@phdthesis{Esen2023,
  author    = {Esen, Cansu},
  title     = {Carbon nitride incorporation in polymer networks},
  doi       = {10.25932/publishup-57625},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-576253},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xvi, 175},
  year      = {2023},
  abstract  = {The urge of light utilization in fabrication of materials is as encouraging as challenging. Steadily increasing energy consumption in accordance with rapid population growth, is requiring a corresponding solution within the same rate of occurrence speed. Therefore, creating, designing and manufacturing materials that can interact with light and in further be applicable as well as disposable in photo-based applications are very much under attention of researchers. In the era of sustainability for renewable energy systems, semiconductor-based photoactive materials have received great attention not only based on solar and/or hydrocarbon fuels generation from solar energy, but also successful stimulation of photocatalytic reactions such as water splitting, pollutant degradation and organic molecule synthesisThe turning point had been reached for water splitting with an electrochemical cell consisting of TiO2-Pt electrode illuminated by UV light as energy source rather than an external voltage, that successfully pursued water photolysis by Fujishima and Honda in 1972. Ever since, there has been a great deal of interest in research of semiconductors (e.g. metal oxide, metal-free organic, noble-metal complex) exhibiting effective band gap for photochemical reactions. In the case of environmental friendliness, toxicity of metal-based semiconductors brings some restrictions in possible applications. Regarding this, very robust and 'earth-abundant' organic semiconductor, graphitic carbon nitride has been synthesized and successfully applied in photoinduced applications as novel photocatalyst. Properties such as suitable band gap, low charge carrier recombination and feasibility for scaling up, pave the way of advance combination with other catalysts to gather higher photoactivity based on compatible heterojunction. This dissertation aims to demonstrate a series of combinations between organic semiconductor g-CN and polymer materials that are forged through photochemistry, either in synthesis or in application. Fabrication and design processes as well as applications performed in accordance to the scope of thesis will be elucidated in detail. In addition to UV light, more attention is placed on visible light as energy source with a vision of more sustainability and better scalability in creation of novel materials and solar energy based applications.},
  language  = {en}
}
@phdthesis{Chea2022,
  author    = {Chea, Sany},
  title     = {Glycomaterials: From synthesis of glycoconjugates to potential biomedical applications},
  doi       = {10.25932/publishup-57424},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-574240},
  school      = {Universit{\"a}t Potsdam},
  pages     = {XVII, 217},
  year      = {2022},
  abstract  = {The importance of carbohydrate structures is enormous due to their ubiquitousness in our lives. The development of so-called glycomaterials is the result of this tremendous significance. These are not exclusively used for research into fundamental biological processes, but also, among other things, as inhibitors of pathogens or as drug delivery systems. This work describes the development of glycomaterials involving the synthesis of glycoderivatives, -monomers and -polymers. Glycosylamines were synthesized as precursors in a single synthesis step under microwave irradiation to significantly shorten the usual reaction time. Derivatization at the anomeric position was carried out according to the methods developed by Kochetkov and Likhorshetov, which do not require the introduction of protecting groups. Aminated saccharide structures formed the basis for the synthesis of glycomonomers in β-configuration by methacrylation. In order to obtain α-Man-based monomers for interactions with certain α-Man-binding lectins, a monomer synthesis by Staudinger ligation was developed in this work, which also does not require protective groups. Modification of the primary hydroxyl group of a saccharide was accomplished by enzyme-catalyzed synthesis. Ribose-containing cytidine was transesterified using the lipase Novozym 435 and microwave irradiation. The resulting monomer synthesis was optimized by varying the reaction partners. To create an amide bond instead of an ester bond, protected cytidine was modified by oxidation followed by amide coupling to form the monomer. This synthetic route was also used to isolate the monomer from its counterpart guanosine. After obtaining the nucleoside-based monomers, they were block copolymerized using the RAFT method. Pre-synthesized pHPMA served as macroCTA to yield cytidine- or guanosine-containing block copolymer. These isolated block copolymers were then investigated for their self-assembly behavior using UV-Vis, DLS and SEM to serve as a potential thermoresponsive drug delivery system.},
