Controlling polymer architectures : high-throughput experimentation, tailor-made macromolecules and glycopolymers via "click" reactions

In nature, complex three-dimensionally ordered macromolecular architectures, such as proteins and DNA, can be found which are dependent on a high level of structural control in order to perform their desired biological tasks. Such systems are up to now not accessible by synthetic methods; however, in the last decades tremendous progress was made in the development of advanced living and controlled polymerization techniques. Besides, several outstanding organic reactions have been discovered and perfectionated with their easy experimental conditions and resulting high yields, which are categorized as "click" reactions. These techniques allow researchers to prepare well–defined tailor–made macromolecules with before not accessible control. However, in particular living and controlled polymerization techniques require a delicate selection of the appropriate catalyst, initiator, and solvent at a certain polymerization temperature and period for each type of monomer. Therefore, high–throughput experimentation (HTE) tools and techniques are required to screen the effect of reaction parameters in relatively short times. These polymerization techniques and the application of HTE in polymer science have been reviewed in the first chapter. A major part of this thesis deal with the optimization of not only controlled radical polymerization techniques but also cationic ring opening polymerization (CROP) process. Nitroxide mediated radical polymerization (NMP) of several monomers have been performed in an automated parallel synthesizer to obtain the most optimum reaction conditions in means of polydispersity indices, number average molar masses, monomer conversions as well as block copolymerization. We have used for this purpose a unimolecular nitroxide initiator (ß-phosphonylated alkoxyamine, Bloc Builder) which has a relatively low decomposition temperature and provides good control over the polymerization progress. Some of the obtained polymer libraries were examined for their thermal properties and lower critical solution temperature behavior. The results of these experiments are discussed in detail in the second chapter. In the third chapter, we have focused on the reversible addition fragmentation chain transfer (RAFT) polymerization technique to synthesize methacrylic acid containing thermo-responsive copolymer libraries. These polymers have been prepared using a synthesis robot and also parallel characterization techniques were employed. Furthermore, water uptake properties of the hydrophilic polymers as well as thermo-responsive polymers have been investigated. It was demonstrated that responsive polymers behave hydrophilic below their LCST and hydrophobic above their LCST, thus exhibiting a reversible water uptake–release profile. Atom transfer radical polymerization (ATRP) is one of the most important controlled/"living" polymerization techniques which has attracted significant attention in many fields of chemistry. We have contributed for the further development by introducing a new tetradentate nitrogen based ligand for the ATRP of methyl methacrylate and styrene. The optimization results revealed that this ligand is suitable to conduct ATRP of methyl methacrylate (MMA) in the presence of Cu(I) and Cu(II) metal ions. Besides, this ligand has been used for the ATRP of styrene initiated from functionalized surfaces. Grafting from the surface resulted in the formation of polymer brushes with controlled lengths depending on the reaction time. Transformation of the polymerization mechanisms by post polymerization modifications or by using functional initiating/terminating agents have been of great interest to combine different classes of monomers on the same backbone. Therefore, we have employed for the first time a heterofunctional initiator for the ATRP of styrene and the CROP of 2-ethyl-2-oxazoline (EtOx) to synthesize amphiphilic block copolymers. Furthermore, we determined the optimum polymerization temperature for EtOx using acetyl halide type of initiators. These reactions have been performed systematically in a microwave synthesizer and the results have been discussed in the fifth chapter. "Click" reactions have been employed in many fields of chemistry since 2001. These efficient reactions attracted also polymer chemists to introduce functional end groups or side groups to well–defined polymers. Several different techniques have been published in the last eight years and we discussed critically the ones which do not require a metal catalyst during the reactions in the last chapter. Besides, we have introduced a metal-free "click" reaction between thiol and pentafluorophenyl groups to synthesize glycopolymers. For this purpose, fluorinated polymers have been prepared by NMP and were further functionalized using this new "click" chemistry route. In conclusion, this thesis provides new insights into the most important controlled radical polymerization techniques by utilizing in the automated parallel synthesis platforms and by the systematical preparation of copolymer libraries. The detailed characterization of these libraries provided fundamental knowledge on the structure-property relationships. Moreover, a new ligand for the ATRP of MMA and styrene, a new type of heterofunctional initiator for the combination of ATRP and CROP, and a new type of "click" reaction for the synthesis of glycopolymers have been introduced during this thesis. These new compounds and routes will be employed further for the preparation of tailor-made macromolecules to be used in specific applications

