聚羧酸系高性能减水剂分子在稀溶液中尺寸及其在体积排除色谱表征中表观分子量的模型研究

Translated title of the contribution: Modelling the Equilibrium Sizes of Comb-shaped MPEG-type Polycarboxylate-type Superplasticizers in Dilute Solution and Their Apparent Molecular Weight in Conventional Size Exclusion Chromatography

Yanwei Wang, Hongxia Zhao, Xin Shu, Yong Yang, Qianping Ran

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
14 Downloads (Pure)

Abstract

A simple "equivalent freely-jointed chain" model, parameterized with literature data on the persistence length of linear poly(methacrylic acid) (PMA) and poly(ethylene oxide) (PEO), and the molecular weight dependence of the radius of gyration of linear PEO in aqueous solution, is developed for the so-called MPEG-type comb-shaped polycarboxylate ester-or ether-based superplasticizers (PCEs). The model yields analytical expressions of the radius of gyration, the hydrodynamic radius, as well as their respective branching parameters and the characteristic size ratio of the radius of gyration to the hydrodynamic radius as a function of backbone molecular weight, side chain molecular weight, and the number of side chains, assumed to be evenly distributed along the polymer backbone, in the continuum limit. Our calculations andexperimental results in the literature showed a fairly good agreement, especially when a correction factor of magnitude 1.1 for the radius of gyration and of 1.4 for the hydrodynamic radius weretaken into account. After model validation, more predictions were made based on this simple model. Results of the radius of gyration and the hydrodynamic radius were presented as a function of the molecular weight of the PMA backbone, the molecular weight of the PEO side chains, and the molar ratio of methacrylic acid to polyalkyleneglycol methacrylate (known as the C/E ratio). It was found that the ratio of the radius of gyration to the hydrodynamic radius of PCEs fell mostly in the range of 0.85 to 1.0, notably less than those commonly found for linear polymers. To further facilitate applications of our theoretical model in practice, predictions were made to the ratio of the apparent molecular weight measured in aqueous size exclusion chromatography by conventional column calibration using linear poly(ethylene oxide) polymer standards to the true molecular weight measured by e.g., light scattering, by assuming that polymers having the same retention volume had approximately the same hydrodynamic radius. While it was common for branched polymers that the apparent GPC molecular weight using a linear polymer standard was less than their true molecular weight, the reverse could also be found for PCEs due to its copolymer feature. The mathematical model developed in this work, besides its simplicity, does not contain undetermined numerical prefactors, which avoids ambiguity in its practice.
Translated title of the contributionModelling the Equilibrium Sizes of Comb-shaped MPEG-type Polycarboxylate-type Superplasticizers in Dilute Solution and Their Apparent Molecular Weight in Conventional Size Exclusion Chromatography
Original languageChinese
Pages (from-to)1008-1018
Number of pages11
JournalActa Polymerica Sinica
Issue number6
DOIs
Publication statusPublished - Jun 2017

Keywords

  • Comb-shaped polycarboxylate-type superplasticizers
  • Freely jointed chain
  • Radius of gyration
  • Hydrodynamic radius
  • Size exclusion chromatography

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