Linear viscoelasticity of complex coacervates

Abstract

Rheology is a powerful method for materials characterization that can provide detailed information about the self-assembly, structure, and intermolecular interactions present in a material. Here, we review the use of linear viscoelastic measurements for the rheological characterization of complex coacervate-based materials. Complex coacervation is an electrostatically and entropically-driven associative liquid-liquid phase separation phenomenon that can result in the formation of bulk liquid phases, or the self-assembly of hierarchical, microphase separated materials. We discuss the need to link thermodynamic studies of coacervation phase behavior with characterization of material dynamics, and provide parallel examples of how parameters such as charge stoichiometry, ionic strength, and polymer chain length impact self-assembly and material dynamics. We conclude by highlighting key areas of need in the field, and specifically call for the development of a mechanistic understanding of how molecular-level interactions in complex coacervate-based materials affect both selfassembly and material dynamics.

Review on plant protein–polysaccharide complex coacervation, and the functionality and applicability of formed complexes

“…Associative phase separation follows two structure‐forming events involving spinodal decomposition or nucleation and growth‐type kinetics . First, the formation of soluble complexes giving the first initial rise in scattering intensity during a pH acid titration (denoted by pH c ); and secondly, the formation of insoluble complexes where macroscopic phase separation occurs and a rapid rise in scattering intensity occurs (denoted by pH ϕ1 ) . These pH values are determined by extending tangent lines from either side of the rise in a plot of scattering intensity (or optical density) versus pH.…”

“…Protein–polysaccharide interactions play an important structural role in biological systems (e.g., for maintaining cellular integrity and cell division), in controlling the macroscopic properties of foods (e.g., flow, stability, texture and mouthfeel), in the production of edible packaging/films and in the design of controlled delivery systems (e.g., for carrying bioactive or pharmaceutical compounds) . They can also be used to tailor protein functionality in foods by altering the surface chemistry of the protein and their aggregating behavior.…”

“…Protein-polysaccharide interactions play an important structural role in biological systems (e.g., for maintaining cellular integrity and cell division), in controlling the macroscopic properties of foods (e.g., flow, stability, texture and mouthfeel), in the production of edible packaging/films and in the design of controlled delivery systems (e.g., for carrying bioactive or pharmaceutical compounds). [1][2][3][4][5][6][7][8] They can also be used to tailor protein functionality in foods by altering the surface chemistry of the protein and their aggregating behavior. Although coacervation research is not novel, the majority of work has been focused on studying interactions involving polysaccharides with animal proteins, such as -lactoglobulin-acacia gum, 9,10 ovalbumin-pectin, 11 bovine serum albumin-pectin, 12 bovine serum albumin-sugar beet pectin 13 and gelatin-gum arabic.…”

“…In addition, biopolymer mixing ratio and the total biopolymer concentration have an important role in optimizing the complexation process. 2,12,[46][47][48][49][50] The nature of the interactions between protein and polysaccharides also plays a key role in governing complexation. 31,51 In very dilute solutions, protein and polysaccharides are co-soluble and remain stable because of the dominating effects of mixing entropy (Fig.…”

Directed Printing and Reconfiguration of Thermoresponsive Silica‐pNIPAM Nanocomposites

“…It should be noted that addition of 10 wt% SiNPs while improves the rheological characteristics of the hydrogel, but it compromises volumetric change in response to temperature, therefore not used in printing shape changing structures. Similar to 3 m NIPAM composites, the viscoelastic behavior of 6 m NIPAM composites shows a characteristic rubbery plateau region, [63,64] where G′ increases with respect to frequency increase and G″ decrease slightly at lower frequencies then increases at higher frequencies. Composites with 6 m NIPAM matrix exhibit more gel-like properties with higher stiffness, which is critical in printing robust structures that change shape in response to external stimuli.…”