THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Thursday, May 3, 2018

10:00 AM
in Love 295

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Ke Qiu

"Cellulose Nanocrystal/Polymer Nanocomposites: Processing Strategies, Structure Variation and Explored Applications"

Committee Members:

Prof. Karl Jacob, Advisor, MSE

Prof. Hamid Garmestani, MSE

Prof. Donggang Yao, MSE

Prof. Preet Singh, MSE

Prof. Kyriaki Kalaitzidou, ME

Abstract:

Interest in the most ubiquitous and abundant organic compound—cellulose, harvested from the forest product industry, has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bio-nanocomposites or in the paper industry. Mainly due to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. The principle reason to utilize cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) as a reinforcing material is because we can potentially exploit the high crystal modulus of cellulose as well as the ability to chemically modify their surface structure. This stiffness arises from the hydrogen bond networks formed on the glucose residues from one chain with oxygen molecules on another chain. By selecting the appropriate polymer of choice, the polymer matrix will be bonded strongly with cellulose.

In our first design, CNC will be used as reinforcement fillers in a two-part epoxy system. Epoxy film containing various CNC loading will be prepared through solvent-assisted dispersion of CNC, followed by different solution processing method. The role of residual solvent and the compatibility between epoxy matrix and CNC will be analyzed through mechanical, thermal and optical characterizations. In our second design, a much more compatible polymer matrix-polyvinyl alcohol (PVA) with CNC will be used. Composite films will be produced with up to 70 wt% CNC content through water-based solution processing. The effect of various CNC loading on the optical, thermal and mechanical properties of the nanocomposite films will be studied. Since the PVA/CNC composite can be potentially used for fuel cell application. After deciding the optimum CNC content in PVA matrix, sulfosuccinic acid (SSA) will be used as both crosslinking agent and proton conductor. Water uptake, ionic conductivity and thermal properties of the crosslinked PVA/CNC/SSA membrane with various amount of crosslinking agent will be explored.

The goal of this research is to optimizing the processing methods to prepare cellulose-based composite films in different polymer systems. The compatibility of CNC in those polymer matrices will strongly affect its reinforcing properties. A low cost, biodegradable polyelectrolyte membrane with promising potential in green power generation will be fabricated.