[diss] Kemian tekniikan korkeakoulu / CHEM

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    Investigation of Thermodynamics and Kinetics of Nitrogen Behavior in Steel Melts for Improved Nitrogen Control in the AOD Process when Producing Nitrogen-Alloyed Stainless Steels
    (Aalto University, 2024) Pitkälä, Jyrki; Holappa, Lauri, Prof. emerit., Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Kemian tekniikan korkeakoulu; School of Chemical Technology; Jokilaakso, Ari, Prof., Aalto University, Finland
    Stainless steel is a fundamental pillar of a developed society, without which our current way of life would not be possible. Stainless steels consist of several alloying elements, of which chromium is the key component regarding corrosion resistance. Nickel, molybdenum, and even manganese also play important roles in influencing the corrosion resistance, mechanical properties, machinability, and usability of stainless steel. Nitrogen has two functions in steels. In ferritic steels, nitrogen is considered a harmful impurity, whereas in austenitic and duplex stainless steels it often serves as a beneficial alloying element. Nitrogen stabilizes the austenitic structure, reducing the need for nickel, and enhances corrosion resistance and mechanical properties. However, its role and acceptable levels vary depending on the steel grade, and even minor changes in content can impact the steel properties. In stainless steelmaking, the argon oxygen decarburization (AOD) converter plays a central role and is primarily responsible for alloying and controlling nitrogen content. The ultimate objective of this work was to develop models for improved nitrogen control in the AOD converter, which is why all the experiments and measurements were carried out in an industrial AOD converter. First, the influence of different alloying elements and temperature on the equilibrium solubility of nitrogen at one-bar nitrogen pressure was investigated. This led to the development of a novel mathematical formula, which includes updated interaction parameters between nitrogen and the main alloying elements. Second, the applicability of Sieverts' law in the AOD Converter was investigated, and provided evidence supporting the idea that the nitrogen content in molten steel can be controlled by adjusting the nitrogen partial pressure in the process gases. Furthermore, to achieve a target nitrogen content in the AOD converter, a comprehensive understanding of the factors influencing the kinetics of nitrogen content change is crucial. On this account, both nitrogen absorption and desorption rates were investigated in several test series. Finally, the thermodynamic-kinetic models developed in this work were tested across a wide range of alloy compositions and nitrogen contents ranging from 0.150% to 0.400%. The results demonstrated that nitrogen content can be accurately predicted using these models. As a result of this work, equations for predicting nitrogen content can be integrated into the control models of the production process to enhance accuracy in achieving the target nitrogen range. These equations enable improved productivity of the AOD converter for nitrogen-alloyed steel grades. Additionally, when the nitrogen content does not need to be further regulated by reblowing, gas costs and quality losses can be reduced.
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    Exploring silk protein assembly mechanisms for high-performance materials
    (Aalto University, 2024) Välisalmi, Teemu; Linder, Markus, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biomolecular Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Linder, Markus, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Silk proteins present remarkable potential as the building blocks for high-performance materials. Due to their unique protein structure, they exhibit a variety of properties, such as a combination very high tensile strength and elasticity, biodegradability, biocompatibility, and ability to be spun in natural conditions — qualities uncommon in synthetic fibres. While challenging to acquire through natural means, the application of gene engineering allows to produce substantial quantities of recombinant silk proteins. However, the assembly pathways leading to the formation of functional materials remain largely unknown, with the evidence suggesting that crucial insights lie within the intricate spinning mechanism of silk-producing animals. Publication 1 delves into an investigation of the native spinning system of Bombyx mori silkworm. Amino acid mapping throughout the middle silk gland revealed a gradual change in various amino acids, attributed to the increase in different sericin proteins. This change correlated with the extensional behaviour of the silk dope, which was further enhanced by a straightforward pH modification inspired by the native spinning system. Publication 2 introduces a more sophisticated silk pulling device designed for controlled pulling and tensile testing, with a focus in automation. The device was employed to pull fibers from regenerated silk solution. Although immune to the pH induced dimerization due to irreversible changes by the regeneration, the fibroin fibers displayed a considerable median tensile strength of 147 MPa. In addition, a recombinant silk protein was observed to preassemble at an air-water interface, allowing pulling of thin fibers from droplets of silk. Liquid-liquid phase separation was found to be a significant factor in creating stronger fibers, demonstrating the necessity of controlling this intricate aspect of molecular assembly. Not limited to fibers, silk proteins find application as building blocks for films. Publication 3 details the development of a simple deposition method to create highly hydrophobic silk films. These films, characterized by the arrangement of intrinsically hydrophobic regions of the silk protein, formed in the presence of a specific salt concentration and high relative humidity during drying. Notably, the phenomenon was not strictly dependent on the silk protein sequence or the type of salt, although certain variations displayed superior performance. The films were altered by wetting, disrupting the interaction between the silk and salt. Although the lack of durability limits applicability of the silk films, this work demonstrates the versatile nature of the amphiphilic silk proteins.
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    Matte–slag interaction simulation in the flash smelting settler using coupled CFD-DEM
    (Aalto University, 2024) Jylhä, Jani-Petteri; Jokilaakso, Ari, Prof. Emeritus, Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Metallurgy; Kemian tekniikan korkeakoulu; School of Chemical Technology; Jokilaakso, Ari, Prof. Emeritus, Aalto University, Department of Chemical and Metallurgical Engineering, Finland
    The flash smelting process is a major copper production method. However, a closed furnace with high temperatures makes physical observations of matte settling through the slag physically impossible and, thus, computer simulations are needed to study settling. Previously, settling simulations have been made using computational fluid dynamics (CFD). In this project, a new method of using coupled CFD-DEM (discrete element method) was developed and used to study copper matte droplets in a flash smelting settler. Traditionally, CFD-DEM is a fluid and solid particle simulation method; however, by simulating soft spheres and creating user-defined submodels for coalescence and reaction kinetics, liquid matte droplets settling through a slag layer could be studied. Due to the impossibility of observing a high-temperature process in situ, a room temperature physical model was needed to validate the chosen simulation method. Plastic spheres were fed into an oil bath, in which their settling was filmed and compared to simulation results of the same system. Both the experiments and the simulation produced a channeling flow, where drag from the settling spheres pulls the flow of droplets into a narrow channel, accelerating the settling velocity significantly. However, at the bottom of the oil, the flow turns sideways and then up, forming a vortex ring around the channel, which may entrain slowly settling objects. Several matte–slag simulations were made with CFD-DEM, utilizing either the coalescence model or the combined coalescence and reaction kinetics model. Channeling flow, similar to the sphere–oil experiment and simulation, occurred with every matte–slag simulation. The flow caused the matte droplets to settle through the slag significantly faster than predicted by Stoke's law. The coalescence and reaction kinetics models further accelerated the matte droplets as coalescence increased the size of the droplets while reaction kinetics caused copper to concentrate in the droplets as iron and sulfur were removed, which increased droplet density. The coalescence rate was increased by the channeling flow as it caused the droplets to enter a narrower channel, causing an increased number of collisions and, thus, coalescence.
