Ladder Oligomers and Polymers: Self-Assemblies and Opto-Electric Properties.

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Luping Yu of the University of Chicago is developing novel luminescent building blocks for the construction of conjugated ladder polymers. Conjugated polymers are a unique class of non-metallic polymers with semiconducting properties resembling that of the chemical element silicon.

They are extensively used in solar cells, LED screens and other applications that utilize the conversion of electricity to light. Ladder polymers, on the other hand, are a type of double stranded polymers with the connectivity of a ladder. They are prepared by interconnecting repeating units along the main polymer chain by four chemical bonds, instead of the two bonds typically seen in conventional plastics.

In this research, structural features of luminescent building blocks will first be optimized using a combination of synthetic and computational techniques. Ladder polymers will then be constructed, and their physical properties systematically studied using a variety of analytical techniques. A strong emphasis will be placed on development of materials that can more efficiently interconvert electricity and light.

This work has the potential to lead to expansion of knowledge in organic semiconducting molecules, syntheses and polymers. Materials prepared in this work are also expected to impact development of more efficient digital displays and optical interconnectors. Students involved in this work will receive a broad training in synthetic polymer chemistry, photophysical characterization techniques and device fabrications.

The outreach activities will focus on The Neighborhood School Program, which is one of the University of Chicago’s longest-standing community programs. In this program, students will play roles as tutors, teaching assistants, pre-school specialists, and technology coordinators with 50 sites on Chicago’s south side and with 4,000 local students each year.

Strong emphasis will be placed on activities that encourage and motivate students from underrepresented groups to pursue education and careers in STEM fields.

This research will focus on rational development of novel synthetic approaches towards ladder oligomers and polymers, with a strong focus on optimization of charge transfer and light emission. Monomers will first be synthesized, and their design guided using DFT calculations . Synthetic chemistry will involve two different approaches.

The first two-step approach will focus on cyclization in which the Heck coupling reaction is used to obtain the ladder structures. The second single-step approach will consist of “ladderization” to simultaneously form the fused ring structures and will be accomplished by utilizing Friedlander condensation reaction. Polymerization of these monomers and oligomers will yield conjugated polymers with well-defined structures and optimized properties.

Detailed characterization of the prepared polymers will also be performed using a variety of analytical techniques and will provide the necessary information for the structure-property correlation and shade light into the aggregation state of these luminescent polymers. The foldable semi-ladder conjugated polymers that will be synthesized as a result of this work can potentially address the big challenge confronted in the OLET (organic light-emitting transistors), by facilitating the fast charge transport while avoiding tight intermolecular H-aggregation that quenches luminescence.

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.