Potential enthalpic energy of water in oils exploited to control supramolecular structure

Water directs the self-assembly of both natural 1,2 and synthetic 3-9 molecules to form precise yet dynamic structures. Nevertheless, our molecular understanding of the role of water in such systems is incomplete, which represents a fundamental constraint in the development of supramolecular materials for use in biomaterials, nanoelectronics and catalysis 10 . In particular, despite the widespread use of alkanes as solvents in supramolecular chemistry 11,12, the role of water in the formation of aggregates in oils is not clear, probably because water is only sparingly miscible in these solvents - typical alkanes contain less than 0.01 per cent water by weight at room temperature 13 . A notable and unused feature of this water is that it is essentially monomeric 14 . It has been determined previously 15 that the free energy cost of forming a cavity in alkanes that is large enough for a water molecule is only just compensated by its interaction with the interior of the cavity; this cost is therefore too high to accommodate clusters of water. As such, water molecules in alkanes possess potential enthalpic energy in the form of unrealized hydrogen bonds. Here we report that this energy is a thermodynamic driving force for water molecules to interact with co-dissolved hydrogen-bond-based aggregates in oils. By using a combination of spectroscopic, calorimetric, light-scattering and theoretical techniques, we demonstrate that this interaction can be exploited to modulate the structure of one-dimensional supramolecular polymers

The social dimensions of a river’s environmental quality assessment

International audienceIntegrated water resources management, promoted in developed countries, obliges to integrate social aspects with hydrological and ecological dimensions when assessing river quality. To better understand these social aspects, we propose a mixed-method to study public perceptions of an impounded river. Since the 1930s, the management of the Ain river (France) has been challenged by conflicts about the river's quality. We surveyed (using interviews and mental maps) various stakeholders along the river. The results based on textual and content analysis show variations in the public's perceptions according to the residence area, practices, and the degree of emotional attachment to the river. The assessment of environmental quality needs to take into account different types of knowledge, sometimes conflicting, that reveal and shape the variety of waterscapes which compose the Ain River. The social dimensions highlight integrated water management's inherent complexity by considering the river basin as a place to live and by involving multiple stakeholders