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  • Öge
    Development and functionalization of novel polymeric materials from poly(oxazoline)s for potential bioapplications
    (Lisansüstü Eğitim Enstitüsü, 2020) Özköse, Umut Uğur ; 659578 ; Kimya Ana Bilim Dalı
    The polyoxazoline polymers (POx) were discovered as poly(N-acylethylenimine) in 1966, and have caught researchers' attention only in recent years. This is because they stand out in many ways as they exhibit high biocompatibility, stealth effect, narrow molecular weight distribution, responsiveness to pH and temperature, high functionalization and copolymerization and versatility. To this respect, they became a popular choice to replace polyethylene glycol (PEG), which infamously suffer from oxidation under in vivo conditions. As a nutritional supplement, poly(2-ethyl-2-oxazoline) (PEtOx) was ratified by FDA, and it is expected that the biomaterials depending upon PEtOx will improve very swiftly with the assent of PEtOx for medical use. It is known that polyoxazolines exhibit very good cellular compatibility for in vitro studies due to their stealth behavior similar to PEG and their structure mimicking peptide. In vitro cytotoxicity studies of PEtOx and their derivatives were generally found to be quite low and PEtOx is the one of most studied polymers for in vivo toxicity. In addition, it was determined that repeated intravenous injections of high dose (2g / kg) to rats, did not cause side-effects on animals and no difference in histological applications in liver, spleen and kidney compared to animals of control group. Within the scope of this thesis, three different studies based on PEtOx were conducted: The first study states that poly(2-ethyl-2-oxazoline)/clay (PEtOx/MMT) nanocomposites were developed for the first time. The living cationic ring-opening polymerization (CROP) of 2-ethyl-2-oxazoline was initiated by the tosyl-functionalized montmorillonite clay, then silicate layers were delaminated in the polymer matrix and nanocomposites were formed. The obtained nanocomposites have been investigated in means of thermal and morphology properties by utilising DSC, TGA, XRD, and TEM. All PEtOx/MMT nanocomposites consisting both intercalated and exfoliated silicate layers have an enhanced thermal stability. In the second part of this thesis, PEtOx based-amphiphilic block copolymers and synthetic routes that enable to reach them were certificated. In this context, a novel procedure was created for the preparation of poly(2-ethyl-2-oxazoline)-block-poly(ε-caprolactone) (PEtOx-b-PCL) to manage the molecular architecture. Hereof, a new electrophilic moiety functionalized PEtOx-b-PCL derivative was described. This methodology opened a way to prepare biomolecule conjugated block copolymers that have enormous importance for various applications. Amphiphilic block copolymers are shown to self-assemble into various morphologies, comprising ellipsoids, tubular structures, toroids, vesicles, micellar structures. In this study, we discuss the preparation PEtOx-b-PCL based copolymeric nanostructures (CNs). Our data indicate that – varying the molecular weight and the number of repeating units dictate the nature of morphology. That is, the formation of self-assembled morphologies from ellipsoid to rod-like architectures are observed in aqueous solution, contingent on the mass ratio of hydrophilic block to total block copolymer (fPEtOx). To best of our information, this is the first document on the morphological transitions of PEtOx-b-PCL amphiphilic block copolymer-based CNs with different fPEtOx values in the literature.
