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The surfactant systems formed in shampoos or soaps have very particular characteristics. Surfactant solutions are dynamic systems, i.e. the structure adopted by these molecules changes and adapts as a result of the total composition of the system. They are responsive to some components and external factors. These factors are, among others, the salt concentration, the pH and the temperature. Within the scope of the thesis solutions of two main surfactants used in the Nizoral shampoo of Janssen Pharmaceutica is studied. These surfactants are sodium lauryl ether sulfate and disodium monolauryl ether sulfosuccinate. This surfactant system is a key feature of the products and understanding the interactions between the surfactants and their response to varying conditions such as pH and salt concentration changes can provide insight into how the viscosity is built in the system and how it is influenced by these conditions. This research is conducted by investigating three sample series. By varying the concentrations of two components while keeping all other parameters fixed, an attempt is made to determine which component and conditions can change the system response and how this happens. The final aim being to verify for a large panel of compositions what the effects are of salt concentration, pH and surfactant concentration on the stability over time and to identify the key parameter responsible for rheological changes, if possible.

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Over the past decade, the pharmaceutical industry has increasingly shifted to developing sensitive large-molecular-weight drugs, the so-called biopharmaceuticals. However, a recent trend within biopharmaceutical developments has seen increasing amounts of these biopharmaceuticals not making it to the market as the result of their decreasing bio-availability and increasing risk of denaturation when processed through traditional production methods, like spray drying or emulsification. The topic of this study, electrospraying, presents an answer to the increasing needs of the pharmaceutical industry by improving bioavailability through amorphization and reducing denaturation by operating under mild processing conditions. Not to mention, electrospraying also improves particle monodispersity and enables the production of core-shell microparticles through coaxial electrospraying for improved controlled release of these biopharmaceuticals. This study investigates the potential of single nozzle and coaxial electrospraying techniques for producing biodegradable microparticles. Therein, the main objective is bifurcated into two independent collaborations with DSM Biomedical and the Laboratory of Clinical and Experimental Endocrinology at the UZ Leuven. The first collaboration explores single nozzle and coaxial electrospraying as production techniques for biodegradable microparticles consisting of a model drug and DSM Biomedical’s novel polymer platform for drug release, TheraPEA. In utilizing a high-molecular-weight PLGA variant as a TherePEA-substitute in combination with water-soluble Bovine Serum Albumin as a model drug, the collaboration with DSM Biomedical successfully achieved core-shell microparticles, which comprised of a PLGA-shell encapsulating a core of BSA and PEG. The approach of co-electrospraying an organic shell phase and a BSA core phase enables scaling by DSM to a standardized strategy for the production of core-shell particles, where TheraPEA encapsulates water-soluble proteïns. The second collaboration continues a longer-standing collaboration with the Laboratory of Clinical and Experimental Endocrinology at the UZ Leuven and targets enabling tissue engineering for bone regeneration of severe bone fractures. Furthermore, this paper also assesses ongoing trends of leveraging digital tools, like Machine Learning, in a scientific environment by extracting insights from a Machine Learning model that predicts electrosprayed particle sizes and develops a solvent selection tool for electrospraying applications. Both exhibit the potential to drastically reduce the lead time of optimizing new drug-polymer electrospraying systems and hence improve the time-to-market for the increasing number of novel biopharmaceuticals.

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This research focuses on the loss of energy due to friction between the chain tensioner and the chain in the drive system of the valvetrain in automotive engines. By using polyamide 46 (PA 46) as surface material of the chain tensioner combined with suitable lubricants, friction in this contact can be reduced. Commercially available lubricants such as 5W-30 are not designed to reduce friction in steel-polymer contact and therefore, the interaction between both is uncertain. This thesis investigates the compatibility of an available commercial lubricant, 5W-30, with PA 46 as countersurfaces. Using tribological experiments, Stribeck curves are generated to compare the coefficient of friction, in function of the Gümbel number, between different systems. In addition to the tribological measurements, rheological measurements are also carried out to determine the viscosity of the lubricants. The first tribological measurements, to compare stainless steel and PA 46 as countersurface, show that PA 46 definitely has friction reducing properties which are especially observable in the mixed lubrication regime. However, the modulus of PA 46 is sensitive to increasing temperature and therefore, the friction in the boundary regime is higher for paraffin oil lubricated systems of steel on PA 46 compared to similar steel on steel systems, at especially higher temperatures. Further tribological measurements focus on the differences between simple paraffin oil and commercial 5W-30 as lubricants and examine the compatibility between PA 46 and 5W-30. The results clearly show that 5W-30 systematically reduce friction in steel on steel systems. In systems of steel on PA 46, 5W-30 has beneficial effects increasing with increasing temperature. At the end of the boundary regime on the transition to the mixed lubrication regime, an increase of the coefficient of friction followed by a decrease is observed, in systems of steel on PA 46 lubricated by 5W-30. Next, it is shown that the height and location of this maximum is susceptible to varying temperature and normal force. Finally, literature is reviewed for possible mechanisms explaining the maximum of the coefficient of friction. According to Yoshizawa et al., interdigitation between the opposing monolayers is the determining factor that causes the friction to increase.

