Collaborative Research: Syntheses and Solution-Phase Properties of Rigid Conjugated Ladder Polymer Chains

University Of Southern Mississippi, Hattiesburg MS

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Lei Fang of Texas A&M University and Xiaodan Gu of the University of Southern Mississippi are preparing and investigating solution-phase properties of rigid-rod conjugated ladder polymers. Conjugated polymers are a unique class of polymers with semiconducting properties resembling that of the chemical element silicon, unlike commonly used insulating polymers. They are extensively used in light emitting devices (LEDs), flexible electronics, sensors, biomedical imaging, and other applications that utilize the optoelectronic property of these polymeric materials. Conjugated ladder polymers, on the other hand, are a type of double stranded polymers with the bond connectivity resembling a ladder, so that the repeating units along the polymer main chain are all fused in the form of conjugated rings. Such a unique constitution imparts a conjugated ladder polymer with distinct polymer physics properties in comparison with conventional single stranded polymers. The studies associated with this project will focus on polymer-solvent interactions, single chain conformation, as well as chain diffusion dynamics in a series of conjugated ladder polymers that are soluble in common organic solvents. Additionally, synthetic methodologies will be developed to further gain control over polymer’s chain lengths and distribution of molar masses. This research has the potential to impact other fundamental scientific disciplines, including synthetic chemistry, polymer physics for semi-rigid polymers, biomacromolecules, polymer processing, and organic electronics. The education plan will focus on revitalizing and modernizing undergraduate chemistry curricula by implementing student-performed “Nobel Prize Reaction” experiments in undergraduate organic laboratory courses at both institutions. Professor Gu will additionally conduct extensive outreach activities among historically regional black colleges and universities in Mississippi via site visits and workshops. This research will aim to develop new fundamental understandings of the solution-phase properties of rigid-rod conjugated ladder polymers. The specific objectives will focus on (1) design and synthesis of defect-free conjugated ladder polymers that can be truly dissolved in organic solvents without aggregation, (2) understanding and quantification of polymer-solvent interaction and chain conformation of these model conjugated ladder polymers in solution, (3) development of controlled chain-growth polymerization methods based on catalyst transfer polymerization to synthesize conjugated ladder polymers featuring precisely tailored molar masses and narrow dispersity, and (4) establishing quantitative correlation between molar masses of conjugated ladder polymers with chain flexibility and diffusion dynamics. The combined collaborative efforts have the potential to advance fundamental knowledge of the synthetic chemistry and solution-phase polymer physics of rigid polymers and enable rational design principles for various applications of conjugated ladder polymers. These applications include organic field effect transistors, organic electrochemical transistors, actuators, electrochromic devices, photo detectors, and other optoelectronic devices. 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.