  • Öge
    Controlled release system including nanoparticles that can be used for hypothyroidism treatment
    ( 2020) Kutlu Kaya, Ceren ; Kök, Fatma Neşe ; 637001 ; Nanobilim ve Nanomühendislik Ana Bilim Dalı
    Thyroxine (T4) and Triiodothyronine (T3) hormones secreted by the thyroid gland are required for many vital functions such as regulation of metabolic rate, heart rate, body temperature, breathing, and development of central and peripheral nervous systems, control of body weight, growth and brain development. Hypothyroid disease, which develops due to the low functioning of the thyroid gland, is a clinical condition that should be treated for lifelong to substitute the function of the thyroid hormones that can not be secreted at the required levels. The immune system of hypothyroid patients produces anti-TPO and anti-Tg antibodies against thyroid peroxidase (TPO) and thyroglobulin (Tg) found in thyroid cells. These antibodies not only destroy TPO and Tg, but also damage thyroid cells over time. As the thyroid gland cells are damaged and diminished, the gland begins to lose its feature further due to the reduced number of cells that produce hormones. While some of the T3 needed is produced in parenchymal cells in healthy people, the rest is produced by the deiodination of T4 and Selenium (Se) plays a very important role in performing the functions of deiodinase enzymes. Cepharanthine (CEP), another active agent used in this thesis, is a natural plant extract and can prevent T cell activation by blocking the binding of Tg peptides to the corresponding sequence (HLA-DRβ1-Arg74). In the light of this information, a double-effect release system was created in order to regulate hormones and prevent autoimmune response formation in hypothyroid disease within the scope of this thesis. Characterization studies of the system was performed, release profiles of CEP and Se, which are the active agents, were followed, and at the last step, cytotoxicity tests of each component of the system were carried out in-vitro cell experiments. In the first part of the thesis, nanoparticles (NP) consisting of poly (ethylene-co-vinyl acetate) (PEVA) and poly (ethylene glycol) (PEG) monomethyether were produced by using emulsion diffusion - solvent evaporation method. Nanoparticle synthesis process was optimized by changing the amount of PEG monomethyether (15, 20, 25 and 30%, w/w) added to PEVA and sonication time. It was determined that PEVA based NPs containing 20% PEG monomethyether by weight of PEVA (PEG20-PEVA) and sonicated for 5 minutes have the most appropriate particle size (166.1 nm) and the most monodisperse (PDI: 0.464) size distribution. The chemical characterization of the produced PEG20-PEVA NPs was performed with Raman spectroscopy, and the physical characterization studies were carried out by zetasizer and Scanning Electron Microscopy (SEM). CEP, with 10%, 20 and 30% by weight of PEVA, was loaded into the NPs and encapsulation efficiency and the amount of encapsulated active agent was determined. Although the amount of encapsulated CEP increased as the initial CEP concentration increased, there was a significant decrease in encapsulation efficiency so it was decided to load 10% of CEP by weight of PEVA to the NPs. It was measured that the average size of the CEP loaded particles was 190.5 nm and the PDI value was 0.54. At the beginning of release studies, the effect of particles' drying method on CEP release profile was analyzed. In the study carried out for 14 days, it was determined that the NPs dried in oven released ~7.7% of encapsulated CEP, while the NPs dried in freeze dryer released ~11.3% of CEP. This difference is probably due to the reduction of surface areas of the particles which were agglomerated while drying in the oven. For this reason, long-term release studies in the following stages were carried out using NPs which were freeze-dried and it was observed that PEG20-PEVA NPs released ~35% of encapsulated CEP in 100 days. In the second part of the thesis, block copolymer containing Se was produced in two successive steps. At first, di-(1-hydroxylundecyl)selenide and then PEG-PUSe-PEG block copolymer were synthesized. Characterization of these materials was performed by Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) spectroscopy. Scale-up could not be achieved during the polymer synthesis, so PEG-PUSe-PEG block copolymer was synthesized in low quantities (~0.45 g/ batch). The synthesized block copolymer was mixed with polyurethane (PU) which is a commercial polymer and matrix production was carried out by using physical mixing - particulate leaching technique. The porosities of the matrices produced by using PU: PEG-PUSe-PEG block copolymers in the ratio of 2: 1 and 1: 1 by weight were both measured as 60% using the liquid exchange method. The pore structures of the matrices were analysed with SEM images and it was seen that matrices had wide pore area distribution with more than half of pore areas are less than 40 μm2. The NPs containing CEP produced in the first stage of the thesis were integrated into the matrices with the help of a micropipette and SEM images showed that the NPs were distributed homogeneously in the matrix. In the parallel study, the release of CEP from both free NPs and NPs loaded into the matrix was followed for 66 days, and it was found that CEP release from NPs are ~23% and ~21.5%, respectively. No hindering effect of matrices to CEP release was observed due to the large pore size. The release of Se which is the second active agent used in the thesis, was followed in ultrapure water and water including 0.1% H2O2 (v/v) and samples taken for 7 days were analysed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). At the end of this period, it was determined that 2:1 and 1:1 (w/w) PU: PEG-PUSe-PEG block copolymers released 0.88 and 11.96 μg Se in ultra pure water, respectively; and 2525.90 μg and 2097.76 μg Se in water containing 0.1% H2O2, respectively. Significant increase in Se release in H2O2 presence was probably caused by the oxidation sensitivity of selenide block copolymers. The responsiveness of Se release to oxidative stress may be an advantage in hypothyroid disease, which has been reported to cause oxidative stress. In the last part of the thesis, three different cytotoxicity tests were done. Firstly, NPs with and without CEP were directly incubated with NIH 3T3 cells. Secondly, matrix effluents of 100% PU, 2:1 and 1:1 PU: PEG-PUSe-PEG block copolymers (w/w) were interacted with cells in cell media (indirect interaction), and finally matrices were seeded with cells (direct interaction). In MTS analysis performed to measure cell viability, it was determined that the cells which interact with the materials showed similar viability with the control groups, in other words, none of the materials had cytotoxic effects on fibroblast cells. The images taken by light microscope, fluorescence microscope and SEM showed that, the cells interacted with the materials, spread on matrices and inside of pores, at the same time, they could interact each other and no difference in the cell morphology was observed compared to the control group. The chemical and physical characterization, imaging, release and cell culture studies carried out within the scope of the thesis have shown that the double-acting system produced by biocompatible materials has the potential to be used as local long-term delivery system for effective treatment of hypothyroidism by reducing the autoimmune response and regulating related hormones.
  • Öge
    Curcuminoids: Analytical chemistry, biochemistry, and potential applications
    ( 2020) Kalaycıoğlu, Zeynep ; Berker, Fatma Bedia ; 634568 ; Kimya Ana Bilim Dalı
    Natural plant products have been utilized for various purposes throughout human history. Many of plants have taken the initial form of crude medicine as being tinctures, teas, and powders. An oral history had been created for certain plants used and their application methods for specific ailments. After all, a cultural knowledge base has been recorded regarding medicinal plants. In more recent history, natural plant products have opened a new research area in modern medicine. Bioactive constituents isolated and characterized have been focused for pharmaceutical drug discovery and drug design. Turmeric (Curcuma longa Linn., family Zingiberaceae), is one of the most popular herb used as spice due to its fragrance and yellowish colour worldwide. Except the uses as a spice, it has been used as traditional medicine due to its beneficial properties on gastrointestinal diseases, diabetic wounds, inflammation, cough, and rheumatism. Modern researches have authenticated turmeric as antioxidant, antimicrobial, anticancer, antidiabetic, anti-inflammatory, anti-HIV etc. Wide spectrum of pharmacological activities made turmeric a highly considerable spice as a universal panacea. One of the essential component of turmeric is curcumin that provides the color and bioactivity to this plant. Extensive researches have revealed that commercial turmeric powder is combined of naturally occuring curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC). Curcuminoid is a collective name, covering these three compounds that only vary in methoxy substitution on the aromatic ring. These structural differences provide different pharmaceutical properties. Individual curcuminoids should be taken into account for the accurate and repetable clinical studies based on the contents of bioactive components. Despite recent progresses in analytical techniques, curcuminoids suffer from poor separation and broad peaks. Therefore, there is a necessity to develop a reliable separation and determination technique to express the individual quantities of curcuminoids in real samples. Comparisons of the individual curcuminoid bioactivities are promising approaches for development into a modern drug. In addition, curcuminoids are also known as natural antibacterial agents. This potency of turmeric can be converted into an application such as food packaging. This thesis aims a series of investigations on curcuminoids to contribute to the large research pool on this subject. To achieve this aim, an isolation method has been developed for turmeric plant. Three curcuminoids were isolated purely by column chromatography and subsequent thin layer chromatography, the structures were determined by nuclear magnetic resonance (NMR) spectroscopy. A capillary electrophoresis-laser induced fluorescence technique was developed for the separation and determination of individual curcuminoids. Both the isolation and analysis method were used for curcuminoids to be used at all levels of the scope of thesis in order to determine of their quantity and purity. In