Hyperbranched polymers (HBP) have drawn much attention and obtained intensive research activities from both industry and academia in the last three decades. They belong to a group of macromolecules called dendritic polymers, which have peculiar and often unique properties, which derive from their three-dimensional structure and the large number of functional groups. These structural characteristics provide high possibilities for controlling functional group interactions and modifications of other polymers in coatings and therefore, they are expected to result in novel materials with desired properties. They own a highly branched backbone, which gives access to many of reactive groups; their structure gives them excellent flow and processing properties, and they are characterized by lower viscosity than those of linear polymers of comparable molecular weight. Such properties make HBP extremely interesting for coatings and UV-curing applications and for this, they have attracted a great deal of attention for application, e.g. for powder coatings, high solid coatings, flame retardant coatings, barrier coatings for flexible packaging,and they have been recently suggested as a component of a dual-cure formulation based on an UV-curable epoxy resin and a functionalized alkoxysilane additive as an inorganic precursor to achieve advanced functional hybrid coatings. By pursuing this research line, we have synthesized an aliphatic–aromatic ethoxysilyl modified hyperbranched polyester system to be used in the preparation of UV-curable epoxy hybrid organic–inorganic coatings. The addition of ethoxysilyl-modified HBP could act as a coupling agent during the formation of the inorganic domains generated in-situ via sol-gel process starting from the alkoxysilane as inorganic precursors. The cured films were characterized in terms of their dynamic-mechanical properties and surface hardness: the obtained properties were discussed in relation to the achieved morphologies. In the present work, some aromatic hyperbranched polyesters (aHBP) and aliphatic-aromatic hyperbranched polyesters (aaHBP), OH terminated have been used as matrices for nanocomposites containing TiO2. The TiO2 nanoparticles were synthesized via sol-gel directly in a solution containing the HBP polyester as a stabilizer, and then the polymer/TiO2 hybrid mixtures were thermally cured by a curing agent to obtain a hard coating or a film. In order to determine the conditions in which it was possible to get the best dispersion and the properties for the final material, the starting HBP-OH was also partially modified with alkoxysilane groups by 3-isocyanatopropyltriethoxysilane (IPTES), yielding modified aliphatic-aromatic hyperbranched polyesters aaHBP(OH)-Si and modified aromatic hyperbranched polyesters aHBP(OH)-Si, enabling it to interact with the TiO2 network. Both materials obtained were then characterized, and their properties compared.

Hyperbranched polymers (HBP) have drawn much attention and obtained intensive research activities from both industry and academia in the last three decades. They belong to a group of macromolecules called dendritic polymers, which have peculiar and often unique properties, which derive from their three-dimensional structure and the large number of functional groups. These structural characteristics provide high possibilities for controlling functional group interactions and modifications of other polymers in coatings and therefore, they are expected to result in novel materials with desired properties. They own a highly branched backbone, which gives access to many of reactive groups; their structure gives them excellent flow and processing properties, and they are characterized by lower viscosity than those of linear polymers of comparable molecular weight. Such properties make HBP extremely interesting for coatings and UV-curing applications and for this, they have attracted a great deal of attention for application, e.g. for powder coatings, high solid coatings, flame retardant coatings, barrier coatings for flexible packaging,and they have been recently suggested as a component of a dual-cure formulation based on an UV-curable epoxy resin and a functionalized alkoxysilane additive as an inorganic precursor to achieve advanced functional hybrid coatings. By pursuing this research line, we have synthesized an aliphatic–aromatic ethoxysilyl modified hyperbranched polyester system to be used in the preparation of UV-curable epoxy hybrid organic–inorganic coatings. The addition of ethoxysilyl-modified HBP could act as a coupling agent during the formation of the inorganic domains generated in-situ via sol-gel process starting from the alkoxysilane as inorganic precursors. The cured films were characterized in terms of their dynamic-mechanical properties and surface hardness: the obtained properties were discussed in relation to the achieved morphologies. In the present work, some aromatic hyperbranched polyesters (aHBP) and aliphatic-aromatic hyperbranched polyesters (aaHBP), OH terminated have been used as matrices for nanocomposites containing TiO2. The TiO2 nanoparticles were synthesized via sol-gel directly in a solution containing the HBP polyester as a stabilizer, and then the polymer/TiO2 hybrid mixtures were thermally cured by a curing agent to obtain a hard coating or a film. In order to determine the conditions in which it was possible to get the best dispersion and the properties for the final material, the starting HBP-OH was also partially modified with alkoxysilane groups by 3-isocyanatopropyltriethoxysilane (IPTES), yielding modified aliphatic-aromatic hyperbranched polyesters aaHBP(OH)-Si and modified aromatic hyperbranched polyesters aHBP(OH)-Si, enabling it to interact with the TiO2 network. Both materials obtained were then characterized, and their properties compared.

