Near-edge x-ray absorption fine structure (NEXAFS) spectra, at the potassium K edge, were obtained for a potassium salt in the following systems : (i) a propylene carbonate (PC) solution, (ii) a modified carbonate (MC3) solution, and (iii) poly(ethylene oxide) (PEO)-potassium salt complexes with either PC or MC3 as a plasticizer. MC3 is a new plasticizer developed in our laboratory which is similar to PC except that, instead of a methyl group, there are three ethylene oxide units attached to the 4-position. By examining the NEXAFS of various potassium salt reference systems, it was found that the white line splitting in the near-edge region was correlated with ion-pairing. The degree of white line splitting was used to study ion-pair dissociation effects of PC and MC3 qualitatively. When used as a solvent, MC3 has a stronger ion-pair dissociation effect compared to PC. When used as a plasticizer in a PEO-potassium salt complex, the enhancement effect on ion-pair dissociation of MC3 is superior to PC. These results were corroborated by Raman spectroscopy which showed that MC3 has a stronger ion-pair dissociation effect than PC.