CAREER: pi-Conjugated Allene Polymers as Conformationally and Electronically Switchable Chiral Materials

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Chemistry Section, Professor Cedric Schaack of Wake Forest University will develop a new class of smart plastics that can controllably change color and electrical properties. These materials will respond to chemical signals by shifting from transparent to deeply colored, while also switching from electrical insulators to conductors. The key innovation lies in incorporating special building blocks called allenes: these twisted molecular units reorganize their structure when triggered by acids. This shape-shifting ability may enable applications ranging from chemical sensors to semiconductors and medicine. Beyond the research training of students in the laboratory to prepare a workforce for STEM fields, this project will strengthen the general public’s engagement with science through "Sip-posiums". These casual science talks at breweries and coffee shops in the Winston-Salem area will feature researchers who explain their work to community members. Furthermore, a separate initiative will partner local high school students with Wake Forest University students to create public art installations that visually communicate scientific concepts, helping to inspire the next generation of scientists and engineers while building trust between researchers and the communities they serve. Professor Schaack's team will focus on developing a largely unexplored class of conjugated polymers by embedding axially chiral allene units within the pi-conjugated backbone. Specifically, a library of functionalized allene monomers will be prepared and polymerized to establish how substituent effects control helical secondary structure, bandgap, and chiroptical properties. The team will probe how protonation transforms electronically isolated repeat units into conjugated polymers, triggering dramatic color changes and substantial conductivity increases. Furthermore, modified monomers will be designed to suppress racemization in the protonated state, enabling the creation of persistent helical polymers that undergo reversible expansion and contraction, analogous to a molecular spring. The goal is to establish the reversibility of this acid/base switching and probe how the helical structure is recovered after deprotonation. These stimuli-responsive helical polymers will be applied to explore chirality-induced spin selectivity and develop materials for chiral sensing, adaptive optics, and future quantum information technologies. 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.