Departmental Seminar - Ayodele Fatona
DATE: Thursday September 12, 2019
TIME: 10:30 a.m.
LOCATION: ABB 163
SUPERVISOR: Dr. Jose Moran-Mirabal and Dr. Mike Brook
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 key challenge well documented 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.
In this presentation, a cost-effective chemistry that is versatile and allows the installation of a broad range of functionalities onto cellulose nanocrystals while preserving its individual nature will be discussed. This work focused on 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 talk 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 we focus on the preparation of self-driven microfluidic devices tuning the interfacial properties and water wettability of silicone