Theoretical Investigations of Structure and Properties in Complex Materials

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Self­-assembly is the process by which the components of a disordered system interact to form an organized pattern or emerging structure. In nanotechnology, miniaturization of devices towards the molecular scale can be efficiently achieved by designing the components to self­-assemble and realize the desired complex or device. Working transistor arrays can be fabricated at the nanoscale using layer-by­-layer assembly onto the gate conductor of an organic dielectric and an organic semiconductor, with potential application in the fabrication of smaller, more powerful computer chips, for charge storage and robotics applications. Block copolymers can be built to self­-assemble into functional materials with designed properties. Self­-assembly procedures are forecast as viable methods for fabrication of solar cells, and for in­-vivo diagnosis and treatment. Despite significant recent advances, the current understanding of the self­-assembly process is still mainly empirical and fragmentary. Theoretical research can provide valuable insight into how a multitude of relevant factors interact and impact the self-assembly process. However, methodologies to account for local interactions when considering the system as a whole are still challenging to develop. By and large, current theoretical investigations either interpret experimental data, such as simulations based on empirical initial structures, or neglect local interactions and treat the entire system in a coarse-­grained fashion. The self­-assembled materials problems we are interested in are the result of a hierarchy of scales, and our research program aims, in the long run, to develop multi­-scale approaches to investigate them. This involves a succession of steps: Developing an understanding of the local, molecular level behaviour, then using this understanding in the treatment of the macroscopic system as a whole, and finally providing feedback about the whole to the local calculations. In the short term, we will focus on two phenomena of significant practical importance: (a) Self­-assembly at the solid surface, with an emphasis on complex interactions, nano­-structured surfaces, the efficient sampling of competing minima on the potential energy surface, and nanocomposite assembly. These phenomena have immediate applications for nanoscale devices, biosensors, and the fabrication of functional materials and separation of enantiomeric drugs. (b) Self­-assembled optical and dielectric materials, with an eye towards applications related to charge storage, photovoltaics and tunable dielectric response.