Aggregation behavior of Pluronic copolymer in the presence of surfactant: Mesoscopic simulation

Abstract The mesoscopic dynamic (MesoDyn) simulation method was used to simulate the aggregation behavior of Pluronic copolymer EO 13 PO 30 EO 13 (L64) and EO 26 PO 40 EO 26 (P85) solutions in the presence of SDS. With a simple copolymer model, the morphology and kinetic formation process of copolymer aggregate were obtained. Some factors influencing the aggregation behavior of the copolymer were discussed, such as concentration, temperature and EO/PO ratio. Simulation results show that the presence of SDS induces the L64 spherical micelles formed at much lower L64 concentration comparing with the system without SDS. At the same L64 concentration, an increase in SDS concentration results in an increase in the size of L64 micelles and decrease in the number of micelles. The morphology of L64 aggregates undergoes transitions from spherical micelles → rod-like micelles → bicontinuous phases with L64 concentration increasing. The kinetic process of micelles formation can be divided into three stages and the first diffusion stage will disappear when L64 concentration is above 30%. Temperature investigation indicates that the formation of aggregates is an exothermic process, and it becomes more difficult and the formation rate decreases with temperature increasing. The size of micelles formed by P85 with higher EO/PO ratio value is larger than that formed by L64 micelles. Further more, P85 is more difficult to form micelles comparing with L64. This is caused by the more hydrophilic EO groups in P85, leading to the fact that there are more water molecules amongst P85 micelles.