A detailed study on understanding glycopolymer library and Con A interactions

Synthetic glycopolymers are important natural oligosaccharides mimics for many biological applications. To develop glycopolymeric drugs and therapeutic agents, factors that control the receptor-ligand interaction need to be investigated. A library of well-defined glycopolymers has been prepared by the combination of copper mediated living radical polymerization and CuAAC click reaction via post-functionalization of alkyne-containing precursor polymers with different sugar azides. Employing Concanavalin A as the model receptor, we explored the influence of the nature and densities of different sugars residues (mannose, galactose, and glucose) on the stoichiometry of the cluster, the rate of the cluster formation, the inhibitory potency of the glycopolymers, and the stability of the turbidity through quantitative precipitation assays, turbidimetry assays, inhibitory potency assays, and reversal aggregation assays. The diversities of binding properties contributed by different clustering parameters will make it possible to define the structures of the multivalent ligands and densities of binding epitopes tailor-made for specific functions in the lectin-ligand interaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2588–259

A(2)B-Miktoarm Glycopolymer Fibers and Their Interactions with Tenocytes

Electrospun biodegradable membranes have attracted great attention for a range of tissue engineering applications. Among them, poly­(ε-caprolactone) (PCL) is one of the most widely used polymers, owing to its well-controlled biocompatibility and biodegradability. However, PCL also has a number of limitations, such as its hydrophobic nature and the lack of functional groups on its side chain, limiting its ability to interact with cells. Herein, we have designed and prepared a series of well-defined A₂B-miktoarm copolymers with PCL and glycopolymer segments to address these limitations. Moreover, copolymers were electrospun to make membranes, which were studied in vitro to investigate cell affinity, toxicity, activity, and adhesion with these materials. The results indicate that incorporating glucose moieties into miktoarm polymers has improved the biocompatibility of the PCL while increasing the cellular interaction with the membrane material

Türk halk bilimi içinde Erzurum manilerinin yeri

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Türk Halk Bilimi çinde Erzurum Manilerinin Yeri çalışması, üç bölümde ele alınmıştır.Çalışmanın giriş bölümünde; konu, çalışmanın amacı, kapsamı, metodu üzerindedurulmuştur. Çalışmanın amacı: Erzurum manilerini konularına göre sınıflandırmak,Erzurum Manilerinin Türk Halk Bilimi içindeki yerini göstermek, Türklerin, Erzuruminsanın sınıflandırılan konularda duygularını maniler yoluyla ifade edişini ortayakoymaktır.Çalışmanın kapsamına, Türk Halk Biliminde mani, Erzurum'un tarihi,coğrafyası, halkbilimi ürünleri, konularına göre sınıflandırılan Erzurum manileri girmektedir.Çalışmada, yüzyüze konuşma, aracı-elçi kullanma, mektuplaşma metodlarıkullanılmıştır.Çalışmanın birinci bölümünde; araştırma alanın, Erzurum'un Aşkale, Hasankale,Pasinler, Köprüköy, Ilıca ilçeleri ve Sakarya-Arifiye olduğu belirtilmiş, Erzurum'untarihinden, coğrafyasından, tarihi eserlerinden bahsedilmiştir.Çalışmanın ikinci bölümünde; kısaca Erzurum halk bilimi ürünlerinden bahsedilmiş vekonularına göre Erzurum manileri sınıflandırılmıştır.Çalışmanın üçüncü bölümünde; Türk Halk Biliminde mani, mani söyleme geleneğiüzerinde durularak, konularına göre sınıflandırılan Erzurum Manilerini yorumlamayoluna gidilmiş, bazıları da metinler halinde verilmiştir.Erzurum manileri çalışmada yorumlama yoluna gidilerek Erzurum insanın aşka,sevgiye, dine, anneye duyulan hürmete verdiği değerler ortaya konulmuş, ayrılık, hasretkarşısındaki hisleri verilmeye çalışılmıştır.Anahtar Kelimeler: Mani, Halk Bilimi Ürünleri, Erzurum ManileriThe study of the place of Erzurum's Manis in Turkish Folks was evaluated into threeparts.In the introduction part of the study; the theme, the aim, the content and themethod of the study were focused on. The aim of the study: To classify theErzurum's Manis according to their themes, to point out the place of the Erzurum'sManis in Turkish Folks, to reveal how Turks and Erzurum's people show theirfeelings with classified themes by manis.In the study; mani, the history, the geography and the products of Folks ofErzurum, theclassified manis according to their themes were included. In the study, talking faceto face, using go-between, writing to each other methods were used.In the first part of the study, the areas to search were declared such as the towns ofErzurum, Aşkale, Hasankale, Pasinler, Koprüköy, Ilıca and Arifiye, one of the townsof Sakarya; and the history, the geography and the historical works of Erzurum werementioned.In the second part of the study; the products of Folks of Erzurum were brieflymentioned and Erzurum's Manis according to their themes were classified.In the third part of the study; by emphasizing telling the mani tradition and mani inTurkish Folks, the Erzurum's Manis classified according to their themes wereinterpreted and some of the manis were given without changing.By interpreting Erzurum's Manis in the study, the importance given to love, toRamadan, to motherhood by Erzurum people were revealed and also feelingsof those people about seperation, longing and marriage were tried to be given.Keywords : Mani, The Products of Folks, Erzurum's Mani

