EAGER: Confined Self Assembly of Fully Conjugated Rod-Rod Diblock Copolymers in Nanofibers

Drexel University, Philadelphia PA

Investigators

Abstract

This EArly-concept Grant for Exploratory Research (EAGER) provides funding to study the confined self assembly in nanofibers of fully conjugated rod-rod diblock copolymers. Nanofibers will be fabricated via a process called electrospinning that uses a strong electric field to elongate and thin a polymer solution jet enabling the formation of fibers with near nanoscale diameters (50-500 nm). Rod-rod block copolymers combine the physics of liquid crystalline ordering of rod-like polymers (at the length scale of 1-10 nm) and microphase-separation of coil-coil block copolymers (at length scale of 10-100 nm) with the potential of forming hierarchically ordered materials. The effects of solvent evaporation rate and extensional deformation (during electrospinning) on self assembly structures at both length scales will be studied. The assembly in nanofibers will be characterized using transmission electron microscopy as well as small and wide angle x-ray scattering. Similar studies on self assembly in solution-cast films will be conducted as reference. If successful, this work will provide a novel active material for the design of high efficiency organic solar cells. In particular, self assembly of conjugated polymeric blocks (with appropriate electronic properties) will provide periodic interfaces of electron donor and electron acceptor materials in the light absorbing active layer of solar cells. This will ensure timely disassociation of bound electron and hole (created on photo-excitation), necessary to produce photocurrent efficiently. Confining fully conjugated rod-rod diblock copolymers within nanofibers will have two benefits. First, it will provide the opportunity to develop a new class of materials, namely, wearable fabrics of organic semiconductors. Secondly, the strong extensional deformation and fast solvent evaporation during electrospinning combined with the physical cylindrical confinement in nanofibers will provide access to novel self assembled structures that may not be possible in equilibrium systems or films.