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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.
61

Isocyanate Functionalization Of Nano-boehmite For The Synthesis Of Polyurethane Organic-inorganic Hybrid Materials

Eroglu, Gulden 01 February 2011 (has links) (PDF)
In this study, organic-inorganic hybrid materials were prepared from polyurethane and boehmite. It was achieved by polymerizing monomers in the presence of functional nano-particles of boehmite with cyanate groups. The produced polyurethane organic-inorganic hybrid materials with enhanced mechanical properties were used for coating applications. Plate-like boehmite nano-particles were produced by hydrothermal process from aluminum hydroxide which was first ground in a high energy ball-mill, and then, processed hydrothermally under pressure and high temperature in a reactor. The surface morphology and crystal structure of boehmite were investigated by Scanning Electron Microscopy and X-Ray Diffraction analyses, respectively. The molecular structures of boehmite particles were investigated by Fourier Transform infrared spectroscopy. Furthermore, Brunauer-Emmett-Teller analysis and Photon Correlation Spectroscopy analysis were carried out to determine the surface area and the size of particles. Then, plate-like boehmite nano-particles were functionalized by the reaction of their hydroxyl groups with 1,6-hexamethylene diisocyanate and 4,4&rsquo / -methylene diphenyl diisocyanate. Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Differential Thermal Analysis-Thermal Gravimetric Analysis, and elemental analysis were performed for both functionalized and non-functionalized particles to confirm the functionalization of the particles. The polyester polyol used in the production of polyurethane was synthesized from 1,4-butanediol and adipic acid (PE-PO-1), and phthalic anhydride (PE-PO-2). Molecular structure of the polyester polyols was confirmed by Fourier Transform Infrared Spectroscopy analysis and molecular weight of the polymers were determined by end group analysis. Then, the produced functionalized nano-particles and polyester polyols were used for producing polyurethane organic-inorganic hybrid materials. Furthermore, polyurethane polymer and polymer-nonfunctionalized boehmite organic-inorganic hybrids were also synthesized for property comparison. Hardness, impact resistance, scratch resistance, abrasion resistance, and gloss property of the samples were determined. It was observed that mechanical properties of organic-inorganic hybrid materials improved significantly. The hardness of the PU produced with PE-PO-1 increased from 82 to 98 Persoz, and the hardness of the PU produced with PE-PO-2 increased from 52 to 78 Persoz when one weight percentage functionalized boehmite was used. The impact resistance of the coatings was found to depend on the type of the polyols used in PU but not in the inorganic component. Therefore PE-PO-2 used PU has higher impact resistance than PE-PO-1 used PU. Scratch resistance of the coatings improved from 2B to 2H when using functionalized boehmite. Abrasion resistance of PUs produced with PE-PO-1 increased from 2 to 10 l/micrometer and abrasion resistance of PUs produced with PE-PO-2 increased from 12 to 20 l/micrometer by addition of functionalized boehmite.
62

Microwave Initiated Polymerization Of Trihalophenyleneoxide And Aniline

Levent, Fulya 01 February 2011 (has links) (PDF)
The aim of the study is to synthesize poly(dibromophenyleneoxide) and polyaniline separately applying different microwave energies (90-900 watt), water amounts (1-5 ml) and time intervals (2-10 min) and investigate the effects of these parameters on the percent conversion of the polymers. The synthesis of poly(dibromophenyleneoxide) (P), radical ion polymer (RIP) and crosslinked polymer (CLP) were achieved by using tribromophenol (TBP) and Ca(OH)2 via microwave energy in a very short time interval. P and RIP were characterized by ATR-FTIR, 1H-NMR, 13C-NMR, TGA-FTIR, ESR, GPC, UV-VIS, DLS and SEM. Crosslinked polymers were characterized by ATR-FTIR and TGA-FTIR and polyaniline was characterized by ATR-FTIR.
63

Synthesis And Characterization Of Solvent Free Alkyd Resin With Hyperbranched Melamine Core

Keskin, Nagehan 01 February 2011 (has links) (PDF)
The use of volatile organic compounds (VOC) in coating materials has adverse effects on both human health and the environment. Due to concern over these problems, coating industry has attempted to decrease the solvent contents of coating materials for the last three decades by developing water dispersed and powder paints. A recently developed method to make solvent free paint is to use highly branched polymers in high solid alkyd resins. Highly branched polymers help to achieve resins with viscosity much lower than its linear counterparts. In this study, a new alkyd based resin was formulated using long oil alkyd and melamine based hyperbranched polymer having 24 functional groups on its structure. The long oil alkyd was synthesized by using an oil mixture (40% linseed + 60% sunflower). Melamine was preferred as core molecule due to its excellent properties such as greater hardness, alkali and solvent resistance with thermal stability. The resin produced has low viscosity because its hyperbranched structure / therefore, it needs no solvent for its application. The chemical characterization of the resins with different compositions was performed using Fourier Transform Infrared Spectroscopy and thermal properties were determined by Differential Scanning Calorimetry. Physical and mechanical tests were conducted to determine hardness, flexibility, impact resistance, abrasion resistance, adhesion power, and gloss property of the samples. The viscosity of the resins decreased from 148 Pa.s to 8.84 Pa.s as the hyperbranched polymer to long oil alkyd ratio was increased from 1:3 to 1:24. On the other hand, the hardness values of the resins decreased from 198 Persoz to 43 Persoz. All resins showed excellent flexibility, formability, adhesion, and gloss.
64

