Functional nanotubes from self-assembling bis-urea macrocycles

University Of South Carolina At Columbia, Columbia SC

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Linda Shimizu of the University of South Carolina will make precise nanoscale assemblies of donut shaped building blocks known as bis-urea macrocycles, which stack to make straw like structures or nanotubes. Different strategies will be tested to control the formation of nanotubular structures of between 3 and 150 macrocyclic monomers. Precise control of assemblies in this size has the potential to open new opportunities to understand chemical, light driven and electron transfer processes that occur over these length scales. The advanced knowledge acquired may have important implications in photochemistry, molecular electronics, photooxidations, and photodynamic therapy. The educational activities include engaging graduate students, undergraduates, and high school students in interdisciplinary research to prepare them to answer challenging scientific questions encountered in the twenty-first century workforce. The program will also continue an outreach program to local K-12 schools to highlight careers in science and to showcase the scientific method by engaging students in chemistry demonstrations. Professor Linda Shimizu’s team will focus on self-limiting growth of urea macrocycles to afford a series of nano assemblies with low length dispersity. Specifically, different strategies, include frustrating their growth by attaching large groups on the exterior of the macrocycles, using chain stopping monomers to halt the growth of the nanotubes, and adding templates to stabilize stacks of specific size, will be employed to precisely guide the formation of nanotubular structures of between three and 150 macrocyclic monomers. The goal is to create a series of ‘molecular rulers’ between 1 to 50 nanometers in length to bridge the gap between single molecules and supramolecular polymers. The new nanometer molecular ‘rulers’ will be applied to probe how nano assembly length, morphology, and dynamics impact photoinduced electron transfer and the formation of reactive oxygen species. In addition, prior experimental results in crystals will be compiled as an initial data set to derive physical models using machine learning. The goal is to identify key parameters that lead to radical cation/anion formation upon irradiation of organized triphenylamine macrocycles and related systems. 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.