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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Molecular Assembly in Block Copolymer-Surfactant Nanoparticle Dispersions: Information on Molecular Exchange and Apparent Solubility from High-Resolution and PFG NMR

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Author(s):
Ferreira, Guilherme A. [1, 2] ; Loh, Watson [1] ; Topgaard, Daniel [3] ; Soderman, Olle [3] ; Piculell, Lennart [3]
Total Authors: 5
Affiliation:
[1] Univ Estadual Campinas, Inst Chem, Univ Campinas, POB 6154, BR-13083970 Campinas - Brazil
[2] Univ Fed Bahia, Inst Chem, Dept Phys Chem, BR-40170115 Salvador, BA - Brazil
[3] Lund Univ, Div Phys Chem, POB 124, S-22100 Lund - Sweden
Total Affiliations: 3
Document type: Journal article
Source: POLYMERS; v. 13, n. 19 OCT 2021.
Web of Science Citations: 0
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 the H-1 NMR signal intensities and self-diffusion coefficients (D, from pulsed field gradient nuclear magnetic resonance, PFG NMR) of trimethyl alkylammonium surfactant ions and the poly(acrylamide)-block-poly(acrylate) (PAAm-b-PA) polyions forming such particles. The results reveal the presence of an ``NMR-invisible `` (slowly exchanging) fraction of aggregated surfactant ions in the particle core and an ``NMR-visible `` fraction consisting of surface surfactant 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 macroscopically 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 contained 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> (AU)

FAPESP's process: 15/25406-5 - Organizing matter: colloids formed by association of surfactants, polymers and nanoparticles
Grantee:Watson Loh
Support Opportunities: Research Projects - Thematic Grants