Extensional Flow and Relaxation of Semi‐dilute Solutions of Schizophyllan

Abstract

Capillary thinning experiments of semi‐dilute solutions of schizophyllan in water and DMSO are performed to determine the relaxation behavior in extensional flows as experienced, for example, in the flow through porous media in enhanced oil recovery. The extensional relaxation time λE is found to scale with concentration following a dissimilar power‐law dependency for the two solvents, λE ∝ c1.52 in water and λE ∝ c0.90 in DMSO. It is shown that the extensional flow fields are strong enough to break, and prevent the rebuilding of, intermolecular structures, due to hydrogen bonding that was observed to alter the viscoelastic response in shearing flows of aqueous schizophyllan solutions.

Probing hydrogen bond interactions in a shear thickening polysaccharide using nonlinear shear and extensional rheology

“…We 180 use the CaBER device to quantitatively measure the changes in the extensional rheology of Mamaku gum upon increasing the urea concentration. Although limited in number, CaBER experiments performed on other polysaccharide systems, such as cellulose/ionic liquid solutions [18], Sundew plant mucilage [9], guar gum solutions [57,7] and Schizophyllan solutions [5], have revealed that 185 capillary breakup rheometry is an accurate technique for quantifying the elongational properties of these fluids. Moreover, the potential application of Mamaku gum solutions as a food thickener necessitates an understanding of its elongational properties; the biomechanics of swallowing is such that a food bolus encounters a squeeze flow [42,46], whose kinematics has elongational deformation 190 components.…”

“…They provide structural reinforcement in plants and animals [19,3,50], are the chief component of the lubricating synovial fluid found in mammalian joints [61,17], are the main source of energy in many foods [54], 5 and are found in various biological slimes and mucus [6,12]. Furthermore, the widespread availability, biocompatibility and biodegradability, plus the ability of polysaccharides to form swollen gels has stimulated much research in using them in controlled drug release systems [22,35].…”

Capillary breakup extensional rheometry of sodium carboxymethylcellulose solutions in water and propylene glycol/water mixtures

“…The power‐law exponent is 2.47 ± 0.11 for λ 0 and 1.56 ± 0.17 for λ E. These results are qualitatively consistent with data published in the literature for the entangled solution of other polymers. In the range of the unentangled semidilute and the entangled semidilute, the extensional relaxation time λ E increases with an increasing polymer concentration, while at the same time λ E < λ 0 and the related slope of λ E = f (c) is smaller than for λ 0 = f (c) . Figure also shows values of the characteristic time λ C of the solutions, obtained by fitting the flow curves with the Cross equation.…”

“…The measurement results obtained using extensional rheometry based on capillary break‐up dynamics are presented in the literature for several aqueous solutions of polysaccharides; however, there are only four studies analyzing the effect of solvent quality on the process of filament thinning of semidilute polysaccharide solutions as well as synthetic polymer solutions …”

“…De Dier et al . studied schizophyllan, which takes on two different configurations in solution: a random coil state in dimethyl sulfoxide (DMSO) and a more rigid triple‐helical structure in aqueous solution.…”