Elastic properties of polyelectrolyte capsules studied by atomic-force microscopy and RICM

Abstract

Mechanical properties of polyelectrolyte multilayer capsules were studied using a new method combining atomic-force microscopy and reflection interference contrast microscopy. By measuring the force vs. deformation for poly(styrene sulfonate)/poly(allylamine) capsules the existence of different deformation regimes depending on the applied deformation was shown. The present paper focuses on the small-deformation regime. The elastic response of the deformed capsule was studied as a function of the wall thickness and the capsule size, and showed the theoretically expected variations. The Young modulus obtained from the experiments ranges between 1.3 and 1.9 GPa.

Mechanics of the Toxoplasma gondii oocyst wall

“…3 E and F). Those elevated E values are similar to the ones reported for artificial polymeric capsules of comparable thicknesses (50). The median E moduli showed no significant variation between the different maturing oocyst stages irrespective of the oocyst pretreatment (SI Appendix, Tables S2 and S4).…”

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

“…The stiffness of PAH/PSS (MnCO 3 ) microcapsules could be increased by a factor of 8 by precipitation of YF 3 nanoparticles onto the PMC surface. 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].…”

“…Very high values of Young's modulus larger than 1 GPa for PAH/PSS PMCs templated with PS were found by Dubreuil et al [892] from the buckling forces at very small deformations (Eq. (9.5)).…”

“…Three different regimes within the deformation profiles for PMCs in water were found for hollow microcapsules [892,896,897] (see Fig. 44) for small loads (j < 0.2-0.3), PMCs showed an elastic response.…”

“…The best characterized pair of polyelectrolytes for layer by layer deposition is poly(allyl amine hydrochloride)/poly(sodium styrenesulfonate) (PAH/PSS) (for a review, see [891]). This pair has also been used for all AFM force experiments on PMCs except for [892], where also polyethyleneimine (PEI) and poly(diallyl-dimethyl-ammonium chloride) (PDADMAC) were used as polycations and [893], where DNA was used as polyanion. As template materials, melamine formaldehyde (MF), polylactic acid (PLA), weakly cross-linked polystyrene (PS), and MnCO 3 have been used.…”