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    Tailoring the properties of polysaccharides-based hydrogels - From cell interactions to biomedical applications
    (Aalto University, 2024) Teixeira Polez, Roberta; Valle-Delgado, Juan José, Aalto University, Department of Bioproducts and Biosystems, Finland; Morits, Maria, Aalto University, Department of Bioproducts and Biosystems, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bioproduct Chemistry; Kemian tekniikan korkeakoulu; School of Chemical Technology; Österberg, Monika, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
     This thesis focused on developing polysaccharides-based hydrogels designed to closely mimic the properties of the human extracellular matrix (ECM) through innovative 3D biofabrication techniques. While nanocellulose hydrogels have shown promise in the fields of biomedical engineering and regenerative therapy, they face challenges related to poor mechanical properties and limited 3D printing resolution. To overcome these challenges, nanocellulose was combined with heteropolysaccharides (tragacanth gum, xanthan gum, and quince seed mucilage). This strategic combination enhanced the processability of the hydrogels by improving their viscosity and shear-thinning behavior, ensuring smooth extrusion and deposition through the printing nozzle. These hydrogels closely resemble the scaffolds typically used in biomedical applications in terms of their porosity, pore size, and porous structure. Additionally, adjusting the nanocellulose content enabled tailoring the stiffness and swelling of the hydrogel, allowing further optimization according to the specific intended application. Furthermore, the study explored controlled drug delivery, particularly the development of chitosan (CS) hydrogels enriched with the phenolic compound phloroglucinol (PG). These hydrogels exhibited versatility, as they could be prepared with varying porosities and morphologies, resulting in distinct release kinetics. This versatility positions them as suitable biocompatible scaffolds and drug delivery systems, particularly for applications like wound dressing. In addition, the research delved into the molecular-level interactions between biomaterials and living cells using advanced Atomic Force Microscopy-based techniques such as colloidal probe microscopy (CPM), and single-cell force spectroscopy (SCFS). These results revealed insights into cell-biomaterial and cell-cell interactions, shedding light on adhesion protein dependencies and cellular behaviors within different biomaterial environments. In summary, this study advanced polysaccharides-based hydrogels for biomedical applications, combining innovative fabrication strategies with a deep understanding of molecular-level interactions. The findings have the potential to significantly impact biomedical research, paving the way for high-performance functional materials in various biomedical domains.
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    Studies on phenomena involved in impregnation of industrial wood chips
    (Aalto University, 2024) Määttänen, Marjo; Tikka, Panu, Prof., Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Kemian tekniikan korkeakoulu; School of Chemical Technology; Dahl, Olli, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    In chemical pulping, cooking chemicals are used to dissolve lignin in wood to release the fibres from the wood tissue. Chemicals must be present in the parts of the wood tissue where delignification takes place before the cooking temperature is reached, as otherwise the quality of the pulp will suffer. The transport of the cooking chemicals takes place by two mechanisms. Penetration fills the fibre cavities with liquid under a pressure gradient enabling faster diffusion of the chemicals into the wood. Diffusion refers to the movement of ions through a liquid from a higher concentration to a lower concentration. Although both mechanisms occur in parallel, their separate and combined influences on impregnation have been seldom studied in the same research. The objectives of this thesis were to clarify and deepen the understanding of the impregnation of industrial chips and the phenomena occurring in the course of impregnation. Therefore, a new experimental method was developed. The experiments were divided into penetration and impregnation experiments. The data collected from the experiments were combined for calculating corrected penetration degree values and the mass and alkali balance involved in impregnation. Based on the data, quantitative results and deeper understanding for impregnation were achieved. The research work confirmed the three defined hypothesis dealing with the influence of the physical properties of industrial chips and the processing conditions on impregnation and the influence of the chemical diffusion and the dissolution of wood on the degree of penetration. Practical outcomes and guidelines for the impregnation of the industrial wood chips were the following. The moisture content and the basic density of wood chips determine the initial penetration degree (PDi) of wood chips: a low basic wood density and a low moisture content result in higher amounts of air inside the wood, which means a lower initial penetration degree of the wood. The lower PDi hinders the whole impregnation process. Therefore, it is recommended to use pre-steaming as a common practice and more emphasis must put on the use of fresh/moist wood chips.The prerequisites for fast diffusion are a high degree of penetration and a high concentration gradient between impregnation liquor and the alkali inside wood chips. On a laboratory scale, for high-concentration liquor, 15 minutes of impregnation time is sufficient for an adequate alkali charge for kraft cooking, but in the case of low-concentration liquor, even 60 minutes is insufficient. Part of the impregnated alkali is consumed during the impregnation, and more at higher temperature. Therefore, there is risk of running out of alkali if the temperature is raised quickly to the cooking temperature after low alkali impregnation. For successful impregnation, proper pre-steaming, a low impregnation temperature and moderate alkali concentration should be used for all wood species.
