The term biopolymers may be used to describe macromolecules that are obtained from a wide variety of biological sources. In the wake of growing concerns surrounding the use of non-biodegradable synthetic polymers, they serve as ideal replacements for a wide range of engineering applications. However, given the versatility of (charged or uncharged) chemical species that form biopolymers, there are considerably large uncertainties in determining their exact chemical structure. The presence of charged species in biopolymers further complicates matters, as they remain sensitive to parameters such as acidity (pH) and ionic strength (conductivity), thereby challenging the traditional physical models that describe polymer dissolved within specific solvents.

The work presented in this thesis tries to overcome these limitations through an abstract and idealised description of their structure, using both, specific knowledge about the type of charges present within the biopolymer, as well as parameters such as pH and conductivity. Further, intentional changes are made to the pH and conductivity by introducing specific (counter) ions that are known to influence the thermodynamic stability of the biopolymer in solution. These include both, changes to the conformation of the biopolymers coils due to electrostatic interactions, as well as intermolecular interactions between neighbouring biopolymer coils due to the formation of (weak→ strong) physical bonds. Naturally, the accompanying changes to the structural conformations has an predictable influence on the properties of the biopolymer solution, which in this case is captured using rheology, i.e. the deformation of (solid, liquid and viscoelastic) materials due to the application of a load.

Specifically, rheology is used to track changes to the following parameters, the intrinsic viscosity: which is a measure for the size of the dissolved macromolecules, the Herschel-Bulkley consistency index: which is a measure for the viscous dissipation of concentrated biopolymer solutions, and the storage modulus and the yield stress. These latter two parameters collectively provide quantitative insight about the packing of weakly bonded biopolymer gel particles. In turn this information, i.e. changes to the rheological properties of a wide variety of representative biopolymer systems, is used to derive relevant structure-property relationships that may be exploited for engineering applications.

Finally, the collective insight gained by establishing these structure-property relationships is condensed to provide a simple rheology experiment. This simple experiment is practically relevant to ensure the on site quality of novel biopolymer formulations, as well as to aid suitable modifications to the existing extraction protocol.

This thesis reports on the “structure and supramolecular assembly in multi-component organogels”. It guides readers how the aim of this research has been achieved by division of the main question into subgoals in different chapters. This introduction chapter gives a brief overview on the research theme, it is followed by the second chapter extracted from our literature review on “From molecular assembly to gel formation: what is going on behind the scenes of supramolecular gel formation”. This tutorial review discusses three different assembly mechanisms in molecular gels namely: supramolecular polymerization, crystallization, and spinodal decomposition. The second chapter of this thesis is based on the section on the crystallization mechanism from the larger tutorial review paper, since crystallization is found to be the dominant mechanism of gel formation in bisamide systems throughout our research. It provides a general background on molecular gels followed by how crystallization can lead to the order in the gel network. The third chapter elaborates the study of single bisamide gelators in the solid state. It aims at understanding how odd-even spacer length in the chemical structure affects the complementarity of hydrogen bonding which determines the molecular structure and gelator properties. The fourth chapter describes the supramolecular arrangement and rheological properties of single bisamide gels. In the fifth chapter of this thesis, we explain how we developed and validated the DSCN(T) analytical model. This model empowered our research toolkit to quantitatively analyze the experimental data obtained from DSC. This reliable analysis enabled us to understand the phase behavior of bisamide molecules in the solid state (chapter 3), gel state (chapter 4), and binary systems (both solid and gel state in the subsequent chapter). The last chapter (chapter 6) focuses on the ultimate goal of this thesis: to develop design rules to control the supramolecular assembly pattern in the solid and gel state of multi-component systems. In the course of this phase of research, we made an attempt to understand how compound formation/ co-assembly and phase separation/ self-sorting impact the rheological properties of bisamide gels. The summary of this scientific journey is provided at the end of this thesis.