the first part, the amount of three curcuminoids in turmeric powder and herbal supplements was determined by capillary electrophoresis technique. Capillary electrophoresis (CE) is a separation and analysis technique which is well-known for its short analysis time, high sensitivity, and low sample and solvent consumption. The developed CE technique was combined with laser induced fluorescent detector (LIF) taking advantage of floresence nature of curcuminoids. LIF detection presents high sensitivity due to the great intensity of the incidental light. Borate buffer (pH: 9.6) was chosen as suitable separation medium. Hydrolytic degradation of curcuminoids in the basic medium is prevented by the addition of 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) to the borate buffer. Presence of 2-HP-β-CD in the separation medium provided also the increasement of fluoresence intensities of curcuminoids. Three curcuminoids of turmeric were completely separated and determined quantitatively in 4.5 min. The method was well-validated and applied to powdered and rhizome turmeric samples and a turmeric herbal supplement in order to find the curcuminoid amounts. Being the first part of the thesis, it was published on a peer-reviewed SCI indexed journal (Electrophoresis 36 (2015) 2516-2521). In the second part, antioxidant, anticholinesterase, and antidiabetic activities of the curcuminoids were determined and compared. The antioxidant potential of curcuminoids were evaluated using 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging activity and ferric-reducing antioxidant power (FRAP) assays. Curcumin showed the highest antioxidant activity with both assays. Antioxidant activities of DMC and BDMC came after those of curcumin, respectively. In order to test the anti-Alzheimer activity, acetylcholinesterase (AChE) and butyrlcholinesterase (BChE) inhibition powers of curcuminoids were evaluated. Since AChE and BChE ezymes have been proven to be the most viable therapeutic target for symptomatic improvement in Alzheimer disease (AD), inhibition of these enzymes are considered to be the most accepted approach for the treatment of AD. BDMC showed substantial inhibitory activity, even better than the activity of galantamine that is a medication used to treat symptoms of Alzheimer's disease. The activity of DMC came after BDMC, whereas curcumin showed very little acetylcholinesterase inhibition activity. BDMC showed inhibitory activity against butrylcholinesterase enzyme, while curcumin and DMC did not show activity. Curcumin and DMC showed no inhibitory activity against butrylcholinesterase enzyme. However, BDMC was active. Antidiabetic activities were determined via their α-glucosidase inhibitory activities. The method of inhibition of α-glucosidase enzyme is one of the most useful way for the control of hyperglycemia in patient with type 2. All curcuminoids showed α-glucosidase inhibitory activities with decreasing order as BDMC > curcumin > DMC. In this context, a manuscript was published on a peer-reviewed SCI indexed journal (Natural Product Research 36 (2017) 2914-2917). In the third part, mechanically stable and antibacterial turmeric incorporated chitosan food packaging films were prepared using solvent-casting method and cross-linked with sodium sulfate. Mechanical, optical, thermal properties, water vapor permeabilities and antimicrobial activities of the films were measured. Tensile strength and the ultraviolet-visible (UV) light barrier of the films were improved with the addition of turmeric extract. Furthermore, turmeric incorporated chitosan film showed a significant antimicrobial effect on two common food pathogens; Salmonella and Staphylococcus aureus. As a result, turmeric extract incorporation into chitosan film improve the functional properties. Thereby, it can be suggested as a strong candidate to be used in food packaging industry. This study was published on a peer-reviewed SCI indexed journal (International Journal of Biological Macromolecules 101 (2017) 882-888). Taking into consideration all of the studies conducted in the present thesis, we report here a systematic study describing chemical and physical properties of turmeric based on curcuminoids which could in turn help develop innovative therapeutic strategies. The developed CE technique is important for the rapid and fully separation and determination of individual curcuminoids in the quality control of herbal tablets and turmeric samples. Each curcuminoid has different biochemical potentials. Inspired by this phenomenon, the differences of antioxidant, anti-Alzheimer, and antidiabetic activities of individiual curcuminoids were revealed and compared. The results may contribute the literature survey dealing with an area of current resarch interest in designing new drugs. All of these properties make turmeric not only as a part of clinical studies but also an important candidate in the ranges of application areas. Food packaging technology has gained a great development since the packaging has an important issue on the conservation and marketing of foodstuffs. There is an increasing interest on films produced by biopolymers. Besides having excellent biodegradability and biocompatibility, biopolymers serve as carriers of many functional ingredients. At this point, utilizing turmeric as natural additive enables the development of film properties.
