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The exploitation of the toughness of steel in steel-polymer hybrids in structuralapplications is limited due to the huge difference in stiffness of thereinforcement (200 GPa for steel) compared to the polymer matrix (between 1 and3 GPa only). This stiffness mismatch leadsto stress concentrations at thesteel-polymer interface, which give rise to either early interface fracture orplastic yielding. The guiding hypothesis within this PhD research, whichfocuses on the optimization of polymer-steel hybrids, is that it is necessaryto decrease the polymer-steel stiffness mismatch and that the steel-polymeradhesion as well as the polymer toughness and/or yield stress in theinterphasial region need to be improved.

Academic collection --- Theses

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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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Multilayer plastics are commonly used in packaging because they can have certain properties like blocking moisture and odours. They are also easy to process, while looking appealing to consumers. These layers of different materials have several benefits; e.g. To create barriers for gases in packaging applications like food packaging or pharmaceuticals. Using multilayer plastics is also cost-effective for industries. However, recycling this type of packaging is challenging because the layers are physically bound together with adhesives, making it hard to separate them for recycling. As a result, multilayer plastics are often burned instead of being recycled. To overcome this challenge, a method using solvents has been proposed to separate the plastics in the multilayer. Previous methods involved dissolving the entire multilayer in solvents, not only requiring the use of different solvents, but also using multiple steps. The new method targets the adhesive specifically, which allows for separation with minimal solvent use in only one step. The research in this study explores this method further by looking at how it can separate different types of plastics and paper that may be present in the multilayer material, such as those found in food labels or cardboard boxes. The study starts by examining sticky tapes with acrylic adhesive and finding suitable solvents that dissolve the adhesive without affecting the tape backing. The results show that different reaction conditions are needed for different tapes, but that one solvent (propanol) can be used on all the different types of tapes. The study also investigates the diffusion of solvents between two attached tape pieces, which is important for understanding the separation process. The findings suggest that more severe conditions are necessary for this diffusion to occur, when compared to single pieces of tape. Finally, the study explores the reuse of solvents after delamination experiments and finds that most tape backings cannot be reused, except for those containing paper. This is likely because the porous structure of paper allows for easier solvent diffusion compared to plastic. The limited reuse of the solvent may be due to saturation with the adhesive over multiple cycles.

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In dit proefwerk wordt gemodificeerde hypervertakte polylysine en hypervertakte polyglycerol gesynthetiseerd. Deze modificaties dienen om de surfactant eigenschappen van deze polymeren te verbeteren, vooral voor het in dispersie brengen van carbon nanotubes. Hiervoor werden polyglycerolen en polylysines gefunctionaliseerd met verschillende functionele groepen. Hierbij werd vooral aandacht besteed aan trifenylgroepen, vermits deze groepen de interactie tussen de polymeren en de carbon nanotubes verbeteren. De polymeren staan in voor de sterische hinder en oplosbaarheid in water. In het eerste deel van het project werden de polyglycerolen en polylysines gefunctionaliseerd met trifenylchloride, waarbij geprobeerd werd om de aantal functionele groepen van de polymeren om te zetten in trifenylgroepen. Ook werden anderen functionele groepen zoals onder andere benzoylchloride en 1,2-epoxy-3-fenoxypropaan geprobeerd. De verkregen functionalisatiegraad voor verschillende reactieomstandigheden was vrij laag, dit voor de meeste functionele groepen. Vervolgens werd voor hypervertakte polyglycerolen de dispersie efficiëntie bepaald. Hiervoor werd zowel trifenylmethyl gefunctionaliseerde als benzoyl gefunctionaliseerde polyglycerolen gebruik. De metingen voor de trifenylmethyl gefunctionaliseerde polyglycerol werd uitgevoerd door Bertels et al.(2014). De dispersie efficiëntie werd bepaald aan de hand van absorbantiemetingen, waarbij geagglomereerd CNT's geen absorbantie vertonen in tegenstelling tot individuele CNT's gedispergeerd in oplossing. Voor deze metingen werd naast de verschillende functionalisatiegraden ook verschillende moleculaire gewichten van polyglycerolen uitgeprobeerd. Hieruit werd geconcludeerd dat trityl gemodificeerde hypervertakte polyglycerolen goede surfactanten zijn voor het in dispersie brengen van CNT's in vergelijking met klassieke surfactanten zoals natriumdodecylsulfaat. Ook werd gemerkt dat het hypervertakt polyglycerol met een moleculair gewicht van 5000 g/mol en een functionalisatiegraad van 5,6% het meest efficiënte dispersie vertoonde. Daarnaast werd hypervertakte polylysine gefunctionaliseerd met propeenoxide en 1,2-epoxy-3-fenoxypropaan. Deze reacties werden uitgevoerd om een model systeem voor de reactie met epoxysilanen op te stellen. Dit kan een voordeel zijn vermits de reacties tussen hypervertakte polylysines en epoxysilanen uitgevoerd zullen worden in een latere stadium van dit project. Om dit modelsysteem op te stellen werd hypervertakte polylysine gereageerd met 1,2-epoxy-3-fenoxypropaan, waarbij de reactie gevolgd werd met 13C-NMR. Uit de analyse van deze spectra werd vastgesteld dat deze reactie een trage kinetica kent. Als besluit kan vermeld worden dat hypervertakte polymeren, vooral de gefunctionaliseerde polyglycerolen een belangrijke impact zullen hebben in het toepassingsgebied van CNT's.