  language  = {en}
}
@phdthesis{Izraylit2021,
  author    = {Izraylit, Victor},
  title     = {Reprogrammable and tunable actuation in multiblock copolymer blends},
  doi       = {10.25932/publishup-51843},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518434},
  school      = {Universit{\"a}t Potsdam},
  pages     = {104},
  year      = {2021},
  abstract  = {Soft actuators have drawn significant attention due to their relevance for applications, such as artificial muscles in devices developed for medicine and robotics. Tuning their performance and expanding their functionality are frequently done by means of chemical modification. The introduction of structural elements rendering non-synthetic modification of the performance possible, as well as control over physical appearance and facilitating their recycling is a subject of a great interest in the field of smart materials. The primary aim of this thesis was to create a shape-memory polymeric actuator, where the capability for non-synthetic tuning of the actuation performance is combined with reprocessability. Physically cross-linked polymeric matrices provide a solid material platform, where the in situ processing methods can be employed for modification of the composition and morphology, resulting in the fine tuning of the related mechanical properties and shape-memory actuation capability. The morphological features, required for shape-memory polymeric actuators, namely two crystallisable domains and anchoring points for physical cross-links, were embedded into a multiblock copolymer with poly(ε-caprolactone) and poly(L-lactide) segments (PLLA-PCL). Here, the melting transition of PCL was bisected into the actuating and skeleton-forming units, while the cross-linking was introduced via PLA stereocomplexation in blends with oligomeric poly(D-lactide) (ODLA). PLLA segment number average length of 12-15 repeating units was experimentally defined to be capable of the PLA stereocomplexes formation, but not sufficient for the isotactic crystallisation. Multiblock structure and phase dilution broaden the PCL melting transition, facilitating its separation into two conditionally independent crystalline domains. Low molar mass of the PLA stereocomplex components and a multiblock structure enables processing and reprocessing of the PLLA-PCL / ODLA blends with common non-destructive techniques. The modularity of the PLLA-PCL structure and synthetic approach allows for independent tuning of the properties of its components. The designed material establishes a solid platform for non-synthetic tuning of thermomechanical and structural properties of thermoplastic elastomers. To evaluate the thermomechanical stability of the formed physical network, three criteria were appraised. As physical cross-links, PLA stereocomplexes have to be evenly distributed within the material matrix, their melting temperature shall not overlap with the thermal transitions of the PCL domains and they have to maintain the structural integrity within the strain ε ranges further applied in the shape-memory actuation experiments. Assigning PCL the function of the skeleton-forming and actuating units, and PLA stereocomplexes the role of physical netpoints, shape-memory actuation was realised in the PLLA-PCL / ODLA blends. Reversible strain of shape-memory actuation was found to be a function of PLA stereocomplex crystallinity, i.e. physical cross-linking density, with a maximum of 13.4 ± 1.5\% at PLA stereocomplex content of 3.1 ± 0.3 wt\%. In this way, shape-memory actuation can be tuned via adjusting the composition of the PLLA-PCL / ODLA blend. This makes the developed material a valuable asset in the production of cost-effective tunable soft polymeric actuators for the applications in medicine and soft robotics.},
  language  = {en}
}
@phdthesis{Kumru2018,
  author    = {Kumru, Baris},
  title     = {Utilization of graphitic carbon nitride in dispersed media},
  doi       = {10.25932/publishup-42733},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-427339},
  school      = {Universit{\"a}t Potsdam},
  pages     = {III, 190},
  year      = {2018},
