蠕虫状链模型下梳状共聚物分子的均方回转半径的理论分析及其在聚羧酸系减水剂分子中的应用

Translated title of the contribution: Radius of Gyration of Comb-shaped Copolymers by the Wormlike Chain Model:Theory and Its Applications to MPEG-type Polycarboxylate-type Superplasticizers

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

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
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Abstract

The expression obtained by Nakamura et al. on the radius of gyration of regular comb-shaped copolymers, where both the backbone and the side chains are described by the wormlike chain (WLC) model, was reformulated. It was demonstrated that in certain limiting cases their result conforms to classical expressions of the radius of gyration for a linear WLC (the Benoit-Doty equation), a symmetric star-shaped polymer with WLC arms (the Mansfield-Stockmayer equation), and the branching parameters for symmetric star and regular comb-shaped, derived by Zimm & Stockmayer and Berry & Orofino, respectively, under the assumption of ideal Gaussian chain statistics. Depending on the synthesis method and monomer reactivity, comb-shaped copolymers often possess a non-even distribution of side chains along the polymer backbone. To understand the effects of side-chain distribution on the radius of gyration of comb-shaped copolymers, the method by Nakamura et al. was extended to the case where the side chains were not regularly distributed, but followed a gradient-type distribution, modelled using geometric progressions. On the application side, the afore-derived WLC theory was applied to comb-shaped copolymers made of a negatively charged poly(methacrylate acid) (PMAA) backbone, partially grafted with poly(ethylene glycol) (PEG) side chains, referred to as polycarboxylate-based superplasticizers, or MPEG-type PCEs, in cement and concrete research. Particular focus was placed on rational choices of model parameters, which is an essential step in applying theory to practice. Based on data in the literature and model fitting, methods and recommended parameter values were developed for converting experimental characteristics of MPEG-type PCEs to their corresponding WLC model parameters. Furthermore, effects of backbone stiffness, side-chain distribution, side-chain persistence length, and grafting density on the unperturbed radius of gyration were explored in detail in the relevant range of parameter values of MPEG-type PCEs. The present work may shed light on how to arrive at a compromise between a mathematically tractable theory and its application to complicated industrial polymeric products. Although the present model is still rather idealized in the sense that it does not take into account of detailed monomer-monomer, monomer-solvent interactions such as the often discussed excluded volume and electrostatic interactions, it can serve as an important reference for assessing the contributions of those complicated interactions in further studies.
Translated title of the contributionRadius of Gyration of Comb-shaped Copolymers by the Wormlike Chain Model:Theory and Its Applications to MPEG-type Polycarboxylate-type Superplasticizers
Original languageChinese
Pages (from-to)1816-1831
Number of pages16
JournalActa Polymerica Sinica
Issue number11
DOIs
Publication statusPublished - Nov 2017

Keywords

  • Comb-shaped copolymer
  • Wormlike chain
  • Radius of gyration
  • Persistence length
  • Polycarboxylate-type superplasticizers

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