Young's Modulus of Polyelectrolyte Multilayers from Microcapsule Swelling

Abstract

We measure Young's modulus of a free polyelectrolyte multilayer film by studying osmotically induced swelling of polyelectrolyte multilayer microcapsules filled with the polyelectrolyte solution. Different filling techniques and core templates were used for the capsule preparation. Varying the concentration of the polyelectrolyte inside the capsule, its radius and the shell thickness yielded an estimate of an upper limit for Young's modulus of the order of 100 MPa. This corresponds to an elastomer and reflects strong interactions between polyanions and polycations in the multilayer.

Elasticity of polyelectrolyte multilayer microcapsules

“…These values (1 − 100 MPa), therefore, give the lowest limit for Young's modulus of polyelectrolyte multilayers. However, our results strongly support the conclusions of the recent swelling experiment [7], which has given a slightly larger, but of the same order of magnitude, value for E. We have argued [7], that the osmotically induced swelling measurements give the upper limit for Young's modulus. Therefore, taking together, these two types of experiment provide the range of possible values for Young's modulus of a PSS/PAH multilayer.…”

“…If the capsule is highly permeable for the solvent (water) the capsule wall bends and a cup-like shape is formed. The second method is based on studying the swelling of microcapsules filled with the solution of a strong polyelectrolyte [7]. The * Corresponding author: vinograd@mpip-mainz.mpg.de third attempt involves measuring the deformation of microcapsules under applied load using atomic force microscope (AFM) [8,9].…”

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

“…For practical applications, understanding the shell permeability and mechanical properties of the PMCs is of importance. The latter can be studied by osmotically induced buckling [889], by osmotic swelling [890] or by direct probing with the AFM.…”

Interactions of neutral semipermeable shells in asymmetric electrolyte solutions

“…Typical examples of such shells are vesicles and liposomes with ionic channels, 1,2 various types of micro-and nanocapsules, [3][4][5][6] cell 7,8 and bacterial [9][10][11] membranes, viral capsids. 12,13 Such shells in a contact with a polyelectrolyte solution have been employed for measuring elastic 5,14,15 and elasto-plastic 16 modulus of the shell's material and for selective encapsulation. [17][18][19] Recent studies have shown that mechanical properties of semi-permeable capsules filled with polyelectrolytes, their aggregation and and sedimentation stability are strongly influenced by ionic Donnan equilibria between the container interior and the surrounding solution.…”