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.

Using a combination of structural and mechanical characterization, we examine the effect of fibrinogen oxidation on the formation of fibrin clots. We find that treatment with hypochlorous acid preferentially oxidizes specific methionine residues on the α, β, and γ chains of fibrinogen. Oxidation is associated with the formation of a dense network of thin fibers after activation by thrombin. Additionally, both the linear and nonlinear mechanical properties of oxidized fibrin gels are found to be altered with oxidation. Finally, the structural modifications induced by oxidation are associated with delayed fibrin lysis via plasminogen and tissue plasminogen activator. Based on these results, we speculate that methionine oxidation of specific residues may be related to hindered lateral aggregation of protofibrils in fibrin gels.

No abstract

The structural, mechanical and electrical properties of poly(3-hexylthiophene) (P3HT) organogels have been probed during the sol-gel transition through combined rheology, AC dielectric spectroscopy and small angle neutron scattering (SANS). SANS shows that structural features of P3HT gels, which are crucial for the optimization of organic photovoltaic devices, evolve throughout the gelation process. In situ structure-property analyses also demonstrate that there are very different mechanisms for the formation and dissolution of fibers and networks prepared from these polymeric semiconductors. It is determined that P3HT gels form conductive pathways that are maintained even after up to 50% of the fibers re-dissolve upon heating. P3HT organogels formed in different aromatic solvents also show differences of more than two orders of magnitude in conductivity despite having similar nanoscale fiber structures. These results demonstrate the importance of controlling the self-assembled morphology of fiber networks for maintaining optimal electronic properties. This work also highlights the potential for using organogels as flexible platforms for designing efficient organic photovoltaic devices.

A structure–property–process relation is established for a diblock bottlebrush copolymer solution, through a combination of rheo-neutron scattering, imaging, and rheological measurements.