Issue 2, 2019

Structural control of polyelectrolyte/microemulsion droplet complexes (PEMECs) with different polyacrylates

Abstract

The ionic assembly of oppositely charged polyelectrolyte–surfactant complexes (PESCs) is often done with the aim of constructing more functional colloids, for instance as advanced delivery systems. However, PESCs are often not easily loaded with a solubilisate due to intrinsic restrictions of such complexes. This question was addressed from a different starting point: by employing microemulsion droplets as heavily loaded surfactant systems and thereby avoiding potential solubilisation limitations from the beginning. We investigated mixtures of cationic oil-in-water (O/W) microemulsion droplets and oppositely charged sodium polyacrylate (NaPA) and determined structure and phase behaviour as a function of the mixing ratio for different droplet sizes and different Mw (NaPA). Around an equimolar charge ratio an extended precipitate region is present, which becomes wider for larger droplets and with increasing Mw of the NaPA. Static and dynamic light scattering (SLS and DLS) and small-angle neutron scattering (SANS) show the formation of one-dimensional arrangements of microemulsion droplets for polyelectrolyte excess, which become more elongated with increasing Mw (NaPA) and less so with increasing NaPA excess. What is interesting is a marked sensitivity to ionic strength, where already a modest increase to ∼20 mM leads to a dissolution of the complexes. This work shows that polyelectrolyte/microemulsion complexes (PEMECs) are structurally very versatile hybrid systems, combining the high solubilisate loading of microemulsions with the larger-scale structuring induced by the polymer, thereby markedly extending the concept of conventional PESCs. This type of system has not been described before and is highly promising for future applications where high payloads are to be formulated.

Graphical abstract: Structural control of polyelectrolyte/microemulsion droplet complexes (PEMECs) with different polyacrylates

Supplementary files

Article information

Article type
Edge Article
Submitted
10 sep 2018
Accepted
15 okt 2018
First published
23 okt 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2019,10, 385-397

Structural control of polyelectrolyte/microemulsion droplet complexes (PEMECs) with different polyacrylates

M. Simon, P. Krause, L. Chiappisi, L. Noirez and M. Gradzielski, Chem. Sci., 2019, 10, 385 DOI: 10.1039/C8SC04013C

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