Bio-based composites have been a viable material choice in aerospace, automobile and construction industries over the past few decades. From day-to-day products like spoons and chairs to the construction of rocket parts, bio-based composites find their applications due to their mechanically enhanced, cost-effective and lightweight structures, with a reduced carbon footprint. This study collaborates with NPSP, one of the companies leading the way towards a circular economy.
However, the manufacturing and testing of bio-based composites is time and resource expensive. Moreover, exploring all natural fillers and fibres ratios is not feasible experimentally. Optimization and analytical models are two potential approaches that accelerate the search towards an optimal bio-based composite recipe when combined with bio-based materials research. A data-scarce Bayesian optimization model was already developed to research the composition of bio-based composites. The proof-of-concept program adjusts the natural materials’ weight ratios to optimize toward user-defined mechanical properties. The objective of this study is to experimentally investigate if the Bayesian Optimization model works by varying the objective functions and adapting the model according to the clients’ needs. By exploiting the machine learning model at an initial stage, the purpose is to test how the model reacts to different objective functions defined at high weight values and observe if the model can generate optimized recipes with better mechanical properties than the defined training set. For this study, four different fillers (calcite, lignocellulosic filler 1, lignocellulosic filler 2, waste-based filler) and two different fibres (flax, bamboo) are used, with calcite as the reference filler. A primary goal to be achieved by NPSP is to reduce or eliminate calcite as the primary filler due to its high density and brittle nature. Promising results have been obtained within two iterations of using the model for the different filler/fibre systems used.
Additionally, the thesis also investigates the rules of mixing for multi-component systems to develop analytical models that predict the mechanical properties of the composite. The Lewis-Nielsen model and the Cox -Krenchel theory have been used to compare theoretical values with experimental data points. The initial binary phase curve fitting followed by applying cascading to obtain ternary and quaternary phase mechanical properties provides approximate results for most recipes made. Finally, recommendations to improve both models have been covered, and a potential to combine both approaches has been shown.

Epoxy resins are one of the most relevant and widely used thermosets in the market covering a wide range of applications. Industries are being forced to quickly transition towards sustainable alternatives due to the pressure from emerging environmental concerns, the depletion of petrochemical supplies, and compliance with environmental legislation. Since the primary component of epoxy resins is derived from petroleum (Bisphenol A (BPA)), companies like Westlake Epoxy have joined the search for innovative, environmentally friendly solutions. Many bio-based substitutes have surfaced in recent years, in efforts to eliminate or reduce the quantity of BPA in epoxy resins. Attention has been focused on lignin biomass as a viable feedstock in the manufacturing of these thermosets because of its large production volume and some structural characteristics.

This study addresses the synthesis of novel lignin-based epoxy resins and the evaluation of their potential application in the field of coatings and composites. For this research, different sources of technical Kraft lignin were employed. Since technical lignin is not very reactive due to the large molecular weight polymers, a Confidential Fractionation process has been developed. For its synthesis, both small- and large-scale glycidation processes were successfully implemented. To understand the chemical structure of lignin and its corresponding resins, different analytical techniques were used such as Gas Chromatography (GC), titrations, Nuclear Magnetic Resonance (NMR), Fourier-Transform Infrared Spectroscopy (FT-IR) and Gel Permeation Chromatography (GPC). Additionally, for the development and characterisation of coatings and composites, a variety of material testing techniques were employed, namely Differential Scanning Calorimetry (DSC), Dynamical Mechanical Analysis (DMA), Thermogravimetric Analysis (TGA), Interlaminar Shear strength (ILSS), Impact testing, Pendulum hardness, among many others.