In this work, hyperbranched aromatic polyesters-polyphenols based on 4,4-bis(4’ hydroxy¬phenyl)pentanoic acid (BHPPA) were prepared and, according to the authors knowledge, for the first time tested as precursors for polyurethane bulk resins and coatings. Comparison of poly-BHPPA with competing products The materials prepared in this work show better properties than their aliphatic polyester-polyol analoga based on 2,2-bis-(hydroxymethyl)propanoic acid (BHMPA). Especially, the solubility of poly-BHPPA in organic solvents is better and poly-BHPPAs also do not tend to microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at elevated temperatures (90°C) in order to avoid undercure. The lower reactivity of phenolic OH groups prevents the reaction from being too fast at that temperature. A drawback of the polyurethanes based on the aromatic polyesters-polyols prepared is the lower thermal stability of their urethane bonds, if compared to aliphatic urethanes. An interesting possibility for future investigations would be the modification of the BHPPA monomer in order to change the OH functionality from phenolic to aliphatic OH, e.g. by replacement of the phenolic OH by hydroxymethyl or hydroxyethyl groups (requires a strong modification of the monomer synthesis) or simpler by reacting the phenolic OH of BHPPA with a suitable reagent like oxirane, which would lead to groups like O-CH2-CH2-OH in the place of the phenolic OH. Such a BHPPA modification should in turn yield modified “poly-BHPPA” polycondensates, which would combine the advantages of poly-BHPPA with those of aliphatic OH precursors of polyurethanes. Poly-BHPPA synthesis Hyperbranched polymers of the 4,4-bis-(4’-hydroxyphenyl)pentanoic acid (BHPPA) were synthesized successfully by the catalyzed (by dibutyltin diacetate) polycondensation of BHPPA. The products obtained were oligomers with number average molecular weight ranging from 1800 to 3400 g/mol (polymerization degree of ca. 6 to 12), displaying a first moment of functionality in the range 7 to 14. Such products were good OH precursors for the preparation of polyurethane coatings, because higher functional polymers would gel at low conversions. The analysis of the functional groups (determination of acid and hydroxyl numbers) and the 1H-NMR and the 13C-NMR spectroscopy were found to be good methods for the determination of molecular weights. The polydispersity of the poly-BHPPA products was in the range 3.5 to 6. Their degree of branching was found to be in the range 0.36 to 0.47. Poly-BHPPA containing aliphatic polyols as core monomers were also prepared successfully. Difunctional and trifunctional core monomers usually reached a full conversion of their OH groups, while the tetra- and hexafunctional core monomers were converted only to 89%. In all these products however, a considerable amount, usually even a majority, of the polymer molecules were core free. The poly-BHPPA products prepared displayed relatively high glass transition temperatures, in the range of 84°C to 114°C, obviously due to interactions between the phenol groups and to hydrogen bridging. The thermal stability of these products was also high, with decomposition occurring near 350°C (at a heating rate of 10°C / min) Kinetics investigations of the poly-BHPPA reactivity towards isocyanates The poly-BHPPA are polyphenols and were expectedly found to react significantly slower with isocyanates than aliphatic alcohols. The reactivity of poly BHPPA was also found to be somewhat lower than that of the monofunctional, low molar-mass 4 ethylphenol. Hexamethylene diisocyanate trimer, Desmodur N3300, was found to be more reactive than hexamethylene diisocyanate (HDI) or butyl isocyanate in all experiments, possibly due to a substitution effect. The substitution effect can be explained by a change of microenvironment caused by conversion of isocyanate group and OH group into urethane groups. The reactions of low-molecular-mass alcohols or phenols with low molecular weight isocyanates followed well the 2nd order kinetics, while the reactions of poly-BHPPA with isocyanates show deviations from