Salt softening of polyelectrolyte multilayer microcapsules

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…The increase of PMC stiffness with shell layer thickness t s was found to be proportional to t 2 s at small deformations (bending rigidity dominates) [892,894], and linear in t s for larger deformations [894]. PMC stiffness was found to be highest in pure water, decreasing slightly with increasing NaCl concentration up to 3 M [897,899]; between 3 and 5 M stiffness did not change any further [899]. Comparison with layer adsorbed electrolyte layer thickness measurements and SEM images led to the conclusion that the shells are in a tethered state for <3 M NaCl and in a melted state at higher concentrations [899].…”

“…PMC stiffness was found to be highest in pure water, decreasing slightly with increasing NaCl concentration up to 3 M [897,899]; between 3 and 5 M stiffness did not change any further [899]. Comparison with layer adsorbed electrolyte layer thickness measurements and SEM images led to the conclusion that the shells are in a tethered state for <3 M NaCl and in a melted state at higher concentrations [899]. Exposing PMCs to high or low pH values leads to softening [897].…”

Radiation-pressure-induced mode splitting in a spherical microcavity with an elastic shell

“…In order to control the elasticity of the PE shell, we used an additional chemical procedure to modify the mechanical properties of the PE layer on the surface of some of the samples. Before these spheres were coated with a QD monolayer, we kept them for 5 days in a highly concentrated NaCl (7 Mol/l) solution as discussed in [14]. This treatment reduces the solidity of the PE layer resulting in a softer, more elastic layer.…”

“…Varying the number of oppositely charged polyelectrolyte bi-layers deposited on MF templates provided the variation in the shell thickness. The value of Young's modulus of PE LbL films (100-200 MPa) falls in the range characteristic for highly cross-linked rubber [14]. Efficient coupling of the quantum dot (QD) emission with the WGM of the microsphere was achieved by coating the spheres with one monolayer of CdTe semiconductor nanocrystals on top of the PE multiplayer [15].…”

Recent developments in the properties and applications of polyelectrolyte multilayers

“…In AFM, a glass sphere glued to a cantilever tip is used to deform the substrate and produce force versus deformation curves from which the elastic modulus is deduced. This technique was used to study the effect of salt on the elastic modulus of PEMCs [32,36]. In contrast to what is observed in systems stabilized exclusively by electrostatic interactions, PAH/DNA microcapsules stiffened as the salt concentration increased [36].…”