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    Highly active catalytic cathode and selective separator for elevated temperature lithium oxygen batteries
    (Aalto University, 2024) Qiu, Qianyuan; Pan, Zhengze, Asst., Prof., Tohoku University, Japan; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Research Group of Industrial Chemistry; Kemian tekniikan korkeakoulu; School of Chemical Technology; Li, Yongdan, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
    Energy plays a vital role in the development of industry and human daily life. Various energy storage technologies have been investigated to meet the demands. Particularly, lithium oxygen battery (LOB) is a uniquely high energy density storage device. Theoretically, LOBs with Li2O2 and Li2O as the discharge products deliver energy densities as high as 3500 Wh kg−1 and 5200 Wh kg−1, respectively. LOB with molten salt electrolyte operating at elevated temperatures is developed which facilitates the reversible 4e−/O2 conversion to achieve Li2O as the discharge product. The molten salt electrolyte relieves the side reactions for the cases with organic solvent in the electrolyte and carbon as the component of the cathode. However, the electrochemical perfor-mance of this LOB still needs optimization. To achieve the high catalytic activity and long-term stability targets, highly active cathode catalyst and effective separator for the LOB operating at elevated temperature are the key enablers. In this work, LaNi0.5Co0.5O3 (LNCO) perovskite was introduced as the LOB cathode catalyst. The physical properties and catalytic activity of LNCO were investigated with different characterization and computational techniques. Moreover, the superior performance of LOB with LNCO cathode operating at 160 °C was demonstrated. A LNCO cathode prepared with a sol-gel method enabled a LOB with an energy efficiency as high as 98.2% and an ultra-low overall overpotential of 50 mV. The preparation of LNCO was further investigated, and a sample prepared with a coprecipitation method with nanostructure effectively reduced the amount of catalyst used to a level as low as 1 mg cm−2 with delivering comparable performance of the LOB. A LOB with a self-supported LNCO@Ni cathode achieved a long-term stability, running for 834 cycles with a 94% capacity retention. The Li2O as discharge product and the corresponding reaction pathways are also confirmed. A metal-organic framework (MOF) based membrane was employed as the separator for the LOB operating at 160 °C. The battery ran stably for over 180 cycles with a coulombic efficiency as high as 99.9%. The membrane not only provided sufficient Li+ transfer rate but also effectively impeded the cross over of discharge product during operation. The LOB with a highly active cathode catalyst and effective separator exhibited good electrochemical performance and stability at elevated temperature. The results also indicate that the LOB operating at elevated temperature is a potential strategy for future development.
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    Exploring structural diversity in quorum sensing signalling systems and strategies to control prokaryotic community-wide behaviour
    (Aalto University, 2023) Jonkergouw, Christopher; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biomolecular Materials Research Group; Kemian tekniikan korkeakoulu; School of Chemical Technology; Linder, Markus B., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Bacteria, despite being single-celled organisms, have the ability to establish intricate communities where individual cells collaborate for the collective benefit. This cooperative behaviours and spatial organization are facilitated by cell-to-cell communication mediated by quorum sensing (QS). Within these communities, bacteria engage in diverse cooperative activities, including the regulation of biofilm formation, virulence, production of antimicrobials, nutrient sharing, and defence against external challenges. The remarkable adaptability and resilience exhibited by bacteria in these communities underscore the significance of intercellular communication and collaboration, even in the most basic organisms. In this work, we studied the function of various QS signalling systems and explore how having control over QS communication, can be utilized towards several biotechnological applications. First, we theoretically explored the wide diversity in QS signalling systems and use novel computational tools to understand how QS signalling systems interact with one another. These predictions were used to experimentally investigate a set of 10 QS signalling systems, among which we identified six fully complementary QS signalling systems. Then, we investigated strategies to control and disrupt communication in bacterial pathogens that utilize QS to regulate their virulence during infections. We further studied the potential of QS disruption as a potent strategy to combat antibiotic resistance bacteria, both in vitro and in vivo. Finally, we explored novel microfluidic culturing techniques to build microbial communities in a bottomup approach. In this, QS signalling was utilized to coordinate the behaviour of distinct populations acting within the community. From these studies, we improved upon the method and developed a novel 2-photon polymerization technique to enable stable microbial communities of bacteria consisting of four individual populations. In summary, QS signalling systems play a crucial role in facilitating coordinated behaviours among bacteria, enabling them to act collectively as a group. Here, we show that by harnessing the power of QS, we can exert control over bacterial communities and shape and functionalize their collective behaviour.
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    CFD modeling of multiphase flows in bottom blown copper smelting furnace
    (Aalto University, 2023) Song, Kezhou; Jokilaakso, Ari, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland.; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Kemian tekniikan korkeakoulu; School of Chemical Technology; Jokilaakso, Ari, Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland.
    The advancement of copper production techniques has witnessed significant developments, with the continual emergence of new copper smelting and converting equipment and processes. The application of Bottom Blown Copper Smelting (SKS, ShuiKouShan) technology has attracted increasing attention since its introduction into production. To reveal the dynamics of agitation within the bath and optimize the variable parameters, Computational Fluid Dynamics (CFD) simulations were conducted on scaled-down and industrial-scale models of SKS furnaces, with various furnace structures and operating conditions. In this modeling research, the Multi-Fluid Volume of Fraction (Multi-Fluid VOF) model wasemployed for the first time in the simulation of SKS furnaces. The simulated results were in good accordance with experimental water models concerning the gas plume geometrics and surface wave characteristics. The numerical model employed exhibits significant potential for broader applicability, not only within the domain of SKS furnaces but also for similar industrial vessels characterized by comparable geometry and gas flow regimes. The simulation results presented the persistent rotation of gas plumes, accompanied by thepresence of low-velocity regions on the opposite side of the plumes. To enhance agitation within these low-velocity regions and minimize the dead zones, it is favorable to install tuyeres on both sides of the furnace bottom centerline. Subsequent investigations revealed that maintaining a certain range for the difference in tuyere angles between the two rows of tuyeres strikes a balance between the enhancement of agitation performance and the extension of refractory lining lifespan. Apart from tuyere arrangements, tuyere diameter and bath depth emerged as influential factors in bath agitation performance. A relatively reduced tuyere diameter and a deeper bath are suggested to enhance fluid motion within the low-velocity regions, thereby improving mixing behavior. While melt density was observed to exert a relatively modest influence on bath agitation, it was noted that lower melt viscosity contributes to enhanced melt fluidity, improved agitation performance, and a weakened impact on refractory lining. It is noteworthy that copper bottom blown smelting technologies have undergone extensive optimization through resource-intensive onsite experiments, without systematic theoretical guidance. Conclusions derived from the simulation presented in this thesis offer valuable references for industrial practice, presenting diverse fundamental principles governing the bath flow field. Furthermore, the CFD modeling provides the industry with important modeling information, as the furnace structure parameters were selected from a commonly employed range, thereby ensuring the usefulness of the simulation results for broad application in SKS furnaces.