ideal 2nd order kinetics at higher conversions. All the kinetics experiments were carried out under catalysis by dibutyltin dilaurate. This catalyst inhibits the undesired reaction of isocyanate groups with moisture. It was also found that the catalysis was necessary to reach reasonable curing times for poly-BHPPA based polyurethane networks. The uncatalyzed systems reacted extremely slowly. Preparation of polyurethane networks from poly-BHPPA The poly BHPPA products prepared were used successfully as OH functional precursors of polyurethane networks. The networks prepared contained only very low sol fractions. Acetone and also ethylene diglycol dimethylether (diglyme) were found to be good swelling solvents for the networks prepared, while methyl propyl ketone was a much poorer solvent and aromatic compounds like toluene or xylene practically did not swell the poly BHPPA based polyurethanes. The networks prepared contain a relatively high amount of cyclic bonds, 40 to 50% in the finally cured state, which is an expected result for systems with precursors of high functionality and with small distances between the functional groups. The temperature of glass transition (Tg) of the networks prepared (ranging from 68°C to 126°C) depends of the poly BHPPA precursor used: it increases with increasing molecular mass and with increasing core functionality. The choice of the isocyanate crosslinker also influences Tg: the networks made from HDI show higher Tg values, than networks made from the same poly BHPPA but crosslinked with Desmodur N3300 (Tri HDI). The urethane bonds in the networks prepared start to decompose near 140°C. The easier degradation of PU with aromatic urethane bonds is a disadvantage in comparison with aliphatic polyurethanes, whose decomposition starts at 200°C. The surfaces of polyurethane coatings prepared are smooth, displaying a roughness of ca. 20-25 nm, and relatively hydrophilic: the contact angle with water was found to be near 80°. The prepared networks are also relatively hard, possessing the Shore D hardness of 70.

In this work, hyperbranched aromatic polyesters-polyphenols based on 4,4-bis(4’ hydroxy¬phenyl)pentanoic acid (BHPPA) were prepared and, according to the authors knowledge, for the first time tested as precursors for polyurethane bulk resins and coatings. Comparison of poly-BHPPA with competing products The materials prepared in this work show better properties than their aliphatic polyester-polyol analoga based on 2,2-bis-(hydroxymethyl)propanoic acid (BHMPA). Especially, the solubility of poly-BHPPA in organic solvents is better and poly-BHPPAs also do not tend to microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at elevated temperatures (90°C) in order to avoid undercure. The lower reactivity of phenolic OH groups prevents the reaction from being too fast at that temperature. A drawback of the polyurethanes based on the aromatic polyesters-polyols prepared is the lower thermal stability of their urethane bonds, if compared to aliphatic urethanes. An interesting possibility for future investigations would be the modification of the BHPPA monomer in order to change the OH functionality from phenolic to aliphatic OH, e.g. by replacement of the phenolic OH by hydroxymethyl or hydroxyethyl groups (requires a strong modification of the monomer synthesis) or simpler by reacting the phenolic OH of BHPPA with a suitable reagent like oxirane, which would lead to groups like O-CH2-CH2-OH in the place of the phenolic OH. Such a BHPPA modification should in turn yield modified “poly-BHPPA” polycondensates, which would combine the advantages of poly-BHPPA with those of aliphatic OH precursors of polyurethanes. Poly-BHPPA synthesis Hyperbranched polymers of the 4,4-bis-(4’-hydroxyphenyl)pentanoic acid (BHPPA) were synthesized successfully by the catalyzed (by dibutyltin diacetate) polycondensation of BHPPA. The products obtained were oligomers with number average molecular weight ranging from 1800 to 3400 g/mol (polymerization degree of ca. 6 to 12), displaying a first moment of functionality in the range 7 to 14. Such products were good