2 research outputs found
Thermoreversible Gelation of Poly(ether ether ketone)
Solutions
of poly(ether ether ketone) in dichloroacetic acid have
been shown to form monolithic, thermoreversible gels at temperatures
ranging from 10 to 140 °C. A phase diagram was constructed over
broad concentration and temperature ranges, and the phase boundary
suggests an upper critical solution temperature (UCST) behavior. Furthermore,
poly(ether ether ketone) (PEEK) gels were solvent-exchanged with water
to form hydrogels and subsequently lyophilized to form PEEK aerogels.
The PEEK aerogels of density 0.2 g/mL were found to be highly porous
and composed of uniform 200 nm morphological features. The crystal
structure of the PEEK hydrogels and aerogels was found to be identical
to that of melt-crystallized PEEK. The mechanical properties of the
PEEK aerogels (in compression) were found to be superior to conventional
silicate aerogels of comparable density. This report is the first
example of a monolithic, thermoreversible gel of PEEK and the first
demonstration of PEEK hydrogels and aerogels
Blocky Ionomers via Sulfonation of Poly(ether ether ketone) in the Semicrystalline Gel State
Blocky sulfonated poly(ether ether
ketone) (SPEEK) ionomers were
synthesized by postpolymerization functionalization in the gel state.
Matched sets of blocky and random SPEEK with ion contents between
3 and 11 mol % were prepared, and the thermal transitions and crystallization
kinetics were examined using differential scanning calorimetry (DSC).
At similar ion contents, the blocky SPEEK exhibited higher crystallizability
and faster crystallization kinetics than random SPEEK. Reduced scattering
contrast in the USAXS/SAXS/WAXD analysis of the blocky SPEEK copolymer
membranes, relative to the random analogues, suggested that the ionic
aggregates in blocky SPEEK were distributed in close proximity to
the crystalline domains. Despite similar water uptake values for the
low ion content random and blocky SPEEK membranes, the blocky SPEEK
exhibited higher proton conductivities than their random analogues.
At significantly higher ion contents (45 mol %), the blocky SPEEK
membranes remained semicrystalline, showed controlled water uptake,
and exhibited a 2.5 times higher conductivity over that of the amorphous,
random analogues. Moreover, these new blocky, semicrystalline SPEEK
membranes were found to exhibit a proton conductivity that was comparable
to that of the benchmark 1100 EW Nafion