Theses and Dissertations

ORCID

https://orcid.org/0000-0002-5471-6173

Issuing Body

Mississippi State University

Advisor

Kundu, Santanu

Committee Member

Rai, Neeraj

Committee Member

Meng, Dong

Committee Member

Schilling, Wes M.

Date of Degree

8-8-2023

Document Type

Dissertation - Open Access

Major

Chemical Engineering

Degree Name

Doctor of Philosophy (Ph.D)

College

James Worth Bagley College of Engineering

Department

Dave C. Swalm School of Chemical Engineering

Abstract

Biological systems are composed of complex materials which are responsible for performing various functions, such as providing structural support, mobility, functional adaptation to the environment, damage repair, and self-healing. These complex materials display excellent mechanical properties and can rapidly adapt to external stimuli. Thus, nature inspires in terms of source materials, functions, and designs to develop new-generation structural and functional materials. Polymers (natural or synthetic) are excellent sources of developing materials to mimic the functions of soft segments in biological systems. This dissertation focuses on synthesizing and characterizing two different materials with tunable structures and properties: complexes from natural polysaccharides or polyelectrolytes and bioinspired hydrogels from synthetic polymers. Oppositely charged polyelectrolytes can form polyelectrolyte complexes (PECs) due to the electrostatic interactions. The structure and properties of PECs can be tuned by varying the salt concentration, as the addition of salt can facilitate associative phase separation. PECs were prepared from two biopolymers, positively charged chitosan and negatively charged alginate. Rheological experiments for the complexes displayed a tunable shear modulus with changing salt concentrations. The microstructural study conducted using small-angle X-ray scattering provided insights regarding the length scales of these complexes, and the results follow the observed rheological and phase behavior. Elastic biopolymers such as resilin display remarkable mechanical properties, including high stretchability and resilience, which many species exploit in nature for mechanical energy storage to facilitate their movement. Such properties of resilin have been attributed to the balanced combination of hydrophilic and hydrophobic segments present in the chain. In this work, we synthesized hydrogels with hydrophilic and hydrophobic components to mimic the properties of resilin. With this system, we determined the tensile, retraction (ability to revert to the original state after stretching), and swelling properties when (i) the concentration of the hydrophobic polymer was varied and (ii) additional hydrophobic components were included. The stretchability, stiffness, and strength of the gels varied as the compositions were altered. The fundamental understanding of the structure-property-function relationship for materials presented in this work provides insights into engineering materials for applications such as tissue engineering, drug delivery, wound healing, artificial muscles, soft robotics, and power amplification.

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