Functional Nanotubes from Self-Assembling Bis-Urea Macrocycles

With the support of the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry, Professor Linda S. Shimizu of the University of South Carolina will develop methods to control the stacking of tiny donut-shaped molecules into straw-like nanotubular structures. Nanotubes are approximately 100,000 times smaller than the width of a strand of hair.

Shimizu's work is inspired by biological systems that can form well-defined, low-energy assemblies as well as higher-energy structures. The Shimizu group will study how these small macrocycles assemble and use different strategies to control their growth, size, and stability. The aim is to develop precise control over the nanotubes, which can then be used to study how size impacts chemical processes, especially those triggered by light.

This work could potentially provide innovative tools and unlock new applications in electronic and smart materials. This project also emphasizes education and mentorship at all academic levels. It promotes public interest in science through a chemistry demonstration program that visits South Carolina K-12 classrooms, supports a summer tutorial series for graduate students, and offers hands-on research opportunities for students from high school to Ph.D. candidates.

These efforts will help recruit a skilled workforce and prepare future scientists to address emerging challenges in science and technology.

Professor Linda Shimizu's team will study the pathway complexity in the supramolecular assembly of urea macrocycles. Specifically, her group will target three innovative objectives: 1. They will examine the mechanisms of supramolecular polymerization in different solvents to regulate the size, dispersity, and dynamics of the assemblies of bis-urea macrocycles in solution. 2.

They will develop templates to stabilize aggregates of specific sizes and investigate methods to maintain kinetically trapped and meta-stable states. Seeded living polymerization will be employed to produce nanotubes with precise lengths. 3. Professor Shimizu will investigate how nanotube length impacts chemical processes, including photoinduced radical formation, molecular guest exchange, and reactions within these nanotubes.

This work will address fundamental questions about energetic landscapes in supramolecular assembly. Establishing control over meta-stable states and tuning assembly-disassembly dynamics will enable transitions between supramolecular polymers, nanotubular host-guest complexes, and monomers. Achieving this precision will advance our knowledge of assembly dynamics, provide innovative tools to study processes at the nanoscale, and unlock new applications in electronic and smart materials.

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.