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ÖgeWhite led induced degradation of polyacrylates as a green alternative for polymer recycling(Graduate School, 2023-06-19)In today's world, plastic materials are used almost every day due to their advantageous properties. However, widespread use of plastics has resulted in serious environmental issues, such as the buildup of plastic waste and its damaging effects on ecosystems. Efforts are underway to find effective recycling methods for widely used polymers as part of the journey towards a greener and more sustainable world, aiming to reduce this dependence. The topic of enhancing the sustainability of polymers is at the forefront of the discipline of polymer science and engineering, and it includes a variety of strategies, from mechanical recycling to degradation and chemical recycling. Poly(methyl methacrylate) (PMMA) is a polymer that holds great significance within the realm of materials due to its remarkable combination of high-impact strength, optical clarity, and lightweight characteristics. Various applications of PMMA have resulted in considerable consumption and generation of noticeable amounts of waste. By 2027, it is projected that the consumption of polymers will reach a level of 4 million tons per year and as the years pass, it could further increase. Since PMMA does not have a hydrolysable main chain, depolymerization or degradation requires advanced recycling methods. These methods involve some requirements that are both economically and environmentally harmful, such as high temperatures and heavy toxic metal catalysts. Despite the challenging conditions, the research conducted contributes to polymer recycling. However, replacing these requirements with some green alternatives is highly appealing. Photochemical reactions, with advantages such as being environmentally friendly and low energy consumption, have gained attention both in industry and academia. The idea of adapting light-induced reactions to this field and using a catalyst other than metal-based catalysts, which are another environmental pollutant factor, shed light on this study. In this study, we take advantage of the efficient properties of light in the field of degradation. We present a novel approach utilizing a white LED light source and a metal-free method for the degradation of PMMA derivatives that contain halogen in the main chain. A copolymerization incorporated PMMA derivatives containing light-triggerable halogen atoms into the main chain. The Reversible Addition-Fragmentation Chain Transfer (RAFT) controlled polymerization technique was employed for the synthesis of methyl methacrylate-methyl α-chloroacrylate and methyl methacrylate-ethyl cis-3 bromoacrylate copolymers. In the presence of organodyes (metal-free catalysts) the synthesized copolymers undergo efficient degradation into low molecular weight oligomers when irradiated with visible light. This study serves as a realistic approach to polymer recycling and leading to the development of more sustainable recycling methods for polymers.
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ÖgeCalix[4]pyrrole based supramolecular polymers via orthogonal interactions(Graduate School, 2022-02-07)Supramolecular polymers are based on reversible intermolecular interactions. Rather than linking the monomers in the desired arrangement via a covalent of polymerization reaction, the monomers are designed in such a way that they self-assemble autonomously into the desired structure. The type and strength of non-covalent interactions varies, ranging from very weak Van der Waals interactions, π-π stacking, hydrogen bonding, solvophobic interactions to dipole-dipole interactions and very strong metal-ligand or ion-ion interactions. A well-known natural supramolecular system is DNA, whose unique architecture results from cooperative non-covalent interactions, such as multiple hydrogen bonds and hydrophobic interactions. By exploiting the reversibility of the interactions, materials with fascinating properties such as self-healing, shape memory and responsive behaviour can be produced. These materials have been prepared by using cationic guests and the host molecules that can interact with