Student Ph.D. Defense - Mohamed Amen Hammami

Nov 01 2017 12:30 AM - Nov 01 2017 01:30 AM

Engineering of Mixed Matrix Membranes for Water Treatment, Protective Coating, and Gas Separation.


Abstract:

Mixed Matrix Membranes (MMMs) have received worldwide attention during the last decades. This is due to the fact that the resulting materials can combine the good processability and low cost of polymer membranes with the diverse functionality, high performance and thermal properties of the inorganic fillers. This work explores the fabrication and application of MMMs. Various fillers and polymers have been combined in this work depending on the desired application. We focused on the design and fabrication of nanofillers to impart target functionality to the membrane for water treatment, protective coating and gas separation.

This thesis is divided into three sections according to the application including: Water Treatment: This part is divided into three chapters (2, 3 and 4), two related to the membrane distillation (MD) (chapter 2 and 3) and one related to the oil spill (chapter 4). Three different nanofillers have been used: Periodic mesoporous organosilica (PMO), graphene and carbon nanotube (CNT). Those nanofillers were homogeneously incorporated into polyetherimide (PEI) electrospun nanofiber membranes. The doped nanoparticle not only improved the mechanical properties and thermal stability of the pristine fiber but also enhanced the MD and oil spill performance due to the functionality of those nanofillers. In these chapters, the antibacterial effect of graphene and the use the highly porous organosilica nanoparticles, which was further utilized to load the eugenol antimicrobial agent, showed an enhancement of the anti-biofouling properties of the membranes as well.

Protective coating: This part includes two chapters 5 and 6 describing the design and the fabrication of a smart antibacterial and anti-corrosion coating, respectively. In the first project, we fabricated colloidal lysozyme-templated gold nanoclusters gating antimicrobial-loaded silica nanoparticles (MSN-AuNCs@lys) as nano-fillers in poly(ethylene oxide)/poly(butylene terephthalate) (PEO–PBT) amphiphilic polymer matrix. MSN-AuNCs@lys dispersed homogeneously within the polymer matrix with no phase separation and zero NPs leaching. The system was coated on a common radiographic dental imaging device (PSP plate) that is prone to oral bacteria contamination. This mixed-matrix coating can successfully sense and inhibit bacterial contamination via a controlled release mechanism that is only triggered by bacteria. Interestingly, the quality of the images obtained with these coated surfaces is the same as uncoated surfaces and thus the safe application of such smart coatings can be expanded to include other medical devices without compromising their utility.

In the second project, the coaxial electrospinning approach has been applied to fabricate smart core-shell nanofiber for controlled release of anti-corrosion material. Acetal-dextran was used as a pH controlled shell of the fibers and polyvinyl alcohol (PVA) as a hydrophilic core. Caffeine, as an anti-corrosion inhibitor was encapsulated in the fiber core to test its potential application as an anticorrosion coating. The almost negligible release was noticed at neutral pH. In acidic pH due to corrosion, the fibers quickly respond by releasing caffeine cargo.

Gas separation: We describe the synthesis and application of novel ethylene-diamine-based PMO. The gas adsorption properties of these materials were investigated for CO2, CH4 and N2 gases at different temperatures. PMO nanoparticles exhibited excellent CO2 uptake and selectivity. The novel PMO nanoparticles were homogeneously incorporated into polydimethylsiloxane to fabricate a MMMs hin layer on a porous polyacrylonitrile support.  Our results prove that our PMOs can be used as nanofillers to enhance the CO2 selectivity of the PDMS polymer.