Tailoring the Viscoelasticity of Polymer Gels of Gluten Proteins through Solvent Quality

• Published in: Macromolecules 2020-11, Vol.53 (21), p.9470-9479
• Main Authors: Costanzo, Salvatore, Banc, Amélie, Louhichi, Ameur, Chauveau, Edouard, Wu, Baohu, Morel, Marie-Hélène, Ramos, Laurence
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Condensed Matter; Mechanics; Mechanics of materials; Physics; Polymers; Soft Condensed Matter
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.0c01466

We investigate the linear viscoelasticity of polymer gels produced by the dispersion of gluten proteins in water/ethanol binary mixtures with various ethanol contents, from pure water to 60% v/v ethanol. We show that the complex viscoelasticity of the gels exhibits a time/solvent composition superposition principle, demonstrating the self-similarity of the gels produced in different binary solvents. All gels can be regarded as near critical gels with characteristic rheological parameters, elastic plateau, and characteristic relaxation time, which are related to one another, as a consequence of self-similarity, and span several orders of magnitude when changing the solvent composition. Thanks to calorimetry and neutron scattering experiments, we evidence a cosolvency effect with better solvation of the complex polymer-like chains of the gluten proteins as the amount of ethanol increases. Overall, the gel viscoelasticity can be accounted for by a unique characteristic length characterizing the cross-link density of the supramolecular network, which is solvent composition-dependent. On a molecular level, these findings could be interpreted as a transition of the supramolecular interactions, mainly H-bonds, from intra- to interchains, which would be facilitated by the disruption of hydrophobic interactions by ethanol molecules. This work provides a new insight for tailoring the gelation process of complex polymer gels.