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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Synthesis And Characterization Of Fluorescent Zinc Phthalocyanine Pigments And Its Combination Pigment With Mica Titania Pig Ment

Kahya, Sevinc Sevim 01 September 2012 (has links) (PDF)
In the present work, zinc phthalocyanine and tetra nitro substituted zinc phthalocyanine were sytnhesized by using phthalic anhydride and nitro phthalic acid precursor respectively under microwave irradiation. Molecular structures of these pigments were confirmed by FT-IR and UV-visible spectroscopy analyses. Furthermore, these pigments were deposited on mica-titania pigment substrate in dimethyl formamide solvent to obtain the combination pigment. FT-IR analysis was conducted to analyze the deposition of pigments onto the mica-titania surfaces. Fluorescence spectroscopy analysis was performed to observe zinc phthalocyanine, tetra nitro zinc phthalocyanine pigments, and their combination pigment with mica- titania pigments. The surface morphologies of zinc phthalocyanines on the mica titania pigments were investigated by scanning electron microscopy. Optimum deposition temperature and deposition time were determined by v depositing varying amounts of zinc phthalocyanines. The paint samples of these combination pigments were prepared by alkyd based paint formulation. L*a*b* values of the paint samples were determined by color measuring spectrophotometry. The optimum deposition temperature was determined as 120 oC and the optimum deposition time was determined as half an hour and effective deposition was obtained at 120 &deg / C. It is observed that, with the increasing amount of ZnPc, the interaction between ZnPc particles increases and they desorp the surface of mica-titania pigment. The best result was obtained with 0.08 g ZnPc at 120 oC.
12

Synthesis Of Electroactive Benzimidazole Derivatives And Their Electrochromic Properties

Ozelcaglayan, Ali Can 01 November 2012 (has links) (PDF)
In order to study their electrochemical and optical properties, two donor-acceptordonor (D-A-D) type monomers / 4&#039 / -(tert-butyl)-4,7-bis(4-hexylthiophen-2- yl)spiro[benzo[d]imidazole-2,1&#039 / -cyclohexane] (BIHT) and 4&#039 / -(tert-butyl)-4,7-bis(2,3- dihydrothieno[3,4-b][1,4]dioxin-5-yl)spiro[benzo[d]imidazole-2,1&#039 / -cyclohexane] (BIED), were electrochemically polymerized. These properties were investigated by cyclic voltammetry and UV&ndash / Vis-NIR Spectroscopy techniques. Effects of different donor groups / 3-hexylthiophene and 3, 4-ethylenedioxythiophene (EDOT), on new benzimidazole group, 4&#039 / -(tert-butyl)spiro[benzo[d]imidazole-2,1&#039 / -cyclohexane], were investigated. These pendant groups cause slight differences in optical band gaps, which are 1.19 eV for PBIHT, 1.15eV for PBIED. PBIHT and PBIED have both nand p- doping. Both of them have broad absorption in the visible region. In NIR region, both polymers revealed 46 % transmittance with high switching times. PBIED and PBIHT showed multichromic properties. PBIED is green at neutral state. For the most oxidized and reduced states, it is blue and red, respectively. PBIHT is blue at neutral state, transmissive-gray in oxidized state and transmissive greenishgray in reduced state.
13

Ph Responsive Nano Carriers For Anti Cancer Drug Delivery

Bagherifam, Shahla 01 March 2013 (has links) (PDF)
In the recent years, development of various organic and inorganic nano-sized systems has gained great interests especially for cancer diagnosis and treatment and intense researches are carried out in this area. Regarding to the recent trends for drug delivery system design, the novel approaches for drug carriers are mainly based on development of smart and nano-size drug carriers which are targeted to cancer cells. Hence, for an effective tumor-targeted delivery device, besides its chemical structure further criteria such as detection of tumor site and sensitivity to the higher temperature and lower pH of the tumor compare to rest of the body gains importance. The aim of this study is to design and prepare polysebacic anhydride (PSA) based nanocapsules (NCs) loaded with Doxorubicin (DOX) which is an anti cancer drug. In order to obtain an intelligent delivery system, drug-loaded nanocapsules were coated with pH sensitive poly (L-histidine). PSA nano-carriers were firstly loaded with DOX and then in order to introduce pH sensitivity, they were coated with poly (L-histidine). PLH-coated NCs were modified with polyethylene glycol (PEG) to prevent their macrophage uptake. Drug release profile from this system was examined in two different buffer solutions prepared as acidic (pH 4) and physiological (pH 7.4) media. The physical and chemical properties of the nano particles were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), ultraviolet and visible absorption spectroscopy (UV-VIS), and scanning electron microscopy (SEM). In vitro studies of the prepared nanocapsules were performed on MDA-MB-231 breast cancer cells by using WST Kit 8 cell viability test. In order to obtained results, pH sensitive nanocapsules with size 230 nm exhibited cellular uptake and promising intracellular release of drug.
14