Simulation of Quantum Infrared Photodetectors

The topic of research is concerned with modelling and simulation of high temperature long wavelength infrared quantum photodetectors using advanced finite element methods. The aim is to devise novel designs based on quantum well structures to improve quantum efficiency, and operating temperature. These new designs rely on quantum confinement of electrons and holes inside a mixture of materials within which the energies of the carriers become discrete and differ from those observed in bulk materials. Type II InAs / GaSb superlattices is one of these meta–materials which offer a large flexibility in the design of infrared photodetectors, including the possibility to adjust the detected wavelength over a very wide range and to realize a suitable absobers’ unipolar barriers to suppress dark current while maintaining a significant portion of photocurrent at high temperatures. In order to validate this interest, A set of rigorous modelling tools based on multi-band k· p band structure theory and Boltzmann transport theory has been developed, which provide a better understanding of the electronic structure and transport in these heterostructures. The framework takes into account in particular the effect of the intrinsic strained property of the unintentional interfaces on the electronic structure and the optical properties. First, the finite element method is used to solve 8 × 8 k · pHamiltonians for InAs/GaSb superlattices with type II alignment to compute the optical and materials’ characteristics. For InAs and AlAsSb and alloys based detectors, An optical material library has been developed to generate all the needed bulk material properties. Secondly, the transfer matrix method or the Beer-Lambert law is used to compute the optical generation profiles in the device. Finally, the the finite volume method has been employed to solve the transport equations to compute the dark- and photo- currents, quantum efficiency among other device properties. Using this tools, new structures based on nBn and nBp architectures have been designed, with optimized design, which contribute to the realization of mid- and long- wave infrared photodetector based on Type-II superlattices InAs / GaSb material system as well as InAs/AlAsSb alloy mterial system. The developed model allows to study the underlying physics of these devices and to explain the factors limiting the device performances. Based on the simulation results, detectors involving absorbers with period composed of 14 Mono-Layer (ML) of InAs and 7 ML of GaSb was found to have a band gap wavelength close v to 11 μm and exhibit a lower dark current than those with period mainly composed of GaSb. The designed LWIR barrier device consists of a 4 μm thick p-type InAs-rich 14 ML InAs / 7ML GaSb LWIR T2SL absorber, a 200 nm thick p-type InAs/AlSb SL barrier and an n-type InAs-rich 14 ML InAs / 7ML GaSb LWIR T2SL contact layer. The 16.5ML InAs / 4ML AlSb superlattice of the BL is designed to give a smooth conduction band alignment and a large VBO of nearly 400 meV with the AL. The optimum doping level of absorber, barrier and contact layer are found to be 1 × 1016cm3, 5 × 1015cm3 and 1 × 1016cm3 respectively. This nBp detector design exhibits at 77 K a diffusion limited dark-current down to -300 mV with a dark-current level plateau as low as 8.5 × 10−5A/cm2 which is more than one order of magnitude lower compared to a similar PIN photodiode. Furthermore, this value is near the level of the MCT ‘rule 07’ demonstrating that InAs/GaSb SL detectors may provide new opportunities to replace the MCT technology in the LWIR spectral window given the MCT material instability problem at longer wavelengths. Moreover, we have demonstrated that the presence of the majority carriers’ barrier improves the current performances and the operating temperature over the standard PIN device. A temperature improvement of 20 K was found for a given current density of 2x10−4 A/cm−2 compared to a similar LWIR PIN device working at 60 K