these guests and found various applications in energy, regenerative medicine, nanotechnology, environment and synthetic chemistry. Calix[4]pyrroles are non-conjugated tetrapyrrolic macrocycles capable of binding anions and neutral substrates in organic media via hydrogen bonding. Moreover, upon anion binding, they change their conformation from 1,3-alternate to cone conformation to facilitate the hydrogen bonding. Apart from that, cation-π interaction between appropriate cations and π-electron cloud of cone-shaped calix[4]pyrroles are also well known. Non-covalent and reversible supramolecular interactions provide functional materials within one polymer system. These specific interactions can be designated independently and simultaneously giving orthogonal self-assembly. The aim of this thesis is to synthesize and characterize supramolecular polymers based on anion recognition chemistry of calix[4]pyrroles via orthogonal self-assembly. In this thesis pyrimidinone functionalized calix[4]pyrrole derivative (UPyCP2) and a bis-carboxylate (TBAS) salt were used as host and guest molecules, respectively. Another supramolecular polymeric system was also prepared by host-guest, cation-π and van der Walls interactions that has been built from a bis-calix[4]pyrrole (BisCP) and bis-carboxylate (CTAS) as host and guest moieties, respectively. These supramolecular polymers prepared in an organic solvent and were found tho have thermo-, chemical-responsive behaviour. The above systems have been analyzed by NMR, viscosity measurements and scanninng electron microscopy.
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ÖgeSwelling dynamics and thermomechanical properties of multifunctional hybrid systems based on N-alkyl methacrylate esters(Graduate School, 2021-12-16)Increasing demand for functional polymers in applications based on smart materials has led to the need for modified synthetic tools and new ways to design advanced materials containing specific functional groups. Improved material design is possible using specific monomers with functional groups that remain proactive under polymerization conditions and can be selectively converted to other functional groups in subsequent steps. N-alkyl methacrylate-based monomers, which can be easily polymerized under mild conditions, are widely used in design of various precisely defined functional materials. Thanks to these extraordinary features of smart gels; hydrogels have many applications in processes ranging from industrial to biological. In particular, it have many uses in many areas from food industry, pharmaceutical applications, drug delivery systems, agriculture, contact lenses, sensors, tissue engineering, controlled drug release and water purification, etc. In the first part of this study, a synthesis group was designed for the preparation of n-alkyl methacrylate ester-based multifunctional hybrid systems. It was aimed to perform the synthesis of a series of n-alkyl-methacrylate estrer-based terpolymer hydrogels consisting 2-(dimethylamino)ethyl-methacrylate (DMAEMA), hydroxypropyl-methacrylate (HPMA), and glycidyl-methacrylate (GMA) using different monomer feed compositions at a fixed crosslinker ratio. The aim of the second part of this study was to successfully synthesize terpolymer cryogels using the monomers and crosslinkers in equal proportions to those synthesized in the first part and to investigate the effect of tertiary amine groups of DMAEMA and epoxy functional groups of GMA on the gel properties. In the third part of the study; the effect of the gel preparation temperature on the gel properties was investigated. For this purpose, the results obtained from the first and second part were interpreted and the terpolymer with 20 mol% HPMA, 70 mol% DMAEMA and 10 mol% GMA structure was selected, and In this part, the terpolymer gel prepared by free radical crosslinking in water at constant monomer and crosslinker concentrations was successfully synthesized by changing the polymerization temperature between -18 and 60 oC. The effect of the change in DMAEMA/GMA mol percent ratio from 80/0 to 0/80 in the terpolymer matrix on the gel properties was investigated and it was observed that the gel properties are controlled