The Characterization Of Some Methacrylate And Acrylate Homopolymers, Copolymers And Fibers Via Direct Pyrolysis Mass Spectroscopy

Ozlem Gundogdu, Suriye 01 December 2012 (has links) (PDF)
THE CHARACTERIZATION OF SOME METHACRYLATE AND ACRYLATE HOMOPOLYMERS, COPOLYMERS AND FIBERS VIA DIRECT PYROLYSIS MASS SPECTROSCOPY &Ouml / zlem G&uuml / ndogdu, Suriye Ph.D., Department of Polymer Science and Technology Supervisor: Prof. Dr. Jale Hacaloglu December 2012, 177 pages Poly(methyl methacrylate) possesses many desirable properties and is used in various areas. However, the relatively low glass transition temperature limits its applications in textile and optical-electronic industries. Monomers containing isobornyl, benzyl and butyl groups as the side chain are chosen to copolymerize with MMA to increase Tg and to obtain fibers with PMMA. In this work, thermal degradation characteristics, degradation products and mechanisms of methacrylate homopolymers, poly(methyl methacrylate), poly(butyl methacrylate), poly(isobornyl methacrylate) and poly(benzyl methacrylate), acrylate homopolymers, poly(n-butyl acrylate), poly(t-butyl acrylate), poly(isobornyl acrylate), two, three and four component copolymers of MMA and fibers are analyzed via direct pyrolysis mass spectrometry. The effects of substituents on the main and side chains, the components present in the copolymers and fiber formation on thermal stability, degradation characteristics and degradation mechanisms are investigated. According to the results obtained, the depolymerization mechanism yielding mainly the monomer is the main thermal decomposition route for the methacrylate polymers, acrylate polymers degradation occurs by H-transfer reactions from the main chain to the carbonyl groups. However, when the alkoxy group involves
15

Substituted Quinoxaline And Benzimidazole Containing Monomers As Long Wavelength Photosensitizers For Diaryliodonium Salt Initiators In Photopolymerization

Corakci, Bengisu 01 January 2013 (has links) (PDF)
In this study / ferrocenyl and naphthalenyl substituted quinoxaline derivatives / 5,8- bis (2,3- dihydrothieno [3,4-b] [1,4] dioxin-5-yl)-2- (naphthalen-2-yl)- 3- ferrocenyl- 4a,8a-dihydroquinoxaline / 5,8- bis (2,3-dihydrothieno [3,4-b] [1,4]dioxin-5-yl) -2- (phenyl) -3-ferrocenylquinoxaline / 5,8-bis (2,3-dihydrothieno [3,4-b] [1,4]dioxin-5-yl) -2,3- di(naphthalen-2-yl)quinoxaline and trihexylthiophene and thiophene coupled benzimidazole derivatives / 4-(tert-butyl)-4,7-bis(4-hexylthiophen-2-yl)spiro[benzo[d]imidazole-2,1-cyclohexane] and 4-(tert-butyl)-4, 7-bis(thiophenyl)spiro[benzo[d]imidazole-2,1-cyclohexane] were used as photosensitizers to broaden the active area of diaryliodonium salts. Both quinoxaline and benzimidazole derivatives are expected to be efficient in cationic photopolymerization with a variety of vinyl and oxide monomers at room temperature upon long wavelength UV irradiation. Photopolymerization will be initiated by diphenyliodonium salts and monitored with Optical Pyrometry. Characterization will be completed with optical absorption, flourescence studies and photopolymerization under solar irradiation.
16

Syntheses And Characterization Of Benzimidazole Containing Polymers: A Comparitative Study On Donor Unit Effect And Influence Of H-bonding

