Document Type



Doctor of Philosophy



First Adviser

Gunton, James D.


One main focus of soft matter physics is to determine the phase diagrams of patchmodel systems to provide insight into clustering both in biological systems andcolloid science. Patch models are designed to model particles that have stronganisotropic and highly directional interactions with their surroundings, and are referredas \Patchy" particles. The best example of a patchy particle can be found innature: protein. Thus, patch models have applications in modeling both proteinproteininteractions along with their self-assembly and those colloids specicallyengineered with directional interactions for photonic crystals, electronic, sensor application,and drug delivery. These applications mostly involve creating a complexcrystal with a specic functionality and require phase diagrams as guidance. In thisthesis we have obtained partial phase diagrams of patch models in two dierent contexts:for a protein case and for colloids . First, we have focused on polyglutamineand obtained a temperature - density phase diagram. Our results showed a clusteringin gas phase. The solubility curve is determined from PLUM model. Clusters inthe gas phase fall into the supersaturation side of solubility curve supporting thatthe two models are in agreement. In the second case, we have investigated polydispersityeects on the phase behavior of binary mixtures. In addition to clusteringin gas phase as in the polyglutamine case, simulation results showed that the widthof gas-liquid coexistence increases with increasing polydispersity. Visualization andstructure analysis showed that small particles decorate patches on large particlesand create bridges between them. We note that manipulation of polydispersity maylead to creation of novel crystals with specic functionality and we discussed someideas for future studies.

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