Effects of Sodium Benzoate and Sodium Chloride on the Aggregation Behaviors of PEO‐PPO‐ph‐PPO‐PEO and PPO‐PEO‐ph‐PEO‐PPO at the Air/Water Interface

AbstractThe effect of sodium benzoate and sodium chloride on the aggregation behavior of PEO‐PPO‐ph‐PPO‐PEO (BPE) and PPO‐PEO‐ph‐PEO‐PPO (BEP) polyethers at the air/water interface was investigated by measuring the equilibrium surface tension, surface dilational viscoelasticity, and surface tension relaxation. The measurements of surface tension showed that sodium benzoate has a better effect on decreasing the surface tension of BPE and BEP solutions than NaCl, especially when the polyether concentrations are low. According to dilational viscoelasticity measurements, the concentration of BPE required for the maximum dilational modulus is lower than that of BEP, indicating that BPE more easily forms a compact adsorbed layer. The dilational modulus values of BPE solutions in the presence of sodium benzoate and NaCl first increase and then decrease after passing through a maximum, and then they increase again with increasing electrolyte concentration. On the other hand, the dilational modulus values of BEP solutions in the presence of sodium benzoate and NaCl first increase to a maximum and then decrease with increasing electrolyte concentration. The surface tension relaxation results are consistent with those of dilational viscoelasticity. The different effects of sodium benzoate and NaCl on the polyether aggregation behaviors are caused by the strong hydrophobic and π‐π interactions between polyethers and sodium benzoate. This work has a great importance for the application and development of polyethers.