OH precursors for the preparation of polyurethane coatings, because higher functional polymers would gel at low conversions. The analysis of the functional groups (determination of acid and hydroxyl numbers) and the 1H-NMR and the 13C-NMR spectroscopy were found to be good methods for the determination of molecular weights. The polydispersity of the poly-BHPPA products was in the range 3.5 to 6. Their degree of branching was found to be in the range 0.36 to 0.47. Poly-BHPPA containing aliphatic polyols as core monomers were also prepared successfully. Difunctional and trifunctional core monomers usually reached a full conversion of their OH groups, while the tetra- and hexafunctional core monomers were converted only to 89%. In all these products however, a considerable amount, usually even a majority, of the polymer molecules were core free. The poly-BHPPA products prepared displayed relatively high glass transition temperatures, in the range of 84°C to 114°C, obviously due to interactions between the phenol groups and to hydrogen bridging. The thermal stability of these products was also high, with decomposition occurring near 350°C (at a heating rate of 10°C / min) Kinetics investigations of the poly-BHPPA reactivity towards isocyanates The poly-BHPPA are polyphenols and were expectedly found to react significantly slower with isocyanates than aliphatic alcohols. The reactivity of poly BHPPA was also found to be somewhat lower than that of the monofunctional, low molar-mass 4 ethylphenol. Hexamethylene diisocyanate trimer, Desmodur N3300, was found to be more reactive than hexamethylene diisocyanate (HDI) or butyl isocyanate in all experiments, possibly due to a substitution effect. The substitution effect can be explained by a change of microenvironment caused by conversion of isocyanate group and OH group into urethane groups. The reactions of low-molecular-mass alcohols or phenols with low molecular weight isocyanates followed well the 2nd order kinetics, while the reactions of poly-BHPPA with isocyanates show deviations from ideal 2nd order kinetics at higher conversions. All the kinetics experiments were carried out under catalysis by dibutyltin dilaurate. This catalyst inhibits the undesired reaction of isocyanate groups with moisture. It was also found that the catalysis was necessary to reach reasonable curing times for poly-BHPPA based polyurethane networks. The uncatalyzed systems reacted extremely slowly. Preparation of polyurethane networks from poly-BHPPA The poly BHPPA products prepared were used successfully as OH functional precursors of polyurethane networks. The networks prepared contained only very low sol fractions. Acetone and also ethylene diglycol dimethylether (diglyme) were found to be good swelling solvents for the networks prepared, while methyl propyl ketone was a much poorer solvent and aromatic compounds like toluene or xylene practically did not swell the poly BHPPA based polyurethanes. The networks prepared contain a relatively high amount of cyclic bonds, 40 to 50% in the finally cured state, which is an expected result for systems with precursors of high functionality and with small distances between the functional groups. The temperature of glass transition (Tg) of the networks prepared (ranging from 68°C to 126°C) depends of the poly BHPPA precursor used: it increases with increasing molecular mass and with increasing core functionality. The choice of the isocyanate crosslinker also influences Tg: the networks made from HDI show higher Tg values, than networks made from the same poly BHPPA but crosslinked with Desmodur N3300 (Tri HDI). The urethane bonds in the networks prepared start to decompose near 140°C. The easier degradation of PU with aromatic urethane bonds is a disadvantage in comparison with aliphatic polyurethanes, whose decomposition starts at 200°C. The surfaces of polyurethane coatings prepared are smooth, displaying a roughness of ca. 20-25 nm, and relatively hydrophilic: the contact angle with water was found to be near 80°. The prepared networks are also relatively hard, possessing the Shore D hardness of 70.

