Combining conjugated polymer end group chemistry and metal-ligand bonds to achieve desirable mechanical and electrical properties

Case Western Reserve University, Cleveland OH

Investigators

Abstract

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Dr. Genevieve Sauve of Case Western Reserve University will explore new chemical strategies to improve the stretchability and strength of semiconducting conjugated polymers (CP), necessary for making the next generation of flexible electronic devices, such as foldable displays and wearable technology. To be effective semiconductors, CP must be able to transport charges effectively. However, optimizing stretchability, strength, and charge transport in these polymers is a challenge. This project will address this by introducing special cross-links between the polymer chain ends. These cross-links will be based on dynamic metal-ligand (ML) bonds, which are known to improve the toughness of non-conjugated polymers. This research will transform the field of organic electronics by providing an easy way to obtain tough CP without compromising charge transport. The enhanced toughness will lead to mechanically stable CP films, essential for preventing cracking of flexible devices. This will impact electronic devices that provide energy, information, or light. The improved toughness will also enable new functionalities such as wearability, compact packaging, and portability. This research will train graduate, undergraduate, and high-school students to be the next generation of scientists. Participation in the American Chemical Society local section will further increase impact. Semiconducting CP have the potential to revolutionize the electronic industry by enabling lightweight and flexible electronic devices, but to reach their true potential, their mechanical properties must be tuned for a given application. Many strategies have been reported to obtain stretchable CP for biomedical applications, but the development of CP that are both stretchable and strong remains a challenge. This project’s main hypothesis is that tough CP with good charge transport properties can be obtained using dynamic ML cross-links between the ends of CP. This hypothesis will be tested by synthesizing ligand-terminated CP and investigating the effect of the ML cross-links on structural, mechanical, and electrical properties. CP tensile strength will be tuned with the ML binding strength and loading. Stretchability will be enhanced using a flexible spacer between the CP and ligand. To simultaneously optimize mechanical and electrical properties, a novel scalable method to introduce cross-links in films will be investigated. The fundamental structure-property relationship will be studied using well-defined regioregular poly(3-hexylthiophene) as a model polymer. The strategy will be expanded to high-performance donor-acceptor CP. This approach will also be applied to fabricate mechanically stable organic photovoltaic devices. This project will explore for the first time how using dynamic cross-links at the CP chain ends can tune film properties, thus advancing fundamnetal knowledge of CP end-group chemistry and its effects on properties. It has the potential to transform the field of organic electronics by providing an easy way to increase toughness of CP while retaining desirable electronic properties. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.