  abstract  = {Utilization of sunlight for energy harvesting has been foreseen as sustainable replacement for fossil fuels, which would also eliminate side effects arising from fossil fuel consumption such as drastic increase of CO2 in Earth atmosphere. Semiconductor materials can be implemented for energy harvesting, and design of ideal energy harvesting devices relies on effective semiconductor with low recombination rate, ease of processing, stability over long period, non-toxicity and synthesis from abundant sources. Aforementioned criteria have attracted broad interest for graphitic carbon nitride (g-CN) materials, metal-free semiconductor which can be synthesized from low cost and abundant precursors. Furthermore, physical properties such as band gap, surface area and absorption can be tuned. g-CN was investigated as heterogeneous catalyst, with diversified applications from water splitting to CO2 reduction and organic coupling reactions. However, low dispersibility of g-CN in water and organic solvents was an obstacle for future improvements. Tissue engineering aims to mimic natural tissues mechanically and biologically, so that synthetic materials can replace natural ones in future. Hydrogels are crosslinked networks with high water content, therefore are prime candidates for tissue engineering. However, the first requirement is synthesis of hydrogels with mechanical properties that are matching to natural tissues. Among different approaches for reinforcement, nanocomposite reinforcement is highly promising. This thesis aims to investigate aqueous and organic dispersions of g-CN materials. Aqueous g-CN dispersions were utilized for visible light induced hydrogel synthesis, where g-CN acts as reinforcer and photoinitiator. Varieties of methodologies were presented for enhancing g-CN dispersibility, from co-solvent method to prepolymer formation, and it was shown that hydrogels with diversified mechanical properties (from skin-like to cartilage-like) are accessible via g-CN utilization. One pot photografting method was introduced for functionalization of g-CN surface which provides functional groups towards enhanced dispersibility in aqueous and organic media. Grafting vinyl thiazole groups yields stable additive-free organodispersions of g-CN which are electrostatically stabilized with increased photophysical properties. Colloidal stability of organic systems provides transparent g-CN coatings and printing g-CN from commercial inkjet printers. Overall, application of g-CN in dispersed media is highly promising, and variety of materials can be accessible via utilization of g-CN and visible light with simple chemicals and synthetic conditions. g-CN in dispersed media will bridge emerging research areas from tissue engineering to energy harvesting in near future.},
  language  = {en}
}
@phdthesis{Willersinn2017,
  author    = {Willersinn, Jochen},
  title     = {Self-Assembly of double hydrophilic block copolymers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-408578},
  school      = {Universit{\"a}t Potsdam},
  pages     = {119, clxxiv},
  year      = {2017},
  abstract  = {The motivation of this work was to investigate the self-assembly of a block copolymer species that attended little attraction before, double hydrophilic block copolymers (DHBCs). DHBCs consist of two linear hydrophilic polymer blocks. The self-assembly of DHBCs towards suprastructures such as particles and vesicles is determined via a strong difference in hydrophilicity between the corresponding blocks leading to a microphase separation due to immiscibility. The benefits of DHBCs and the corresponding particles and vesicles, such as biocompatibility, high permeability towards water and hydrophilic compounds as well as the large amount of possible functionalizations that can be addressed to the block copolymers make the application of DHBC based structures a viable choice in biomedicine. In order to assess a route towards self-assembled structures from DHBCs that display the potential to act as cargos for future applications, several block copolymers containing two hydrophilic polymer blocks were synthesized. Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone) (PEO-b-PVP) and Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone-co-N-vinylimidazole) (PEO-b-P(VP-co-VIm) block copolymers were synthesized via reversible deactivation radical polymerization (RDRP) techniques starting from a PEO-macro chain transfer agent. The block copolymers displayed a concentration dependent self-assembly behavior in water which was determined via dynamic light scattering (DLS). It was possible to observe spherical particles via laser scanning confocal microscopy (LSCM) and cryogenic scanning electron microscopy (cryo SEM) at highly concentrated solutions of PEO-b-PVP. Furthermore, a crosslinking strategy with (PEO-b-P(VP-co-VIm) was developed applying a diiodo derived crosslinker diethylene glycol bis(2-iodoethyl) ether to form quaternary amines at the VIm units. The formed crosslinked structures proved stability upon dilution and transfer into organic solvents. Moreover, self-assembly and crosslinking in DMF proved to be more advantageous and the crosslinked structures could be successfully transferred to aqueous solution. The afforded spherical submicron particles could be visualized