Electrical, Mechanical, and Structural Characterization of Self-Assembly in Poly(3-hexylthiophene) Organogel Networks

An electrically percolated network structure of conjugated polymers is critical to the development of organic electronics. Herein, we investigate the potential to rationally design an interconnected network of conjugated polymers using the gelation of poly(3-hexylthiophene) (P3HT) as a model system. The three-dimensional network structure is evaluated through small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS). The analytical models used for data fitting provide relevant structural parameters over multiple length scales. Structural parameters include the fiber cross section (height and width), the specific surface area, and the network density (i.e., fractal dimension). Simultaneous rheological and conductivity measurements also provide insight into the development of the mechanical and electrical properties of organogels and allow us to propose a detailed gelation mechanism for P3HT. The fiber shape is found to be relatively independent of the solvent type, but P3HT organogels show distinct differences in conductivity, which can be directly linked to differences in the branching network structures. These results suggest that the gelation of fiber-forming conjugated polymers offers an excellent platform for designing electrically percolated networks that can be used for structural optimization in organic electronic devices.