A molecular-mechanical link in shear-induced self-assembly of a functionalized biopolymeric fluid

• Published in: Soft matter 2023-05, Vol.19 (17), p.3228-3237
• Main Authors: Pavlovskaya, Galina E, Meersmann, Thomas
• Format: Article
• Language: English
• Subjects: Biopolymers; Carrageenan; Carrageenan - chemistry; Carrageenans; Chemistry; Coils; Helices; Ion concentration; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Molecular dynamics; NMR; Nuclear magnetic resonance; Phase Transition; Phase transitions; Self-assembly; Shear; Shear thinning (liquids); Sodium
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/d2sm01381a

23 Na multiple quantum filtered (MQF) rheo-NMR methods were applied to probe the molecular foundation for flow induced self-assembly in 0.5% κ -carrageenan fluid. This method is sensitive enough to utilize an endogenous sodium ion concentration of approximately 0.02%. Rheo-NMR experiments were conducted at different temperatures and shear rates to explore varying molecular dynamics of the biopolymer in the fluid under shear. The temperature in the rheo-NMR experiments was changes from 288 K to 313 K to capture transition of κ-carrageenan molecules from helices to coils. At each temperature, the fluid was also tested for flow and oscillatory shear behaviour using bulk rheometry methods. It was found that the 23 Na MQF signals were observed for the 0.5% κ -carrageenan solution only under shear and when the fluid demonstrated yielding and/or shear-thinning behaviour. At temperatures of 303 K and above, no 23 Na MQF signals were observed independent of the presence or absence of shear as the molecular phase transition to random coils occurs and the fluid becomes Newtonian. 23 Na multiple quantum filtered (MQF) rheo-NMR methods were applied to probe the molecular foundation for flow induced self-assembly in 0.5% κ -carrageenan fluid.