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    Thin films of self-assembled materials by dip-coating technique
    (Aalto University, 2023) Nguyen, Hoang M.; Vapaavuori, Jaana, Prof., Aalto University, Department of Chemistry and Materials Science, Finland; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Multifunctional Materials Design; Kemian tekniikan korkeakoulu; School of Chemical Technology; Vapaavuori, Jaana, Prof., Aalto University, Department of Chemistry and Materials Science, Finland
    Self-assembly processes, which manifest in various natural phenomena, involve the constituents merging to construct intricate and well-structured material systems. Motivated by nature's elegance, synthetic self-assembled materials have experienced remarkable progress over the past two decades, facilitating the creation of structures spanning diverse length scales, ranging from the molecular level to larger macromolecular systems and microscale particles. An essential determinant for the practical application of self-assembled materials lies in the ability to fine-tune their self-assembly behavior, within which various complex physicochemical processes can take place. Among the techniques for depositing self-assembled thin films, dip-coating emerges as a particularly promising candidate. It shares the simplicity and expediency of drop-casting and spin-coating, while retaining the exceptional control over film thickness characteristic for layer-by-layer deposition. Moreover, it offers unrestricted substrate shape and size as well as permits the minimization of solution waste. Dip-coating, therefore, appears as an ideal approach for generating self-assembled thin films. Nevertheless, research efforts in this area remain limited, and a thorough comprehension of the interplay between dip-coating parameters and self-assembly behavior remains elusive. This thesis attempts to fill this knowledge gap by expanding the scope of materials combining dip-coating and self-assembly process. The thesis begins with an extensive review of the dip-coating technique, followed by distinct chapters exploring the self-assembly of various materials, including block copolymers, breath figure, and virus nanoparticles. Within these chapters, the thesis strives to establish systematic relationship between dip-coating parameter and the behavior of the specific material, thereby providing valuable insights that can steer future research in this field.
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    Computational modelling of adsorption and aggregation in bio oils at multiple length scales
    (Aalto University, 2023) Vuorte, Maisa; Sammalkorpi, Maria, D.Sc. (Tech), Aalto University, Soft Materials Modelling, Finland; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Soft Materials Modelling; Kemian tekniikan korkeakoulu; School of Chemical Technology; Laasonen, Kari, Prof., Aalto University, Computational Chemistry, Finland
    Surfactants in apolar solvents, such as common bio oils self-assemble into various colloidal assemblies, for example reverse micelles. The assemblies may also adsorb at interfaces. The shape and size of these assemblies is sensitive to factors such as surfactant chemistry, concentration, temperature, as well as the presence of co-surfactants, water, and other additives. Although the responses are qualitatively understood in chemical engineering processes, molecular scale understanding of surfactant assembly in apolar solvent environments remains sparse. In this thesis, self-assembly and adsorption of surfactants and colloidal species at solid – liquid interfaces in bio oils is critically assessed using three modelling approaches applicable to research questions at different length and time scales: atomistic detail classical molecular dynamics (MD), coarse-grained dissipative particle dynamics (DPD), and equilibrium state thermodynamics modelling. This combined approach, together with comparison to real chemical systems, allows discerning the effect of individual molecular features and e.g., hydration on adsorption strength and aggregation propensity in bio oils, but also simulation of large scale adsorption and aggregation equilibrium structures. The results presented identify the driving forces of adsorption and aggregation equilibria of bio surfactants, mostly lipids, in common bio oils. On the atomistic scale, hydrogen bonding and electrostatic interactions drive adsorption of single molecules. The interactions are affected by the presence and steric availability of functional groups, as well as, adsorbent surface chemistry and density of adsorption site functional groups. This may result in competitive intra-surface interactions. Water in the bio oil may mediate adsorption via water bridging. The findings show that surfactant aggregate in oil following a step-wise aggregation response, even at low surfactant concentrations and in the absence of water. Addition of water promotes growth and elongation of the aggregates. The surface packing is tunable by adsorbate chemistry, mainly surfactant head group charge, oil water content, and adsorbent surface hydrophilicity. On hydrophilic surfaces, water also acts as a competitive wetting agent. Overall, this thesis provides via multi scale modelling methods guidelines for understanding and manipulating surfactant adsorption/aggregation response in bio oils in terms of molecular architecture, oil water content, and adsorbent chemistry. The work also highlights the challenges and provides solutions associated with modelling self-assembly in apolar environments with sensitive self-assembly and adsorption equilibria.
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    Exploring the envelope of physical vapor deposition: Nano- and microstructured films for electrochemical applications
    (Aalto University, 2023) Etula, Jarkko; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Physical Characteristics of Surfaces and Interfaces; Kemian tekniikan korkeakoulu; School of Chemical Technology; Koskinen, Jari Prof., Aalto University, School of Chemical Engineering, Head of Department of Chemistry and Materials Science, Finland; Laurila, Tomi, Prof., Aalto University, Department of Electrical Engineering and Automation, Finland
    Physical vapor deposition (PVD) methods are established scalable industrial processes for creating high-quality functional films in various industries. PVD deposited films are commonly dense and smooth with structural features in the nanoscale, but by variation of deposition parameters, film properties and structure can be modified to enhance application-specific performance. In electrode materials for electrochemistry, for instance, a larger accessible surface area commonly increases the number of electrochemical reactions occurring at the same time on the electrode. In this work, PVD methods are used to deposit film materials for electrochemical applications: Nanostructured carbon thin films are investigated as electrochemical biosensors, and microstructured titanium oxide films are demonstrated in microbattery and photocatalysis applications. The aim is to explore and determine how PVD methods can be utilized to construct film structures with a high degree of application-specific tailorability in terms of nano- and microstructural features. Comprehensive structural and physicochemical characterization is carried out for the deposited materials, providing the fundamental tools and insight required to understand and link the observed application performance to changes in material properties. In the first part, the nanostructure of thin and ultrasmooth chemically inert carbon films high in sp3-bonded carbon are modified by alloying with iron, doping with nitrogen, and by embedding carbon nanodiamonds into the film structure. The addition of iron into the films as well as doping with nitrogen are found to enhance the performance of electron transfer on the carbon electrodes in electrochemical sensing applications. It is however also found that these modifications open and alter the initially high sp3-carbon nanostructure, exposing it to atmospheric contaminants. In the second part, a higher gas pressure is applied during PVD deposition, inducing cluster and nanoparticle formation of the deposited material. This gas nucleation technique is leveraged with titanium oxide as the deposition material to construct thick and porous microstructures. In the first subsection, a large permanent magnet is used to collect and self-assemble the gas nucleated titanium oxide nanoparticles into a hierarchical film structure several micrometers in thickness comprising particle clusters of varying sizes. This microstructure offers a considerably large specific surface area, which is important in its application as a photocatalyst. In the second subsection, in an otherwise conventional PVD process, substrate biasing in combination with gas nucleation of lithium-titanate-carbon material is found to result in an unidentified growth mechanism of micrometer-sized pillars. The performance of this micropillar structure is demonstrated as an anode material in Li-ion microbattery. These findings showcase the adaptability of conventional PVD methods for depositing films with diverse nano- and microscale features. Thorough characterization is essential for understanding material changes and in uncovering unidentified phenomena in films deposited via physical vapor deposition.
