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Stimuli-induced nonequilibrium phase transitions in polyelectrolyte–surfactant complex coacervates

DOI: 10.1021/acs.langmuir.0c01177 DOI Help

Authors: Chloe Seyrig (Sorbonne Université) , Gertrude Kignelman (KU Leuven) , Wim Thielemans (KU Leuven) , Patrick Le Griel (Sorbonne Université) , Nathan Cowieson (Diamond Light Source) , Javier Perez (Synchrotron Soleil) , Niki Baccile (Sorbonne Université)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Langmuir

State: Published (Approved)
Published: July 2020
Diamond Proposal Number(s): 23247

Abstract: Polyelectrolyte–surfactant complexes (PESCs) are important soft colloids with applications in the fields of personal care, cosmetics, pharmaceutics, and much more. If their phase diagrams have long been studied under pseudoequilibrium conditions, and often inside the micellar or vesicular regions, understanding the effect of nonequilibrium conditions, applied at phase boundaries, on the structure of PESCs generates an increasing interest. In this work we cross the micelle–vesicle and micelle–fiber phase boundaries in an isocompositional surfactant–polyelectrolyte aqueous system through a continuous and rapid variation of pH. We employ two microbial glycolipid biosurfactants in the presence of polyamines, both systems being characterized by their responsiveness to pH. We show that complex coacervates (Co) are always formed in the micellar region of both glycolipids’ phase diagram and that their phase behavior drives the PESC stability and structure. However, for glycolipid forming single-wall vesicles, we observe an isostructural and isodimensional transition between complex coacervates and a multilamellar walls vesicle (MLWV) phase. For the fiber-forming glycolipid, on the contrary, the complex coacervate disassembles into free polyelectrolyte coexisting with the equilibrium fiber phase. Last but not least, this work also demonstrates the use of microbial glycolipid biosurfactants in the development of sustainable PESCs.

Journal Keywords: Lipids; X-ray scattering; Chemical structure; Phase transitions; Polyelectrolytes

Subject Areas: Chemistry

Instruments: B21-High Throughput SAXS

Other Facilities: Soleil