Interaction of sodium and potassium ions with PEO-PPO copolymer investigated by FTIR, Raman and NMR

Many papers have reported that salt ions can exert a great influence on the self-assembly behavior of PEO-PPO copolymers in the aqueous solution. Whereas the mechanism through which salt ions influence the self-assembly behavior of PEO-PPO copolymers is unclear and the dispute is mainly focused on whether the salt ions have a direct interaction with PEO-PPO copolymers. In this paper, the interaction of sodium and potassium ions with PEO-PPO copolymer was investigated by using FTIR, Raman and 23Na NMR spectroscopy. Experimental results reveal that direct interactions between salt cations and PEO-PPO macromolecular chains indeed occur in appropriate conditions. The present work highlights the role of cations in the self-assembly process of PEO-PPO copolymer.