Tiz Mekonnen

Sustainable polymer systems

The utilization of renewable resources for polymer production is receiving substantial interest. My group is interested in bio-based and renewable macromolecules (e.g. starch, cellulose, cellulose nanocrystals, lignin, biocarbon, tannins, and chitosan) as a feedstock to fabricate nanomaterials and a variety of sustainable materials including elastomers, plastics, hydrogels, engineering polymers, and nanocomposites. We employ various chemical tailoring strategies and polymer processing technologies to make these feedstocks more suitable for polymeric materials.

Polymer modification

The chemical modification of polymers is a post-polymerization process which is used for the following purpose:

• to improve and optimize the properties of existing polymers
• to introduce desirable functional attributes in the polymer

We focus on the design and development of modification processes/systems by utilizing Chemistry and Engineering tools. Some of the approaches we undertake to modify polymers includes reactive extrusion processes, hydrogenation, epoxidation, hydroxymethylation, and hydrosilylation of various polymers and elastomers/rubber; Grafting – from and grafting – to modification of polysaccharides and polymers; Reactive extrusion processes.

Nanomaterials and nanocomposites

My research interest in nanomaterials focuses on innovating novel techniques for the synthesis, modification, characterization, and applications of renewable polymer-based nanomaterials. I have targeted functional nanomaterials with attributes for antimicrobial carriers, UV shielding properties, corrosion inhibiting additives, oxygen scavenging films, superhydrophobic coatings, and dipped rubber goods. A critical challenge in nanocomposite research is to translate the exceptional nanoscale properties of nanomaterials to the macroscale, which relies on the dispersion of nanomaterials, selection of matrices, and optimization of composite microstructures. Various load-bearing natural composites such as teeth, turtle and eggshells, bones, and wood exemplify the importance of order and hierarchy starting at the nanoscale to tangible macroscopic levels. Drawing from these inspirations, my team aims to achieve similar multiphase and multifunctional polymeric materials via appropriate polymeric matrix selection along with composite architectures to ensure the multi-parameter property optimizations for corresponding applications. We develop nanocomposites based on cellulose nanocrystals, lignin nanoparticles, fumed silica, nanoclays, nano-biocarbon, carbon nanofibers, and graphene.

Polymer processing and application development

My research in polymer processing is focused on polymer blend morphology development and stabilization with a focus on multiphase renewable polymers. We target addressing the challenges associated with microstructure –processing – properties of polymer blends and their stabilization. We specifically target using chemistry and polymer processing tools to optimize the dispersion of nanoparticles in various single and multiphase polymer matrices for functional applications. We work with industrial collaborators and support application development efforts in packaging materials, lightly cured rubber latex products (e.g., gloves, condoms), highly cured rubber products (tire treads, shoe soles, conveyor belts), barrier films, coatings and paint, adhesives, engineering composites with functional attributes.

• Esmizadeh, E., Cheng, B., Jubinville, D., Ojogbo, E., Seto, C. Tzoganakis, C., Mekonnen, T. Can medical-grade gloves provide protection after repeated disinfection? ACS Applied Polymer Materials. 2021, 3, 1, 445–454.
• Trinh, B., Ogunsona, E., Mekonnen, T. Thin-structured and compostable wood fiber-polymer biocomposites: fabrication and performance evaluation. Composites Part A. 2021, 140, 106150,
• Mekonnen, T., Haile, T., Ly, M. Hydrophobic Functionalization of Cellulose Nanocrystals for Enhanced Corrosion Resistance of Polyurethane Nanocomposite Coatings. Applied Surface Science. 2021, 540(1) 148299.
• Saikirshnan, S., Jubenville, D., Tzoganakis, C., Mekonnen, T. Thermo-mechanical degradation of polypropylene (PP) and low-density polyethylene (LDPE) blends exposed to simulated recycling. Polymer Degradation and Stability. 2020. 182, 109390.
• Ogunsona, E., Mekonnen, T. Multilayer assemblies of polysaccharides - polymer films for enhanced oxygen barrier packaging applications. Journal of Colloid and Interface Science. 580, (2020), 56-67.
• Blanchard, R., Ogunsona, E., Hojabr, S., Berry, R., Mekonnen, T. Synergistic crosslinking and reinforcing enhancement of rubber latex films with cellulose nanocrystals for glove applications. ACS Applied Polymer Science. 2020, 2(2), 887–898.
• Mekonnen, T. Behabtu, N., Lenges, C. Enzymatic Polymerization Derived Engineered Polysaccharides as Reinforcing Fillers of Ethylene vinyl acetate. Carbohydrate Polymers. 241 (220) 116252.
• Ojogbo, E. Ward, V., Mekonnen, T. Functionalized starch microparticles for contact-active antimicrobial polymer surfaces. Carbohydrate Polymers. 229 (2020) 115422.
• Ogunsona, E.O., Panchal, P., Mekonnen, T. Surface grafting of acrylonitrile butadiene rubber onto cellulose nanocrystals for nanocomposite applications. Composite Science and Technology. 184 (10) 2019, 107884.
• Ogunsona, E.O., Muthuraj, R., Ojogbo, E., Valero, O., Mekonnen, T. Engineered nanomaterials for antimicrobial applications: A review. Applied Materials Today. 18, 2020, 100473.
• Panchal, P., Mekonnen, T.* Tailored Cellulose Nanocrystals as a Functional Ultraviolet Absorbing Nanofiller of Epoxy Polymers. Nanoscale Adv., 2019, 1, 2612-2623.
• Ojogbo, E., Blanchard, R., Mekonnen, T. Hydrophobic and Melt Processable Starch–Laurate Esters: Synthesis, Structure–Property Correlations. Journal of Polymer Science Part A: Polymer Chemistry. 56, 2611–2622
• Trinh, B., Mekonnen, T. Hydrophobic esterification of cellulose nanocrystals for epoxy reinforcement. Polymer. 2018; 155, 64- 74.