(180bk) Structure and Property Development of Poly(3-hexylthiophene) Organogels Probed with Combined Rheology, Conductivity and Small Angle Neutron Scattering

An electrically percolated network structure of conjugated polymers is critical to the development of organic electronic devices. In this talk we discuss the potential to rationally design an interconnected network of conjugated polymers using the isothermal gelation of poly(3-hexylthiophene) (P3HT) as a model system. Complementary small angle neutron scattering (SANS), AC dielectric spectroscopy and rheology are utilized simultaneously to study the self-assembly of poly(3-hexylthiophene) (P3HT). This poster will shows that nanoscopic structural features of fibrillar P3HT organogels, which are crucial for the optimization of organic photovoltaic devices, evolve throughout the gelation process. By performing cooling (i.e. gelation) and heating (i.e. dissolution) cycles we find substantial structure-property hysteresis that suggests the formation and dissolution mechanisms are drastically different, both of which are proposed in this poster. We also find that P3HT organogels formed in different solvents show differences of more than two orders of magnitude in conductivity. The similarity in nanoscale structural features between these gels suggests that the mesoscale network structure plays a critical role in the determination of charge transport efficiency. In fact, the degree of fiber branching can be directly correlated to increases in charge transport properties. This poster demonstrates the importance of controlling self-assembly towards improving charge transport properties and demonstrates the potential to rationally design specific network structures using organogels as a generally applicable platform.