The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes

Abstract

Abstract:Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation using two vinyl polyelectrolytes, poly(acrylic acid sodium salt) (pAA) and poly(allylamine hydrochloride) (pAH), as simple models for industrial and biological coacervates. We confirmed the dominant role of salt valence on the extent of coacervate formation, while demonstrating the presence of significant secondary effects, which can be described by Hofmeister-like behavior. These results revealed the importance of ion-specific interactions, which are crucial for the informed design of coacervate-based materials for use in complex ionic environments, and can enable more detailed theoretical investigations on the role of subtle electrostatic and thermodynamic effects in complex coacervation.

Linear viscoelasticity of complex coacervates

“…Turbidimetric analysis of the impact of increasing NaCl concentration on both the optimal 50/50 PAH/PAA at pH 6.5, and the 67/33 PAH/PAA sample at pH 8.5 show a sharp increase in the turbidity signal with the addition of small amounts of salt, followed by a slow loss of signal at higher salt concentrations. Finally, a critical salt concentration is reached, above which no coacervation is observed (Figure 2b) [77]. The turbidity measurements demonstrate a difference in the critical salt concentration for samples prepared at the two different pH conditions.…”

“…The qualitative nature of turbidity-style measurements allows a phenomenological characterization of coacervate phase behavior, rather than a more direct quantification of the binodal phase space [8,15,71,[73][74][75][76][77]83,88,[91][92][93]104,105,108,112,114,. Typical characterization experiments include evaluation of the stoichiometric ratio of polycation to polyanion, the effect of increasing salt concentration, and the effect of variable pH.…”

PRISM-Based Theory of Complex Coacervation: Excluded Volume versus Chain Correlation

“…1 Polymeric complex coacervates demonstrate a rich phenomenology that is a function of the presence of salt as well as the nature of the charged polyions, 1,32,[34][35][36][37][38][47][48][49][50] with a vast parameter space that spans the molecular features of all four components. Experimentalists have begun to systematically explore this space, looking at effects such as chain solubility and length, ion identity, and valency.…”

“…Experimentalists have begun to systematically explore this space, looking at effects such as chain solubility and length, ion identity, and valency. 1,32,[34][35][36][37][38][47][48][49][50][51] Nevertheless, a comprehensive physical picture of these systems remains to be elucidated.…”

Polyelectrolyte Coacervates Deposited as High Gas Barrier Thin Films

“…PEC coacervates are composed of weakly bound polyelectrolytes, and have viscous liquid-like behavior that can be exploited to quickly apply them as thin films. [18,[21][22][23][24] In the present study, polyelectrolyte coacervates were applied to substrates using Meyer rod coating (a common type of blade coating), [25] in an effort to quickly fabricate thin oxygen barrier films in a single step. The Meyer rod is drawn across a substrate, doctoring off coating fluid, Multilayer coatings consisting of oppositely charged polyelectrolytes have proven to be extraordinarily effective oxygen barriers but require many processing steps to fabricate.…”