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NMR studies of aggregation in the octylamine/water system
YKI – Ytkemiska institutet.
1992 (English)In: Organized Solutions / [ed] Friberg, S. & Lindman, B., Marcel Dekker, 1992, p. 221-235Chapter in book (Refereed)
Abstract [en]

INTRODUCTION; Short chain alkylamines, such as octylamine, constitute a technically important group of amphiphiles. They are used as hydrophobing agents, emulsifiers, and as flotation agents. Their solution chemistry, however, has received relatively little attention. In the case of octylamine, phase diagrams have been reported for the binary aqueous system [1,2] and for the ternary system with added pxylene [3-5]. For octylamine/water solutions a lower consolute temperature (LCT) occurs at 25°C for a critical concentration of 10 wt % surfactant. The presence of a LCT is caused by a complex interplay of temperature dependent interactions, the origins of which are poorly understood for the system presently under studz corresponding phenomena in surfactants of the poly(ethylene oxide) type are at present a subject of intense discussion [6]. We feel that an understanding of the clouding phenomena in the octylamine system is desirable, although we make little attempts in the present study to explain it. Rather, we report a study of the aggregate size/shape in the isotropic solution phase in the octylamine/water system, since these quantities are necessary starting points when discussing the clouding phenomenon. Thus we have investigated the octylamine system by means of NMR methods. From 2H multifield relaxation rate measurements of a deuterated octylamine, it is possible to deduce quantitative information on the reorientational dynamics of the surfactant molecules . We have used the two step model for the interpretation of the measured relaxation rates t7,8]. In this model the motion of the aggregated surfactant is separated into two time regimes: a fast regime corresponding to the local motion of the molecule within the aggregate, and a slow regime corresponding to the global motions of the aggregate and/or surfactant lateral diffusion over the curved aggregate surface. We have also used multicomponent selfdiffusion measurements, which give an opportunity to judge whether an individual component is confined to an aggregate or not [9]. They also serve as a critical test of the interpretation of the relaxation data, since the suggested structures and their dimensions must not be at variance with the selfdiffusion data.

Place, publisher, year, edition, pages
Marcel Dekker, 1992. p. 221-235
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-13602OAI: oai:DiVA.org:ri-13602DiVA, id: diva2:989992
Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2016-09-29Bibliographically approved

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CiteExportLink to record
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  • apa
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