Kohlenstoff 2D-Nanoschichten wie Graphen und Graphenoxid sind vielversprechend, aber schwierig in Bezug auf multivalente Wechselwirkungen zu kontrollieren. Das Verständnis, wie neuartige Funktionalisierungsmethoden die Geometrie, Wechselwirkungen und elektronischen Eigenschaften der Graphenblätter beeinflussen, ist der Schwerpunkt dieser Arbeit. Diese Arbeit untersucht zwei Methoden zur Modifikation von 2D-Graphennanoschichten: "Graft to" und "Graft from" Techniken, unter Verwendung von „[2+1] Nitren-Cycloaddition“ und ringöffnender Polymerisation von Glycerin, zusätzlich zum Wachstum von 2D-Triazin-Kohlenstoffstrukturen. Diese modifizierten Nanoschichten wurden hinsichtlich ihrer Wechselwirkung mit dem Vesikulären Stomatitis-Virus (VSV) und ihrer Zweidimensionalität mittels Rastersondenmikroskopie und Raman-Spektroskopie untersucht. Die Studie zeigt das Potenzial funktionalisierter Graphen in der Virologie und liefert Einblicke für zukünftige Forschungen. Ergebnisse zeigten, dass funktionalisierte 2D-TRGO an VSV-Partikel bindet und flexibel genug bleibt, um auf einer flachen Glimmeroberfläche Falten zu bilden, aber sie können die Virushüllen nicht vollständig umschließen. Dies liegt an den hohen Energiekosten für das Biegen großer lateraler Dimensionen (~1-2 μm) im Vergleich zur 200 nm Länge der VSV-Partikel. Eine optimale laterale Dimension von ~300 nm für funktionalisierte 2D-TRGO-Blätter maximiert virale Wechselwirkungen, Hemmungseffizienz und Anzeichen viraler Umhüllung. Triazin, ein Schlüsselmolekül in der Funktionalisierung, kann zur Herstellung von 2D-Triazin-Strukturen im Gramm-Maßstab verwendet werden. Potenzielle Anwendungen funktionalisierter Graphene umfassen spezialisierte antivirale Therapien und die Verwendung als Plattform für antivirale Medikamente. Zudem zeigten die Ergebnisse minimale Störungen der elektronischen Struktur von Graphen durch Triazin-Funktionalisierung. / Carbon-based 2D nanosheets like graphene and graphene oxide are promising but challenging to control in terms of multivalent interactions. Understanding how novel functionalization methods affect graphene sheets' geometry, interaction specificity and electronic properties is the focus of this thesis, which is crucial for advancing the design of 2D nanomaterials. This thesis examines two novel methods for modifying 2D graphene nanosheets: "graft to" and "graft from" techniques, using [2+1] nitrene cycloaddition reactions and ring-opening multibranch polymerization of glycerol in addition to in plane growth of 2D triazine -carbon based structures. These modified nanosheets were studied for their interaction with vesicular stomatitis virus (VSV) and their two-dimensionality using scanning probe microscopy methods and Raman spectroscopy. The study highlights the potential of functionalized graphene nanosheets in virology and provides insights for future research. Results revealed that functionalized 2D TRGO binds to VSV particles and remains flexible enough to wrinkle on a flat mica interface but they cannot completely wrap the viral envelopes. This is due to the high energy cost of bending large lateral dimensions (~1-2μm) compared to the 200 nm length of VSV particles. An optimum lateral dimension of ~300 nm for functionalized 2D TRGO sheets was found to maximize viral interactions, inhibition efficiency, and signs of viral envelopment. Triazine, a key molecule in functionalization, can also be used to create 2D triazine structures on a gram scale. Functionalized graphene's potential applications include specialized antiviral therapies, such as targeted therapies exploiting multivalent interactions between viruses and cellular receptors, and using functionalized graphene as a delivery platform for antiviral drugs. Additionally, results showed minimal disturbance of graphene electronic structure via Triazine functionalization.