Experimental results showed an average fractionation yield of 50-60% of technical Kraft lignin using the Confidential Fractionation process. Compositional differences in the fractionated lignin substrates studied via NMR analysis, predict some differences in the reactivity of these substrates towards glycidation, which is supported by different Epoxy Group Content (EGC) of the corresponding epoxy resins. The EGC of the lignin-based epoxy resin is significantly lower than that of the reference resin due to the presence of bulky moieties that hinder the reactivity of active sites. While lignin-based coatings exhibit comparable performance in hardness and direct impact resistance, however, its high viscosity and stiffness results detrimental in other areas. On the other hand, this high viscosity is a major challenge in the processes of prepreg laminates leading to poor adhesion of the fibres to the matrix, which has a negative effect when it comes to mechanical performance. However, adding lignin to epoxy resins has proved to improve the thermal stability of these materials.

The superior nature of long fiber reinforced thermoplastics (LFTs) in terms of properties such as specific modulus, strength, and excellent impact resistance, along with their lightweight properties, ease of processability and recyclability make them one of the most competitive materials leading to their growth in various fields of applications.
With the growing rise of LFTs, the research on their mechanical properties and their processing has grown as well. Injection molding method has been one of the most widely applied production method for LFTs processing. Research has shown that the mechanical edge offered by the LFT products obtained from injection molding is dependent on the lengths of the fibers in the final product. This makes it important to understand the breakage of fibers during processing.
This work addresses the breakage of fiber in injection molding by conducting a thorough review of the industrial, experimental and theoretical research done in the field. Following this, simulation approach has been undertaken to understand the fiber breakage in geometries which represent slightly complex shapes as compared to the conventionally used shapes. Based on the theoretical research, the state-of-the-art models have been reviewed and compared in their ability to produce reliable fiber breakage results.
The results showed the influence of rheology and geometry on fiber breakage in simulations, where shear rates led to higher fiber breakage and increasing viscosity led to a slight reduction in breakage. Further, the simulation study provided inconsistent results with variation in geometry, and a need for further fine tuning of simulation parameters was observed. The theoretical models applied in the study gave reliable results in terms of the trends of the fiber breakage, with a novel model, called Bechara model, showing acceptable and more time efficient results, in comparison with the currently applied commercial model, Phelps model.

Anaemia affects a third of women and almost 50% of infants and toddlers worldwide. Iron deficiency is the most common cause of anaemia, and the most common nutritional disorder in the world. To increase dietary iron intake, iron fortification of staple foods commonly consumed by the general public is an effective approach to prevent and control iron deficiency anaemia. It is important to maximise the iron bioavailability (absorption by the human body) in these fortified products, since iron overload is also known to cause Since the diet of infants and toddlers revolves around milk, milk is a good food carrier to address iron deficiency anaemia in children. The aim of this project is to assess the influence of five factors on the bioavailability of iron fortified skim milk: (1) iron concentration, (2) molecular form of the added iron, (3) storage time after fortification, (4) the addition of an iron enhancer and (5) the addition of an iron inhibitor.
Skim milk was fortified with FeC l2 and FeC l3 to 5 and 20 mmol Fe L−1
and stored for 24 hours or one week.
Part of the milk was further left untreated and to another part ascorbic acid (vitamin C) or tannic acid were added as respectively iron enhancer and iron inhibitor. The bioavailability of the iron in these milk samples was assessed on phase distribution and oxidation state, since it is believed that iron in the soluble phase of the milk and in the oxidation state Fe2+ is more bioavailable.
Analysis showed that the difference in iron concentration induced a pH decrease, which was greater for the higher concentrations of iron and the molecular form FeC l3. The pH difference caused the percentage of iron present in the casein fraction to increase, in the protein fraction to decrease and did not influence the iron in the soluble phase. It was also found that the 20 mmol L −1 FeC l2 showed more iron in the soluble phase and more Fe2+, whereas no statistical difference was observed for the 5 mmol L −1 , which might also be due
to the pH difference. The increase in storage time to one week was reflected by an increase in iron bound to the caseins. This shift was not reflected in a change of oxidation state. The addition of the iron enhancer (ascorbic acid) increased the iron present in the protein fraction and soluble phase, which was strengthened by the further decrease in pH. The chelation of iron by ascorbic acid did not necessarily reduce Fe3+ tot Fe2+; the Fe2+ decreased for the 20 mmol L −1 FeC l2, whereas it increased for the 20 mmol L −1 FeC l3. Lastly the
addition of the iron inhibitor resulted in a significant decrease of Fe2+. Most iron was bound to the casein or precipitated as iron-tannic acid complex.
Overall, this research confirmed that the bioavailability of milk is not easily evaluated, since the behaviour of iron in milk depends on many different factors that can not be studied isolated. Only by evaluating many possible combinations of concentration, molecular forms, additives and storage conditions, the bigger puzzle can be solved. This project attributed to a part of the solution and is therefore a valuable contribution in the development of bioavailable milk products, that will reduce iron deficiency anaemia in children.

