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The advancement of polymer science has given rise to the development of sequence-controlled polymers. Within this domain, sequence-defined polymers stand out as a remarkable subclass characterized by an unprecedented level of uniformity. These sequence-defined polymers exhibit precise positioning of each monomer, offering perfect control over their structural arrangement. While strategies using click chemistry and living polymerizations still face limitations of dispersity and positioning, the iterative synthesis approach proves to be the most suitable solution. The application of sequence definition in conjugated polymers holds great potential for advancing the field of polymer science. It offers the opportunity to synthesize novel materials with precisely controlled optoelectronic properties. However, limited research has been performed in this area thus far. Form initial investigations, it is evident that the AB+CD method, incorporating orthogonal reactions, represents the most efficient approach with minimal steps. Nevertheless, further exploration is needed for its applicability in sequence-defined conjugated polymers. In a previous study conducted in our group, a novel strategy was developed utilizing alternating Suzuki-Miyaura cross-coupling reactions and Horner-Wadsworth-Emmons reactions. This approach preserves conjugation, achieves high yields, and minimizes the formation of by-products. The aforementioned approach is employed to synthesize sequence-defined macromolecules, allowing for the investigation of the influence of chiral monomers. However, prior to conducting this investigation, it is necessary to synthesize the monomers that will serve as the building blocks. All monomers in this study are phenyl-based, with functional groups positioned at the 1 and 4 positions. One type contains a phosphonate and a bromide, while another consists of a boronate ester and an aldehyde. In total, 4 monomers are synthesized, including a chiral type with a (S)-2-methylbutyl sidechain and an achiral type with an octyl sidechain. Additionally, an achiral starting monomer with one active and one protected functional group is applied, featuring a bromide and a protected hydroxyl group. After the successful synthesis of the monomers, the oligomers are synthesized by employing the aforementioned strategy. Two distinct sequences are synthesized, wherein the position of the chiral monomers serves as the differentiating factor. This allows for the investigation of the influence of chiral monomer position. The oligomers are gradually expanded until they reach the size of hexamers, ensuring an adequate level of variability in the positioning of the chiral monomer. The characterization of both sequences, spanning from dimers to hexamers, is carried out extensively using various measurement techniques. The purity and structure of the oligomers are confirmed using 1H-NMR and 13C-NMR spectroscopy. The smaller chains are also characterized via mass spectroscopy. The determination of the number average molar mass and dispersity is achieved through GPC, which confirms the desired growth of the oligomers and their monodisperse nature. UV-VIS spectroscopy is employed to validate the preservation of the conjugated backbone by observing a red shift as the sequence expands. This technique also reveals the presence of a push-pull mechanism in specific structures. Insights into molecular dynamics and interactions are obtain through fluorescence spectroscopy

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The last few years gene therapy has been a very popular topic in modern medicine. It has the potential to treat a disease at the genetic level by replacing or counteracting a malfunctioning gene. However, for this the therapeutic genes have to overcome multiple cellular barriers to arrive at their target destination. Many viral and non-viral delivery systems have been developed to mediate this transfer and increase gene transfer efficiency. Recently polymers have gained a lot of attention as delivery systems because of their low immunogenicity and easy synthesis. Polycationic star polymers are one of those non-viral gene delivery systems. Via the ‘core first’ method these star polymers can be synthesized starting from a multifunctional initiator. Because of their large amount of reactive groups and high degree of branching, hyperbranched poly(arylene oxindole)s are a good choice for such a multifunctional initiator. In this work a hyperbranched poly(arylene oxindole) was synthesized via an A2 + B3 strategy. An isatin derivate with a hydroxyl function as well a derivative with a carboxylic acid function were tested in the polymerization reaction. Unfortunately, only polymerization using the isatin derivate with the carboxylic acid function lead to the formation of a hyperbranched polymer without significant side reactions occurring. Although the molecular weight and polydispersity should still be optimized for its application as a multifunctional initiator, some functionalization reactions with the polymer were already tested. For in vivo visualization the hyperbranched polymer was functionalized with a suitable fluorescing BODIPY dye. Therefore, the BODIPY core molecule was first synthesized and functionalized via palladium catalyzed C-H arylation to obtain the desired functional group for coupling. Next, this functionalized BODIPY was coupled with the polymer using a Mitsunobu reaction. Furthermore, an attempt was made to introduce an ATRP-initiator function into the polymer structure. These ATRP- initiator sites are necessary for its function as a macroinitiator in the synthesis of a star polymer. However, due to time shortage only one coupling reaction could be tested and this coupling reaction was unsuccessful.