by the tertiary amino groups in the structure of DMAEMA as well as the GMA monomer. In order to evaluate the macroscopic properties of terpolymer gels, the specific structural properties of the groups in the terpolymer matrix and their physico-chemical properties that vary depending on the monomer feed composition and gel preparation temperature were investigated. In the first part of the experimental work, it is aimed to develop a new polycationic ternary gel system with different functional groups and to evaluate the scaling relationships between the network parameters and the elastic properties. Multifunctional ternary-gels based on 2-(dimethylamino)ethyl methacrylate (DMAEMA), hydroxypropyl methacrylate (HPMA) and glycidyl methacrylate (GMA) were prepared in a wide gel preparation concentration range. The resulting gels denoted as terpolymeric poly(hydroxypropyl methacrylate-co-glycidyl methacrylate-co-2-(dimethylamino)ethyl methacrylate), PHDm/Gn-Hgs, were characterized by ATR-FTIR, and TGA measurements. The thermal stability of the terpolymer hydrogels was observed to be improved with the increase in GMA content. Swelling of ternary-gels in different solvents showed that cyclohexanol was a good solvent for the present terpolymer gel system. Swelling is controlled by DMAEMA portion of terpolymers and DMAEMA-rich gels tended to swell more than GMA-rich gels and increase in GMA content increased the polymer-solvent interaction parameter. It was determined that the addition of hydrophobic GMA to the terpolymer matrix led to a significant increase in the stiffness. The increase in elastic modulus as-prepared state is not monotonic and can be thoroughly controlled by adjusting DMAEMA/GMA ratio since tertiary amine groups triggers cascading epoxy ring-opening reaction. Dependence of swelling on the gel preparation concentration as a function of solvent quality was examined. A good solvent prediction indicated a crossover between entanglement-dominated case and strongly cross-linked case corresponding to low and moderate degrees of swelling. It has been observed that the reduced modulus decreased with increasing degree of swelling. The scaling relationship between the modulus and degree of swelling which indicates that ternary-hydrogels, limited to weak stretching regime, obey Gaussian statistics. In the second part of the experimental work, pH/thermo-responsive cationic terpolymer cryogels were successfully prepared by varying the feeding DMAEMA/GMA mol ratio. Terpolymer cryogels with different DMAEMA/GMA ratio have been extensively characterized with ATR-FTIR, X-ray diffraction analysis (XRD) and TGA measurements. The presence of GMA imparts hydrophobic character that reduces the swelling and provides additional crosslinks leading to a significant increase in the flexibility. Reducing the polymerization temperature below the freezing point of the solvent resulted in harder and non-brittle cryogels. With the increase in the amount of DMAEMA in the terpolymer matrix, the pH-dependent transition point was found to be 7.7. The water transport was strongly affected by incorporation of hydrophobic component GMA and protonation of amine functional groups. The swelling mechanism was shifted from anomalous to diffusion controlled with increasing GMA and overall swelling processes followed Schott second order dynamic equation. It was observed that lower equilibrium volume swelling at constant temperature was achieved by increasing GMA content of the terpolymers. In low temperature range, while DMAEMA-rich terpolymer gels were swollen, swelling decreased significantly when the gels were enriched in GMA. A significant difference was observed in salt-sensitive swelling in dilute salt solution, which is controlled by the amount of DMAEMA in terpolymer structure. This part of the work is important in that it provides new ideas for the design of (meth)acrylate ester-based cationic terpolymer cryogels and explains the relationship between the gel matrix and their specific swelling behavior. From the first and second part of the experimental study, the terpolymer PHDG structure containing 10% mol of GMA, 70% mol% of DMAEMA and 20 mol% of HPMA was selected and an attempt was made to establish