Therefore, the stronger inter-DMSO solute repulsion hinders the formation of the hydration cells, as the halide ions do because of their larger ionic volumes . The narrower O-H peak in PDPS for the DMSO solutions (Figure ) than that for the THF ((Figure )) indicates the higher structure order at the DMSO hydration interface because of its stronger local electric field. Upon hydration, the presence of the excess protons breaks the pair-number conservation of protons and electron lone pairs of water, which results in the interfacial C-H↔H-O interactions. The H↔H repulsion has the same effect as mechanic compression