pH-induced conformational changes of comb-like polycarboxylate investigated by experiment and simulation

Zhang, Qian; Ran, Qianping; Zhao, Hongxia; Shu, Xin; Yang, Yong; Zhou, Huaxin; Liu, Jiaping

doi:10.1007/s00396-016-3932-5

Cited by 28 publications

(13 citation statements)

References 39 publications

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“…[18][19][20] It is widely accepted that conformational properties of flexible polyelectrolyte molecules are sensitive to the concentration and valence of salt ions in solution. Recent studies have tried to elucidate conformational properties of PCEs in solution by theory, [21,22] experiments, [19,[23][24][25][26][27] and computer simulations. [20,28,29] However, to the best of our knowledge, most of those studies focus on dilute solutions and are done at the single-chain level, and the phase behavior of PCEs in salt solutions and at liquid-solid interfaces remain poorly understood.…”

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confidence: 99%

Phase Behavior of Partially Charged Polyelectrolyte Solutions with Salt: A Theoretical Study

Qiu

Wang

2021

Macro Theory & Simulations

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Weakly (or partially) charged polyelectrolytes represent an important subset of the polyelectrolyte family. For instance, polycarboxylate-based superplasticizers, or PCEs, are comb-shaped polyelectrolytes possessing anionic backbones grafted with neutral side chains. PCEs play an important role in modern concrete production. However, their behavior in salt solutions remain poorly understood. The present work builds upon a recently developed liquid-state theory for fully charged polyelectrolyte solutions and extends it to describe the phase behavior and salt partitioning of PCEs in a 2:1 salt solution. Previous studies have shown that there can be an additional short-range attraction, often referred to as the "calcium-binding" interaction between calcium ions and the negatively-charged carboxylate groups of PCEs. Such a calcium-binding interaction and how its strength affects the phase behavior are investigated. It is found that increasing the calcium-binding strength expands the phase-separated region and increases the critical extra salt concentration, and it also leads to a wider phase-separated region for salting-out and salting-in phenomena. The structural parameters of PCEs also affect the phase behavior. Increasing the side-chain length shrinks the phase-separated region, while increasing the acid-to-ether ratio expands the phase-separated region. Those results may find applications in molecular design of weakly charged polyelectrolytes like PCEs.

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confidence: 99%

Phase Behavior of Partially Charged Polyelectrolyte Solutions with Salt: A Theoretical Study

Qiu

Wang

2021

Macro Theory & Simulations

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“…It was generally believed that a greater amount of S-PCE could provide higher dispersion capacity. However, if PEO were wrapped or covered by hydration products or precipitates, PEO would not be stretched into the solution to efficiently provide the steric hindrance, which meant that the wrapped or covered PCE would be invalided [64][65][66]. Based on this, the effect of phosphate on formation of S-PCE, which would obviously affect the water/solid interface performance at the very beginning, should be associated with the dispersion of PCE-phosphate system.…”

Section: Dispersion Modelmentioning

confidence: 99%

Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

Zhang

Liu

et al. 2019

Materials

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Enhancement in dispersion of polycarboxylate superplasticizer (PCE) could be obtained by incorporating retarders in normal concrete. The generally believed reason was that the consumption of free water and polymer at the beginning was reduced by retarding cement hydration. This theory could not convincingly explain why sodium hexametaphosphate (SHMP) was able to promote the dispersion capacity of PCE, while trisodium phosphate (TSP) could not, despite that both TSP and SHMP could obviously retard the cement hydration. The adsorption behavior of PCE and phosphate was investigated and the mechanism was analyzed in order to gain deeper understanding. The results showed that TSP and SHMP delayed the cement hydration, impeded adsorption process of PCE, and increased thickness of adsorption layer. It was interesting that TSP reduced the dispersion, but SHMP enhanced. The reason for this contradiction was due to the difference in composition of adsorption layer. In the PCE-TSP system, this layer was composed of the precipitates (formed by TSP and Ca 2+ ) and the invalided PCE (caused by these precipitates in the immediate vicinity of the cement grains); the invalided PCE was due to the decrease of PCE dispersion. In the PCE-SHMP system, "Inner-phosphate (multi-layers) + Outer-PCE (single layer)" structure was formed to make the PCE work more effective, hence enhancing the dispersion. These results were expected to be useful for the design of highly efficient dispersants. dispersion capacity [26][27][28][29][30]. Based on this, the retarder might hinder the adsorption process of PCE and it was referred to as competitive adsorption [31][32][33][34][35], thereby reducing the dispersion. In addition, the thickness of the adsorption layer should also be accepted as a factor influencing the dispersion of PCE [36,37]. In spite of the decline in adsorption amount of PCE in the presence of retarder, as reported in previous study, the adsorption layer was obviously thickened to enhance the dispersion [37]. On the basis of discussion above, the conclusion could be made that the dispersion capacity of the PCE-retarder system should be associated with the retarding effect of retarder, adsorption behavior of PCE, and the thickness of the adsorption layer.Poly-phosphates, such as sodium tripolyphosphate and sodium hexametaphosphate (SHMP), have been widely used to promote the dispersion ability and dispersion retention ability of the superplasticizer system in real engineering practice. However, mono-phosphates, such as trisodium phosphate (TSP) and sodium hydrogen phosphate, cannot play the same roles as poly-phosphate in commercially available PCE products. If the retardation was the main reason for the enhancement, poly-phosphate and mono-phosphate would both have a similar effect on dispersion of PCE system, because both TPS and SHMP could retard the cement hydration [38]. Therefore, the reason why the poly-phosphate could effectively enhance the dispersion, whilst the mono-phosphate failed cannot be simply explained by the retard...

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“…self-assembling or stimuli-responsive materials). [13][14][15][16] Functional copolymers can also offer different properties depending on their grafting density and distribution of functional groups. 17,18 The control of monomer sequence/distribution itself has been observed to be of interest to control some physical properties of copolymers such as solubility, amphiphilicity, assembly and thermal properties.…”

Section: Introductionmentioning

confidence: 99%

Influence of Grafting Density and Distribution on Material Properties Using Well-Defined Alkyl Functional Poly(Styrene-co-Maleic Anhydride) Architectures Synthesized by RAFT

et al. 2019

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pH-induced conformational changes of comb-like polycarboxylate investigated by experiment and simulation

Cited by 28 publications

References 39 publications

Phase Behavior of Partially Charged Polyelectrolyte Solutions with Salt: A Theoretical Study

Phase Behavior of Partially Charged Polyelectrolyte Solutions with Salt: A Theoretical Study

Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

Influence of Grafting Density and Distribution on Material Properties Using Well-Defined Alkyl Functional Poly(Styrene-co-Maleic Anhydride) Architectures Synthesized by RAFT

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