The rheology and dynamic properties of biopolymers in a colloidal suspension

Given their biodegradable, biocompatible, renewable and non-toxic nature as well as favourable rheological properties, many industries have now opted to use biopolymers in their products and operations. Biopolymers, such as xanthan gum, provide good suspension and stability to solutions and exhibit excellent resistance against high shear and high temperature environments. To further expand the application of these biopolymers, there is a need to understand their rheological properties and the mechanism of biopolymer-water interactions. To date, there is still no consensus on the measurement of the solid-like behaviour or yield stress that is an important physical property to suspending particles in viscoelastic fluids. An understanding of the mechanism of hydrogen bonding (HB), which plays a crucial role in the biopolymer-water interactions, is also lacking in the existing literature. In this thesis, both experimental and simulation approaches were employed to conduct the research. From the various rheological measurement methods conducted, it was found that the small amplitude oscillatory shear measurement provides a reliable yield stress value that is well matched with the steady shear and creep test results. Following these experimental studies, molecular dynamics (MD) simulations that can probe atomic interactions at a fine temporal and spatial resolution were run, given that the unique rheological properties of biopolymers arise from their atomic interactions. Here, the MD simulation studies were presented in a systematic progression that first begins with the study of water-water, biopolymer-water and finally carbon nanotube (CNT)-biopolymer-water interactions. From the simulation results, it was found that HB is pivotal in determining the thermodynamic properties of water. In both water and biopolymers, the number of HB is found to decrease with increasing temperature and this helps in explaining the changes in macroscopic properties (e.g. density and dynamic viscosity) when the temperature varies. Due to the presence of extensive hydroxyl groups, HB is found to be important in the conformational properties of biopolymers such as maintaining their helical conformation to suspend CNTs and adopting a more extended conformation that increases the van der Waals interaction between biopolymers and CNTs. The current research sheds some light on the rheology and dynamic properties of biopolymers.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2019

Author dc:creator

• Ong, Ern Seang

• Yield stress
• Xanthan gum
• Rheology
• Molecular dynamics
• Hydrogen bonding
• Conformational properties
• Biopolymers

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/21420

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/63385