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    Expression of recombinant proteins in Lactococcus lactis – an application in D-tagatose production
    (Aalto University, 2023) Salonen, Noora; Nyyssölä, Antti, D. Sc. (Tech.), VTT Technical Research Centre of Finland, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bioprocess Engineering; Kemian tekniikan korkeakoulu; School of Chemical Technology; Frey, Alexander, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Lactococcus lactis is a commercially attractive host for recombinant protein production with many potential applications, for example, in the food and pharmaceutical industries. Production of recombinant proteins requires a suitable expression system, and the aim of this study was to develop new inducible recombinant protein expression systems for L. lactis. In addition, a special application for a developed expression system in D-tagatose production was investigated. D-Tagatose is a functional low-calorie sweetener, but the production costs still limit its use. Two new protein expression systems were developed, of which the first was based on a phosphate starvation-inducible pstF promoter of L. lactis MG1363. High expression levels of intracellular β-galactosidase (670 µkat g-1) and secreted α-amylase (3.6 μkat l-1) were achieved using this strictly regulated expression system. The other new protein expression system was based on the salt-inducible BusA promoter and the BusR repressor gene of L. lactis MG1363. To achieve salt-inducible protein expression, the BusR expression was adjusted by generating random mutations to its promoter area. In the bioreactor, a 6.0 μkat l-1 α-amylase activity was reached, however, without strict regulation. Inducing agents were not needed with either expression system in the bioreactor. Due to strict regulation and high expression levels, the phosphate starvation-inducible expression system was chosen to overexpress Bifidobacterium longum L-arabinose isomerase. The purified enzyme was characterized, and it turned out to be active and stable at acidic pH (optimum 6.0-6.5), and optimally active at 55 °C. The Km values were 120 mM and 590 mM, and Vmax values were 42 U mg-1 and 7.7 U mg-1, for L-arabinose and D-galactose, respectively. The enzyme bound the metal cofactors (Mg2+, Ca2+) tightly, but the metal ion requirement was low for catalytic activity. Divalent metal ions, preferably Mg2+, were required for enzyme stability at higher temperatures. Because of the promising characteristics of the enzyme and high expression level, the use of resting L. lactis cells harboring B. longum L-arabinose isomerase to produce D-tagatose was investigated. Optimization analysis showed high pH, temperature, and borate concentration favored D-tagatose production. Almost quantitative conversion (92 %) was reached in a borate buffer after five days (20 g l-1 D-galactose, 37.5 °C). D-Tagatose production was also investigated with high substrate concentration (300 g l-1 D-galactose, 1.15 M borate, 41 °C) in a 10-day batch process, changing the production medium every 24 h. A D-tagatose production rate of 185 g l-1 day-1 was achieved, comparable with reported numbers in the literature. The results indicated that the use of resting cells stabilized the enzyme. There was no loss in productivity during the ten sequential batches. To further develop the D-tagatose production process, the cells could be immobilized in a packed-bed bioreactor to enable continuous production. Developing the new expression systems to be food-grade could enable more applications.
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    DNA Origami as a Tool for Assembling Functional Biohybrid Nanomaterials
    (Aalto University, 2023) Julin, Sofia; Kostiainen, Mauri A., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland; Linko, Veikko, Ass. Prof., University of Tartu, Estonia; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biohybrid Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Kostiainen, Mauri A., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Recent advances in nanotechnology have given us a versatile toolbox of nanoscale objects with different functionalities. However, approaches for constructing stimuli-responsive and highly ordered macroscopic materials from these nanometer-sized components are still needed. The DNA origami technique enables the fabrication of custom-designed, well-defined, and highly addressable DNA-based structures and could therefore aid in the development of more advanced nanomaterials. In this doctoral thesis, the use of DNA origami in bottom-up nanofabrication was explored with the aim to construct functional biohybrid nanomaterials with high structural order. In publications I and II, the co-assembly of (negatively charged) DNA origami and cationic lipids was studied. The results demonstrated that DNA origami may serve as templates and nucleation sites for the formation of ordered lipid assemblies. The formed lipid matrix encapsulated the DNA origami, which also enhanced the DNA origami stability against endonuclease digestion. Moreover, the encapsulated DNA origami could be released from the lipid assemblies on demand by addition of competitive polyanions (publication I) or by illumination with long-wavelength UV light (publication II). In publication III, for one, highly ordered gold nanoparticle (AuNP) superlattices were assembled by employing electrostatic interactions between the cationic AuNPs and DNA origami. The ionic strength of the solution was used to control the assembly, and well-defined three-dimensional tetragonal superlattices were formed by gradually decreasing the salt concentration. Finally, in publication IV, pH-responsive and dynamically reconfigurable DNA-origami based lattices were constructed. Two pH-sensitive latches relying on Hoogsteen-type triplex formation were incorporated into the arms of the lattice-forming DNA origami unit, and thus the unit and the whole lattice could switch between an open and a closed state depending on the pH of the surrounding solution. The work shows that the library of stimuli-responsive elements initially developed for small DNA-based devices could be used to induce dynamicity also in considerably larger, hierarchical DNA origami lattices. In conclusion, the results demonstrate that DNA origami could function as a versatile self-assembling building block for advanced nanomaterials. The thesis highlights the potential of using DNA origami to fabricate highly ordered nanomaterials by electrostatic self-assembly and contributes to a broader understanding of such assemblies in bottom-up nanofabrication. In addition, the developed methods could aid in the engineering of more sophisticated stimuli-responsive hierarchical nanomaterials.
