Date of Award

19-1-2024

Document Type

Thesis

School

School of Chemical & Biotechnology

Programme

Ph.D.-Doctoral of Philosophy

First Advisor

Dr.K.Lalitha

Second Advisor

Dr.S.Nagarajan

Keywords

Molecular Self Assembly, Amphiphilic Gelators, CNSL Derived Materials, Drug Delivery, Methanol Detection

Abstract

Among various molecular self-assemblies, low molecular weight gelators (LMWGs), that can form gels in organic solvents/water/oils, have gained much research attention due to their huge potential applications. Generally, gels are soft nanomaterials formed by the self-assembly of amphiphilic molecules into a three-dimensional fibrous network entrapping the solvent.

As these gels are formed by self-assembly via non-covalent interactions they are reversible and differ from macromolecular gels. To synthesize LMWGs, biomolecules such as fats, oils, fatty acids, lignocelluloses, sugars, amino acids, and peptides are commonly used as their inherent property favors self-assembly. In the current scenario, interest in synthesizing bio-based gelators has risen owing to their intrinsic characteristics like biodegradability, non-toxicity, and bio-compatibility that brand their suitability for applications such as food, pharmaceuticals, sensors, cosmetics, and drug delivery systems.

Additionally, the increasing environmental concern, the enormous usage of petroleum-based feedstocks, and their ensuing demand paved the way for the use of bio-based raw materials. In this context, it is planned to synthesize bio-based LMWGs using phenolic lipids, fatty acids, and sugars as starting material and to explore their self-assembly behavior in this work.

In Chapter 1, the significance of bio-based materials, and the concept of self-assembly were briefly discussed by citing examples of natural self-assembly. After providing the literature evidence for the synthesis of amphiphiles and utilization of their self-assembling characteristics in fabricating functional materials of nanostructures, the scope and objective of the thesis work were discussed.

In Chapter 2, N-acyl amides were synthesized from renewable building blocks using a simple synthetic protocol and studied their self-assembly behavior. It is observed that compounds 2.6a and 2.7a formed a hydrogel, organogel and oleogel. Their morphology was identified using microscopic techniques like the optical microscope, SEM, and using rheological analysis, the viscoelastic properties, thermoresponsive and thixotropic behavior are evaluated. Further, the composite gel prepared by encapsulating curcumin in the hydrogel from 2.7a is shown to act as a drug carrier by using its pH stimuli-responsiveness.

In Chapter 3, the fluorescent bio-based amphiphiles were synthesized using methyl ricinoleate, investigated their molecular self-assembly, gel morphology, and probed the viscoelastic properties. Further, the sensing character was measured by using the xerogel decorated electrode and identified its ability to sense 250 ppm of 1-butanol, acetone, ethanol, formaldehyde, isopropanol, methanol, and trimethylamine with a selective response towards methanol

In Chapters 4 and 5, acetal-based gelators were synthesized using sorbitol and examined their gelation tendency, morphology, and the rheological properties of the self-assembled structure. Further, the dye adsorption and desorption characteristics of the hybrid hydrogel were investigated and shown the possibility of using them to develop a mini-column gel-filter bed, gel-coated cotton ball, capable of adsorbing dyes such as methylene blue, crystal violet, rhodamine B and Congo red rapidly and efficiently.

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