On the Stability and Morphology of Complex Coacervate Core Micelles: From Spherical to Wormlike Micelles

We present a systematic study of the stability and morphology of complex coacervate core micelles (C3Ms) formed from poly­(acrylic acid) (PAA) and poly­(N-methyl-2-vinylpyridinium)-b-poly­(ethylene oxide) (PM2VP-b-PEO). We use polarized and depolarized dynamic and static light scattering, combined w...

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Bibliographic Details
Published in:Langmuir 2012-10, Vol.28 (40), p.14180-14191
Main Authors: van der Kooij, Hanne M, Spruijt, Evan, Voets, Ilja K, Fokkink, Remco, Cohen Stuart, Martien A, van der Gucht, Jasper
Format: Article
Language:English
Subjects:
block-copolymer micelles
Chemistry
Colloidal state and disperse state
delivery
diblock copolymer
Exact sciences and technology
General and physical chemistry
light-scattering
Micelles. Thin films
polyelectrolyte complexes
polymer
polystyrene surfaces
polysulfone surfaces
protein adsorption
silica
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Summary:We present a systematic study of the stability and morphology of complex coacervate core micelles (C3Ms) formed from poly­(acrylic acid) (PAA) and poly­(N-methyl-2-vinylpyridinium)-b-poly­(ethylene oxide) (PM2VP-b-PEO). We use polarized and depolarized dynamic and static light scattering, combined with small-angle X-ray scattering, to investigate how the polymer chain length and salt concentration affect the stability, size, and shape of these micelles. We show that C3Ms are formed in aqueous solution below a critical salt concentration, which increases considerably with increasing PAA and PM2VP length and levels off for long chains. This trend is in good agreement with a mean-field model of polyelectrolyte complexation based on the Voorn–Overbeek theory. In addition, we find that salt induces morphological changes in C3Ms when the PAA homopolymer is sufficiently short: from spherical micelles with a diameter of several tens of nanometers at low salt concentration to wormlike micelles with a contour length of several hundreds of nanometers just before the critical salt concentration. By contrast, C3Ms of long PAA homopolymers remain spherical upon addition of salt and shrink slightly. A critical review of existing literature on other C3Ms reveals that the transition from spherical to wormlike micelles is probably a general phenomenon, which can be rationalized in terms of a classical packing parameter for amphiphiles.
ISSN:0743-7463
1520-5827
DOI:10.1021/la303211b