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    Hydrometallurgical recycling of Li-ion batteries
    (Aalto University, 2023) Chernyaev, Alexander; Lundström, Mari, Asst. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Wilson, Benjamin, D.Sci., Aalto University, Department of Chemical and Metallurgical Engineering, Finland; Kemian tekniikan ja metallurgian laitos; Department of Chemical and Metallurgical Engineering; Hydrometallurgy and Corrosion; Kemian tekniikan korkeakoulu; School of Chemical Technology; Lundström, Mari, Asst. Prof., Aalto University, Department of Chemical and Metallurgical Engineering, Finland
    Lithium-ion batteries (LIBs) have become an integral part of the increased electrification aimed at tackling environmental and power supply challenges. LIB volumes as well as their range of uses from mobile devices to electric vehicles (EVs) have steadily increased, leading to an unprecedented demand for their related critical metals. Consequently, this study focused on LIB recycling, including characterization, leaching of black mass (industrially crushed waste LIBs), solution purification through precipitation and graphite recovery. It was found that black mass concentrates often consist of several types of LIBs. Electron microscope characterization results reported in this thesis include identification of inorganic impurities – such as Fe-Cr alloys, SiO2, and AlO(OH) particles which did not dissolve during leaching. Also, CO, CO2, and SO2 were detected during pyrolysis. In the leaching studies, the reductive power of metallic impurities, such as Fe, Cu, and Al was investigated in detail using synthetic materials and black mass. The results demonstrated that scrap current collectors can be utilized as reductants to achieve leaching efficiencies of 99%. For example, Fe can catalyze NMC and LCO dissolution in the presence of Cu and/or Al, while Cu was found to cement on the Al surface and simultaneously redissolve by reducing the active material. H2O2 decomposed due to Fe, Cu, and Al oxidation, hence decreasing reductive leaching efficiency. Fe and Al were precipitated from synthetic battery leach solution at a pH value of approx. 3.5. Findings demonstrated that losses of Ni, Co, and Li were due to co-precipitation in Fe and Al hydroxide removal, dependent on the Al concentration. The addition of H3PO4, prior to neutralization, precipitated Fe and Al as phosphates at the lower pH of 3, resulting in decreased co-precipitation, faster nucleation, metal precipitation, and better cake filterability. Additional investigations of graphite recovery from leach residues showed that the quality required for battery use was maintained after leaching (2 M H2SO4, 60 °C, 3 h, 2 vol.% H2O2) and pyrolysis (800 °C, 1 h in Ar atmosphere). Organic impurity removal by pyrolysis gave a higher surface area graphite that favors Li+ intercalation. Despite some inorganic impurities, when used as a LiB cell anode, the residual graphite from EV battery black mass showed good performance (av. specific capacity = 350 mAh/g), whereas that of portable device battery black mass was lower (250 mAh/g). Capacity retention was 80% after 100 cycles, indicating good performance.y retention was 80% after 100 cycles, indicating good performance.
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    Scalable Surface Chemistry for Lignin Modification - Creating Value for a Forest-Based Society
    (Aalto University, 2023) Henn, Karl Alexander; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Bioproduct Chemistry Group; Kemian tekniikan korkeakoulu; School of Chemical Technology; Österberg, Monika, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Lignins is a highly abundant biomaterial produced as a side-stream in chemical pulping. Kraft lignin is the most common technical lignin, but it is difficult to utilize. Kraft lignin's properties can be improved, but chemical modification processes often struggle with balancing costs, performance, and environmental burden. The recent emergence of technologies to prepare and apply colloidal lignin nanoparticles (LNPs) has however increased lignin's potential, as it allows lignin to be used in multiple water-based applications. This thesis aims to demonstrate the usefulness of lignin and LNPs by presenting new scalable ways to modify lignin, in native and colloidal form, for both high-value and high-volume applications. LNPs are formed through a solvent shifting process, where an anti-solvent is added to a lignin solution. Lignin's hydroxyl group content and overall chemical structure determine how the particles are assembled during solvent shifting. Reducing lignin's hydroxyl group content through acetylation allowed smaller particles to be prepared at higher concentrations than what is possible with non-modified lignin. The acetylated particles' small size made them optically clear, which allowed them to be used for both antifogging coating and photonic films. The LNPs' inner structure could be changed by including hydrophobic fatty acids in the solvent shifting process. This resulted in hybrid nanocapsules whose cores consisted mainly of fatty acids and the shell mainly of lignin. Many fatty acids can be used as latent heat storage, but their meltingand solidification temperatures are prone to shift. However, the fatty acids' melting and solidification temperatures were effectively stabilized when encapsulated by lignin. LNPs outer structure could be hydrophobized for water-repellent surface coatings by adding a hydrophobic glycerol-based epoxy cross-linker to LNP dispersions. The LNPs allowed the epoxy to fuse with the aqueous dispersion phase despite its poor water solubility, and simultaneously acted as a curing agent. By combining LNPs with epoxidized lignin, strong and thermally stable adhesives with exceptionally high lignin contents could be prepared. The thesis also presents new methods for performing lignin epoxidation and acetylation. Both methods were designed to be scalable and material efficient, and therefore utilized short reaction times, moderate temperatures, and recycling of all excess chemicals. Overall, this thesis demonstrates how lignin's utility is improved in colloidal form, and by doing so provides examples of how lignin could be successfully valorized and applied.