Nurioglu, Ayda Goycek 01 January 2013 (has links) (PDF)
The first part of this work reports a comparative study on electrochromic properties of two Donor-Acceptor-Donor (DAD) type polymers, namely poly(2-heptyl-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole) (BImTh) and poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-heptyl-1H-benzo[d]imidazole) (BImEd). DAD type polymers are designed to bear the same acceptor unit, benzimidazole and two different donor units, thiophene and 3,4-ethylenedioxy thiophene (EDOT) to make a comparison based on the donor unit effect. The resulting polymers are both multichromic and have low band gap values (1.93 eV for PBImTh and 1.74 eV for PBImEd). In the second part, 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-phenyl-1H-benzo[d]imidazole (BImBEd) is synthesized. In order to figure out the presence of an intramolecular hydrogen bonding between the amine bond of the imidazole ring and the oxygen of the EDOT molecule, different amounts of trifluoroacetic acid (TFA) and concentrated sodium hydroxide (NaOH) solutions were added during electrochemical polymerization. These treatments caused protonation of the imine and deprotonation of the amine bonds respectively. In order to prove the changes in the optical properties of the polymers due to different number of protonated and deprotonated imine and amine bonds, 1,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzene (BEDOT-B) was also synthesized and treated with the same procedures. Results showed that it is possible to control the main chain conformation of even an insoluble polymer via acid and base treatments during in situ polymerization.
17

Modified Acrylic Hydrogels As Controlled Release Systems

Pinardag, Fatma Esra 01 May 2006 (has links) (PDF)
In this study, pH-sensitive poly(acrylamide-co-acrylic acid) hydrogels were synthesized as controlled release systems in the presence of N,N-methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. A set of hydrogels were used in the form they were prepared. One set of hydrogels were prepared as porous networks by incorporating sodium chloride into the reaction medium and then leaching of it after the completion of polymerization reaction. Two sets of hydrogels were modified by argon-plasma at different discharge powers. Hydrogels were characterized by 13C-NMR, XPS, SEM, ATR-FTIR, ESR as well as equilibrium degree of swelling (EDS) and contact angle measurements. Prepared hydrogels were loaded with a model antibiotic, ciprofloxacin-HCl (CPFX), and in-vitro release of CPFX from hydrogel matrices were examined in buffer solutions of varying pH values. There are two factors determining the release rates of CPFX / one is the pH-dependent solubility of CPFX and the other is EDS of the hydrogel samples. For porous samples drug loading and release rates were higher when compared to the control samples and CPFX solubility dominated over release kinetics. Plasma treatment resulted in prolonged release rates in acidic medium.
18

Effect Of Polymer Additives On The Physical Properties Of Bitumen Based Composites

Dogan, Mehmet 01 September 2006 (has links) (PDF)
Polymer modified bitumen is a binder obtained by the incorporation of various types of polymers in bitumen using mechanical mixing or chemical reactions. There are several factors affecting the properties of polymer modified bituminous composites such as / chemical composition of bitumen, kind of polymer and filler, compatibility of bitumen and polymer, amount of bitumen, polymer and filler, particle size of filler and process conditions. The main objective of this study is to determine the effects of polymer type and concentration on mechanical, thermal, properties and morphologies of bitumen based composites. It was also aimed to determine the effect of process temperature on mechanical and thermal properties of bituminous composites. Bituminous composites were prepared by using Brabender Plastic Coder, PLV 151. Mixing was made at two different temperatures (150 &ordm / C and 180 &ordm / C) at 60 rpm for 20 minutes. Three different kinds of polymer and four different polymer concentrations were used to understand the effect of polymer type and polymer concentration on bituminous composites properties. Low density polyethylene (LDPE), styrene-butadiene-styrene copolymer (SBS) and ethylene-vinyl-acetate (EVA) were chosen as polymer. The compositions were adjusted as the polymer volumes were equal to 5%, 10%, 20% and 50% of bitumen volume. According to the test results, addition of polymer increases the mechanical properties, reduces the melt flow index and thermal conductivity values of bituminous composites. Morphological analysis results show that, fibrillation occurs at tensile fractured surfaces of composites which contain LDPE and EVA when the polymer concentration reaches 20% of bitumen volume.
19

