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will be held the

DISSERTATION PROPOSAL DEFENSE

for

Daria Bukharina

"Dynamic Chirality of Tailored One-Dimensional Polysaccharide Nanocrystals"

Committee Members:

Prof. Vladimir Tsukruk, Advisor, MSE

Prof. Valeria Milam, MSE

Prof. Robert J. Moon, MSE

Prof. Paul Russo, MSE

Michael McConney, Ph.D., AFRL

Abstract:

Compounds of biological origin have the ability to self-organize into complex structures and function as systems possessing hierarchical and long-range order. Yet, there are numerous challenges arising when trying to use nature for inspiration- the mechanisms established by nature are difficult to determine, imitate and/or adjust, let alone the fact that nature builds its structures over many years- very time-consuming processes. Therefore, the variety of bioderived materials application and structures, as well as their functions are being limited. The applicational potential of polysaccharides is vast as they can be utilized not only as bioderived materials- using naturally occurring biosystems or its chemical or genetic modifications but also as biotemplates- biological template for guiding photos active structures’ self-assembly.

This work will focus on fundamental understanding of the mechanisms of 1D polysaccharides assembly-cellulose nanocrystals, and their further chemical modification in order to control their chiral structure for various future applications. The understanding of how one-dimensional nanocrystals organization results in the twisted structure is a pivotal step in order to tailor and control this organization. Manipulation of the hierarchical organization of the materials requires precise control, down to molecular level, of the assembling components. As it will be further described, it is still of debate to date, what is the source of chiral interactions between cellulose nanocrystals. The work proposed seeks to in-situ study the organization of CNCs via AFM, precisely control the assembly via selective interactions achieved by specific surface modifications of the nanocrystals and implement dynamic control of the chirality in order to pave way for the new generation of responsive materials for photonics application. Therefore, the first task of the proposed research will elevate the fundamental study of the origins of chirality of individual CNCs by exploring how single nanocrystals with different dimensions and surface chemistry form twisted aggregates. We believe that being able to control the nanocrystals’ behavior at the very initial assembly stage will allow to control the resulting structure and therefore, emerging from it chirality.  Then, in the second task, we will focus on chemical modification of the nanocrystals’ surface with DNA-oligonucleotides seeking to control inter-particle interactions. DNA-sequences will direct highly selective interactions/assembly and by exploiting the knowledge gained in the first task, we hope it will become possible to control the local chirality. Finally, in the last task, we will construct hierarchical structures resulting from the assembly of modified CNCs.

This work will inspire implementation of biopolymers nanocrystals for materials application by demonstrating how their properties can be optimized by changing their functionality and tailoring structure. The fundamental knowledge expected to be discovered in this work will be further transferred to other 1D nanocrystals, such as chitin, for example, due to their similar to the CNCs nature.