Molecular simulation to discover rheological properties and soil‐binding ability of PHPA polymer on montmorillonite surface

Abstract

Synthetic polymer fluids are increasingly being applied to support excavations in deep foundations. As these fluids are molecularly engineered, their underlying microstructure interaction with in situ soils significantly affect excavation stability and soil dispersion. However, little molecular‐scale research has been done on the rheological behavior of partially hydrolyzed polyacrylamides (PHPA) polymer fluids on the clay surface. Molecular models of the clay–polymer systems are constructed using PHPA on montmorillonite (MMT) clay surface. Initial rheological properties and soil‐binding ability at different shear rates, temperatures, and polymer concentrations are first studied using molecular dynamics (MD) simulations. It is found that the functional groups of PHPA can interact with the MMT surface and form a viscous film under the atomic interaction of hydrogen bonds, water bridges, and electrostatic attraction. The shear stress, σ increases with the shear rate and follows the power‐law model. And the viscosity, η decreases as the shear rate increases, which is consistent with the experimental trend. However, the σ and η decrease with the increase of temperature. And the action mode of PHPA concentration has been identified from the MD perspective. This work provides insight into the molecular mechanism for PHPA's rheology on the clay surface and their interaction.

Synthesis and characterization of a novel functionalized silica/polyacrylamide composite for advanced water‐based drilling design

“…The bonding associated with the particles in a drilling fluid model affects the thermal stability of the fluid. This study demonstrated that the chemical bonding between the polymer and silica composite is probably van der Waals or electrostatic forces since it is physical mixing between PAM, functionalized SiO 2 , and SDS 5,66‐69 . According to the interfacial chemistry of substances, a composite with electrostatic or van der Waals forces is poorer than a composite developed through covalent bonding 67 .…”

“…This study demonstrated that the chemical bonding between the polymer and silica composite is probably van der Waals or electrostatic forces since it is physical mixing between PAM, functionalized SiO 2 , and SDS. 5,[66][67][68][69] According to the interfacial chemistry of substances, a composite with electrostatic or van der Waals forces is poorer than a composite developed through covalent bonding. 67 Additionally, the covalent bonding between the polymer chains and the polymer molecules is present in bare PAM.…”

A molecular dynamics study on adsorption mechanisms of polar, cationic, and anionic polymers on montmorillonite

“…In many studies, the authors focused on predicting the mechanical, 66–68 rheological, 69,70 or thermodynamical properties 71,72 of the PCNC materials. On the other hand, many other researchers investigated the adsorption mechanisms of polymers and provided insights on how to enhance the adsorption.…”

“…62 While most researchers chose montmorillonite (MMT) to represent clay, some other studies considered other types of clay including quartz, 63 kaolinite, 64 and silica. 65 In many studies, the authors focused on predicting the mechanical, 66-68 rheological, 69,70 or thermodynamical properties 71,72 of the PCNC materials. On the other hand, many other researchers investigated the adsorption mechanisms of polymers and provided insights on how to enhance the adsorption.…”

Molecular Dynamics Simulation in the Interlayer of Mixed-Layer Clays Due to Hydration and Swelling Mechanism

“…Furthermore, their applications in some micro-scale geotechnical problems have become a research hotspot [24], as these problems occur in frozen, saline, and expansive soils. As the main component of most soils, clay minerals have been widely studied, including the micro-mechanisms of surface wettability [25], matter adsorption [26], mechanical properties [27], and, most importantly, clay swelling [28]. With the advancement of computer power and algorithms [29], they are increasingly used to obtain information on clay swelling, where the interlamellar spacings are smaller than the Debye length (∼20 Å), and the hydration effects become essential [30].…”