Self-Assembling Hydrogels Based on a Complementary Host-Guest Peptide Amphiphile Pair

Supramolecular polymer-based biomaterials play a significant role in current biomedical research. In particular, peptide amphiphiles (PAs) represent a promising material platform for biomedical applications given their modular assembly, tunability, and capacity to render materials with structural and molecular precision. However, the possibility to provide dynamic cues within PA-based materials would increase the capacity to modulate their mechanical and physical properties and, consequently, enhance their functionality and broader use. In this study, we report on the synthesis of a cationic PA pair bearing complementary adamantane and β-cyclodextrin host–guest cues and their capacity to be further incorporated into self-assembled nanostructures. We demonstrate the possibility of these recognition motifs to selectively bind, enabling noncovalent cross-linking between PA nanofibers and endowing the resulting supramolecular hydrogels with enhanced mechanical properties, including stiffness and resistance to degradation, while retaining in vitro biocompatibility. The incorporation of the host–guest PA pairs in the resulting hydrogels allowed not only for macroscopic mechanical control from the molecular scale, but also for the possibility to engineer further spatiotemporal dynamic properties, opening opportunities for broader potential applications of PA-based materials

Single-chain glycopolymer folding via host-guest interactions and its unprecedented effect on DC-SIGN binding

Reversible self-folding actions of natural biomacromolecules play crucial roles for specific and unique biological functions in Nature. Hence, controlled folding of single polymer chains has attracted significant attention in recent years. Herein, reversible single-chain folded glycopolymer structures in α-shape with different density of sugar moieties in the knot were created. The influence of folding as well as the sugar density in the knot was investigated on the binding capability with lectins, such as ConA, DC-SIGN and DC-SIGNR. The synthesis of triblock glycocopolymers bearing β-CD and adamantane for the host-guest interaction and also mannose residues for the lectin interaction was achieved using the reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The reversible single-chain folding of glycopolymers was achieved under a high dilution of an aqueous solution and the self-assembled folding was monitored by 2D nuclear overhauser enhancement spectroscopy (NOESY) NMR and dynamic light scattering. The lectin binding profiles consistently provided an unprecedented effect of single chain folding as the single-chain folded structures enhanced greatly the binding ability in comparison to the unfolded linear structures

Ugi multicomponent reaction to prepare peptide–peptoid hybrid structures with diverse chemical functionalities

Monodisperse sequenced peptides and peptoids present unique nano-structures based on their self-assembled secondary and tertiary structures. However, the generation of peptide and peptoid hybrid oligomers in a sequence-defined manner via Ugi multicomponent reaction has not yet been studied. Herein, we report a synthetic strategy that enables both the modification of peptides as well as the generation of sequence-defined peptide–peptoid hybrid structures. Our synthetic methodology rests on the fusion of solid phase peptide synthesis with Ugi multicomponent reactions. We evidence that a diversity of chemical functionalities can be inserted into peptides or used in the design of peptide–peptoid hybrids exploiting a wide functional array including amines, carboxylic acids, hydrocarbons, carbohydrates as well as polymers, introducing a sequence-defined synthetic platform technology for precision peptoid hybrids