Synthesis And Characterization Of Polythiophene/montmorillonite And Polythiophene/polypropylene Composites

Dulgerbaki, Cigdem 01 October 2006 (has links) (PDF)
In this study, polythiophene(PTP)/montmorillonite(MMT) nanocomposites were synthesized by in situ intercalative polymerization and chemical oxidative polymerization. In in situ intercalative polymerization method, composites containing 90 and 95% MMT were prepared. In chemical oxidative polymerization method, a series of composites ranging from 1 to 15% by weight MMT were synthesized. Thermal and morphological properties of samples were investigated by Differential Scanning Calorimeter (DSC), Thermal Gravimetric Analysis (TGA), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) / electrical conductivities were measured by four probe technique. Since PTP/MMT composites are unprocessable PTP/polypropylene(PP) composites were prepared. Amounts of PTP were changed in the range 2-30 % by weight in the composites. Mechanical properties were investigated by tensile tests. Four probe technique was used for measurement of electrical conductivities. Morphological characterizations were made by SEM. Formation of PTP and its incorporation in PTP/MMT composite were confirmed by FTIR analysis. DSC results showed that PTP does not have any thermal transition in the range 25-300 0C. TGA results showed that PTP/MMT composites have outstanding stability compared to that of PTP. XRD analysis revealed the formation of nanocomposites resulting from intercalation of thiophene in MMT at high MMT contents. Composites were observed as globular particles and clusters in SEM studies. Conductivity values of PTP/MMT composites were in the order of 10-3 S/cm. It is observed that tensile modulus of PTP/PP composites increases by the addition of PTP, but percentage strain at break does not appreciably change. Increasing PTP content increased electrical conductivity.
20

Synthesis And Characterization Of A New Soluble Polythiophene Derivative And Its Electrochromic Application

Tarkuc, Simge 01 December 2006 (has links) (PDF)
The Knorr-Paal reaction of 1,4-di(2-thienyl)-1,4-butanedione with aniline to yield 1-phenyl-2,5-di(2-thienyl)-1H-pyrrole (PTP) was performed in the presence of catalytical amounts of p-toluenesulfonic acid (PTSA). Chemical polymerization of the monomer yielded a soluble polymer. Structures of both the monomer and the polymer were investigated by Nuclear Magnetic Resonance (1H and 13C NMR) and Fourier Transform Infrared (FTIR) Spectroscopy. The average molecular weight of the chemically synthesized polymer was determined by Gel Permeation Chromatography (GPC) as Mn = 7.2 x 103 g/mol. The electrochemical oxidative polymerization of PTP was carried out via potentiodynamic electrolysis in the presence of LiClO4, NaClO4 (1:1) being the supporting electrolyte in acetonitrile. Electrochemical copolymerization of PTP with 3,4-ethylenedioxythiophene (EDOT) was carried out in acetonitrile (ACN)/ NaClO4/LiClO4 (0.1M) solvent-electrolyte couple system via potentiodynamic electrolysis. Cyclic voltammetry was used to investigate electrochemical behavior of the monomer and redox reactions of conducting polymers. Conductivities of films of the polymers were measured by four-probe technique. Surface morphologies of the films were investigated by Scanning Electron Microscope (SEM). Electrochromic properties of the conducting polymers were investigated via spectroelectrochemistry, kinetic and colorimetry studies. Spectroelectrochemical analysis of P(PTP) revealed electronic transitions at 413, 600 and 900 nm corresponding to &amp / #960 / -&amp / #960 / * transition, polaron, and bipolaron band formations, respectively. The spectroelectrochemical behavior of the P(PTP-co-EDOT) in comparison to those of the respective homopolymers revealed solid evidence of copolymerization based upon the differences in the spectral signatures. Switching time of the polymers was evaluated by kinetic studies upon measuring the percent transmittance (%T) at the maximum contrast point. As an application, absorption/transmission type electrochromic devices with ITO/homopolymer(copolymer)/gel electrolyte/PEDOT/ITO configuration was constructed, where homopolymer (copolymer) and PEDOT functioned as the anodically and the cathodically coloring layers, respectively. Spectroelectrochemistry, switching ability and open circuit memory of the devices were investigated. The results revealed that these devices have good switching times, reasonable contrasts and optical memories.

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