a relationship between the the gel preparation temperature and the elasticity as well as pH/temperature sensitivity of n-alkyl methacrylate ester-based cationic gels. In the third part of the experimental study, the gel preparation temperature Tprep was changed and terpolymer gels were prepared at -18, 1, 5, 8, 24, and 60 oC. The structure and physical properties of ternary gels was fully characterized using TGA, ATR-FTIR and XRD. Tprep has been shown to be an effective independent variable to adjust both macroscopic and microscopic properties of ternary gels as desired. The dependence of the swelling and compressive elasticity on the gelation temperature was investigated and it was determined that terpolymer gels synthesized at 5 °C showed maximum swelling capacity. A significant change in the elastic modulus was observed as Tprep decreased from 60°C to -18°C. Terpolymer gels showed pH-sensitive swelling characteristic of cationic DMAEMA monomer and exhibited high swelling ratio in acidic solutions induced by the electrostatic repulsion between quaternary amine groups. It was observed that the swelling ratio decreased due to hydrophobic effect of the alkyls when environmental pH is higher than 7.7. Regardless of Tprep, the gels gradually contracted as the swelling temperature increased from 25°C to 75°C. The effectiveness of terpolymer gels to remove the anionic dye Methyl Orange from aqueous solution was tested and the results showed that the terpolymer gels prepared under low temperature conditions were promising for removing anionic dyes from wastewater. The adsorption was spontaneous and found to be a multistep process with the surface adsorption followed by the intraparticle diffusion. The results obtained will assist in the design of n-alkyl methacrylate ester-based ternary gels as an effective adsorbent for dye removal from wastewater and pharmaceutical preparations.
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ÖgeYeni tip Aza-BODIPY bileşiğinin sentezi ve karakterizasyonu(Lisansüstü Eğitim Enstitüsü, 2023-06-15)Yakın kızılötesi bölgesinde (NIR) absorpsiyon ve emisyon yapabilen boyalar sensörler, lazerler, fotovoltaik hücreler ve optoelektronik dahil olmak üzere geniş uygulama yelpazesi nedeniyle uzun yıllardır önemli bir rol oynamaktadır. NIR bölgesinde absoriyon ve emisyon yapan bu boyalar, biyogörüntüleme, boron nötron yakalama terapisi ve fotodinamik terapi dahil olmak üzere biyouygulamada da kullanım bulabilmektedir. Bu boyalar, ışığı absorbe edebilmekte ve daha yüksek bir enerji seviyesine uyarabilmekte ve daha sonra ışık emisyonu ile temel duruma dönerek floresans meydana getirmekte ve böylece biyouygulama için önemli bir araç haline gelmişlerdir. NIR ışığı daha uzun dalga boylarına kayarak, azaltılmış saçılma ve azaltılmış foto hasar ve derin doku penetrasyonu avantajı sağlar. Porfirin ve porfirazin bileşikleri, NIR bölgesinde absorpsiyon ve emisyon yapabilen organik boyalardır. Porfirin ve porfirazinler, fotofiziksel ve fotoelektrokimyasal özelliklerinden dolayı birçok alanda geniş uygulamalara sahiptir. Ne yazık ki zahmetli sentez yöntemleri, saflaştırma adımlarındaki zorluklar ve verimlerinin düşük olması gibi kullanımlarını sınırlayan bazı nedenler vardır. Bu zorluklar, dipirometenler ve aza-dipirometenler boyaları olarak adlandırılan yapısal analoglarının keşfi ile çözülmüştür. Bu dipirometen ve aza-dipirometen bileşiklerinin fotofiziksel özellikleri, BF2+ ve d blok geçiş metali bileşiklerinin şelatları ile ayarlanabilir. Ayrıca bu dipirrometen ve aza-dipirometen boyaları ucuz başlangıç malzemelerinden hazırlanabilir ve basit ve zahmetsiz sentetik yöntemlerle hazırlanabilir. Bu bileşikler düşük konjugasyona sahip olmalarına rağmen, yoğun floresans, yüksek elektron afinitesi ve yüksek molar absorpsiyon katsayısı değerleriyle görünür ve yakın kızılötesi bölgede absorpsiyon ve emisyon özellikleri gibi göze çarpan fotofiziksel özelliklere sahiptirler. Aza-BODIPY adı verilen organoboron NIR boyaları, aza-dipirometenlerin bor kompleksleri olmakla birlikte BODIPY çekirdeğinin mezo konumunda karbon yerine bir nitrojen atomu bulunan BODIPY boyalarının yapısal analoglarıdır. BF2 şelatlanması, aza-dipirometen bileşiklerine kıyasla Aza-BODIPY bileşiklerine