(Georgia Institute of Technology, 2022-05-03)
Bullard, Krista K.
The use of cellulose nanocrystals (CNCs) in material science as nontoxic, inexpensive, and biorenewable reinforcing agents is a rapidly growing field. These rigid, needle-shaped nanomaterials have promising mechanical properties that can improve polymer composites if properly dispersed.1-3 Due to the hydrophilic nature of the CNC surface chemistry, they are prone to agglomeration through intermolecular hydrogen bonding, therefore preventing the even dispersion needed for reinforcement in commonplace hydrophobic polymeric matrices. The long-term goal of this project is to modify the CNC surface chemistry with the addition of cyclodextrin to impart supramolecular interactions which will physically bind polymers to the surface without forming a chemical bond. Cyclodextrins are inexpensive, cyclic oligomers of amylose that take on the shape of a conical cylinder and readily form host-guest complexes with small molecules and thread along the backbone of polymers.4-7 The first step of the project was to efficiently attach cyclodextrin motifs to the surface the CNCs which required the invention a new synthetic modification route. Then a cleavable linker system was devised and synthesized for attachment of cyclodextrins to the CNC surface that allowed for subsequent removal with an external stimulus. Finally, polymers were threaded on the particles, and the cleavable linker system was used to study the rotaxanes that were cleaved from the CNC.