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    Photoluminescence and upconversion properties of lanthanide-based atomic and molecular layer deposited thin films
    (Aalto University, 2023) Ghazy, Amr; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Inorganic Materials Chemistry; Kemian tekniikan korkeakoulu; School of Chemical Technology; Karppinen, Maarit, Prof., Aalto University, Department of Chemistry and Materials Science, Finland
    Photoluminescence of trivalent lanthanide (Ln) ions is highly relevant to applications such as solar cells, light emitting devices and biological imaging. Organic molecules may potentially be utilized to enhance and tune the luminescence of Ln3+ ions when properly combined into Ln-organic hybrids. Such on-demand tailored materials could pave the way to various next-generation applications, especially if the materials could be produced in high-quality thin-film form. However, the conventional thin-film techniques of Ln-organic materials lack the ability to combine the well-controlled deposition and the tunability of the luminescence proper-ties to the needs of various applications. To address these challenges, efforts to apply the strongly emerging atomic/molecular layer deposition (ALD/MLD) method for lanthanide-organic thin films started recently. While ALD/MLD offers well controlled process development and growth of thin films, the tunability of the luminescence properties of such films has been critically difficult to achieve. In this thesis, the tunability issue was one of the central research questions, and it was addressed by developing a number of ALD/MLD processes with novel organic components. Within the scope of the thesis, the following organic precursors were inves-tigated for the first time in the context of ALD/MLD: pyridine-3-carboxylic acid (PDA), cytosine (Cyt), 1,3,5-triazine-2,4,6-triol (TZO), and 2-hyrdoxyquinoline-4-carboxylic acid (HQA). Among these, PDA and Cyt were found particularly interesting as they allowed the remarkable tuning of the absorption and excitation properties of the lanthanide-organic thin films by shifting the excitation wavelength from the typical 250 nm up to 365 nm. More careful selection during this work led to the development of Eu-HQA thin films, which can be excited through an exceptionally wide excitation wavelength range from ultraviolet light of 185 nm up to visible light of 400 nm. Luminescent thin films that can be excited with visible light are of particular interest to biological imaging applications. Therefore, the new Eu-HQA thin films were tested for the Förster resonance energy transfer mechanism, which is used in various bioimaging and detection techniques. As another way to tune the luminesce properties challenged in the thesis, different Ln3+ were combined into a single thin-film. Here, the combination of Eu3+, Tb3+, and Er3+ yielded interesting thin films with photoluminescence emissions that could be controlled between green, red and white light. On the other hand, using Er3+ and Ho3+ provided a promising means to achieve upconversion emission, through which near-infrared light can be converted to visible light. These latter results could provide a route to enhance the performance of solar cells that suffer from weak absorption of infrared light.
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    Atomic/Molecular Layer Deposition of Photoresponsive Azobenzene-Containing Thin Films
    (Aalto University, 2023) Khayyami, Aida; Kemian ja materiaalitieteen laitos; Department of Chemistry and Materials Science; Inorganic Materials Chemistry; Kemian tekniikan korkeakoulu; School of Chemical Technology; Karppinen, Maarit, Prof., Aalto University, Department of Chemistry and Materials Science, Finland
    Owing to their rapid and reversible photoisomerization, azobenzenes are efficient molecular photoswitches that could potentially provide effective control over various properties of their host surroundings. This unique ability has opened up a wide array of potential applications spanning across diverse fields, from electronics and medicine to environmental monitoring and security. This thesis aims to unveil new possibilities for the application of the atomic/molecular layer deposition (ALD/MLD) thin-film technique to incorporate fully functional azobenzene moieties into an inorganic matrix. Several new ALD/MLD processes with azobenzene-4, 4'-dicarboxylic acid (AzoBDC) as the source of the azobenzene moiety were developed. Three types of novel thin-film materials were fabricated: amorphous zinc-azobenzene hybrids, zinc oxide:azobenzene superlattice (SL) structures, and metal-organic framework (MOF) type structures with azobenzene as the linker. In zinc-azobenzene hybrids (Zn-O-C14H9N2-O4-), diethyl zinc (DEZ) was used as the source of zinc in combination with AzoBDC. The fabrication route developed for the Zn-AzoBDC hybrid films was then combined with the DEZ/H2O ALD process for zinc oxide thin films to grow SL structures where single azobenzene layers are sandwiched between thin crystalline ZnO blocks. The ratio of the ALD-ZnO and MLD-(Zn-O-C14H9N2-O4-) cycles was varied between 199:1 and 1:1. The photoreactivity was confirmed for all the films upon 360 nm irradiation, and the kinetics of the resultant trans−cis photoisomerization was found to somewhat depend on the SL structure. Crystalline photoresponsive MOFs were prepared by using FeCl3, Ca(thd)2, Li(thd), Na(thd), or Sr(thd)2 as the metal precursor in combination with AzoBDC. Isomerization of azobenzene units within the strictly crystalline, highly porous environment of Fe-AzoBDC, Li-AzoBDC, and Ca-AzoBDC films was confirmed despite their different crystal structures. Furthermore, the gas absorption and release capability of the films was demonstrated. The ALD/MLD synthesis of Fe-AzoBDC MOFs was also modified by using in parallel with AzoBDC terephthalic acid (TPA) as another organic precursor to obtain structures with two types of organic linkers. These films were deposited by mixing the FeCl3 + AzoBDC and FeCl3 +TPA deposition cycles on a 1:1 frequency to deposit Fe-AzoBDC–Fe-TPA films. It was shown the dilution of the photoactive AzoBDC linkers with the nonactive TPA linkers increased the stability of the crystal structure.
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    Development of Leaf-Inspired Functional Structures from Cellulose Nanofibers - Matrix Scaffolds for Solid-State Photosynthetic Cell Factories
    (Aalto University, 2023) Rissanen, Ville; Tammelin, Tekla, Prof., VTT Technical Research Centre of Finland Ltd, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Materials Chemistry of Cellulose; Kemian tekniikan korkeakoulu; School of Chemical Technology; Kontturi, Eero, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    This thesis pioneered an interdisciplinary investigation of the use of cellulose nanofibers as immobilization matrices for photosynthetic cells. This was achieved by exploiting the inherent properties of 2,2,6,6-tetramethylpiperidine-1-oxyl radical oxidized cellulose nanofibers (TCNF) to create hydrogel matrix structures with high mechanical stability, porosity, and biological compatibility in aqueous conditions. Moreover, this thesis developed analytical tools to reliably assess and optimize the crucial physical parameters of the hydrogel matrices and link them to the performance of the immobilized cells. Ultimately, the goal was to create tailored matrix structures that enhance the efficiency of photosynthetic cell factory platforms producing volatile chemicals. By screening different matrix structures based on TCNF and alginate as a reference, it was found that TCNF cross-linked with Ca2+ -ions and polyvinyl alcohol (PVA) yielded hydrogel matrices with high wet strength and good compatibility with photosynthetic cells. By establishing a surface-sensitive investigation setup using quartz crystal microbalance with dissipation monitoring (QCM-D), this thesis revealed that the photosynthetic cells are passively entrapped within the TCNF network, but direct attachment can be induced via a cationic surface treatment. Furthermore, this thesis developed a rheological measurement technique to study the behavior of the hydrogel matrices under shear stresses. It was found that alginate-based matrices have higher elastic and viscous moduli (G' and G'', respectively) at rest than TCNF-based matrices, but the latter have higher resistance to yielding. These properties can be explained through the innate structural differences between the materials and their interactions with Ca2+ -ions. Following a similar trend, TCNF-based matrices were discovered to have higher porosity and a more heterogeneous structure than Ca-alginate matrices. They also form hierarchical mesoporous networks with small additions of PVA or alginate. Finally, these results were combined with biological characterization techniques to assess how the matrix properties affect cell factory performance. TCNF and alginate matrices were observed to provide long-term cell viability to immobilized cells. The O2/CO2 exchange rates of the immobilized cells indicated that both the cells and matrices are in a dynamic state over time, affected by both matrix porosity and wet strength. Finally, TCNF matrices were shown to be more stable and enable higher hydrogen and ethylene production in submerged conditions. To gain further control in optimizing these properties, a method to prepare TCNF hydrogels with accurate porosity-density control was developed using osmotic dehydration. Overall, these findings highlight the prowess of TCNF-based hydrogels as versatile im-mobilization scaffolds and showcase how the development of efficient cell factory platforms can be assisted via interdisciplinary efforts.
