Abstract NEW SYNTHETIC STRATEGIES FOR IMPROVED GAS SEPARATION BY NANOPOROUS ORGANIC POLYMERS Suha S. Altarawneh, Ph.D. The emission of carbon dioxide (CO2) from fossil fuel combustion is a major cause of climate change. Therefore, the efficient separation of CO2 from mixtures of gases such as flue gas and impure sources of CH4 (e.g. natural gas and landfill gas) is an essential step in meeting the ever increasing demands on natural gas and creating a cleaner environment. Carbon capture and storage technology (CCS) is one of the methods employed for gas separation using chemisorption and/or physisorption processes. Several materials such as porous polymers and amine solutions have been used as gas adsorbents. However, the amount of energy required for the adsorbent regeneration is one of the main concerns that needs to be addressed. In this regard, porous organic polymers (POPs) with defined porosity and preferential binding affinity for CO2 over N2 and CH4 are some of the most attractive materials that could fulfill the above requirement and are also applicable for use in gas storage and separation. Suitable POPs that can be used for gas storage applications need to have high porosity and mechanical stability under high pressure conditions (~100 bar). Alternatively, the most effective POPs in gas separation are those that have preferential binding affinity for CO2 over other gases present at low pressure settings. In all cases, the chemical nature of POPs and their textural properties are key parameters, however, the modest surface area of most POPs limits their efficiency. With the above considerations in mind, the aim of our research is to develop benzimidazole–linked polymers (BILPs) that have variable porosity levels and chemical functionality to enhance gas separation (CO2/CH4, CO2/N2). We have established new synthetic routes that utilize polycondensation reactions between aryl-aldehydes and aryl-o-diamine building units to construct new BILPs with improved gas separation properties. Our strategy targeted structural and textural modifications of BILPs. We used longer linkers (building units) to improve porosity; however, the flexible linkers offered only low porosity due to network interpenetration. To overcome this challenge, a more controlled network growth rate was assessed by adjusting imine-bond formation rates through different acid loading. The acid, HCl, was used to catalyze imine-bond formation. The new resulting acid-catalyzed BILPs have shown an improved porosity up to 92% compared to the non-catalyzed BILPs. We also used the “rational ligand design” approach to introduce new functionalities into BILPs (-OR) to alter the hydrophobic nature of their pores. In this regard, we have illustrated the applicability of this strategy to BILPs containing flexible aryl-o-diamine linkers. The bulky alkoxy groups were incorporated into the aryl-aldehyde building unit prior to polymerization. The resulting polymers have proven that the presence of the bulky pendant alkoxy-chains plays a significant role during the polymerization process which allows for increased control over network formation, and in turn, porosity. Sorption measurements, selectivity, and heats of adsorption data have confirmed the positive impact of the alkoxy-groups and shown that varying the pendant groups is a promising method for designing highly porous BILPs. In addition to pore functionalization with alkoxy-chains, we used pi-conjugated and N-rich building units to prepare new BILPs that have semiconducting properties in addition to their porous nature. This class of BILPs has shown that the extended-conjugated system improved BILPs electronic properties. The other studies performed in this research, involved the use of DFT theory to investigate CO2/BILPs interaction sites and binding affinities. The computational outcomes of DFT have shown that (C-H) bond of the aryl system is a possible site for CO2 interaction beside the free-N side and hydrogen bonding. All new polymers were characterized by spectral and analytical characterization methods and their sorption data were collected to evaluate their capability as candidates for gas separation applications.

Additive manufacturing (AM) is a particularly useful manufacturing method for components designed using topology optimization (TO) since it allows for a greater part complexity than any traditional manufacturing method. However, the AM process potentially leads to anisotropic material properties due to the layer-by-layer buildup of parts and the fast and directional cooling. For Ti6Al4V tensile specimens built using electron beam melting (EBM), it has been observed that flat built specimens show superior strength and elastic moduli compared to top built specimens. Designs with the loading direction parallel to the build layers are therefore expected to show greater reliability. In this thesis a procedure is developed to optimize the AM build orientation considering anisotropic elastic material properties. A transversely isotropic material model is used to represent the in-plane and out-of-plane characteristics of AM produced parts. Two additional design variables are added to the TO formulation in order to control the orientation of the material using a coordinate transformation. Sensitivity analysis for the material direction variables is conducted for compliance as well as maximum von-Mises stress using a -norm stress aggregation function. The procedures for the AM build orientation optimization and stress constraints are implemented in the finite element software TRINITAS and evaluated using a number of examples in 2D and 3D. It is found that the procedure works well for compliance as well as stress but that a combination of these may lead to convergence issues due to contradicting optimal material orientations. An evaluation of the -norm stress aggregation function showed that a single global stress measure in combination with a stress correction procedure works well for most problems given that the mesh is refined enough to resolve the stresses accurately.

