Program Highlights

Nucleation Control of Conjugated Polymers

Ramin Hosseinabad and Lucia Fernandez-Ballester
 Nebraska MRSEC

Rafael Verduzco
Rice University

Conjugated polymers are large organic macromolecules that have alternating single and double bonds along the backbone, which confer remarkable optical and electronic properties. These materials are attractive for applications in solar cells, field-effect transistors, and light-emitting diodes because of their low cost and easy processability. Regulating the crystallization of conjugated polymers is key to optimizing their properties. Nucleation is the first step in the formation of crystallites and its control allows rational design of materials with desired morphology and properties. However, the basic mechanism of nucleation and crystallization of conjugated polymers remains obscure and must therefore be thoroughly explored.

Nebraska MRSEC researchers in collaboration with Rice University are exploring the melt crystallization and self-seeding behavior of Poly(3-Hexylthiophene) (P3HT) – a conjugated polymer with significant charge-carrier mobility. Results show that populations of P3HT crystallites with different stabilities can be obtained by using well-defined crystallization temperatures, and that self-seeding thermal protocols can effectively be used to increase the number of nuclei that emerge in the melt under fixed conditions—thus increasing kinetics of crystallization and influencing the final morphology.  Initial findings indicate that imposition of a well-defined flow can impact the location and geometry of nucleation. This research provides new insights on the relationship between processing conditions, nucleation and crystallization, and morphology, leading towards rational design and optimal control of properties of conjugated polymers.

These programs are supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant DMR-1420645.

Oriented crystallization of conjugated polymer P3HT.  Flow direction is indicated by the arrow.