Premium
Local organization of water and its effect on the structural heterogeneities in room‐temperature ionic liquid/H 2 O mixtures
Author(s) -
Fazio B.,
Triolo A.,
Di Marco G.
Publication year - 2008
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1825
Subject(s) - ionic liquid , raman spectroscopy , chemistry , alkyl , polar , molecule , fourier transform infrared spectroscopy , ionic bonding , hydrogen bond , mole fraction , chemical physics , tetrafluoroborate , intermolecular force , micelle , saturation (graph theory) , ion , chemical engineering , organic chemistry , aqueous solution , optics , physics , astronomy , engineering , catalysis , mathematics , combinatorics
Abstract Fourier‐transform infrared and Raman spectroscopies have been used to investigate the role played by water on the structural organization of 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate and H 2 O mixtures, over a wide composition range at room temperature. Our measurements provide clear experimental evidence of the prompt association between ‘free’ water molecules and anions at very small water contents. Moreover, in the case of higher water contents, we obtain indications of the local aggregation of water molecules in the network. Such an aggregation is found to occur even before the saturation of all the anions that are available for H‐bonding. We propose that the water clusters favour the organization of ionic liquid in the polar network, where they are embedded, and the aggregation of hydrophobic alkyl tails in a micelle‐like structure. When mixtures with water molar fraction exceeding 0.7 are considered, this local organization starts to weaken owing to the gradual break up of the ion‐pair interactions. Copyright © 2007 John Wiley & Sons, Ltd.