Bulunan: 10 Adet 0.000 sn
Koleksiyon [17]
Tam Metin [2]
Yayın Türü [1]
Yazar [20]
Yayın Yılı [8]
Konu Başlıkları [20]
Yayıncı [1]
Yayın Dili [1]
Dergi Adı [1]
γ-Ray induced graft copolymerization of methyl methacrylate onto poly(ß-hydroxynonanoate)

Eroğlu, Mehmet S. | Çaykara, Tuncer | Hazer, Baki

Article | 1998 | Polymer Bulletin41 ( 1 ) , pp.53 - 60

Copolymers of poly(3-hydroxy-nonanoate), PHN, with methyl methacrylate, MMA, were prepared using 60Co-gamma irradiator. The bulk solutions of PHN in MMA were prepared at different PHN feed concentration and they were irradiated to 8.5 kGy at room temperature. Polymer fractions obtained by solvent-nonsolvent fractional precipitation were carefully characterized using gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), and thermal gravimetric analysis (TGA) techniques. High copolymerization yield was observed and the copolymer compositions obtained from the TGA measurements were consistent with the NMR . . .results. PHN contents of the copolymer samples changed from 5 to 35 wt.-%. The strain at break and tensile strength values of copolymers were between the values of their respective homopolymers. It was observed that pure copolymer samples showed up to 13% strain at break Daha fazlası Daha az

2,6-Bis-benzimidazolylpyridines as new catalyst in copper-based ATRP

Arslan H. | Avcı Ç. | Tutkun B. | Şengül A.

Article | 2017 | Polymer Bulletin74 ( 4 ) , pp.931 - 948

The ligands, 2,6-bis(NH-benzimidazol-2-yl)pyridine (L1) and 2,6-bis(N-methyl-benzimidazol-2-yl)pyridine (L2), were synthesized by a one-step reaction of 2,6-pyridinedicarboxylic acid with a diamine (o-phenylenediamine or N-methyl-1,2-phenylenediamine), respectively, in syrupy phosphoric acid at ca. 200 °C. Their efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methylmethacrylate (MMA) was investigated. The linear first-order kinetic plots were observed; indicating that the number of active species is constant during the polymerization and termination reactions are limited. The apparent rate consta . . .nt values of ATRP of MMA with CuCl/L1 catalyst system at 90 °C in acetonitrile were found to be between 3.83 × 10-5 and 1.33 × 10-4 s-1, while they were between 1.86 × 10-4 and 4.40 × 10-4 s-1 in the case of CuCl/L2 catalyst, indicating the presence of lower radical concentration throughout the polymerization of MMA using CuCl/L1 catalyst system. In both the cases, low apparent rate constant values are obtained. This indicates that ATRP proceeded at reasonable rates and a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of two. Mn,GPC values increased slightly linearly with conversion and molecular weight values were closer to Mn,th in the case of ATRP of MMA using CuCl/L2 catalyst complex. Cyclic voltammetry measurements confirmed that CuCl/L1 and CuCl/L2 complexes in acetonitrile give reversible redox couples and copper(I) centers in CuCl/L1 and CuCl/L2 catalyst complexes that are readily oxidized and they potentially suit to facile ATRP. © 2016, Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Biodegradable and biocompatible radiopaque iodinated poly-3-hydroxy butyrate: synthesis, characterization and in vitro/in vivo X-ray visibility

Erol, Arzu | Rosberg, Derya B. Hazer | Hazer, Baki | Göncü, Beyza S.

Article | 2019 | Polymer Bulletin , pp.931 - 948

Some novel radiopaque biodegradable and biocompatible iodinated polymers based on poly-3-hydroxy butyrate (PHB) were obtained. Following the attachment of diethanol amine to PHB, the hydroxyl ends were capped with 4-iodobenzoic acid and 2,3,5-tri-iodobenzoic acid. In this manner, tri-novel radiopaque polymers were obtained. The resulting polymers were structurally characterized by NMR technique. They were evaluated with respect to their possible use as radiopaque implant biomaterials indicating X-ray visibility in a noninvasive manner using routine X-ray absorption imaging techniques. These polymers exhibited good radiopacity with c . . .onventional imaging X-ray techniques in vivo. Additionally, biocompatibility of these iodinated polymers was also evaluated. There were no signs of infection or abscess formation on the surgical area. These novel radiopaque PHBs should be promising biomaterials for a new-generation radiopaque materials. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature Daha fazlası Daha az

Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

Balcı, Murat | Allı, Abdulkadir | Hazer, Baki | Güven, Olgun | Cavicchi, Kevin | Çakmak, Mükerrem

Article | 2010 | Polymer Bulletin64 ( 7 ) , pp.691 - 705

Free radical crosslinking of unsaturated bacterial polyesters obtained from soybean oily acids

Hazer, Baki | Demirel, Songun I. | Borcaklı, Mehlika | Eroğlu, Mehmet S. | Çakmak, Miko | Erman, burak

Article | 2001 | Polymer Bulletin46 ( 5 ) , pp.389 - 394

Poly(-3-hydroxy alkanoate) containing unsaturated side chains, PHA-soybean, were produced by feeding Pseudomonas oleovorans with soybean oily acids obtained from soybean oil. Unsaturation of PHA-soybean were found to be 10 mol-% of unsaturated side chains. Main saturated part of the biopolymer was Poly(3-hydroxy octanoate) with minor hexanoate and decanoate units. PHA films were crosslinked via free radical mechanism by means of thermally or under UV irradiation in the presence of benzoyl peroxide, benzophenon, and/or ethylene glycol dimethacrylate (EGDM). Crosslinking yield of the PHA films were found to be from 81 to 93 wt.-% from . . . the sol-gel analysis. Swelling properties of the crosslinked PHA films in chloroform and toluene were also studied. Mc values of crosslinked PHAs were also calculated using Flory-Rehner equation. The crosslinked biopolyester obtained by thermally at 60 °C with benzoyl peroxide indicated the highest crosslinking density. Glass transition temperatures (Tg) of crosslinked biopolyester samples were changed from -33 to -45 °C while that of PHA-soybean was -60 °C Daha fazlası Daha az

Osteogenic activities of polymeric soybean oil-g-polystyrene membranes

Tığlı-Aydın, Rahime Seda | Hazer, Baki | Acar, Merve | Gümüşderelioğlu, Menemşe

Article | 2013 | Polymer Bulletin70 ( 7 ) , pp.2065 - 2082

A novel biocompatible copolymer membrane was synthesized and characterized for use in guided bone regeneration using polymeric soybean oil-g-polystyrene (PSO-g-PS) graft copolymer which was successfully obtained by free radical polymerization of styrene initiated by PSO peroxide as a macroinitiator at 80 C. Osteoblastic cellular activities of MC3T3-E1 cells on PSO-g-PS membranes with different soybean oil composition (PSO-g-PS1, PSO-g-PS2, and PSO-g-PS3) were evaluated. Nuclear magnetic resonance (1H NMR) spectra showed that PSO inclusion (mol%) was found to be 27, 69, and 51 % for PSO-g-PS1, PSO-g-PS2, and PSO-g-PS3 membranes, resp . . .ectively. Superior biocompatibility of the PSO-g-PS membranes was determined compared to polystyrene tissue culture plates (TCPS) as positive control. Cell proliferation was enhanced on PSO-g-PS2 and PSO-g-PS3 membranes compared to PSO-g-PS1 membranes (p < 0.001), and a statistically significant higher ALP value of MC3T3-E1 cells on PSO-g-PS2 membranes (p < 0.05) suggested that proliferation and differentiation of preosteoblastic on PSO-g-PS membranes were enhanced with regard to soybean oil content within the membranes. Thus, the present study suggests that PSO-g-PS2 membranes, which showed a favorable biological environment for the preosteoblastic cells, can be well suited for bone tissue engineering applications. © 2013 Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

The synthesis of (N1E,N4E)-N1,N 4-bis(pyridine-2-YL) ethylene benzene-1,4-diamine and investigation of its efficiency as new binuclear catalyst complex in copper-based ATRP

Arslan H. | Kaptan M.G. | Zirtil O. | Hanhan M.E. | Şen S.