Synthesis Of Benzimidazole Containing Donor Acceptor Electrochromic Polymers

Akpinar, Hava Zekiye 01 February 2011 (has links) (PDF)
ABSTRACT SYNTHESIS OF BENZIMIDAZOLE CONTAINING DONOR ACCEPTOR ELECTROCHROMIC POLYMERS Akpinar, Hava Zekiye M. Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare February 2011, 60 pages Donor-acceptor-donor (DAD) type benzimidazole (BIm) and 3,4-ethylenedioxythiophene (EDOT) bearing monomers (4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3 dihydrothieno[3,4b][1,4] dioxin-7-yl)-2-benzyl-1H-benzo[d]imidazole (M1), 2,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-1H-benzo[d]imidazole (M2) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-2-ferrocenyl-1H-benzo[d]imidazole (M3)) were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance were reported in detail. Keywords: Benzimidazole, EDOT, Donor-Acceptor Type Polymers, Electrochromism, Conjugated Polymers.
65

Synthesis Of Benzimidazole Containing Donor Acceptor Electrochromic Polymers

Akpinar, Hava Zekiye 01 February 2011 (has links) (PDF)
ABSTRACT SYNTHESIS OF BENZIMIDAZOLE CONTAINING DONOR ACCEPTOR ELECTROCHROMIC POLYMERS Akpinar, Hava Zekiye M. Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare February 2011, 60 pages Donor-acceptor-donor (DAD) type benzimidazole (BIm) and 3,4-ethylenedioxythiophene (EDOT) bearing monomers (4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3 dihydrothieno[3,4b][1,4] dioxin-7-yl)-2-benzyl-1H-benzo[d]imidazole (M1), 2,4-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-1H-benzo[d]imidazole (M2) and 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3,4-b][1,4]dioxin-7-yl)-2-ferrocenyl-1H-benzo[d]imidazole (M3)) were synthesized and electrochemically polymerized. Pendant group at 2-C position of the imidazole ring was functionalized with phenyl (P1), EDOT (P2) and ferrocene (P3) in order to observe substituent effect on electrochemical and electrochromic properties of corresponding polymers. Spectroelectrochemical results showed that different pendant groups resulted in polymers with slightly different optical band gaps (1.75, 1.69 and 1.77 eV respectively) and different number of achievable colored states. Optoelectronic performance were reported in detail.
66

Synthesis And Characterization Of Hydrogels From Allyl Methacrylate And Acrylamide Copolymer

Ayazoglu, Neslihan 01 February 2011 (has links) (PDF)
Acrylamide based hydrogels were synthesized through copolymerization reaction of allyl methacrylate with acrylamide. Copolymerization reactions were carried out with solution polymerization in tetrahydrofuran by using &alpha / -&alpha / -azoisobutyronitrile as an initiator at 60 0 C. Three copolymer compositions were studied having 5, 15, 25 molar percentage of allyl methacrylate as feed concentrations. The synthesized copolymers were characterized by FTIR, NMR, DSC, TGA and GPC. 1H-NMR spectra were used to confirm the chemical structures of the copolymers and to determine the comonomer compositions of the copolymers. DSC and TGA analysis were conducted to determine the thermal properties of the copolymers and TGA results showed that copolymers have two step degradation behavior. Molecular weights of the copolymers were determined by GPC. Swelling capacities of the obtained hydrogels were investigated and swelling capacity of the gels reached to 77% as maximum value.
67

Soluble Alkyl Substituted Poly(3,4propylenedioxyselenophne)s: A Novel Platform For Optoelectronic Materials

Atak, Samed 01 March 2011 (has links) (PDF)
In this study, optical and electrochemical properties of regioregular and soluble alkyl substituted propylenedioxyselenophene based electrochromic polymers, namely poly(3,3-dibutyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C4), poly(3,3-dihexyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C6), and poly(3,3-didecyl-3,4-dihydro-2H-selenopheno[3,4-b][1,4]dioxephine) (PProDOS-C10), which were synthesized via electrochemical polymerization, were investigated. It is noted that these unique polymers have low band gaps (1.54 &ndash / 1.64 eV) and they are exceptionally stable under ambient atmospheric conditions. For example, polymer films retained 84-96 % of their electroactivity after five thousands cycles. The percent transmittance of PProDOS-Cn (n= 4, 6, 10) films found to be between 55-59 %. Furthermore, these novel soluble PProDOS-Cn polymers showed electrochromic behavior: a color change form pure blue (L = 57.31, a = -13.18, b = - 42.68) to highly transparent state (L = 91.74, a = 2.52, b = -1.30) state in a low switching time (1.0 s) during oxidation with high coloration efficiencies (328 &ndash / 864 cm2/C) when compared to their close analogues.
68

