Study on the molecular behavior of hydrophobically modified poly(acrylic acid) in aqueous solution and its emulsion-stabilizing capacity

Interaction of synthetic and lignin-based sulfonated polymers with hydrophilic, hydrophobic, and charged self-assembled monolayers

There is a need to understand the role of polymer structure on its interaction with surfaces to produce effective functional surfaces. In this work, we produced two anionic polymers of lignin-3-sulfopropyl methacrylate (L-S) and poly(vinyl alcohol-co-vinyl acetate)-3-sulfopropyl methacrylate (PVA-S) with similar charge densities and molecular weights. On the gold-coated surface, we deposited self-assembled monolayers (SAM) bearing different terminal moieties namely, hydroxyl, carboxyl, methyl, and amine groups of alkanethiols. This study highlighted the difference between the interaction of L-S and PVA-S and functionalized self-assembled surfaces. The information was generated using advanced tools, such as an X-ray photoelectron spectroscopy (XPS), and a quartz crystal microbalance with dissipation (QCM-D), which facilitated the correlation development between polymer properties and deposition performance on the functionalized surfaces. The higher deposition of PVA-S than L-S onto OH and COOH surfaces was observed due to its greater hydrogen bonding development and higher solubility. The solubility and structure of PVA-S were also beneficial for its higher adsorption than L-S onto CH₃ and NH₂ surfaces. However, the variation in pH, temperature, and salt significantly affected the adsorption of the macromolecules.

The interaction mechanism of synthetic and lignin based sulfonated materials with well-designed functional surfaces was investigated systematically.

Effect of Polyacrylic Acid on Rheology of Cement Paste Plasticized by Polycarboxylate Superplasticizer

Viscosity-enhancing agents (VEA) have been widely employed in high flowability cement-based materials, so as to ensure that no bleeding and segregation would occur. However, in most cases, interaction between VEA and superplasticizer would be unavoidable. In this study, the effect of polyacrylic acid (PAA), known as one of the most commonly used VEAs, on rheology performance of cement paste containing polycarboxylate superplasticizer (PCE), was studied. The initial fluidity was assessed with mini slump, and rheological behavior of cement paste was evaluated with rotor rheometer. Adsorption amount was examined with total organic carbon (TOC) analyzer, and the zeta potential was also tested. The interaction between PAA and PCE in the presence of calcium ion (Ca²⁺) was analyzed with conductivity, X-ray photoelectron spectroscope (XPS), and dynamic light scattering (DLS). The results illustrate that PAA can adsorb onto the surface of cement particles to plasticize cement paste, being similar to PCE. In the presence of Ca²⁺, PAA can be curled and crosslinked, as a result of the combination between carboxyl groups (COO^−) and Ca²⁺, thereby affecting the adsorption performance and conformation behavior. It is interesting that negative impact of PAA on dispersion efficiency of PCE can be demonstrated; one reason is the reduced adsorption amount of PCE by PAA competitively adsorbing onto the cement surface, and another possible reason is the invalided PCE by adsorption of PAA. Additionally, molecular weight of PAA should be considered if being used as VEA in PCE system.

Rheological Properties and Salt Resistance of a Hydrophobically Associating Polyacrylamide

The rheological properties of electrolyte solution of a hydrophobically associating acrylamide-based copolymer (HA-PAM) containing hydrophobically modified monomer and sodium 2-acrylamido-2-methylpropanesulfonic sulfonate were investigated in this paper. The study mainly focussed on effects of electrolyte concentration, temperature, and shear rate on the solution rheological properties. HA-PAM exhibited much stronger salt tolerance and shearing resistance than the commonly used partially hydrolyzed polyacrylamide, and has great potential for application in tertiary oil recovery of oilfields with high salinity. The salt resistance mechanism of HA-PAM in solution was investigated by combining molecular simulation and experimental methods. The structure–performance relationship of the salt-resisting polymer may provide useful guidance for design and synthesis of novel water-soluble polymers with high salt resistance.