On the dual behaviour of water in octanol-rich aqueous n-octanol mixtures: an x-ray scattering and computer simulation study - Archive ouverte HAL Accéder directement au contenu
Pré-Publication, Document De Travail Année : 2023

On the dual behaviour of water in octanol-rich aqueous n-octanol mixtures: an x-ray scattering and computer simulation study

Martina Požar
Aurélien Perera
Eric Schneider
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Résumé

Aqueous n-octanol (n = 1, 2, 3, 4) mixtures from the octanol rich side are studied by x-ray scattering and computer simulation, with focus on structural changes, particularly in what concerns the hydration of the hydroxyl-group aggregated chain-like structures, under the inuence of various branching of the alkyl tails. Previous studies have indicated that hydroxyl-group chain-cluster formation is hindered in proportion to the branching number. Here, water mole-fractions up to x = 0.2 are exam- ined, i.e. up to the miscibility limit. It is found that water molecules within the hydroxyl-chain domains, participate to the chain formations in dierent manner for the 1-octanol and the branched octanols. The hy- dration of the octanol hydroxyl chains is conrmed by the shifting of the scattering pre-peak to low momentum transfer both from measured and simulated x-ray scattering intensities, which corresponds to an increased size of the clusters. Experimental x-ray scattering amplitudes are seen to increase with increasing water content for 1-octanol, while this trend is reversed in all branched octanols, with the amplitudes decreasing with the increase of branching number. Conjecturing that the amplitudes of pre- peaks are related to the density of corresponding aggregates, these results are interpreted as water breaking large OH hydroxyl chains in 1-octanol, hence increasing the density of aggregates, while enhancing hydroxyl ag- gregates in branched alcohols by inserting itself into the OH chains. Hence, water acts as a structure maker or breaker in inverse proportion to the hindering of OH hydroxyl chain structures arising from the topology of the alkyl tails (branched or not).
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Dates et versions

hal-04258497 , version 1 (25-10-2023)

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  • HAL Id : hal-04258497 , version 1

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Martina Požar, Jennifer Bolle, Christian Sternemann, Aurélien Perera, Susanne Dogan-Surmeier, et al.. On the dual behaviour of water in octanol-rich aqueous n-octanol mixtures: an x-ray scattering and computer simulation study. 2023. ⟨hal-04258497⟩
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