Micromechanical theory for pH-dependent polyelectrolyte multilayer capsule swelling

P. Maarten Biesheuvel, Tatjana Mauser, Gleb B. Sukhorukov, Helmuth Möhwald

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)


Hollow polyelectrolyte multilayer capsules made of ionizable segments (e.g., carboxylic acid, amine, pyridine) have an equilibrium size that is independent of salt concentration and pH in a wide pH range but swell to a larger size at lower and higher pH. Besides, at the edges of the stability plateau their equilibrium size increases with increasing ionic strength. We set up a micromechanical theory in which we combine an expansive force due to ion entropy with an elastic contractive force and derive from balance of forces a simple expression for the equilibrium capsule size. The theory describes the influence of pH on size (including the wide plateau region as well as the steep increase in size at the edge of the pH plateau) almost quantitatively without fitting parameters as well as the increase in size with increasing ionic strength. This effect is contrary to what would be expected when the polymer charge would directly depend on solution pH instead of local pH within the shell and is a phenomenon comparable to the osmotic regime found for ionizable ("annealed") polyelectrolyte brushes at very low ionic strength, for which it is also observed that the brush expands when the salt concentration is increased.

Original languageEnglish
Pages (from-to)8480-8486
Number of pages7
Issue number24
Publication statusPublished - 28 Nov 2006
Externally publishedYes


Dive into the research topics of 'Micromechanical theory for pH-dependent polyelectrolyte multilayer capsule swelling'. Together they form a unique fingerprint.

Cite this