Macroion Complexation and Conformation of Neutral Polymer in Solution

Unusual electric charging and conformational behavior of neutral polymers, such as poly (ethylene oxide) (PEO), in polar solvents have been reported in the past. To further explore the charging mechanism, we compare the effect of simple small ions and multivalent macroions on the electrical potential and conformation of PEO in solutions of varied polarity. Measured electrical potential indicates that multivalent macroions can effectively bind with PEO to cause significant increase of the effective charges of a PEO chain, which is accompanied with the collapse of PEO chain in polar solvents as determined by single-molecule laser spectroscopy. In contrast, little change of PEO electrical potential and conformation is observed with lithium salt added solutions. More interestingly, as further increasing macroion concentration, unconventional liquid-liquid separating coacervate complexation is observed with macroion-added PEO solution, leading to a facile process of PEO-based ionomers.