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Emulsions stabilized with polyelectrolyte complexes prepared from a mixture of a weak and a strong polyelectrolyte

Bago Rodriguez, Ana Maria; Binks, Bernard P.; Sekine, Tomoko

Authors

Ana Maria Bago Rodriguez

Tomoko Sekine



Abstract

The possibility of stabilizing emulsions with polyelectrolyte complexes (PEC) obtained from the interaction of two non-surface-active oppositely charged polyelectrolytes (PEL) is described. Poly(allylamine hydrochloride) (PAH) and poly(4-styrene sulfonate) sodium salt are selected as the weak cationic and the strong anionic polyelectrolyte, respectively. Aqueous polymer mixtures are investigated by light scattering to determine the size of the complexes and whether precipitation or complex coacervation occurs. The effects of PEL mixing ratio, pH, and PEL concentration are studied in detail. By increasing the pH, the transition precipitate–precipitate/coacervate–coacervate–polymer solution is observed. At low pH, both PEL are fully ionized and therefore precipitates (soft particles) arise as a result of strong electrostatic interactions. By increasing the pH, the degree of ionization of PAH decreases and weak electrostatic interactions ensue, supporting the formation of coacervate droplets. The most stable oil-in-water emulsions are prepared from aqueous mixtures around charge neutralization. Although emulsions can be prepared from coacervate droplet dispersions, their coalescence stability is worse than those stabilized by soft PEC particles. By increasing the PEL concentration, the average droplet diameter decreases and the fraction of cream in the emulsion increases for emulsions prepared with PEC particles, following the limited coalescence model. However, at high concentrations, emulsion stability is slightly worse probably due to extensive aggregation of the particles. Viscous high internal phase emulsions can be prepared at low pH in which oil droplets are deformed. Here, PEC particles are detected only at the oil–water interface. At lower oil content, excess particles form a network in the aqueous phase aiding emulsion stability to coalescence.

Journal Article Type Article
Publication Date May 21, 2019
Journal Langmuir
Print ISSN 0743-7463
Electronic ISSN 1520-5827
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 35
Issue 20
Pages 6693-6707
APA6 Citation Bago Rodriguez, A. M., Binks, B. P., & Sekine, T. (2019). Emulsions stabilized with polyelectrolyte complexes prepared from a mixture of a weak and a strong polyelectrolyte. Langmuir : the ACS journal of surfaces and colloids, 35(20), 6693-6707. https://doi.org/10.1021/acs.langmuir.9b00897
DOI https://doi.org/10.1021/acs.langmuir.9b00897
Keywords Spectroscopy; Electrochemistry; General Materials Science; Surfaces and Interfaces; Condensed Matter Physics
Publisher URL https://pubs.acs.org/doi/10.1021/acs.langmuir.9b00897