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|Title:||TUNING THE INTERFACIAL PROPERTIES OF CELLULOSE AND SILICONES THROUGH TRIAZINYL AND THIOACETAL CHEMISTRY|
|Advisor:||Brook, Michael A.|
Moran-Mirabal, Jose M.
|Department:||Chemistry and Chemical Biology|
|Keywords:||Functional Cellulose and Silicones;Triazinyl and thioacetal chemistry|
|Abstract:||Interest in the incorporation of renewable, environmentally friendly materials, particularly nanocellulose due to its unique mechanical, optical, electrical and magnetic properties, into consumer products has progressed rapidly because these materials could lead to nanocomposites with enhanced functionality and mechanical properties. However, a well documented challenge that prevents nanocellulose from being widely used is the fact that cellulose is insoluble, relatively inert, and difficult to disperse in non-aqueous solvents and polymeric matrices. Available methods for the surface modification of cellulose to make it dispersible in polar and non-polar systems are complex, cost-prohibitive and difficult to implement on a large scale. To address these challenges accordingly, the first part of this thesis aims to explore a cost-effective chemistry that is versatile and allows the installation of a broad range of functionalities onto nanocelluloses including cellulose nanocrystals/microfibrils while preserving their individual nature. Chapter 2 demonstrates a simple one-step triazinyl surface modification approach for tuning the interfacial properties of cellulosic materials using cyanuric chloride as a versatile linker to graft aliphatic (C18), polymeric (oligo-polyethylene glycol), alkyne (propargyl) chains and aromatic rings (benzyl) onto nanocelluloses, including CNCs and BMCC. We observed that the crystallinity of all triazine-modified CNCs was preserved, while the thermal stability was slightly enhanced compared to unmodified nanoparticles. CNCs modified with different triazinyl derivatives also formed colloidal suspensions in chloroform, isopropanol, ethanol, and methanol, which were stable over periods of months. In addition, propargyl-modified BMCC was linked to an azido fluorescein dye via a coper-catalyzed Huisgen 1,3-dipolar cycloaddition reaction, demonstrating for the first time the production of triazinyl-based reactive nanocellulose. Next, a companion study, examines the development of a colorimetric and fluorescent “off-on” cellulose based chemosensors for heavy metal detection in water as a potential lab-on-a-molecule system for biomedical and environmental diagnostics. The use of cyanuric chloride as a covalent linker to install pegylated rhodamine Schiff bases onto cellulose filter paper was explored. The factors required to create on demand selectivity and sensitivity towards specific heavy metals was determined. This resulted into the detection of Cu2+ and Hg2+ ions in 100% aqueous environment within 5 seconds of contact with 6.3 ppb and 20 ppb as the limit of colorimetric detection respectively. Lastly, in addressing the challenges of traditional preparative methods for silicone elastomers largely dependent on several issues associated with current cure strategies mainly cost, toxicity and functional group intolerance of these heavy metal catalyzed reactions (platinum, tin or titanium). Alternative routes based on organic chemistry have been exploited to mitigate these effects. The second part of this thesis introduces organic cure chemistries based on triazinyl and thioacetal linkages as catalyst-free and organic acid catalyzed silicone elastomer preparative methods to control physical properties of silicones while chapter 6 focuses on the preparation of self-driven microfluidic devices tuning the interfacial properties and water wettability of silicones.|
|Appears in Collections:||Open Access Dissertations and Theses|
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|Fatona_Ayodele_T_2019Sep_PhD.pdf||11.14 MB||Adobe PDF||View/Open|
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