Fat intra-body communication is a newly proven concept that is built on using human fat tissues as a communication channel for electromagnetic waves inside the body. This allows for two implanted external devices to connect through an intra-body closed-loop communication channel. This concept utilizes the fact that the fat tissues have low dielectric properties and are located between two tissue layers, skin and muscle, which have high dielectric permittivity and high loss tangent so that the signal propagates and confines with lower losses within the fat tissue. In this study, the eligibility of using monkey fat tissues as a communication channel for intra-body communication is being investigated. This comes as a first step in a long process of testing implementing medical devices, mainly prosthetic limbs, on non-human primates using fat-IBC at microwave frequencies. To be able to do that, an experimental characterization of ex-vivo monkey fat, skin, and muscle tissues to explore their dielectric properties compared to those of humans is being carried out. This study of the dielectric properties of monkey tissues is the first of its kind to be carried out on two samples of ex-vivo monkey tissues. Calf tissues have also been investigated in the study to get an insight on the potential differences between human and non-human body tissues in general before doing measurements on monkey tissues. For the measurements, an RF network analyzer and an open-ended coaxial probe method have been implemented. Phantoms that mimic the human tissues have been fabricated to be used as a reference point. The initial investigation demonstrates that calf fat tissues have much higher dielectric properties than human fat tissues. Monkey fat, muscle, and skin tissues showed many similarities to human tissues regarding their dielectric properties. This indicates that monkey tissues can be used for fat intra-body communication. Future numerical and analytical modeling of the monkey tissues needs to be conducted to confirm and strengthen this finding.

Les globules gras du lait sont entourés d’une membrane biologique extrêmement complexe en composition et en structure, appelée MFGM (milk fat globule membrane). L’investigation de cette membrane, in situ dans le lait, par microscopie confocale nous suggère que les lipides polaires à haute température de transition de phase (Tm) forment des domaines en phase gel ou liquide ordonné, dispersés dans une phase continue fluide. Sur la base de cette observation, ce projet vise à comprendre en quoi la composition en lipides polaires laitiers et leur état de phase peuvent moduler les propriétés élastiques de la MFGM, en vue d’une meilleure maîtrise de la stabilité des globules gras en industrie laitière.L’hétérogénéité mécanique générée par la coexistence de différents types de phase a ainsi été caractérisée par spectroscopie de force AFM en utilisant des bicouches de lipides modèles de la membrane réelle, à basse (T<Tm) et haute températures (T>Tm). Pour analyser finement les déterminants de l’élasticité de la membrane, et tenir compte de la courbure, une étude approfondie des effets de l’état de phase et de la composition hétérogène en lipides polaires a été entreprise par spectroscopie de force atomique, en complément d’une analyse structurale par microscopie électronique ou diffraction des rayons X. Nous y avons montré, en particulier, que la présence de molécules de longueur de chaîne acyles et d’insaturation variables rend les membranes de sphingomyéline de lait en phase gel moins rigides qu’attendu, bien que significativement plus rigide qu’une membrane fluide. Cette approc / The milk fat globules are enveloped by a biological membrane, called MFGM, of highly complex composition and structure. Investigation of this membrane, in situ in milk, using confocal microscopy suggested that polar lipids with high transition temperature (Tm) form domains in gel or liquid-ordered phase, dispersed in a continuous fluid phase. From this observation, the aim of this project was to understand how the composition and organization of dairy polar lipids can modulate the elastic properties of the MFGM, in order to better control stability of the fat globules in the dairy industry. The mechanical heterogeneity created by the coexistence of phases was then characterized by AFM force spectroscopy using lipid bilayers models at low (T<Tm) and high temperatures (T>Tm).In order to closely analyze the factors that direct membrane elasticity, force spectroscopy measurements were undertaken on curved liposome membranes, in combination with structural characterization by TEM and SAXS. We showed, in particular, that heterogeneity in acyl chain length and unsaturation made gel-phase milk sphingomyelin membranes less rigid than expected, although more rigid than a fluid phase membrane. This approach was finally applied to native milk fat globules, where mechanical heterogeneity was visible. However, elasticity values were somewhat different from those calculated on model systems, probably because of the presence of membrane proteins.