Adsorbed layer thickness of polycarboxylate and polyphosphate superplasticizers on polystyrene nanoparticles measured via dynamic light scattering

Synthesis, Performance Evaluation, and Adsorption-Dispersion Mechanism of Sulfonic Acid-Terminated Long Side Chain Polycarboxylate Superplasticizers

Polycarboxylate superplasticizers (PCEs) achieve dispersion mainly via steric hindrance from poly(ether) side chains. However, long side chains may cause structural collapse. This study mitigates this issue by introducing sulfonic acid terminations to the long side chains, synthesizing sulfonic-terminated polycarboxylates (PCEPS). Electrostatic repulsion between sulfonic and carboxyl groups on the main chain reduces the level of collapse, enhancing PCE dispersion in cement. PCEPS-4000 showed the strongest dispersion compared with conventional PCEs (PCEC). PCEPS-4000 formed an adsorption layer thickness (ALT) of 11.65 nm, showing a significant improvement over the 7.93 nm observed in the carboxyl-terminated long side chain polycarboxylate (PCETA). Stronger negative charge and lower complexation of sulfonic acid groups enhance the side chain extension. PCEPS also shows good clay tolerance and slump retention, proving its versatility as a concrete admixture.

The synthesis and adsorption-dispersion properties of PPEGMA-PVPA copolymers in cement paste

This study reports the synthesis of a novel superplasticizer, poly(poly(ethylene glycol)methacrylate)-poly(vinylphosphonic acid) (PPEGMA-PVPA), containing phosphate moieties via solution radical polymerization. By adjusting the feed ratios of monomers, PPEGMA-PVPA copolymers with different phosphate group densities were obtained, and their chemical structure was characterized via FT-IR, 1H NMR spectroscopy and ICP-OES. The results demonstrated that about 70% of the VPA monomer was polymerized. The thermostability of PPEGMA-PVPA was also determined through DSC and TGA. The adsorption-dispersion performance onto cement pastes was investigated using mini-slump test, TOC and zeta potential analysis. It was demonstrated that the adsorption capacity of PPEGMA-PVPA onto cement paste was about 1.4 times stronger than that of the reference polycarboxylate superplasticizer and exhibited excellent adsorption-dispersion performance.

Advances in Organic Rheology-Modifiers (Chemical Admixtures) and Their Effects on the Rheological Properties of Cement-Based Materials

Organic rheology modifiers, especially superplasticizers and viscosity-modifying admixtures (VMAs), have become key components for the workability optimization of modern concrete. The development of these admixtures is crucial to the further performance improvement of modern concrete under different casting and service conditions. Many of the former reviews have summarized research advances in respect of these admixtures from chemical and material perspectives, focusing on the effects of structure and the performance. In this paper, from a rheological perspective, an overview is provided of the microscale behavior of polycarboxylate (PCE) superplasticizers and VMAs (e.g., adsorption, conformation, and bridging) in terms of the evolution of the microstructure of the paste, the effect of chemical structure on the yield stress, the apparent viscosity and thixotropy of cement-based materials, and the structure design of these admixtures. Most importantly, in addition to a general discussion with assumptions (monolayer adsorption of a "flat" conformation, with each molecule on a single particle; statistical polymer composition), special conditions (e.g., preferential adsorption, depletion effects, hydration modification effects, and the polydispersity of the polymer composition) are discussed. Newly developed admixtures, realized through regulation of the microscale behavior, and by the modification of adsorption, topological structure, and molecular frame, are introduced.

Selective adsorption of various phosphorus species coexistence in water-soluble ammonium polyphosphate on goethite: Experimental investigation and molecular dynamics simulation

The geochemical processes of polyphosphates (poly-Ps) are important for phosphorus (P) management and environmental protection. Water-soluble ammonium polyphosphate (APP) containing various P species has been increasingly used as an alternative P-fertilizer. The various P species coexistence and the chelation of poly-Ps with mental would trigger the P's competitive adsorption and affect the APP's adsorption intensity on goethite, compared to single orthophosphate (P₁). P adsorption behaviors of APP1 with two P species and APP2 with seven P species on goethite were investigated via batch experiments in comparison to the traditional P-fertilizer of mono-ammonium phosphate (MAP). Coadsorption of P₁ and pyrophosphate (P₂) on goethite was investigated by molecular dynamics (MD) simulation. The more Fe³⁺ dissolved from goethite as a bridge due to the chelation of poly-Ps in APP and contributed to the stronger APP adsorption on goethite compared with MAP. Ion chromatography and spectral analysis showed P₁ and P₂ in APP were mainly adsorbed by goethite via mainly forming bidentate complexes. The goethite preferentially adsorbed P₁ at lower APP concentration but increased the poly-Ps' adsorption at higher APP concentration. MD simulation showed that electrostatic interaction and hydrogen bonds played a key role in water-phosphates-goethite systems. The P₁ pre-adsorbed on goethite could be replaced by P₂ at high P₂ concentration. The results develop new insights regarding the selective adsorption of various P species coexistence in goethite-rich environments.

Comb-type polymer-hybridized MXene nanosheets dispersible in arbitrary polar, nonpolar, and ionic solvents

Solution-based processing of two-dimensional (2D) nanomaterials is highly desirable, especially for the low-temperature large-area fabrication of flexible multifunctional devices. MXenes, an emerging family of 2D materials composed of transition metal carbides, carbonitrides, or nitrides, provide excellent electrical and electrochemical properties through aqueous processing. Here, we further expand the horizon of MXene processing by introducing a polymeric superdispersant for MXene nanosheets. Segmented anchor-spacer structures of a comb-type polymer, polycarboxylate ether (PCE), provide polymer grafting-like steric spacings over the van der Waals range of MXene surfaces, thereby reducing the colloidal interactions by the order of 10³, regardless of solvent. An unprecedented broad dispersibility window for Ti₃C₂T_x MXene, covering polar, nonpolar, and even ionic solvents, was achieved. Furthermore, close PCE entanglements in MXene@PCE composite films resulted in highly robust properties upon prolonged mechanical and humidity stresses.

Concrete Strengthening by Introducing Polymer-Based Additives into the Cement Matrix-A Mini Review

The modern types of concrete are a mixture of aggregates, cement, water and optional additives and admixtures. In particular, polymer additives seem to be a promising type of component that can significantly change concrete and mortar properties. Currently, the most popular polymer additives include superplasticizers, latexes and redispersible powders. Moreover, in order to improve the properties of concrete-based composite admixtures, which enhance the resistance to cracking, polymer fibres and recycled polymers have been researched. All the types of polymeric materials mentioned above are broadly used in the construction industry. This work summarizes the current knowledge on the different types of popular polymeric additives. Moreover, it describes the correlation between the chemical structure of additives and the macro-behaviour of the obtained concrete.