  • Öge
    New synthetic methodologies for benzoxazine based thermosets
    (Fen Bilimleri Enstitüsü, 2013) Demir, Kübra ; Yağcı, Yusuf ; 332886 ; Chemistry ; Kimya
    Özellikle mekanik ve ısısal olarak dayanıklı polibenzoksazinlerin keşfedilmesinden sonra fenolik reçineler endüstriyel ve ticari termoset uygulamalarında önemli bir yer tuttu. Polibenzoksazinlerin kimyasallara ve suya dayanıklılık, uzun raf ömrü, katalize ihtiyaç duymadan ve yan ürün oluşturmadan hazırlanabilmesi, kürleme esnasında hacimsel büzülme olmayışı gibi çekici özellikleri son yıllarda keşfedilmiştir. Esasen, benzoksazin monomerlerinin esnek dizayn özelliği, ticari olarak elde edilebilen başlangıç malzemeleri olan fenol ve aminin subsitüsyonlarını değiştirerek fonksiyonlandırma seçeneği sunar. Saf polibenzoksazinler termosetik reçine ailesini genişletmesine rağmen, bu termosetlerin endüstriyel uygulamalarda kullanımını daraltan bazı sınırlamaları hala vardır. Kürlenme sıcaklığını (~200 ºC ve üstü) ve kırılganlığı azaltmak ve işlemesini kolaylaştırmak için birçok kimyager farklı stratejiler geliştirmeye çalışmıştır. Bir kısmı ısısal işlem ile çapraz bağlı termosetik reçineler oluşturan benzoksazin monomerinin fonksiyonlandırılmasına yoğunlaşır. Diğer bazı çalışmalar benzoksazin monomerini başka bir polimerleşebilen üniteye veya polimer zincirinin ucuna bağlar. Dayanıklı polibenzoksazin kompozitleri üretmek için benzoksazin ünitelerini inorganik maddelerle harmanlamak da birçok araştırmada uygulanır. Bu çalışmada, bir polibenzoksazin/kil nanokompoziti ilk defa benzoksazin monomerinin bezoksazin ile modifiye edilmiş kil varlığında ısısal polimerleşmesi ile in situ yöntemi takip edilerek hazırlanmıştır. Bunlara ek olarak, ana zincirde veya yan zincirde benzoksazin halkası bulunduran öncü polimerlerin hazırlanması stratejisi de, kürlenmiş polibenzoksazine esneklik, ısısal ve mekanik direnç gibi birçok avantajlar sağlamıştır. Çapraz bağlanabilme potensiyelinin yüksekliği nedeniyle, ana zinciri benzoksazin olan öncü polimerlerin hazırlanması gelişen bir yöntemdir. Bu öncü polimerlerin elde edilmesi için benimsenen genel strateji bisfenol ve bisaminlerin formaldehit varlığında Mannich kondenzasyonu ile benzoksazin halkası oluşturmasıdır. Poliester, poliamide, poliüretan oluşumu ile hidrosilasyon, Diels-Alder ve çıt-çıt reaksiyonları da bu lineer polimerlerin elde edilmesinde kullanılan diğer kondenzasyon yöntemleridir. Ana zincirinde benzoksazin halkası içeren öncü polimerlerin üretimi için sunulan birçok farklı yol arasında, iki fonksiyonlu benzoksazinlerin kenetlenme reaksiyonları ilk kez bu çalışmada sunulmuştur.Bu tezin ilk bölümünde ana zincirinde farklı sayılarda ısısal olarak kürlenebilen benzoksazin ve asetilen grupları bulunduran öncü polimerler sentezlenmiş ve daha sonra yüksek sıcaklıklarda polimerleştirilerek polibenzoksazinler elde edilmiştir. İki ucu iyotlu iki fonksiyonlu benzoksazin ve iki fonksiyonlu asetilen Sonogashira kenetlenmesi ile lineer polimerlere dönüştürülmüştür. Bunun