daha rijit bir yapı sağlar. BODIPY ve Aza-BODIPY boyaları, güneş pilleri, biyogörüntüleme, lazerler ve fotodinamik terapi gibi çok çeşitli uygulamalarda kullanımları dikkate alındığında karakteristik özellikleri nedeniyle büyük ilgi görmüştür. BODIPY ve Aza-BODIPY boyaları olarak adlandırılan d blok geçiş metali şelatları ile dipirometen ve aza-dipirometen bileşiklerinin temel farkı biyolojik uygulamalarda çok önemi bulunan floresans emisyonunun olmamasıdır. Aza-BODIPY bileşikleri iki farklı yöntemle sentezlenebilir. İlk yöntem, 2,4-diaril pirolden başlayan sentezi içerir. Diğer yöntem, uygulanabilirliğe daha uygun olan O-Shea yöntemi denir. Nispeten daha az sentetik yöntem içermektedir ve bu yöntemler xx kullanılarak reaksiyonlarda yüksek verimle BODIPY ve Aza-BODIPY bileşikleri hazırlanmaktadır. Aza-BODIPY bileşiğinin hazırlanmasına yönelik bu 4 adımlı O-Shea sentetik yöntemi, kalkon bileşik sentezi ile başlar. Birinci adımda, aldol kondenzasyon reaksiyonu ile kalkon türevi bileşik sentezi gerçekleştirilir. Bu O-Shea yönteminin ikinci adımı, Michael ilavesiyle kalkon türevinin nitrasyonunu içerir. Aza-dipirometen türevi üçüncü adımda dimerizasyon yoluyla elde edilir. O-Shea yönteminin son adımında oda sıcaklığında BF3.OEt2 kullanılarak BF2 şelatanmasıyla ile Aza-BODIPY bileşiği elde edilir. Aza-BODIPY boyaları terapötik pencerede güçlü absorpsiyon ve emisyon bantlarına sahip olduğundan, bu bileşikler Fotodinamik Terapi (PDT) için ideal bir ışığa fotouyarıcılardır. Fotodinamik Tedavinin (PDT) işlevsel olabilmesi için doku penetrasyonunun sağlanması ve bunun için NIR bölgesinde (özellikle NIR-II bölgesinde) penetrasyon derinliği için güçlü absorpsiyonun sağlanması gerekir. Aza-BODIPY bileşikleri, BODIPY boyalarınınkine kıyasla nispeten yüksek singlet oksijen kuantum verimlerine sahiptir, çünkü BODIPY'lerin Fotodinamik Terapide (PDT) bir fotouyarıcı olarak uygulamalarını sınırlayan şiddetli floresansları vardır. Aza-BODIPY boyalarının maksimum absorpsiyon ve emisyon dalga boyları, BODIPY bileşiklerine kıyasla belirgin şekilde daha yüksek dalga boylarında görülmektedir. BODIPY bileşikleri genellikle 550 ila 600 nm civarında absorpsiyon piklerine sahipken, Aza-BODIPY bileşiklerinin absorpsiyon pikleri, yüksek penetrasyon sağlayan biyolojik uygulamalar için uygun olan 650 nm'nin ötesinde bulunabilir. Aza-BODIPY boyalarının absorpsiyon pikleri, 1300 nm'ye kadar batokromik olarak kaydırılabilir. Bu batokromik kayma, HOMO-LUMO enerji aralığındaki azalma ile açıklanabilir. Bu modifikasyon, elektron veren grubun 3,5-fenillerin para konumuna veya elektron çeken grubun 1,7-fenillerin para konumuna sokulmasıyla uygulanabilir. İki ana modifikasyon yöntemi uygulanabilir: Distal ve proksimal fenil gruplarına elektron alıcı ve donörü fonksiyonel grupların eklenmesi. Ayrıca Aza-BODIPY emisyonları, BODIPY türevlerine kıyasla yaklaşık 80 nm daha fazla batokromik kaydırılabilir. Aza-BODIPY bileşikleri ile ilgili çalışmalar son yıllarda dikkat çekici fotofiziksel ve fotokimyasal özelliklerinden dolayı önemli ölçüde artmıştır. Ayrıca, güçlü ve keskin absorpsiyon ve emisyon özellikleri, distal ve proksimal fenil gruplarına elektron alıcı ve donör fonksiyonel grupların eklenmesi veya π konjugasyonunun arttırılması ile ayarlanabilir. Bu modifikasyonlar fotostabiliteye, yüksek floresans kuantum verimine, yüksek singlet oksijen kuantum verimlerine, yüksek moleküler absorpsiyon katsayılarına, görünür aralıkta ve NIR bölgesinde güçlü absorpsiyon ve emisyon dalga boylarına neden olur. Günümüzde PDT gibi biyouygulamalarda kullanılabilecek en umut verici organik bileşiklerden biri, yukarıda belirtilen karakteristik özellikleri nedeniyle Aza-BODIPY boyalarıdır. Bununla birlikte, Aza-BODIPY'nin biyomedikal uygulamalarda kullanımını sınırlayan ana dezavantajı, aromatik halkaların varlığı ve Aza-BODIPY çekirdeğinin oldukça düzlemsel yapısı nedeniyle agregasyondan kaynaklanan suda zayıf çözünürlükleridir. Bu tez kapsamında, etkinlik alanını genişletmek ve farklı uygulamalara kapı açmak amacıyla suda çözünür polimerlerin sentezinde kullanılabilecek Aza-BODIPY türevi içeren monomer bileşiğinin sentezi ve karakterizasyonu hedeflenmiştir. Bu amaçla, öncelikle distal fenil gruplarının para pozisyonlarında hidroksil grupları taşıyan bir Aza-BODIPY türevi sentezlenmiş ve akabinde bu hidroksil gruplarını içeren Aza-BODIPY, polimerleşebilen bir metakrilat sübstitüe Aza-BODIPY monomerine dönüştürülmüştür. Elde edilen monomer bileşiği, FT-IR, UV-Vis ve 1H-NMR spektroskopik yöntemleri ile karakterize edilmiştir. Elde edilen Aza-BODIPY yapılı monomer bileşiğinin, UV-Vis absorbansında Aza-BODIPY bileşiğine göre 6 nm hipsokromik kayma yaptığı gözlemlenmiştir.
