The tacticity effect on phase separation
process of poly(N-isopropylacrylamide) (PNiPAM) aqueous
solutions was investigated
by dynamic light scattering (DLS) and small angle neutron scattering
(SANS) measurements. SANS measurement revealed that hydrophobicity
of PNiPAM consisting of meso- and racemo-isomers increased with increasing
the meso-content. This result is in accordance with the result of
the previous experimental and simulation study on NiPAM dimers (DNiPAM)
and trimers (TNiPAM) [
Katsumoto
Y
Katsumoto
Y
J. Phys. Chem. B20101141331213318, and
Autieri
E.
Autieri
E.
J. Phys. Chem. B201111558275839]; i.e., meso-diad is more hydrophobic than racemo-diad.
In addition, a series of scattering experiments revealed that the
ratio of meso-diad does not affect the static structure or the shrinking
behavior of a single chain, but strongly affects the aggregation behavior.
The PNiPAMs with low meso-content suddenly associate around the phase
separation temperature, while that of the high meso-content gradually
aggregate with increasing temperature. We propose that phase transition
behavior of PNiPAM aqueous solutions can be controlled by changing
the stereoregularity of the polymer chain.
Purpose To evaluate the diagnostic performance of chest CT to differentiate coronavirus disease 2019 (COVID-19) pneumonia in non-high-epidemic area in Japan. Materials and methods This retrospective study included 21 patients clinically suspected COVID-19 pneumonia and underwent chest CT more than 3 days after the symptom onset: six patients confirmed COVID-19 pneumonia by real-time reverse-transcription polymerase chain reaction (RT-PCR) and 15 patients proved uninfected. Using a Likert scale and its receiver operating characteristic curve analysis, two radiologists (R1/R2) evaluated the diagnostic performance of the five CT criteria: (1) ground glass opacity (GGO)-predominant lesions, (2) GGO-and peripheral-predominant lesions, (3) bilateral GGO-predominant lesions; (4) bilateral GGO-and peripheral-predominant lesions, and (5) bilateral GGO-and peripheralpredominant lesions without nodules, airway abnormalities, pleural effusion, and mediastinal lymphadenopathy. Results All patients confirmed COVID-19 pneumonia had bilateral GGO-and peripheral-predominant lesions without airway abnormalities, mediastinal lymphadenopathy, and pleural effusion. The five CT criteria showed moderate to excellent diagnostic performance with area under the curves (AUCs) ranging 0.77-0.88 for R1 and 0.78-0.92 for R2. The criterion (e) showed the highest AUC. Conclusion Chest CT would play a supplemental role to differentiate COVID-19 pneumonia from other respiratory diseases presenting with similar symptoms in a clinical setting.
A robust hydrogel with a reliable deformation region in an aqueous environment is proposed. The gel has a homogeneous network where hydrophilic/hydrophobic components are uniformly distributed. In an aqueous environment, aggregated hydrophobic segments serve as "mechanical fuse links," inhibiting sudden macroscopic fracture. The gel endures threefold stretching for more than 100 cycles in water without mechanical hysteresis.
Structural analysis of inhomogeneity-free poly(ethylene glycol)− poly(dimethylsiloxane) (PEG−PDMS) amphiphilic conetwork gels has been performed by the complementary use of small-angle X-ray and neutron scattering. Because of the hydrophobicity of PDMS units, the PEG−PDMS gels exhibit a microphase-separated structure in water. Depending on the volume fraction of PDMS, the microphase-separated structure varies from core−shell to lamellar. The obtained X-ray and neutron scattering profiles are reproduced well using a core− shell model together with a Percus−Yevick structure factor when the volume fraction of PDMS is small. The domain size is much larger than the size of individual PEG and PDMS unit, and this is explained using the theory of block copolymers. Reflecting the homogeneous dispersion conditions in the as-prepared state, scattering peaks are observed even at a very low PDMS volume fraction (0.2%). When the volume fraction of PDMS is large, the microphase-separated structure is lamellar and is demonstrated to be kinetically controlled by nonequilibrium and topological effects.
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