In this thesis several aspects of PEM fuel cells are discussed. From an atomic scale, e.g. crystal and electronic structure of a non-noble metal material, e.g. (H)zLiMn2O4 (protonated spinel lithium manganese oxide) for electrocatalysis and its dynamics, to meso-macro scale effects such as those concerning transport resistances at the membrane/electrode interface.

Because diagnostics have improved tremendously, nowadays breast cancer is more frequently detected at an early stage. Long-term prognosis is excellent and therefore the new treatment should focus on minimizing long-term side effects and treatment burden. This research proposes cancer treatment using nanoparticles (NPs) for a combination of heat therapy and brachytherapy. For the NP design, superparamagnetic iron-oxide nanoparticles (SPIONs) will be used. Because of their biocompatibility and good magnetic properties, they are suitable candidates for heating using an alternating magnetic field. To make the NPs applicable for brachytherapy, the NPs are doped with holmium (Ho), a lanthanide with high magnetic moment and radioisotope Ho-166. Furthermore, SPIONs and Ho change the relaxivity of water
protons and therefore they can be used as contrast agents for magnetic resonance imaging. This makes it possible to image the NPs during the treatment and enables thermal planning and dose-rate calculations delivered to the cancer tissue to be performed. The incorporation of Ho inside the iron-oxide structure is expected to change the magnetic properties of the NPs. The success of using Ho as contrast agent and for brachytherapy purposes have been proven in several researches. However, the influence of Ho on the heating performance of these SPIONs is unknown. This research will characterize the magnetic properties of undoped and Ho-doped SPIONs and compare them, in order to examine the heating possibilities of Ho-doped NPs. For the synthesis of the NPs a spark discharge generator was used. Spark ablation is a synthesis
method able to yield narrow size distribution of different metallic particles and alloys. However, since spark ablation is relatively new, the synthetic methodology itself had to be developed. Therefore, this research was divided into two parts: 1) the synthesis of NPs using spark ablation and 2) the characterization of Ho-doped iron NPs and the comparison with undoped SPIONs. Since the first part focused on the spark ablation synthesis, the influence of the generator settings on the primary particle size was investigated using DLS and TEM. The VS-Particle generator was able to produce 4 nm Fe-Fe and Ho-Fe NPs, a size that is smaller than expected. The generator settings did not influence the primary particle size and therefore, the settings of the generator were chosen to maximize the yield. The initial set-up had low yield and therefore, the influence of micro-bubbler, electrode configuration and bubbling column were examined and changed to improve the yield. A bronze sintered filter with pore size 0.4-20 ��, solid iron electrodes and 60 mL bubbling column volume appeared to be the most optimal. During the second part of this research, 4 nm Ho-doped iron oxide NPs and un-doped iron oxides were produced. They were characterized using TEM, DLS, XRD, ICP, SEM-EDX, Mössbauer spectroscopy, SQUID and NMR. As a result of low concentrations obtained, no good qualification of the produced particles could be obtained. All particles showed superparamagnetic behavior and influenced the relaxivity times of water protons. To what extend the relaxivity was changed upon doping remains unfortunately unclear, because the composition of the NPs is unknown. It can be concluded that the used set-up was not able to produce reproducible NPs and therefore no reliable characterization could be done on the Ho doped particles. Future research should focus on a more controllable synthesis method to be able to examine the possibilities of Ho for heating purposes.

