Polymeric Surfactant P84/Polyoxometalate α-PW12O403−—A Model System to Investigate the Interplay between Chaotropic and Hydrophobic Effects

Low charge density nanometric ions were recently shown to bind strongly neutral hydrated matter in aqueous solution. This phenomenon, called the (super-)chaotropic effect, arises from partial dehydration of both nano-ion and solute, leading a significant gain enthalpy. Here, we investigate chaotropic effect polyoxometalate α-PW12O403− on triblock copolymer P84: (EO)19(PO)43(EO)19 with (EO)19 polyethoxylated (PO)43 polypropoxylated chains. The combination phase diagrams, spectroscopic (nuclear magnetic resonance) scattering (small angle neutron/X-ray scattering) techniques revealed that: (i) below micellization temperature P84, PW12O403− exclusively binds propylene oxide moiety P84 unimers; (ii) above temperature, mostly adsorbs ethylene micellar corona. preferential binding PPO chain over PEO chains suggests that is driven by reinforced hydrophobic effect. At higher temperatures, leads displacement study deepens our understanding subtle interplay between effects complex salt-organic solutions.