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Characterization of the Ultralow Interfacial Tension in Liquid-Liquid Phase Separated Polyelectrolyte Complex Coacervates by the Deformed Drop Retraction Method.

ABSTRACT: Dilute droplets form upon changing the temperature of a phase separated polyelectrolyte complex coacervate. This provides an in situ approach to measure the interfacial tension between supernatant (dilute droplet) and dense coacervate by the deformed drop retraction (DDR) method. The aqueous coacervate, formed via a model 1:1 by charge stoichiometric polyelectrolyte blend, exhibits ultralow interfacial tension with the coexisting phase. DDR finds the interfacial tension scales as ? = ? 0(1 - C s/C s,c) ? , with ? = 1.5 ± 0.1, ? 0 = 204 ± 36 ?N/m, and C s,c = 1.977 mol/L. The value of ? independently validates the classical exponent of 3/2. The scaling holds between C s/C s,c of 0.75 to 0.94, the closest measurements to date near the critical salt concentration (C s,c). The temperature dependence of the interfacial tension is consistent with observed lower critical solution phase behavior and classical scaling. A detailed account of the DDR method and validation of assumptions are demonstrated.

SUBMITTER: Ali S

PROVIDER: S-EPMC7340275 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Characterization of the Ultralow Interfacial Tension in Liquid-Liquid Phase Separated Polyelectrolyte Complex Coacervates by the Deformed Drop Retraction Method.

Ali Samim S Prabhu Vivek M VM

Macromolecules 20190927 19

Dilute droplets form upon changing the temperature of a phase separated polyelectrolyte complex coacervate. This provides an in situ approach to measure the interfacial tension between supernatant (dilute droplet) and dense coacervate by the deformed drop retraction (DDR) method. The aqueous coacervate, formed via a model 1:1 by charge stoichiometric polyelectrolyte blend, exhibits ultralow interfacial tension with the coexisting phase. DDR finds the interfacial tension scales as <i>γ</i> = <i>γ ...[more]

PMID: 32636534

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Project description:We systematically investigate in this work the surface activity of polyelectrolyte complex (PECs) suspensions as a function of the molar charge ratio Z (= [-]/[+]) from two model systems: the weakly and strongly interacting poly (diallyldimethylammonium chloride)/poly (acrylic acid sodium salt) (PDADMAC/PANa) and poly (diallyldimethylammonium chloride)/poly (sodium 4- styrenesulfonate) (PDADMAC/PSSNa) pairs, respectively. For both systems, the PEC surface tension decreases as the system approaches charge stoichiometry (Z = 1) whenever the complexation occurs in the presence of excess PDADMAC (Z < 1) or excess polyanion (Z > 1) consistent with an increased level of charge neutralization of PEs forming increasingly hydrophobic and neutral surface-active species. The behavior at stoichiometry (Z = 1) is also particularly informative about the physical nature of the complexes. The PDADMAC/PANa system undergoes a liquid-liquid phase transition through the formation of coacervate microdroplets in equilibrium with macroions remaining in solution. In the PDADMAC/PSSNa system, the surface tension of the supernatant was close to that of pure water, suggesting that the PSSNa-based complexes have completely sedimented, consistent with a complete liquid-solid phase separation of an out-of-equilibrium system. Besides, the high sensitivity of surface tension measurements, which can detect the presence of trace amounts of aggregates and other precursors in the supernatant, allows for very accurate determination of the exact charge stoichiometry of the complexes. Finally, the very low water/water interfacial tension that develops between the dilute phase and the denser coacervate phase in the PDADAMAC/PANa system was measured using the generalized Young-Laplace method to complete the full characterization of both systems. The overall study showed that simple surface tension measurements can be a very sensitive tool to characterize, discriminate, and better understand the formation mechanism of the different structures encountered during the formation of PECs.

Dataset Information

Characterization of the Ultralow Interfacial Tension in Liquid-Liquid Phase Separated Polyelectrolyte Complex Coacervates by the Deformed Drop Retraction Method.

Publications

Characterization of the Ultralow Interfacial Tension in Liquid-Liquid Phase Separated Polyelectrolyte Complex Coacervates by the Deformed Drop Retraction Method.

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