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Electrophoretic NMR characterisation of charged sidechain cationic polyelectrolytes and their interaction with the anionic surfactant, sodium dodecyl sulfate

Electrophoretic NMR characterisation of charged sidechain cationic polyelectrolytes and their interaction with the anionic surfactant, sodium dodecyl sulfate

Patel, Leesa, Mansour, Omar, Crossman, Martin and Griffiths, Peter ORCID: 0000-0002-6686-1271 (2019) Electrophoretic NMR characterisation of charged sidechain cationic polyelectrolytes and their interaction with the anionic surfactant, sodium dodecyl sulfate. Langmuir, 35 (28). pp. 9233-9238. ISSN 0743-7463 (Print), 1520-5827 (Online) (doi:https://doi.org/10.1021/acs.langmuir.9b01324)

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Abstract

Oppositely charged polymers and surfactants show a complex phase behaviour, with large regions of solubility and insolubility dependent on the concentrations of the species present. Here, a series of quaternized hydroxyethyl cellulose (cationic) polymers have been characterised by pulsed-gradient spin-echo NMR (PGSE-NMR) and electrophoretic NMR (eNMR) in simple aqueous (D2O) solutions and in combination with the oppositely charged (anionic) surfactant, sodium dodecyl sulfate (SDS). Analysis of the effective charge on the polymer derived from both the eNMR and PGSE-NMR results yields a readily interpretable insight into the polymer behaviour – the effective charge on the polymer at infinite dilution shows a linear relationship with the degree of modification. On addition of low concentrations of SDS, typically Csurf < 5mM, the surfactant interacts with the charged polymers, leading to substantial changes in the dynamics of the system (polymer diffusion, viscosity). At these levels of surfactant addition, there is no macroscopic phase separation. Further, the absence of an interaction with the parent, uncharged polymer strongly suggests that the SDS only interacts with the charged moieties present on the functionalized side-groups, and not the polymer backbone. Ultimately, the charge on the soluble polymer/surfactant complex was found to depend linearly on the level of surfactant binding, across a series of polymers with differing levels of modification, with the charge becoming effectively zero at the macroscopic phase separation boundary.

Item Type: Article
Uncontrolled Keywords: diffusion NMR, electrophoretic NMR, charge, coacervation
Subjects: Q Science > QC Physics
Q Science > QD Chemistry
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Materials & Analysis Research Group
Last Modified: 31 Jul 2019 09:35
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
Selected for GREAT 2019: None
URI: http://gala.gre.ac.uk/id/eprint/24692

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