB. Non-Fickian behavior was observed for
both the solution-cast and free-standing PMMA due to the nonequilibrium
state of the polymer. However, the rate of water sorption did not
match between the two; the former was attributed to diffusion-relaxation
and the latter was attributed diffusion-compression due to the differences
in the apparatus. The solution-cast PMMA data were regressed to a
previously developed diffusion-relaxation model, while a new model
that incorporates diffusion-compression was developed and regressed
to the free-standing PMMA data. Liquid water diffusion in the cross-linked
polymer exhibited Fickian behavior and was attributed to the suppressed
polymer strain response to the diffusant.
in Wiley Online Library (wileyonlinelibrary.com)Porous, flexible, reactive electrochemical membranes (REMs) for water purification were synthesized by a novel simultaneous electrospinning/electrospraying (E/E) technique, which produced a network of poly(sulfone) fibers and Ti 4 O 7 particles as evidenced by scanning electron microscopy. Cyclic voltammetry indicated that the kinetics for water electrolysis reactions and the Fe(CN) 6 42/32 redox couple were enhanced by Ti 4 O 7 deposition using the E/E technique. Membrane filtration experiments using phenol as a model contaminant showed a 2.6-fold enhancement in the observed first-order rate constant for phenol oxidation (k obs,phenol ) in filtration mode relative to cross-flow operation. Phenol oxidation in filtration mode was approaching the pore diffusion mass transfer limit, and was 6 to 8 times higher than measured in a previous study that utilized a ceramic Ti 4 O 7 REM operated in filtration mode and is comparable to rate constants obtained with carbon nanotube flow-through reactors, which are among the highest reported in the literature to date.
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