için öncelikle Bisfenol-A, formaldehit ve iyodoanilin reaksiyona sokularak iki ucu iyotlu iki fonksiyonlu benzoksazin (DIBB) elde edilmiştir. Bu monomer ile iki fonksiyonlu asetilenin (DABE) veya iki fonksiyonlu asetobenzoksazinin (DABB) Sonogashira kenetlenmesi, paladyumtetrakis trifenilfosfin katalizörlüğünde ana zincirde benzoksazin bulunduran 2300-3500 Da molekül ağırlıklı öncü polimerleri oluşturmuştur. Monomerlerin ve öncü polimerlerin yapıları FT-IR ve 1H-NMR analizleri ile doğrulandı. Monomerlerin ve polimerlerin kürlenme davranışları difransiyel taramalı kalorimetri (DSC) cihazı ile incelenmiştir. Öncü polimerlerde bulunan asetilen grubunun benzoksazin ünitesinden daha erken kürlendiği yapılan aşamalı kürleme ve IR analizleri sayesinde kanıtlanmıştır. Kürlenmiş polimerlerin ısısal özellikleri de termogravimetrik analizler (TGA) ile incelenmiştir. Bu analizlerde benzoksazin halkası yoğunluğunun ısısal kararlılığa katkısı elde edilen farklı lineer polimerler karşılaştırılarak kanıtlanmıştır.Kenetlenme reaksiyonları ile hazırlanan bir diğer öncü polimer ise yapısında benzoksazin halkasının yanı sıra eterik bağ ve farklı sayılarda flor grupları bulundurmaktadır. Ana zincirinde benzoksazin bulunduran florlu öncü polieterler Ullmann kenetlenmesi yöntemi ile sentezlenmiştir. Polimerleşmeye sunulacak monomerik iki fonksiyonlu benzoksazinler Bisfenol-A, formaldehit ve farklı sayıda flor grubu içeren floroaminlerin tipik benzoksazin oluşum reaksiyonu olan Mannich kondenzasyonu sonucu elde edilmiştir. Oluşan iki ucu florlu iki fonksiyonlu benzoksazinler, iki fonksiyonlu fenoller ile nano-bakıroksit ve sezyumkarbonat varlığında reaksiyona sokularak 830-3500 Da molekül ağırlıklı lineer polimerlere dönüştürülmüştür. Monomer yapısı, sıcaklık, katalizör etkisi gibi değişik parametrelerin polimerizasyona etkileri incelenmiştir. Elde edilen lineer polimerlerin molekül ağırlıklarının flor gruplarının sayısından ve bu grupların bulundukları bölgeden etkilendiği molekül ağırlığı analizleri ile gözlenmiştir. Öncü polieter yapısında bulunan benzoksazin grupları katalizör eklenmeden ısısal halka açılma reaksiyonuna girerek çapraz bağlı networklere dönüşmüştür. Kürlenmiş polimerlerin ısısal kararlılıkları klasik polibenzoksazinlerle karşılaştırılarak TGA ile incelenmiştir. Flor grubu sayısının ve bulunduğu bölgenin ısısal polimerleşmeye de etki ettiği bu analizlerle kanıtlanmıştır. Florlu benzoksazinlerin ince filmleri (~20 nm kalınlığında) kürleme ile hazırlandığında düşük yüzey enerjilerinden dolayı ıslanmaya karşı dayanıklılık sağlamış ve katı yüzeylerde pürüzsüz bir kaplama oluşturmuştur.Yeni bir polibenzoksazin/montmorillonit (PBz/MMT) nanokompoziti tipik bir akışkan benzoksazin monomeri olan 3-pentil-5-ol-3,4-dihidro-1,3-benzoksazin'in benzoksazin fonksiyonlu montmorillonit kili varlığında in situ polimerizasyonu ile hazırlanmıştır. Öncelikle piridin sübstitüsyonlu bir benzoksazin 11-bromo-1-undekanol ile quaternize edilmiştrir. Daha sonra kili modifiye ederek