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ÖgeThe interaction of CD-based chalcogenide quantum dots with raw photosynthetic pigments(Graduate School, 2023-08-28)The detrimental effects of global warming caused by usage of fossil fuels and toxic gas emission to the atmosphere could be dramatically decreased by environmental sustainability and renewable energy resources. Moreover, coal, oil and gas classified as fossil fuels which almost the whole energy of the world derived from is going to respectively be over in 107, 35 and 37 years. That is why alternative renewable energy sources are quite important according to scientists. It is possible to utilise renewable energy resources in almost all areas where fossil fuels have a usage. Renewable energy is able to be used in the production of electricity, in transportation and logistics as a fuel, in buildings and industrial processes as a heat release after conversion. Wind, flowing water, sunlight, the internal heat of the earth and biomass are natural resources of renewable energy. Biomass is a significant renewable energy source because of its economic potential, easiness in production and functional usage in many areas. Biomass is defined as organic materials in total produced by a living organism like plants and animals in a stated time and place in the world. Biomass could be manufactured by almost all organic materials we know such as seed waste, wood, wastewater, paper waste, straw and manure. These days, better half of biomass production is produced by products of agriculture which are known as energy crops. That makes photosynthesis that underlies formation of food and fibre along with biomass-based biofuels quite an important process. Photosynthesis and the energy conversion required for the production of biomass are utterly related to each other. In this thesis, quantum dots having three various structures were interacted with photosynthetic pigments which are responsible for light harvesting to increase and simplify biomes production by enhancing the efficacy of photosynthesis. In addition, photosynthetic pigments were extracted by spinach leaves that are easily provided and they are kept intact during the interactions. The compositions of quantum dots' structures were designated in accordance with the absorption wavelengths of photosynthetic pigments. The quantum dots interacted were oleic acid-capped CdSSe QDs, CdSTe QDs with the Te-riched core and CdSTe QDs with the outer S-enriched region. Also, all quantum dots were synthesis two-phase synthesis method which is one of the bottom-up approaches. The CdSSe QDs were synthesised as they have an emission in the same UV range in electromagnetic spectrum that photosynthetic pigments absorb light. The CdSTe QDs with the Te-riched core have a stated composition owing to the same reason and emission spectrum in the near IR region that pigments have also absorption. The CdSTe QDs with the outer S-enriched region have no emission of light in any common region with photosynthetic pigments that absorb radiation. Those quantum dots are synthesised to examine the quantum dot-photosynthetic pigment interaction when there is no possibility of energy transfer. The results of the interactions were analysed by UV-Visible Spectrophotometer and Fluorescence Spectroscopy and experimental data was exhibited in the section of Results & Discussion in detail. As a result of all experiments, the absorption intensity of the photosynthetic pigments interacted with the Te-enriched CdSTe QDs was increased by 50% at the excitation wavelength of 410 nm. Additionally, the light harvesting capacity of photosynthetic pigments was enhanced at 500-575 nm in the green-light range of spectrum in the presence of the CdSTe QDs with the Te-riched core.