Self-consistent-field analysis of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) surfactants: Micellar structure, critical micellization concentration, critical micellization temperature, and cloud point

The self-assembly of a series of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) surfactants into spherical micelles has been analyzed by a numerical self-consistent-field model. A united atom description is used in which three segment types are identified, that is, CH2, CH3, and O groups. The aqueous solution is modeled as water dimers. A thorough parameter study has been performed to investigate the influence of the six Flory-Huggins parameters on the micellization behavior. A thorough thermodynamic analysis leads to the identification of the critical micellization concentration, the critical micellization temperature (CMT), and the cloud point temperature (CPT). The temperature dependence of the system is linked to the variation of the Flory-Huggins parameter for the O-water interactions. With this temperature dependence, good agreement is found between experimental results and theoretical predictions for the CMT and CPT. Calculated results for the structural characteristics of different PEO-PPO-PEO aggregates, such as the aggregation number, the radial density distributions, the core radius, and the headgroup areas, are also discussed.