katmanların arasını açmak için, bu quaternize benzoksazin montmorillonit'deki sodyum iyonlarının iyon değişimi reaksiyonunda kullanılmıştır. Sonunda organik olarak modifiye edilmiş kil, in situ ısısal halka açılma polimerizasyonu yapmak için akışkan benzoksazin monomerinde farklı yükleme derecelerinde dağıtılmış ve ısıtılmıştır. Açılmış kil galerileri arasında modifikasyon için tutturulan monomerik quaternize benzoksazinin ve akışkan benzoksazin monomerinin ısısal halka açılma polimerizasyonu PBz/MMT nanokompoziti oluşumunu sağlamıştır. Nanokompozitlerin kimyasal yapısı IR spektroskopisi ile kanıtlanmıştır. Ayrıca benzoksazin monomerlerin kürlenme özellikleri % 1-10 arasında değişen kil yükleme derecelerinde ve farklı kürlenme sıcaklıklarında incelenmiş ve artan kil miktarının polimerleşmeyi hızlandırdığı kanıtlanmıştır. Nanokompozitlerin morfolojileri hem XRD hemde TEM teknikleri ile incelenmi ve polibenzoksazin matrisinde kısmen açılmış/dağılmış yapılar ortaya çıkmıştır. Kil varlığının in situ yöntemi ile sentezlenen polibenzoksazin/montmorillonit nanokompozitlerinde ısısal kararlılığı nasıl etkilediği de TGA analizlerinde gözlemlenmiştir. Bu analizler kil miktarı arttıkça polibenzoksazin nanokompozitlerinin ısısal dayanıklılığının da arttığını kanıtlamıştır. Özellikle % 60'lık kütle kaybının olduğu sıcaklıklar karşılaştırıldığında fazla miktarda kil bulunduran nanokompozitlerin ısısal dayanıklılıkları daha çok meydana çıkmıştır.
  • Öge
    Bor sübstitüe ftalosiyaninler ve öncü bileşikleri
    (Fen Bilimleri Enstitüsü, 2013) Özçelik, Şennur ; Gül, Ahmet ; 332884 ; Kimya ; Chemistry
    Çalışmanın ilk kısmında, 4-(4-formil-3- hidroksifenoksi)ftalonitril bileşiği ve 4-(3-hidroksi-4-(((2-hidroksifenil)imino)metil)fenoksi)ftalonitril bileşiği sentezlenmiştir. Bu Schiff bazı yapısındaki dinitril türevinin boronatı, fenilboronik asit ile reaksiyonuyla hazırlanmıştır. 11B NMR spektrumunda tetrakoordine bor atomunun karakteristik pikinin gözlenmesi, boronat bileşiğinde N?B bağının varlığını kanıtlamıştır. Çalışmanın ikinci kısmında; tetra-[4-(4-salisilideniminofenoksi)-]ftalosiyaninato çinko(II) bileşiğinin fenilboronik asit ile reaksiyonuyla periferal konumlarında 4 adet Schiff bazı gruplarının benzenboronik asit esterlerini taşıyan ftalosiyanin bileşiği elde edilmiştir. Çalışmanın üçüncü kısmında; tetra(salisilaldimino)-ftalosiyaninato çinko(II) bileşiğinin difenilborinik asit esteri hazırlanmıştır. Tetrakoordine bor atomu içeren bu ftalosiyaninin fotofiziksel ve fotokimyasal özellikleri de incelenmiştir. Çalışmanın son aşamasında; 4-[2-(bis(2-hidroksietil)amino)etoksi]ftalonitril bileşiği ve bu dinitril bileşiğinin fenilboronik asit ile kompleksleşme reaksiyonuyla yeni bir dioksazaborakan elde edilmiştir. Bu dietanol amin grupları içeren dinitrilin siklotetramerizasyonuyla elde edilen tetrakis-[2-(bis(hidroksietil)amino)etoksi]-ftalosiyaninato çinko (II) bileşiği fenilboronik asit ile reaksiyona sokularak dioksazaborakan sübstitüe çinko ftalosiyanin sentezlenmiştir.