Molecular Breakage Research Articles

Mechanical Degradation of Biopolymers for Enhanced Oil Recovery Applications

Summary Polymer degradation is detrimental to enhanced oil recovery (EOR) because it ultimately leads to solution viscosity loss. Molecular breakage during flow owing to high stresses, known as mechanical degradation, can occur in numerous stages during field polymer injection. One of the reasons biopolymers are promising for EOR is their enhanced mechanical stability compared to their polyacrylamide counterparts. This study presents a comparative investigation of the mechanical degradation of biopolymers with potential applications in EOR. The mechanical degradation was evaluated by flowing the solutions through a short-length capillary (internal diameter of 0.127 mm and length of 10 mm) and then testing their viscosity loss through a rheometer. Nine flow velocities were tested between 0.13 and 66 m/s (shear rates between 8.29 × 103 and 1.66 × 107 s−1) in addition to the undegraded baseline. Four biopolymers were evaluated [xanthan gum (XG), scleroglucan (SCLG), schizophyllan (SCP), and guar gum (GG)] and compared to two polyacrylamides [hydrolyzed polyacrylamide (HPAM) and HPAM-AMPS (2-acrylamido-2-methylpropane sulfonic acid)] that serve as benchmarks for EOR processes. All the polymers were evaluated in three different concentrations (100, 500, and 2,000 ppm) in synthetic seawater (3.01% total dissolved solids). The degradation was evaluated through the Ostwald-de Waele indices. The consistency index (K) indicates loss of overall viscosity, and the behavior index (n) accounts for the loss of pseudoplasticity. Overall, the mechanical degradation correlated positively with shear rate and negatively with polymer concentration. When increasing the polymer concentration, the dominant mechanisms at play were macromolecule extension inhibition, caused by interactions with surrounding molecules, and hydrodynamic volume reduction. The biopolymers displayed superior resistance to mechanical degradation than the synthetic ones, with XG being the most resistant polymer. In this work, the main factors for the mechanical degradation resistance of different polymers were rigidity of the polymer structure in solution and the molar mass of the polymer chains.

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage

Formatting and ligating biopolymers using adjustable nanoconfinement

Sensitive visualization and conformational control of long, delicate biopolymers present critical challenges to emerging biotechnologies and biophysical studies. Next-generation nanofluidic manipulation platforms strive to maintain the structural integrity of genomic DNA prior to analysis but can face challenges in device clogging, molecular breakage, and single-label detection. We address these challenges by integrating the Convex Lens-induced Confinement (CLiC) technique with a suite of nanotopographies embedded within thin-glass nanofluidic chambers. We gently load DNA polymers into open-face nanogrooves in linear, concentric circular, and ring array formats and perform imaging with single-fluorophore sensitivity. We use ring-shaped nanogrooves to access and visualize confinement-enhanced self-ligation of long DNA polymers. We use concentric circular nanogrooves to enable hour-long observations of polymers at constant confinement in a geometry which eliminates the confinement gradient which causes drift and can alter molecular conformations and interactions. Taken together, this work opens doors to myriad biophysical studies and biotechnologies which operate on the nanoscale.

The Ambiguity of the Viscometric Method for the Deter-Mination of Dextranase Activity

Abstract In earlier studies it was found that the tissue pellets of Avena seedlings decrease the viscosity of dextran solutions. By the use of direct methods for investigating the breakage of these molecules, it is shown that the lowering of viscosity of dextran solutions under the influence of tissue pellets of Avena coleoptiles is not due to an intramolecular process of molecular breakage (dextranase-like activity) but rather to an intermolecular process of still unknown nature. This conclusion is supported by the finding that solutions of entirely different macromolecules than dextrans are also affected by the tissue pellets. The observed changes in viscosity can therefore not be due to dextranase activity and the viscometric method for the determination of this activity is clearly ambiguous.