CPOS SEMINAR: "Utilization of ionic interactions in imparting processability and tuning optoelectronic properties of conjugated polymers"

Speaker: MY LINH LE, Graduate Student Researcher, Materials Department, UCSB

Abstract: The limited solubility of conjugated polymers inhibits the capability to process these materials as solvent-lean or solvent-free solutions, preventing the formation of bulk/shaped structures that are needed in many applications. In this talk, I will illustrate how electrostatic interactions can be utilized to formulate a dense conjugated coacervate that contains nearly 50% solid loading. Such coacervate was achieved via the complexation between a conjugated polyelectrolyte (CPE) and an oppositely charged polymeric ionic liquid (PIL). The CPE:PIL coacervate enabled casting of films that are 4 um in thickness, more than an order of magnitude higher than the thickness commonly achieved via conventional solution casting. Subsequent acid doping of the film increased the electrical conductivity of the coacervate to twice that of a doped film of neat CPE. This higher conductivity of the doped coacervate film suggests an enhancement in charge carrier transport along the CPE backbone, in agreement with spectroscopic data, which shows an enhancement in the conjugation length of CPE upon coacervation. In the 2nd part of the talk, I will present our ongoing efforts in elucidating the role of electrostatic interactions in modifying the microstructure and the optoelectronic properties of the CPE:PIL complex. Lastly, I will briefly discuss the potentials of leveraging ionic interactions to compatibilize conjugated polymers with other functional polymers, suggesting exciting pathways for engineering semiconducting materials that have unique properties and are compatible with advanced processing methods.