Study of structural changes of water confined in Brij-30 reverse micelles: Revealing influence of ionic additives

Abstract The microenvironment of water droplets of nonionic polyoxyethylene (4) lauryl ether reverse micelles was investigated using infrared, ultraviolet-visible and nuclear magnetic resonance spectroscopy, also by dynamic light scattering. The different influence of kosmotropic and chaotropic ionic additives on the microstructure of reverse micelles was revealed. The values of chemical shift in the presence of structure-breaking perchlorate ions are higher than their values in case of structure-making acetate ions according to measurements by proton magnetic resonance spectroscopy. Deconvolution of the O H stretching vibrational absorption spectra in the region of 3000–3800 cm −1 into three subpeaks with a Monte Carlo method showed that perchlorate ions promote an increasing of free water fraction in the water pools of the reverse micelles, whereas acetate ions support formation of bound water. Influence of salt additives results in slight different sizes of water droplets, measured by dynamic light scattering method. Different influence of kosmotropic and chaotropic anions on binding constant K b of optical probe to ethylene oxide groups was revealed.