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Crowding effects on the structure and rheology of ultrasoft PNIPAM-PEGMA copolymer microgels

Bassu, Gavino ; Vialetto, Jacopo ; Ruiz-Franco, José ; Scotti, Andrea LU orcid ; Houston, Judith E. ; Mata, Jitendra ; Zaccarelli, Emanuela and Laurati, Marco (2024) In Soft Matter 21(1). p.68-76
Abstract

We investigate the link between the internal microstructure of poly(N-isopropylacrylamide)-poly(ethylene glycol) methyl ether methacrylate (PNIPAM-PEGMA) microgels, their bulk moduli and the rheological response and structural arrangement in dense suspensions. The low degree of crosslinking combined with the increased hydrophilicity induced by the presence of PEGMA results in a diffuse, star-like density profile of the particle and very low values of the bulk modulus in dilute conditions, as determined by small angle neutron scattering (SANS). The ultrasoft nature of the particle is reflected in the changes of the structural arrangement in dense suspensions, which evidence a strong deswelling and a sharp rise of the bulk modulus at... (More)

We investigate the link between the internal microstructure of poly(N-isopropylacrylamide)-poly(ethylene glycol) methyl ether methacrylate (PNIPAM-PEGMA) microgels, their bulk moduli and the rheological response and structural arrangement in dense suspensions. The low degree of crosslinking combined with the increased hydrophilicity induced by the presence of PEGMA results in a diffuse, star-like density profile of the particle and very low values of the bulk modulus in dilute conditions, as determined by small angle neutron scattering (SANS). The ultrasoft nature of the particle is reflected in the changes of the structural arrangement in dense suspensions, which evidence a strong deswelling and a sharp rise of the bulk modulus at moderate packing fractions. At larger packings the single particle morphology and softness saturate, and we observe a structural transition from a dispersion-like to a hydrogel-like behavior. The transition is also reflected in the rheological response in the form of a two-step yielding at large packing fractions, characteristic of systems in which a network structure is present. Our results demonstrate that a knowledge of the internal structure and mechanics of individual microgels is needed to determine and tune the properties of dense suspensions, and optimize their response for applications in biomedicine and as filtration systems.

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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
21
issue
1
pages
9 pages
publisher
Royal Society of Chemistry
external identifiers
  • pmid:39625381
  • scopus:85211074773
ISSN
1744-683X
DOI
10.1039/d4sm01103a
language
English
LU publication?
yes
id
b30c015d-e017-4779-8e31-5f9657bd5e7d
date added to LUP
2025-01-21 14:54:35
date last changed
2025-07-09 04:41:36
@article{b30c015d-e017-4779-8e31-5f9657bd5e7d,
  abstract     = {{<p>We investigate the link between the internal microstructure of poly(N-isopropylacrylamide)-poly(ethylene glycol) methyl ether methacrylate (PNIPAM-PEGMA) microgels, their bulk moduli and the rheological response and structural arrangement in dense suspensions. The low degree of crosslinking combined with the increased hydrophilicity induced by the presence of PEGMA results in a diffuse, star-like density profile of the particle and very low values of the bulk modulus in dilute conditions, as determined by small angle neutron scattering (SANS). The ultrasoft nature of the particle is reflected in the changes of the structural arrangement in dense suspensions, which evidence a strong deswelling and a sharp rise of the bulk modulus at moderate packing fractions. At larger packings the single particle morphology and softness saturate, and we observe a structural transition from a dispersion-like to a hydrogel-like behavior. The transition is also reflected in the rheological response in the form of a two-step yielding at large packing fractions, characteristic of systems in which a network structure is present. Our results demonstrate that a knowledge of the internal structure and mechanics of individual microgels is needed to determine and tune the properties of dense suspensions, and optimize their response for applications in biomedicine and as filtration systems.</p>}},
  author       = {{Bassu, Gavino and Vialetto, Jacopo and Ruiz-Franco, José and Scotti, Andrea and Houston, Judith E. and Mata, Jitendra and Zaccarelli, Emanuela and Laurati, Marco}},
  issn         = {{1744-683X}},
  language     = {{eng}},
  number       = {{1}},
  pages        = {{68--76}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Soft Matter}},
  title        = {{Crowding effects on the structure and rheology of ultrasoft PNIPAM-PEGMA copolymer microgels}},
  url          = {{http://dx.doi.org/10.1039/d4sm01103a}},
  doi          = {{10.1039/d4sm01103a}},
  volume       = {{21}},
  year         = {{2024}},
}