The society of Delft Aerospace Rocket Engineering (DARE) aims at launching the Stratos IV sounding rocket to an apogee of 100km; thus cementing their place as one of the few student teams that have had the unique opportunity to design and build a rocket that is capable of reaching the frontiers of space. In doing so, DARE has entered flight supersonic regimes during atmospheric entry. With the development of cryogenic engines in the pipeline, future DARE missions look at reaching the hypersonic velocity regimes resulting in the current cork and carbon fibre composite heat shield design becoming redundant. Thus, hypersonic flight brings with it the challenge of designing new a heat shield; capable of withstanding the elevated temperatures.

Alginate and montmorillonite nanoclay based biopolymer nanocomposites have become a well-researched topic in recent years. This stems from the ability of the nanoclay fillers to align themselves within the suspension to mimic natural materials such as nacre (mother of pearl). The alignment of the nanoclay not only reinforces the biopolymer to provide a high storage modulus but also provides a tortuous path for transport phenomenon such as diffusion to take place; thereby making them flame retardant.

In their native state, the nanocomposites are film-like and offer limited viability. But, simple production practices may be borrowed from culinary disciplines to transform the nanocomposites into foams with different relative densities. The introduction of the gaseous voids should further heighten the thermal characteristics; allowing them to function as heat shields. However, in transforming the nanocomposite to a foam, little is understood about the impact it will have on the mechanics of the native nanocomposite. As multiple analytical and numerical models have been provided over the years to estimate the mechanical properties of foams, a careful assessment of the various literature sources becomes necessary. Once a suitable model is identified, a detailed experimental campaign can be carried out to characterise the biopolymer nanocomposite foams mechanically.

The increasing energy demand of the world population in combination with tangible climate change effects stemming from rising carbon dioxide emissions is currently characterizing a large portion of the political and societal debate. Despite huge technological advancement in the field of renewable energy resulting in energy prices lower than that of fossil based energy, the rate of greenhouse gas emissions has not even levelled off but rather kept increasing. A part of the problem lies in the very nature of season and weather dependent energy conversion technologies producing electricity peaks that are hard to buffer. The solar and wind powered scenario is not yet able to completely replace the relatively demand flexible fossil fuel based power plants. The gap between energy production and energy use, in essence meaning storage and distribution of sustainable energy, constitutes one of the largest challenges of our times. Hydrogen has been proposed as a molecule with the potential of being an important energy carrier in a renewable energy based economy. In a fuel cell, hydrogen can be electrochemically oxidized to water, releasing its chemical energy without the emission of combustion by-products like carbon dioxide. Commonly platinum is used as a catalyst to speed up the anode and cathode reactions in a fuel cell. Reversibly, an electrolyser uses electricity to electrochemically split water into its constituents; hydrogen and oxygen. Ideally, hydrogen could be produced where and when the electricity is available or cheap and be stored or transported to the location where it is needed, although technical challenges as well as infrastructural hurdles are still to be solved. If electrochemical devices, such as fuel cells, are to play a major role in the future energy landscape a better understanding of catalytic processes along with cheap and scalable non-noble metal catalysts are still needed.

