| Ionic systems can be found in a wide range of applications, from food and consumer products to biological molecules such as proteins and DNA. A good understanding of a system's phase behavior and the factors that affect it is important as it provides an effective way to control the properties of the system. In this thesis, we investigate the phase behavior of several ionic systems using grand canonical Monte Carlo simulation methods.; First, we investigated systems of asymmetric electrolytes to understand the effects of charge and size asymmetries on electrolyte phase behavior. Highly charge-asymmetric electrolytes can be used to model colloids, charged micelles, globular proteins, etc. Previous simulation studies were only able to study small charge asymmetries up to 3:1. We developed more efficient simulation methods that enabled us to extend the study to higher charge asymmetries up to 10:1. We then considered neutral polyampholytes, or polymer chains containing equal number of positive and negative charges, and investigated the effects of chain length and charge distribution on the phase behavior. We found that diblock polyampholytes phase separate much more easily than random polyampholytes, while end-charged polyampholytes undergo gelation and phase separation. Finally, we developed a simple lattice model for ionic surfactants and studied the micellization properties of sodium dodecyl sulfate, an anionic surfactant. The model was able to capture the micellization process, and we obtained predictions for the critical micelle concentration, cluster size distribution, degree of counterion binding, and their dependence on temperature and surfactant concentration. While there are discrepancies between the absolute numerical values, the model predicts the correct trends and order of magnitude for all quantities when compared to experimental values. |
