Robert W. Vaughan Lecture in Chemical Engineering

The ability to contol nanoscale structure in functional systems such as semiconducting polymers for energy generation or biologically inspired polymers would enable new applications, but control over self-assembly in these systems presents new challenges. In particular, the thermodynamics of self-assembly in these systems is significantly altered from that of well-characterized classical block copolymers due to differences in chain topology and the liquid crystalline and/or crystalline interactions. Further, careful control over the organic/inorganic interface appears to play a vital role in thermoelectric effects. We have studied both the fundamental self-assembly of molecules of unusual shapes as well as applied these principles to conjugated rod-like blocks for photovoltaic and thermoelectric devices and to bioinspired polymers with tunable molecular conformations. In both cases, we find that careful molecular design to moderate molecular interactions is essential in creating controllable systems. In particular, both sidechain substitution and sequence control can be used to control melting temperatures and liquid crystalline interactions in order to create a processing window in which self-assembly can occur. The role of intermolecular interactions as well as mechanisms for pattern control will also be discussed.