(608a) Experiments and Simulations On Controlling the Assembly of Block Copolymers and Polymer Blends within Nanofibers

Advances in materials synthesis and fabrication techniques allow an unprecedented control over the creation of novel building blocks such as polymers and particles. The first principle for effective utilization of these building blocks is to create techniques to control their assembly at length scales ranging from nanoscale to macroscopic scale. We study the development of hierarchically structured materials using nanofibers of self assembling block copolymers (with and without nanoparticles) and polymer blends. Owing to the short time-scale of the nanofiber fabrication (electrospinning) process, the driving factors for the final assembly of materials within nanofibers may be primarily kinetic. For the case of block copolymers, a novel methodology was utilized to overcome such limitation, thereby forming thermodynamically stable structures within nanofibers. In addition, the effect of cylindrical confinement on block copolymer self assembly was studied. In the second half of the talk, we will present the advantage of such short electrospinning time-scale with the formation of kinetically controlled assembly, which may be desired in certain situations, for example to prevent nanoparticle aggregation or to form a homogenous blend of immiscible polymers. Molecular dynamics study will be presented to understand the effect of interplay of time scale of polymer relaxation and time scale of deformation (an important constituent of nanofiber fabrication process) on the final assembly.