Molecular assembly in block copolymer-surfactant nanoparticle dispersions : Information on molecular exchange and apparent solubility from high-resolution and pfg nmr
(2021) In Polymers 13(19).- Abstract
Internally structured block copolymer-surfactant particles are formed when the complex salts of ionic-neutral block copolymers neutralized by surfactant counterions are dispersed in aqueous media. Here, we report the1H NMR signal intensities and self-diffusion coefficients (D, from pulsed field gradient nuclear magnetic resonance, PFG NMR) of trimethyl alkylammonium surfac-tant ions and the poly(acrylamide)-block-poly(acrylate) (PAAm-b-PA) polyions forming such parti-cles. The results reveal the presence of an “NMR-invisible” (slowly exchanging) fraction of aggre-gated surfactant ions in the particle core and an “NMR-visible” fraction consisting of surface sur-factant ions in rapid exchange with the surfactant ions... (More)
Internally structured block copolymer-surfactant particles are formed when the complex salts of ionic-neutral block copolymers neutralized by surfactant counterions are dispersed in aqueous media. Here, we report the1H NMR signal intensities and self-diffusion coefficients (D, from pulsed field gradient nuclear magnetic resonance, PFG NMR) of trimethyl alkylammonium surfac-tant ions and the poly(acrylamide)-block-poly(acrylate) (PAAm-b-PA) polyions forming such parti-cles. The results reveal the presence of an “NMR-invisible” (slowly exchanging) fraction of aggre-gated surfactant ions in the particle core and an “NMR-visible” fraction consisting of surface sur-factant ions in rapid exchange with the surfactant ions dissociated into the aqueous domain. They also confirm that the neutral PAAm blocks are exposed to water at the particle surface, while the PA blocks are buried in the particle core. The self-diffusion of the polyions closely agree with the self-diffusion of a hydrophobic probe molecule solubilized in the particles, showing that essentially all copolymer chains are incorporated in the aggregates. Through centrifugation, we prepared mac-roscopically phase-separated systems with a phase concentrated in particles separated from a clear dilute phase. D values for the surfactant and block copolymer indicated that the dilute phase con-tained small aggregates (ca. 5 nm) of surfactant ions and a few anionic-neutral block copolymer chains. Regardless of the overall concentration of the sample, the fraction of block copolymer found in the dilute phase was nearly constant. This indicates that the dilute fraction represented a tail of small particles created by the dispersion process rather than a true thermodynamic solubility of the complex salts.
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- author
- Ferreira, Guilherme A. ; Loh, Watson LU ; Topgaard, Daniel LU ; Söderman, Olle LU and Piculell, Lennart LU
- organization
- publishing date
- 2021-10-01
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Block copolymer–surfactant complexes, Diffusion NMR, Molecular exchange
- in
- Polymers
- volume
- 13
- issue
- 19
- article number
- 3265
- publisher
- MDPI AG
- external identifiers
-
- pmid:34641081
- scopus:85116681066
- ISSN
- 2073-4360
- DOI
- 10.3390/polym13193265
- language
- English
- LU publication?
- yes
- additional info
- Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
- id
- a0582bc4-0b2d-43d2-95f0-52742f05136b
- date added to LUP
- 2021-10-20 15:36:02
- date last changed
- 2024-04-06 11:05:15
@article{a0582bc4-0b2d-43d2-95f0-52742f05136b,
abstract = {{<p>Internally structured block copolymer-surfactant particles are formed when the complex salts of ionic-neutral block copolymers neutralized by surfactant counterions are dispersed in aqueous media. Here, we report the<sup>1</sup>H NMR signal intensities and self-diffusion coefficients (D, from pulsed field gradient nuclear magnetic resonance, PFG NMR) of trimethyl alkylammonium surfac-tant ions and the poly(acrylamide)-block-poly(acrylate) (PAAm-b-PA) polyions forming such parti-cles. The results reveal the presence of an “NMR-invisible” (slowly exchanging) fraction of aggre-gated surfactant ions in the particle core and an “NMR-visible” fraction consisting of surface sur-factant ions in rapid exchange with the surfactant ions dissociated into the aqueous domain. They also confirm that the neutral PAAm blocks are exposed to water at the particle surface, while the PA blocks are buried in the particle core. The self-diffusion of the polyions closely agree with the self-diffusion of a hydrophobic probe molecule solubilized in the particles, showing that essentially all copolymer chains are incorporated in the aggregates. Through centrifugation, we prepared mac-roscopically phase-separated systems with a phase concentrated in particles separated from a clear dilute phase. D values for the surfactant and block copolymer indicated that the dilute phase con-tained small aggregates (ca. 5 nm) of surfactant ions and a few anionic-neutral block copolymer chains. Regardless of the overall concentration of the sample, the fraction of block copolymer found in the dilute phase was nearly constant. This indicates that the dilute fraction represented a tail of small particles created by the dispersion process rather than a true thermodynamic solubility of the complex salts.</p>}},
author = {{Ferreira, Guilherme A. and Loh, Watson and Topgaard, Daniel and Söderman, Olle and Piculell, Lennart}},
issn = {{2073-4360}},
keywords = {{Block copolymer–surfactant complexes; Diffusion NMR; Molecular exchange}},
language = {{eng}},
month = {{10}},
number = {{19}},
publisher = {{MDPI AG}},
series = {{Polymers}},
title = {{Molecular assembly in block copolymer-surfactant nanoparticle dispersions : Information on molecular exchange and apparent solubility from high-resolution and pfg nmr}},
url = {{http://dx.doi.org/10.3390/polym13193265}},
doi = {{10.3390/polym13193265}},
volume = {{13}},
year = {{2021}},
}