2 research outputs found
Cononsolvency Effect: When the Hydrogen Bonding between a Polymer and a Cosolvent Matters
Despite
the fact that the observation of cononsolvency was reported
as early as four decades ago, its phase-transition mechanism is still
under debate. In this work, we provided a comprehensive study of the
phase behaviors of poly(N-isopropylacrylamide) (PNiPAAm)
in sulfoxide or sulfone aqueous solutions. We observed a sharp collapse
transition of PNiPAAm brushes in sulfoxide but not in sulfone aqueous
solutions by equilibrium measurements of in situ spectroscopic ellipsometry.
We found that the hydrogen-bond formation between sulfoxide oxygens
and amide hydrogens of the polymer chains plays a critical role in
regulating the cononsolvency of PNiPAAm. We have extended the concept
of preferential adsorption by taking into account hydrophobic interactions
between cosolvent molecules, which are adsorbed on the polymer by
hydrogen bonds. This can explain the experimental observations of
PNiPAAm brushes in these solvent mixtures and sheds light on understanding
the phase behaviors of polymer solutions where hydrogen bonds and
hydrophobic interaction play a critical role. Our results can also
be of interest for the liquid–liquid phase separation in the
living cell where the condensation of proteins bound to large biomacromolecules
plays an essential role
Additional file 1: Figure S1A–E. of Tuning Tribological Performance of Layered Zirconium Phosphate Nanoplatelets in Oil by Surface and Interlayer Modifications
Surface roughness of five metal balls examined by a 3D profiler. The average surface roughness is 155.0 ± 14.8 nm. Figure S2. FTIR of various surface modified-ZrP samples. The strong characteristic bands associated with the asymmetric and symmetric stretching of the C−H, between 2900 and 3000cm−1, and bending at ca. 1450 cm−1 are an indication of the attachments of alkyl chains from various silanes on ZrP nanoplatelets. Figure S3. SEM and EDS results for the original metal surface before testing. Figure S4. SEM and EDS results for the worn metal surface after testing with the C16-ZrP-N6 oil sample. Figure S5. SEM and EDS results for the worn metal surface after testing with the C16-ZrP oil sample. (DOCX 3672 kb