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    Pilot-scale filler-reinforced biodegradable coatings for paperboard packaging
    (Aalto University, 2023) Helanto, Karoliina; Talja, Riku Dr., Metsä Board Oyj, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Kemian tekniikan korkeakoulu; School of Chemical Technology; Rojas, Orlando, Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Environmental impact and regulation of packaging materials are topics that critically influence the adoption of alternatives to fossil-based systems that are in current use. In this context, paperboards represent suitable renewable and biodegradable options that also have the advantage of recyclability. However, the nature and structure of paperboard-based products limit their use and undermine other competitive advantages. A main reason is the limited barrier properties displayed by paperboard products. Gaining control of the transport of moisture, grease, liquids and gases is the most relevant requirement for packaging materials together with heat sealability. A possible route to achieve barrier control includes consideration of biodegradable thermoplastic polymer coatings, such as poly(lactic acid) (PLA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(butylene adipate terephthalate) (PBAT). However, the application of these materials needs adjustments in the processability aspects. They also affect the interactions with the packaged goods and the overall functionality, demanding the adoption of auxiliary components, including plasticizers, nucleating agents and fillers. These subjects are complex and should be examined carefully, not only from the fundamental viewpoint but for actual deployment. This thesis discusses these topics from the perspective of scalable and deployable technologies. The effect of mineral fillers on biodegradable polymer coatings for paperboard packaging is examined at a pilot scale. The utilized thermoplastic polymers included PLA and PLA-based blends, PHBV and PBAT. The fillers introduced to the polymer matrices included talc, kaolin and calcium carbonate. Production processes typical of the packaging industry were contemplated, such as injection and compression moulding and pilot-scale extrusion coating. The potential of the packaging materials and their combinations was evaluated from the perspective of processability to the end-of-life. The addition of fillers benefited processability in the extrusion coating process by reducing neck-in and improving adhesion formation. As a drawback, they contributed to the formation of pinholes at lower coating weights. The barrier properties of intact films and coatings were improved, whereas the introduction of the fillers did not significantly impact on the biodegradability characteristics. This thesis provides insights on the filler-reinforcement of biodegradable polymers and their utilization as coating layers. This work is expected to serve as a guide for future developments of sustainable extrusion coatings for paperboard packaging.
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    Hybrid Architectures at the Nanoscale: Constructing Materials through Electrostatic Interactions
    (Aalto University, 2023) Shaukat, Ahmed; Anaya-Plaza Eduardo, Dr., Aalto University, Finland; Biotuotteiden ja biotekniikan laitos; Department of Bioproducts and Biosystems; Biohybdrid Materials; Kemian tekniikan korkeakoulu; School of Chemical Technology; Kostiainen, Mauri A., Prof., Aalto University, Department of Bioproducts and Biosystems, Finland
    Nature's intricate biomolecular assemblies inspire crafting nano- and microscale functional materials. Comprising nucleotides, amino acids, and saccharides, these structures orchestrate cellular functions with precision. Replicating this complexity artificially is challenging, but nanoscale techniques, especially nature-mimicking self-assembly, offer atomic-level precision through non-covalent interactions. Electrostatic self-assembly stands out for versatility, enabling diverse functional materials. This reversible process facilitates the exact arrangement of charged components. Moreover, the utilization of biomolecule-based materials as building blocks in nanomaterials presents a promising avenue, leading to the development of highly biocompatible functional systems. This convergence of principles is exemplified in this thesis, which demonstrates how functional and self-assembling biohybrid materials can be constructed precisely by synergistically combining DNA origami and protein cages with molecular glues. Thus, Publication I opens the study by designing hybrid bundles, uniting cationic dyes like zinc phthalocyanine with negatively charged DNA origami. This synergy enhances optical properties and stability, effectively showcasing the potential of electrostatic self-assembly in customizing material traits. Publication II extends the study by introducing Janus-type phthalocyanines with two different DNA origami structures, resulting in optically active biohybrids resistant to aggregation. This underscores the role of ionic strength in self-assembly and disassembly processes, deepening the insights into biohybrid material formation. Publication III delves into crystalline assemblies, harnessing electrostatic self-assembly of pillar[5]arene with apoferritin, unveiling promising prospects for water remediation. This endeavor highlights the versatile capabilities of biomolecular self-assembly in addressing pressing environmental challenges. Publication IV demonstrates the formation of protein-protein co-crystals involving cationic fluorescent protein and negatively charged apoferritin, thereby showcasing robust optical properties with potential applications in biological light-emitting diodes. In summation, the collective body of work presented in this thesis underscores the potential of electrostatic self-assembly in crafting intricate biohybrid materials. These findings provide understanding of electrostatic self-assembly, establishing a path for preparing cutting-edge nanomaterials with applications in nanomedicine, optoelectronics, and water treatment. This research effectively links intricate biomolecular assemblies and synthetic constructs, potentially finding utility in novel solutions across multifarious sectors.