Cellulose is a biopolymer commonly used as a renewable constituent in the production of green materials. Wastewater solids can be an attractive source of cellulose, mainly originating from toilet paper. Cellulosic solids can be recovered (i) through sieving before the sewage treatment - resulting in a Fine Sieve Fraction (FSF), or (ii) after biological treatment in the waste sludge – such as in Nereda® Excess Sludge (NES). Its recovery and valorisation into high-end bio-based products, such as crystalline nanocellulose, could improve the techno-economic feasibility of cellulose recovery from wastewater. A cellulose extraction method from wastewater solids was developed during this project. Reference materials (microcrystalline cellulose and toilet paper) and wastewater-extracted cellulosic pulps were studied for the production of cellulose nanocrystals (CNCs). CNCs were prepared by controlled acid hydrolysis followed by centrifugation, filtration, dialysis, neutralisation and ultrasonication. A detailed protocol for CNCs isolation from toilet paper and wastewater-recovered pulps can be found in the appendix section. CNCs could be extracted at around 30 % yield (g g pulp-1). FSF showed to be an attractive source of nanocellulose since the yield per g FSF was 22 %, while for NES it was only 4 %. The wastewater-CNCs presented rod-like morphology with high aspect ratio (10 – 14), crystallinity (62 – 68 %), and chemical structure very similar to commercially available CNCs. However, there is still great extent for improvements since impurities might be still present and the isolation process needs reproducibility and optimization. Bionanocomposites consisting of CNCs (commercial and lab-made) and alginate materials were investigated by measuring the stiffness of freestanding films. A 50 % loading of commercial-CNCs reinforced alginate films by a factor of 1.6 (19 GPa). For the same loading, CNCs isolated from toilet paper and FSF reinforced alginate by a factor of 1.8 and 1.5 (22 – 18 GPa) respectively. Both characterisation results and reinforcement efficiency of CNCs isolated from toilet paper and wastewater-recovered pulps confirm the good quality of this potential product. Furthermore, we have observed changes in the nematic-isotropic phase diagram of CNCs in alginate suspensions. We developed a model hypothesizing that an alginate-shell decorates the CNCs rods increasing its volume fraction and allowing the nematic phase to appear at lower concentrations. The model was highly representative to the experimental data. Lastly, the market relevance of wastewater-CNCs is discussed together with a research outlook.

Nature displays a multitude of fascinating materials, from beautiful colors of butterfly wings to the toughness of mullosc shells, which are formed in mild enviornmental conditions with commonly occuring materials, such as chitosan or calcium carbonate. These composite materials display an intricate interplay of biopolymers and minerals forming highly ordered structure. The function of these materials is primarily determined by the selective pressure of the enviornment that certain organisms are placed in. It varies from the “delicate” signaling colors to a robust impact resistence.

Crude oil, coal and gas are currently the main resources of energy in the world. The World Energy Outlook claimed in 2007 that the major source of energy (about 84%) would still be generated from fossil fuels in 2030. By these projections, the world's fossil fuel reserves will be consumed within a few decades, making it necessary to have a well stablished replacement for fossil fuels to fulfil our energy demands. Furthermore, the environmental impacts of fossil fuels are becoming clearer to scientists and governments. Among the population, environmental awareness is increasing as well, which leads to an increase in the demand for energy that does not harm the environment.
Fuel Cells are one of the most promising clean energy technologies, which are in clear consideration to replace fossil fuels in the future. They work as electrochemical energy conversion devices, similar to batteries, but do not require the recharging process, since they just depend on the presence of fuel to keep producing electricity. In most fuel cells, hydrogen is supplied to the anode and oxygen to the cathode, which results in production of water, heat and what is the most important, electricity. Unfortunately, several drawbacks with fuel cells have been identified. Probably the most important one is the very high cost, which is caused by use of the expensive electrolyte membrane and the catalyst...

In this work, properties of Calcium alginate-reduced graphene oxide and Barium alginate‐reduced graphene oxide composite films are explored. In addition, the properties of the divalent metal ion-cross-linked alginate composite films are compared to the analogous properties of uncross‐linked Sodium alginate-graphene oxide composite films of the corresponding compositions. As the filler, used in the preparation of the composite films, is obtained by chemical oxidation of graphite, the prevailing knowledge of the process coupled with in situ X-ray diffraction investigation of the samples prepared by such a method is presented as well.