via LSCM, cryo SEM and Cryo TEM. Double hydrophilic pullulan-b-poly(acrylamide) block copolymers were synthesized via copper catalyzed alkyne azide cycloaddition (CuAAC) starting from suitable pullulan alkyne and azide functionalized poly(N,N-dimethylacrylamide) (PDMA) and poly(N-ethylacrylamide) (PEA) homopolymers. The conjugation reaction was confirmed via SEC and 1H-NMR measurements. The self-assembly of the block copolymers was monitored with DLS and static light scattering (SLS) measurements indicating the presence of hollow spherical structures. Cryo SEM measurements could confirm the presence of vesicular structures for Pull-b-PEA block copolymers. Solutions of Pull-b-PDMA displayed particles in cryo SEM. Moreover, an end group functionalization of Pull-b-PDMA with Rhodamine B allowed assessing the structure via LSCM and hollow spherical structures were observed indicating the presence of vesicles, too. An exemplified pathway towards a DHBC based drug delivery vehicle was demonstrated with the block copolymer Pull-b-PVP. The block copolymer was synthesized via RAFT/MADIX techniques starting from a pullulan chain transfer agent. Pull-b-PVP displayed a concentration dependent self-assembly in water with an efficiency superior to the PEO-b-PVP system, which could be observed via DLS. Cryo SEM and LSCM microscopy displayed the presence of spherical structures. In order to apply a reversible crosslinking strategy on the synthesized block copolymer, the pullulan block was selectively oxidized to dialdehydes with NaIO4. The oxidation of the block copolymer was confirmed via SEC and 1H-NMR measurements. The self-assembled and oxidized structures were subsequently crosslinked with cystamine dihiydrochloride, a pH and redox responsive crosslinker resulting in crosslinked vesicles which were observed via cryo SEM. The vesicular structures of crosslinked Pull-b-PVP could be disassembled by acid treatment or the application of the redox agent tris(2-carboxyethyl)-phosphin-hydrochloride. The successful disassembly was monitored with DLS measurements. To conclude, self-assembled structures from DHBCs such as particles and vesicles display a strong potential to generate an impact on biomedicine and nanotechnologies. The variety of DHBC compositions and functionalities are very promising features for future applications.},
  language  = {en}
}
@phdthesis{Mai2016,
  author    = {Mai, Tobias},
  title     = {Polymerunterst{\"u}tzte Calciumphosphatmineralisation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-89056},
  school      = {Universit{\"a}t Potsdam},
  year      = {2016},
  abstract  = {Im Verlauf dieser Arbeit sind Blockcopolymere verschiedener Ladung auf Basis von PEO mit hohen Molekulargewichten durch lebendende freie radikalische Polymerisation hergestellt worden. Die Polymere sind einfach im Grammmaßstab herstellbar. Sie zeigen sowohl einen großen Einfluss auf die Nukleation als auch auf die Aufl{\"o}sung von Calciumphosphat. Gleichwohl scheint das Vorhandensein von positiven Gruppen (Kationen, Ampholyten und Betainen) keinen dramatischen Einfluss auf die Nukleation zu haben. So verursachen Polymere mit positiven Ladungen die gleiche Retentionwirkung wie solche, die ausschließlich anionische Gruppen enthalten. Aus der Verwendung der kationischen, ampholytischen und betainischen Copolymere resultiert allerdings eine andersartige Morphologie der Niederschl{\"a}ge, als aus der Verwendung der Anionischen hervorgeht. Bei der Stabilisierung einer HAP-Oberfl{\"a}che setzt sich dieser Trend fort, das heißt, rein anionische Copolymere wirken st{\"a}rker stabilisierend als solche, die positive Ladungen enthalten. Durch Inkubation von menschlichem Zahnschmelz mit anionischen Copolymeren konnte gezeigt werden, dass die Biofilmbildung verglichen mit einer unbehandelten Zahnoberfl{\"a}che eingeschr{\"a}nkt abl{\"a}uft. All dies macht die Polymere zu interessanten Additiven f{\"u}r Zahnpflegeprodukte. Zus{\"a}tzlich konnten auf Basis dieser rein anionischen Copolymere Polymerb{\"u}rsten, ebenfalls {\"u}ber lebendende freie radikalische Polymerisation, hergestellt werden. Diese zeichnen sich durch einen großen Einfluss auf die Kristallphase aus und bilden mit dem CHAP des AB-Types das Material, welches auch in Knochen und Z{\"a}hnen vorkommt. Erste Cytotoxizit{\"a}tstests lassen auf das große Potential dieser Polymerb{\"u}rsten f{\"u}r Beschichtungen in der Medizintechnik schließen.},
  language  = {de}
}
@phdthesis{tenBrummelhuis2011,
  author    = {ten Brummelhuis, Niels},
  title     = {Self-assembly of cross-linked polymer micelles into complex higher-order aggregates},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-52320},
  school      = {Universit{\"a}t Potsdam},
  year      = {2011},
  abstract  = {The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios.},
  language  = {en}
}