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Microplastic pollution is one of the most critical environmental issues in the world right now. Many studies about human exposure to these micro-and nanoplastics (MNP) and the toxic effects they can cause are being conducted at this moment. Quantification and identification of these MNP lie at the bottom of solving this global problem. The most popular identification methods are Fourier-transform infrared spectroscopy and Raman spectroscopy. These techniques are lacking in non-destructive analysis with high sensitivity and low background noise. This thesis aims to develop an optical spectroscopy method to detect and identify microplastics after staining with Nile Red. The latter is a lipophilic solvatochromic dye. Staining will cause the particle to fluoresce, with its emission spectrum depending on its polarity. More polar plastics will have a more red-shifted emission maximum. Via hyperspectral analysis, the MNP can be identified based on this spectrum. Fluorescence lifetime imaging microscopy is also implemented. The fluorescence lifetime is the time that a fluorophore spends in the excited state, after absorbing a photon, before returning to the ground state. The lifetime depends on the fluorophore's micro-environment and therefore is also different for each MNP type. Differentiation is possible based on this lifetime value, but a graphical, fit-free phasor approach is also used. This allows for the mapping of the lifetime distribution in an image. When two different MNP types are present in one sample, they will each have a separate distribution cloud on the phasor plot, allowing for the graphical distinguishment of MNP. The plastics used are PP, PVC, HDPE, PET, and PS, these samples contain a range of shapes and sizes. A bought suspension of pure PS polymer particles of a fixed shape and size of 0,6 μm was also examined. The spectral data were processed in two ways. By calculating a ‘weighted average’ with the intensity values at each wavelength. This resulted in each MNP being attributed a weighted average value. After recording spectra of different particles, a statistical analysis, ANOVA and t-test, was done. This showed that the weighted averages of PP & HDPE and PS (self-made) & PVC do not differ significantly. The second option is through comparing the spectra themselves, using a relative similarity percentage. Because of the low similarity MNP gave when compared with themselves, only MNP with a significantly large similarity percentage could be distinguished. The same statistical tests were done on lifetime data. Measurements done on different particles of the same plastic showed that only HDPE & PET lifetimes did not differ significantly. Multiple measurements done on the same particle showed slightly different lifetimes. It could be concluded that HDPE & PET and PS (self-made and 0,6 μm) & PET cannot be differentiated. Finally, phasor plot analysis of samples containing two different plastics showed a possibility of recognizing MNP types based on the location of their phasor cloud on a phasor plot. When combining these two techniques, making use of the ’weighted average’ value and lifetime analysis, it could be possible to identify each plastic. The combination with similarly weighted averages, PP & HDPE give significantly different fluorescent lifetimes values and are possible to separate on a phasor plot. Still, both techniques have some flaws and improvement is possible.

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Carbon fibers are used in a broad area of applications in which a strong and lightweight material is needed. Reduction of the weight without diminishing the strength can contribute to a more sustainable environment by reducing the fuel consumption. However, the production of these materials comes at a high cost, making large scale industrial applications not feasible yet. The current production process, which starts from polyacrylonitrile (PAN), is expensive and has a severe impact on the environment. The monomer acrylonitrile (AN) is very toxic and the production of the actual carbon fiber requires high temperatures. In the past decades a lot of research has been done on looking for alternative precursor materials among others lignin, cellulose, polyethylene. Their applicability is limited, because the final mechanical properties of the carbon fibers are inferior to the current PAN-based carbon fibers. Alternatives that can reach a certain minimal strength value can be used to fill in the gap of rapidly growing market of low-end applications, where it is not required to utilize high end fibers. This project mainly focused on polyethylene-like precursor polymers as possible alternatives. Synthesis of the polymers was done via ring-opening metathesis polymerization of eight-membered rings whether or not substituted with functional groups. The investigated functionalities are the hydroxyl, epoxide and nitrile group and also a photoinitiator moiety. The amount of double bonds in the polymer could be changed by choosing different monomers such as cyclooctene and cyclooctadiene. Both the degree of functionality and the amount of double bonds were investigated regarding carbon yield by making copolymers with functionalized and non-functionalized monomers. The synthesized polymers are characterized and their thermal stability is researched in the second part of this work. Characterization showed that some polymers underwent stabilization reactions during heat treatment in air. Thermal crosslinking was observed and leads to the formation of carbonized material that is stable at high temperatures. Experiments showed that prestabilization should always be performed in air, because no stabilized fiber is formed in nitrogen atmosphere. Proper stabilization of the fibers requires very slow heating rates and new methods need to be found to accelerate this process. Looking at the degree of functionalization shows that higher amounts of functional groups leads to a decrease in melting point and crystallinity, which could be disadvantageous for the final carbon yield. It is important to have a polymer with a high degree of crystallinity and a melting point that is higher than the temperature needed for thermal crosslinking. All these problems can possibly be avoided with the addition of a photoinitiator, which can be activated by irradiation with UV light. Polymers can form crosslinks without applying heat so that the precursor fiber stays in the solid state. This approach requires further research and can possibly lead to even higher carbon yields, making it a worthy alternative.