Allı, Sema | Allı, Abdulkadir | Hazer, Baki

Article | 2012 | Journal of Applied Polymer Science124 ( 1 ) , pp.536 - 548

Macromonomer initiators behave as macro cross-linkers, macro initiators, and macromonomers to obtain branched and cross-linked block/graft copolymers. A series of new macromonomer initiators for atom transfer radical polymerization (MIM-ATRP) based on polyethylene glycol (M n = 495D, 2203D, and 4203D) (PEG) were synthesized by the reaction of the hydroxyl end of mono-methacryloyl polyethylene glycol with 2-bromo propanoyl chloride, leading to methacryloyl polyethylene glycol 2-bromo propanoyl ester. Poly (ethylene glycol) functionalized with methacrylate at one end was reacted with 2-bromopropionyl chloride to form a macromonomeric . . .initiator for ATRP. ATRP was found to be a more controllable polymerization method than conventional free radical polymerization in view of fewer cross-linked polymers and highly branched polymers produced from macromonomer initiators as well. In another scenario, ATRP of N-isopropylacrylamide (NIPAM) was initiated by MIM-ATRP to obtain PEG-b-PNIPAM branched block/graft copolymers. Thermal analysis, FTIR, 1H NMR, TEM, and SEM techniques were used in the characterization of the products. They had a thermo-responsive character and exhibited volume phase transition at â 36°C. A plasticizer effect of PEG in graft copolymers was also observed, indicating a lower glass transition temperature than that of pure PNIPAM. Homo and copolymerization kinetics were also evaluated. © 2011 Wiley Periodicals, Inc Daha fazlası Daha az

Hazer, Baki | Baysal, Bahattin M. | Köseoğlu, Ayşe G. | Beşirli, Necati | Taşkın, Elif

Article | 2012 | Journal of Polymers and the Environment20 ( 2 ) , pp.477 - 484

The synthesis of polylactide (PLA)-b-poly (dimethyl siloxane) (PDMS) linear block copolymers and their use in blends with pure-PLA are described. PLA-b-PDMS linear block copolymers were obtained by the transesterification reaction in chloroform solution between poly(dimethyl siloxane) bis (2-aminopropyl ether) (molecular weight 2,000 Da) with PLA in the presence of stannous octoate. Molecular weights (Mw) of the block copolymers were varied from 53,800 to 63,600 Da while that of pristine PLA was 73,600 Da. The copolymers obtained were purified by fractional precipitation and then characterized by 1 H NMR, FTIR, GPC, viscometry and D . . .SC techniques. Blends of pure PLA with PLA-b-PDMS block copolymers displayed improved elastic properties (elongation up to 140%) compared to pure PLA (elongation ~9%). Thermal, mechanical and morphological characterization of the blends were also conducted. © 2011 Springer Science+Business Media, LLC Daha fazlası Daha az

Yıldız, Ufuk | Hazer, Baki | Tauer, Klaus

Review | 2012 | Polymer Chemistry3 ( 5 ) , pp.1107 - 1118

Taşkın, Elif | Hazer, Baki | Beşirli, Necati | Çavuş, Gökhan

Article | 2012 | Journal of Macromolecular Science, Part A: Pure and Applied Chemistry49 ( 2 ) , pp.164 - 170

The synthesis of polylactide (PLA)-b-polyethylene glycol (PEG) linear block copolymers and their use in blends with pure-PLA is described. PLA-b-PEG linear block copolymers were obtained by the reaction between poly(ethylene glycol) bis (2-aminopropyl ether) (molecular weight 2000 Dalton) with PLA in the presence of stannous octoate via trans esterification. Molecular weight measurements of the block copolymers indicated that AB and ABA type block copolymers were obtained by controlling the feed ratio in the trans esterification reactions. The copolymers obtained were purified by the fractional precipitation and then characterized b . . .y 1H-NMR, FTIR, GPC and DSC techniques. Blends of pure PLA with PLA-b-PEG displayed improved mechanical properties compared to pure PLA. Thermal, mechanical and morphological characterization of the blends were also conducted. © 2012 Taylor and Francis Group, LLC Daha fazlası Daha az

