Ibrahim, Mervat S., Valencony, Jordane, King, Stephen, Murray, Martin, Szczygiel, Agnieszka, Alexander, Bruce D. and Griffiths, Peter C. ORCID: https://orcid.org/0000-0002-6686-1271 (2018) Studying the interaction of hydrophobically modified ethoxylated urethane (HEUR) polymers with sodium dodecylsulphate (SDS) in concentrated polymer solutions. Journal of Colloid and Interface Science, 529. pp. 588-598. ISSN 0021-9797 (doi:10.1016/j.jcis.2018.06.042)

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Abstract

Hypothesis:
Hydrophobically modified ethoxylated urethane polymers (HEURs) are widely used to control the rheological profile of formulated particulate dispersions through associative network formation, the properties of which are perturbed by the presence of surfactants. At high polymer concentrations and in the presence of surfactants, it is hypothesised that the dominant factors in determining the rheological profile are the number and composition of the mixed hydrophobic aggregates, these being defined by the number and distribution of the hydrophobic linkers along the polymer backbone, rather than the end-group hydrophobe characteristics per se that dominate the low polymer concentration behaviour.

Experiments:
Three different HEUR polymers with formulae (C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10 and C18-L-(EO200-L)7-C18 (where L = urethane linker, Cn = hydrophobic end-group chain length, and EO = ethylene oxide block) have been studied in the absence and presence of SDS employing techniques that quantify (a) the bulk characteristics of the polymersurfactant blend, (b) the structure and composition of the hydrophobic domains, (c) the dynamics of the polymer and surfactant, and (d) the polymer conformation. Collectively, these experiments demonstrate how molecular-level interactions between the HEURs and sodium dodecylsulphate (SDS) define the macroscopic behaviour of the polymer/surfactant mixture.

Findings:
Binding of the SDS to the polymer via two mechanisms - monomeric anti-cooperative and micellar cooperative - leads to surfactant-concentration-specific macroscopic changes in the viscosity. Binding of the surfactant to the polymer drives a conformational rearrangement, and an associated redistribution of the polymer end-groups and linker associations throughout the hydrophobic domains. The composition and size of these domains are sensitive to the polymer architecture. Therefore, there is a complex balance between polymer molecular weight, ethylene oxide block size, and number of urethane linkers, coupled with the size of the hydrophobic end-groups. In particular, the urethane linkers are shown to play a hitherto largely neglected but important role in driving the polymer association.

Item Type:	Article
Uncontrolled Keywords:	HEUR, SDS, viscosity, PGSE-NMR, surface tension, fluorescence, EPR, SANS, polymer/surfactant complex, telechelic polymers
Subjects:	Q Science > QD Chemistry
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Science (SCI)
Last Modified:	21 Jun 2019 01:38
URI:	http://gala.gre.ac.uk/id/eprint/20472

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