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In this thesis, the relation between the tumbling motion of disk-like particles in shear flow and the structure that the particles form is studied for two systems: Gibbsite platelets in the nematic phase and aggregates of two red blood cells.Using time-resolved small-angle X-ray measurements, we investigate the dynamic nonlinear response to Large Amplitude Oscillatory stress and strain of a nematic dispersion of colloidal Gibbsite platelets.By combining an X-ray beam deflected into the vertical direction with the plate-plate and the concentric cylinder Couette geometries, we track the nematic director's full 3D rotational motion.We observe a large offset in the rheological response and an asymmetrical behavior in the microscopic structural response under controlled stress conditions.This offset and asymmetry are connected to the yielding behavior of the platelets, they diminish for high stress amplitudes, and the microscopic response becomes more symmetric.However, this strongly depends on the input stress frequency, hence the time necessary for the system to yield.Confinement also strongly affects nematic Gibbsite's flow behavior due to the strong wall anchoring of colloidal disks.We show the confinement effect by varying the gap size in plate-plate geometry and scanning the structure throughout the gap in the Couette geometry.Analysis, using the sequence of physical processes approach, reveals indeed a gap size dependence and that the structural response is enslaved by the mechanical response.The gap scan reveals an erratic structural response in bulk, unhindered by the wall's presence, which reduces the viscous drag.We prove that sheared nematic Gibbsite also displays a nonlinear response in steady shear flow, both in terms of structure and local flow rate.To this end, we introduce a new method to attain the velocity profile along the gradient in a Couette cell using X-ray Photon Correlation Spectroscopy (XPCS).Blood is a complex fluid with strong shear-thinning behavior that depends on the ability of the red blood cells (RBCs) to form aggregates in the form of stacks, called rouleaux.Both depletion and bridging between RBCs have long been believed to play a role in rouleaux formation, mediated by the presence of macromolecules such as fibrinogen in blood plasma.However, despite numerous investigations, the formation and breakup of RBC aggregates have not been fully elucidated.The most commonly used macromolecule to induce these interactions is the neutral dextran molecule.However, experimental evidence shows that the RBCs adsorb dextran.In order to distinguish the mechanisms behind RBC aggregation, we will employ a depletant agent with a very long-ranged interaction force, namely the filamentous fd bacteriophage.We study the cell-to-cell interactions with the help of optical tweezers, probing the aggregation and disaggregation force between two cells as a function of the interaction time and the depletants used.Our results show that the interaction forces driven by a pure depletant are linearly dependent on the depletant concentration versus the bell-shaped dependence displayed by dextran.We subject pairs of aggregated RBCs to shear flow to study the breakup behavior, and we observed that indeed the doublets break up when the drag force is comparable with the aggregation force we measured previously.However, at high shear rates, we still find doublets probably due to the complex interplay of tumbling and deformation of the cells.

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Air pollution was responsible for 4.2 million deaths in 2016. Next to toxic gasses, particulate matter (PM) was the main culprit as particulate matter below 2.5 µm (PM 2.5) can reach the lung alveoli and damage lung tissue. However, by filtering this particulate matter at the source via filters with a high filtration efficiency, this damage can be prevented. By using a nanofiber mesh supported by a substrate, PM2.5 is captured without drastically increasing the pressure buildup. One of the most efficient ways to make these nanofibers is electrospinning. This technique has seen an increased interest in the last two decades due to its versatility, simplicity and speed. However, most nanofibers are currently made from polymers that are not biodegradable or biosourced and the manufacturing process often utilises toxic solvents such as chloroform and DCM. This poses a problem as in the last decade there has been a worldwide push to focus attention on sustainability. In order to transition in the filtration market to more sustainable nanofiber production, new polymer-solvent systems (PSS) need to be developed. In this exploratory study PEO in water, PVP in water, PVP in ethanol, PVDF in DMF, cellulose acetate in acetic acid/water (75/25wt\%), cellulose acetate in acetone/DMF (80/20vol\%) and polyvinyl alcohol in water are tested to see if (1) a uniform nanofiber solid morphology can be obtained by electrospinning and (2) to see what the filtration efficiencies of these nanofibers on a cellulose or nylon substrate are. In order to predict the processability and solid morphology of the polymer-solvent systems a processability map is set up by plotting for each sample of a concentration range going from dilute to concentrated solutions the Deborah (De) number over the Ohnesorge (Oh) number. This reports shows that the processability map provides a qualitative indication of the attainable solid morphology (beads, beads-on-string or uniform fibers) as samples with a De and Oh number below 0.2 always produce beads and De numbers above 1 prove necessary in order to transition to a beads-on-string solid morphology. The change in solution parameters (µ, γ, λ), processability and solid morphology as a function of polymer concentration is discussed on an individual basis. All tested PSS can produce nanofibers and the addition of nanofibers can increase the overall filtration efficiency up to 31\%. Future testing of the CA in acetic acid and water and PVA in water polymer-solvent systems is highly recommended as they are considered the most sustainable tested PSS. CA in acetic acid and water had the best filtration efficiency and only PVA in water could form uniform electrospun fibers already at a semi-dilute regime.