Article | 2014 | Polymer Bulletin71 ( 5 ) , pp.1043 - 1059

(N1E,N4E)-N1,N4-bis(pyridin-2- yl) ethylene benzene-1,4-diamine (BPEBD) was synthesized by condensation of 2-acetyl pyridine and 1,4-diaminobenzene and its efficiency as a catalyst in Cu-based atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) and styrene (S) was investigated. Linear first-order kinetic plots were obtained. However, there were induction periods. The apparent rate constant values of ATRP of MMA with CuCl/BPEBD catalyst system in toluene were found to be between 2.10 × 10-5 and 9.83 × 10-5 s -1, while they were between 6.67 × 10-6 and 3.30 × 10-5 s-1 in the case of acetonitrile, indicating the p . . .resence of a low radical concentration throughout the polymerizations. Low apparent rate constant values denote a good control over ATRP in general. Apparent rate constant vs [ligand]/[catalyst] ratio plots showed a maximum at the [ligand]/[catalyst] ratio of 1. In the ATRP of MMA in toluene, M n,GPC values increased linearly with conversion and these molecular weight values were close to M n,th in comparison to that of in acetonitrile. In the polymerization of S, the control of molecular weights was not good, although the reactions were first-order kinetics. Cyclic voltammetry measurements confirmed that CuCl/BPEBD complex in acetonitrile gives quasi-reversible redox couples, and copper (I) centers in CuCl/BPEBD binuclear catalyst complexes are readily oxidized and it potentially suits to facile ATRP. © 2014 Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

One-step synthesis of triarm block copolymers by simultaneous atom transfer radical and ring-opening polymerization

Öztürk, Temel | Yavuz, Mahmut | Göktaş, Melahat | Hazer, Baki

Article | 2016 | Polymer Bulletin73 ( 6 ) , pp.1497 - 1513

One-step synthesis of poly(MMA-b-CL) triarm block copolymers was carried out by atom transfer radical polymerization of methyl methacrylate (MMA) and ring-opening polymerization of ?-caprolactone (CL) using 3-chloro-1,2-propanediol trifunctional initiator. The triarm block copolymers comprising one poly-MMA arm and two poly-CL arms were synthesized by changing some polymerization conditions such as monomer/initiator concentration, polymerization time. The effect of the reactions conditions on the polydispersity and molecular weights was also investigated. The block lengths of the block copolymers were calculated by using 1H-nuclear . . .magnetic resonance (1H-NMR) spectrum. It was observed that the block length could be altered by varying the monomer and initiator concentrations. The characterization of the products was achieved by using 1H-NMR, Fourier-transform infrared spectroscopy, gel-permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and fractional precipitation techniques. © 2015, Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Synthesis of novel biodegradable elastomers based on poly[3-hydroxy butyrate] and poly[3-hydroxy octanoate] via transamidation reaction

Hazer, Baki | Akyol, Elvan | Şanal, Timur | Guillaume, Sophie | Çakmaklı, Birten | Steinbuchel, Alexander

Article | 2019 | Polymer Bulletin76 ( 2 ) , pp.919 - 932

Poly(3-hydroxyalkanoate)s (PHAs) are a class of polymers receiving attention because of their potential as renewable, biodegradable and high-technology properties. Unlike most short chain length (scl) PHAs such as poly(3-hydroxybutyrate) (PHB), medium chain length (mcl) PHAs such as poly(3-hydroxyoctanoate) (PHO) exhibit low crystallinity and are elastomeric in character. PHB-b–PEG-b–PHO block copolymers can combine both properties in block copolymer matrix. In this study, we report the synthesis of the block copolymers combining the PHB and PHO blocks. Transamidation reactions of PHB with polyethylene glycol with primary amine yiel . . .d equimolar amounts and PHB with amine ends. PHO reacts with the modified PHB containing the amine end to give PHB-b–PEG-b–PHO block copolymers. Structural analysis of the products was performed by using 1H–, 13C, heteronuclear single quantum coherence NMR techniques. Thermal and mechanical properties of the block polymers were also evaluated. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature Daha fazlası Daha az

Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

Kalaycı, Özlem A. | Cömert, Füsun B. | Hazer, Baki | Atalay, Turgay | Cavicchi, Kevin A. | Çakmak, Mükerrem

Article | 2010 | Polymer Bulletin65 ( 3 ) , pp.215 - 226

The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (Mw = 140,000 Da) with polyethylene glycol (PEG) (Mn = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by reducing solutions of the salts of silver or gold and the copolymer in tetrahydrofuran. The optical properties of the metal nanoparticle embedded copolymers . . . were determined by using UV-visible spectroscopy. Surface plasmon resonance (SPR) of the gold and silver nanoparticle embedded copolymers in toluene was observed at a maximum wavelength (?max) of 428 and 551 nm in the UV-VIS absorption spectra, respectively. The average particle diameters of the gold and silver nanoparticles were found to be 50 nm from the high resolution scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Amphiphilic polymer films containing silver and gold nanoparticles were found to be highly antimicrobial by virtue of their antiseptic properties to Escherichia coli and Staphylococcus aureus. © Springer-Verlag 2009 Daha fazlası Daha az

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