Hazer, Derya Burcu | Kılıçay, Ebru | Hazer, Baki

Review | 2012 | Materials Science and Engineering C32 ( 4 ) , pp.637 - 647

Biomaterials have played an important role in the treatment of disease and the improvement of health care. Synthetic and naturally occurring biodegradable and biocompatible polymers have been used as biomaterials. Polyhydroxyalkanoates (PHAs) are promising materials for biomedical applications because they are biodegradable, non-toxic and biocompatible. We will shortly summarize the modification reactions, which include functionalization and grafting reactions, to improve the mechanical, thermal and hydrophilic properties of PHAs. The use of the modified PHAs in numerous biomedical applications, such as sutures, cardiovascular patch . . .es, wound dressings, scaffolds in tissue engineering, tissue repair/regeneration devices, drug carriers will be discussed in this review. © 2012 Elsevier B.V. All rights reserved Daha fazlası Daha az

Hazer, Baki

Letter | 2012 | Yükseköğretim ve Bilim Dergisi2 ( 3 ) , pp.205 - 206

Fen Edebiyat fakültelerinin fen bölümlerinin büyük çoğunluğu lisans öğrencisi bulamamaktan dolayı bu sene kapanma durumuna geldi. Çok sayıda fen bölümünün kapanması halinde buralardaki kadrolu yetişmiş öğretim üyelerinin 4-5 yıl içinde ders yüklerinde büyük bir azalma olacaktır. Diğer bölümlere verilen servis dersleri ve lisansüstü programların devam etmesi bu ders eksikliği zafiyetini kısmen giderecektir. Lisans öğrencilerini özendirecek yeni açılımlarla kapanma durumunda olan bölümlere yeni bir görüntü kazandırma görüşleri tartışılmaktadır. Science Departments of Faculty of Art and Sciences are closing this year in many Turkish Un . . .iversities because of shortage of registered students. Tutorial task of stuff s working for these departments will decrease in 4-5 years. Th e teachers in these Universities will be busy with lectures to other departments. Th e service lectures of the teachers and the graduate students can make the teachers busy for a while. New future solutions for encouragement of the undergraduate students are being discussed Daha fazlası Daha az

Hazer, Derya Burcu | Mut, Melike | Dinçer, Nazmiye | Sarıbaş, Zeynep | Hazer, Baki | Özgen, Tunçalp

Article | 2012 | Child's Nervous System28 ( 6 ) , pp.839 - 846

Purpose: Catheter-related infection is a major complication of ventriculoperitoneal shunt in children. The aim of this study is to determine inflammatory response and the efficacy of polypropylene-grafted polyethylene glycol (PP-g- PEG) copolymer and silver nanoparticle-embedded PP-g- PEG (Ag-PP-g-PEG) polymer-coated ventricular catheters on the prevention of catheter-related infections on a new experimental model of ventriculoperitoneal shunt in rats. Methods: Thirty six Wistar albino rats were divided into six groups: group 1, unprocessed sterile silicone catheterembedded group; group 2, sterile PP-g-PEG-coated catheter group; gro . . .up 3, sterile Ag-PP-g-PEG-coated catheter group; group 4, infected unprocessed catheter group; group 5, infected PP-g-PEG-coated catheter group; and group 6, infected Ag-PP-g-PEG-coated catheter group, respectively. In all groups, 1-cm piece of designated catheters were placed into the cisterna magna. In groups 4, 5, and 6, all rats were infected with 0.2 mL of 10×106 colony forming units (CFU)/mL Staphylococcus epidermidis colonies before the catheters were placed. Thirty days after implantation, bacterial colonization in cerebrospinal fluid and on catheter pieces with inflammatory reaction in the brain parenchyma was analyzed quantitatively. Results: Sterile and infected Ag-PP-g-PEG-covered groups revealed significantly lower bacteria colony count on the catheter surface (ANOVA, 0±0, p<0.001; 1.08±0.18, p< 0.05, respectively). There was moderate inflammatory response in the parenchyma in group 4, but in groups 5 and 6, it was similar to that of the sterile group (ANOVA, 16.33± 3.02, p<0.001; 4.00±0.68, p<0.001, respectively). Conclusions: The PP-g-PEG, especially Ag-PP-g-PEG polymer-coated ventricular catheters are more effective in preventing the catheter-related infection and created the least inflammatory reaction in the periventricular parenchyma. © Springer-Verlag 2012 Daha fazlası Daha az