32 research outputs found
Structural Investigation of a Self-Cross-Linked Chitosan/Alginate Dialdehyde Multilayered Film with in Situ QCM-D and Spectroscopic Ellipsometry
A chitosan/alginate
dialdehyde multilayered film
was fabricated using the layer-by-layer assembly method. Besides electrostatic
interaction that promotes alternate adsorption of the oppositely charged
polyelectrolytes, the Schiff base reaction between the amine groups
on chitosan and the aldehyde groups on alginate dialdehyde provides
a covalently cross-linked film, which after reduction by sodium cyanoborohydride
is stable under both acidic and alkaline conditions. Moreover, the
cross-linked film is responsive to changes in pH and addition of multivalent
salts. The structural properties of the multilayered film such as
thickness, refractive index, and water content were examined using
simultaneous quartz crystal microbalance with dissipation monitoring
and spectroscopic ellipsometry
PPEGMEMA-based cationic copolymers designed for layer-by-layer assembly
We have synthesized three PPEGMEMA-based cationic copolymers with similar amine contents but with systematic variation in the average length of the PEG side chains. The positively charged copolymers were paired with alginate to fabricate layer-by-layer assembled multilayered films. It was demonstrated that the polymeric design, in terms of the systematic variation in the average length of the PEG units, affects the polyelectrolyte multilayer growth mechanism and can be used to tune the structural properties and the water content of the layers. In addition, by partial cross-linking of the amine groups present in the copolymer backbone, disintegration of the film induced by pH changes was prevented. Finally, it was demonstrated how the cross-linked multilayered film can exhibit cationic, zwitterionic and anionic properties depending on the pH value and how these changes are associated with swelling, layer contraction and changes in water content
Hofmeister Effect on PNIPAM in Bulk and at an Interface: Surface Partitioning of Weakly Hydrated Anions
The
effect of sodium fluoride, sodium trichloroacetate, and sodium
thiocyanate on the stability and conformation of polyÂ(<i>N</i>-isopropylÂacrylamide), in bulk solution and at the gold–aqueous
interface, is investigated by differential scanning calorimetry, dynamic
light scattering, quartz crystal microbalance, and atomic force microscopy.
The results indicate a surface partitioning of the weakly hydrated
anions, i.e., thiocyanate and trichloroacetate, and the findings are
discussed in terms of anion-induced electrostatic stabilization. Although
attractive polymer–ion interactions are suggested for thiocyanate
and trichloroacetate, a salting-out effect is found for sodium trichloroacetate.
This apparent contradiction is explained by a combination of previously
suggested mechanisms for the salting-out effect by weakly hydrated
anions