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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Friday, March 13, 2020
12:00 PM
in MRDC 3515
will be held the
DISSERTATION DEFENSE
for
Cameron William Irvin
"Understanding the Impact of Cellulose and Chitin-based Nanomaterials in Various Polymer Matrix Constructs"
Committee Members:
Prof. Meisha Shofner, Advisor, MSE
Prof. Donggang Yao, MSE
Prof. Blair Brettmann, ChBE/MSE
Prof. Carson Meredith, ChBE
Prof. Yulin Deng, ChBE
Abstract:
Cellulose nanocrystals (CNCs) and chitin nanofibers (ChNFs) are two emerging nanomaterials that are garnering significant interest recently. CNCs and ChNFs can be derived from trees and crab shells, respectively, and possess remarkable mechanical properties that make them ideal for use as reinforcement materials in polymer composites. When processed through sulfuric acid hydrolysis, CNCs are left with a negative charge along the surface of the nanocrystals. In contrast, ChNFs produced through high-pressure homogenization possess a positive charge due to chemical side groups along the nanofiber. These opposite charges allow for electrostatic interactions between the particles that can be tuned to allow for certain nanoscale structure formation. When incorporated into a water soluble, commercially available polymer such as poly(vinyl alcohol) (PVA), there is potential for understanding the impact of these nanofillers in a variety of polymer constructs. PVA offers the unique ability to be formed into films, hydrogels, and aerogels without the aid of additional chemicals, which expands the range of commercial applications that CNCs and ChNFs can be applied. Additionally, there are certain characterization techniques that can be applied to one construct that cannot be applied to another, resulting in a large range of studies that can be performed in order to uncover individual characteristics about how the nanofillers are interacting with the each other and the polymer matrix.
Results of this study indicate that charge-matched ratios between the nanofillers results in a reduction in properties relative to other composites, likely due to a mass aggregation between particles destabilizing the particles and, thus, the reinforcement mechanisms. However, other ratios between CNCs and ChNFs enhance the mechanical properties beyond that of what is capable with singular nanofillers. In addition to the improved capabilities as a result of their interactions, the combination of these two nanofillers also allows for certain characteristics of each nanofiller type to influence the properties of the overall structure that cannot be achieved with the other. For instance, while CNCs were shown to increase the elasticity of composite hydrogels, ChNFs were shown to increase the polymer structure’s water absorption and retention capabilities. The combination of these two materials into a tricomponent composite could then possess several desirable qualities that are applicable in biomedical or membrane technologies. The purpose of this research is to more fully understand the impact of these renewable, abundant nanomaterials when used in these three PVA constructs both as individual nanofillers and when used in conjunction. This study aims to better understand the electrostatic interactions between different nanofillers and how these can affect the polymer matrix to optimize customizable, high-performance polymeric composite materials.
