Résumé
Beyond electrostatic, the interaction of ions with their close environment depends also on their hydration shell and the water dynamic in this environment. Non-negligible water mediated effects can indeed influence many physical chemistry processes such as cloud point, protein salting-in or out, bubble coalescence, the topology of bilayers...and polymer self-assemblies. This type of interaction is qualified of "ion specific". During the last 10 years, our team have shown that these effects can be exalted with nanometer-sized ions. These latter can indeed bind to electrically neutral matter in solution although these ions are highly charged but always characterized by low charge density. This nano-ion specific effect, called also superchaotropic effect in referring to an extension of the “Hofmeister series”, arises from the partial dehydration of both the nano-ion and the solute or surface in interaction that lead to a significant gain in enthalpy of the combined system.[1] The characterization of this effect is strongly supported by scattering experiments, neutron and x-ray, always in a very complementary manner (to build phase diagram) and by other spectral techniques that allow to precisely defined the predominant chemical functions in interaction with the nano-ions that can vary depending on their supramolecular environment. In this presentation we will describe two examples of Keggin-type polyoxometalate nano-ions in interaction with either Poly(N-isopropylacrylamide) PNIPAM polymers [2]- probably the most studied among thermo- and stimuli-responsive “smart” polymers or with the triblock copolymer P84 exhibiting an ABA architecture (A: ethylene oxide, B: propylene oxide).[3]