Electrochemical Polymerization Of Trihaloalkane Monomers To Form Branched C-backbone Polymers

Nur, Yusuf 01 April 2011 (has links) (PDF)
Polycarbynes ( poly(hydridocarbyne), poly(methylcarbyne) and poly(phenylcarbyne) ) are a class of network polymers which are primarily composed of tetrahedrally hybridizated carbon atoms which have hydrogen, methyl or phenyl pendant group linked via three carbon-carbon single bonds to form a three dimensional network of fixed rings. This backbone oers unusual properties on the polymer including thermal decomposition to form diamond and diamondlike carbon. In this thesis, polycarbynes were synthesized by electrolytical reduction of trihaloorganocompounds, namely chloroform, hexachloroethane, 1,1,1-trichloroethane and 1,1,1-trichlorotoluene. Poly(hydridocarbyne) was synthesized using chloroform and hexachloroethane. Poly(methylcarbyne) was synthesized from 1,1,1-trichloroethane. Poly(phenylcarbyne) was synthesized from 1,1,1-trichlorotoluene. Polycarbynes were characterized by UV/Vis spectroscopy, 1H and 13C NMR spectroscopy, FTIR and GPC. All results are found to be consistent with literature / and thus a single step cheap, safe and easy method was introduced to scientists and manufacturers in diamond science. The resulting polymers were heated upon 1000oC under nitrogen atmosphere for 24 hours yielding in the formation of diamond and diamond-like carbon. Results indicated that both diamond films and powders were successfully produced from polycarbynes. Diamonds formed from the polymers were characterized via optical microscope, SEM, X-ray and Raman spectroscopy. All results shown in thesis are completely consistent with studies previously done for polycarbynes and diamond.
69

Bone Marrow Targeted Liposomal Drug Delivery Systems

Baki, Mert 01 June 2011 (has links) (PDF)
Homing is the process that stem cells move to their own stem cell niches under the influence of chemokines like stromal-derived factor-1&alpha / (SDF-1&alpha / ) upon bone marrow transplantation (BMT). There is a need for increasing homing efficiency after BMT since only 10-15% of the transplanted cells can home to their own niches and a limited amount of donor marrow can be transplanted. In this study, we aimed to develop and characterize bone marrow targeted liposomal SDF-1&alpha / delivery system prepared by extrusion method. Alendronate conjugation was chosen to target the liposomes to bone marrow microenvironment, particularly the endosteal niche. Optimization studies were conducted with the model protein (
70

Production And Characterization Of Boron Containing Flame Retardant Polyamide-6 And Polypropylene Composites And Fibers

Dogan, Mehmet 01 May 2011 (has links) (PDF)
The main objective of this study was to produce flame retardant polyamide-6 (PA-6) and polypropylene (PP) composites and fibers containing boron compounds. The synergistic effect on flame retardancy of boron compounds (boron silicon containing oligomer (BSi), zinc borate (ZnB), boron phosphate (BPO4), metal oxide doped BPO4 and lanthanum borate (LaB)) with conventional flame retardants were investigated. The synergistic effect of nano-clay with commercial flame retardants was also investigated in order to reduce the total amount of flame retardant that is essential for fiber applications. The UL-94, limiting oxygen index (LOI), differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), fourrier transform infrared spectroscopy (FTIR) and cone calorimeter tests were conducted on composite materials in order to investigate the effect of synergy agents on the flame retardant and thermal properties of conventional flame retardant containing PA-6 and PP composites. According to the results from composite materials, boron compounds and clay showed synergistic effect with phosphorus based commercial flame retardants by acting generally with a condensed phase mechanism by increasing the char formation and/or by increasing the barrier effect of the final char residue. Inspired from the previous studies, firstly, only nano-sized BPO4 containing flame retardant fibers were produced and characterized. In the view of the results obtained from the composite trials, the boron compounds and organo clay were used with phosphorus based flame retardants to produce flame retardant fibers. The characterization of fiber samples were made with mechanical testing, melt flow index measurements (MFI), TGA, DSC, SEM and Micro Combustion Calorimeter (MCC) tests. According to the results from fiber samples, the inclusion of BPO4 reduced the peak heat release rate of the pure PA-6 and PP fiber. The reduction for PA-6 is higher than the PP fiber due to char forming character of PA-6. The usage of boron compounds and clay with phosphorus based flame retardants caused further reduction of peak heat release rate (PHRR) and total heat release values and increased the char formation. The amount of reduction of PHRR and total heat release (THR) is not so much due to the thermally thin character of fiber samples of nearly 40 microns. It is evident that a fabric made with these fibers will show better flame retardant behavior than single fiber tests due to its thick character with respect to the fiber samples.

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