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Effect of nitrocarburizing and post-oxidation processes on the microstructure and surface properties of AISI 4140 steel
(Gazi Univ, 2023) Yılmaz, Ümmihan; Pehlivanli, Burak; Erkan, Ayşe; Kılıçlı, Volkan
AISI 4140 steel is in the class of medium carbon low-alloy steels and is widely used in industry due to its high hardenability and being a relatively economical steel. AISI 4140 steel is also among the steels that can be nitrided. With the nitriding process, thanks to the hard nitride layer obtained on the surface, not only a wear-resistant surface is provided, but also an increase in fatigue strength. In this study, the microstructural and surface properties of AISI 4140 steel, which has been treated with low pressure gas nitrocarburizing and post-oxidation process at different times, has been investigated. For this aim, AISI 4140 steel samples were austenitized at 850 degrees C for 60 min and quenched into oil at 60 degrees C. After quenching, the samples were tempered at 630 degrees C for 60 min. Gas nitrocarburizing process steps; pre-oxidation at 350 degrees C for 45 minutes, nitriding at 550 degrees C for 90 minutes and nitrocarburizing at 550 degrees C for 480 minutes were applied, and then the samples were subjected to post-oxidation using steam for 45 to 180 minutes. Microstructural characterization studies were performed by optical microscope, scanning electron microscope (SEM), energy-dispersive X-ray spectrum analysis (EDX), X-ray diffraction (XRD) analysis, microhardness and surface roughness measurements. The X-ray analysis results revealed that the surface layer of the samples consisting of iron-nitride phases of e-Fe2-3N and gamma'-Fe4N during nitrocarburizing and iron oxide (Fe3O4). It was determined that the iron oxide (Fe3O4) layer thickness increased with increased post-oxidation time. Among the AISI 4140 steel samples that nitrocarburized and post-oxidized, the best combination of hardness depth, surface hardness, and surface roughness was obtained after 150 minutes of post oxidation.
Hydroxyapatite-based nanoparticles as a coating material for the dentine surface: An antibacterial and toxicological effect
(ELSEVIER SCI LTD, 2020) Erdem, Umit; Dogan, Mustafa; Metin, Aysegul U.; Baglar, Serdar; Turkoz, Mustafa B.; Turk, Mustafa; Nezir, Saffet
In this study, nano sized hydroxyapatite (nHAp) and Ag(I) doped hydroxyapatite (Ag-nHAp) particles were synthesized by the precipitation method and used as a coating material for remineralization on caries-affected dentine samples. Characterization studies of both the synthesized hydroxyapatite-based particles and the coated dentine samples were performed using instrumental techniques such as SEM and FFIR, and then toxicity and antibacterial properties were also evaluated. It was observed that dentine samples were effectively coated by both nHAp and Ag center dot nHAp particles which have no toxic effects. Furthermore, the costing of nano-hydroxyapatite on dentine samples positively contributed to the viability of L929 fibroblast cells and also provided an antibacterial effect against to bacteria such as S. mutants, C. albicans and E. coli bacteria that are most frequently caused caries in the teeth. While all type of bacteria was eliminated by the nHAp coated dentine samples at 24th, Ag-nHAp coated dentine samples removed to all bacteria type at 1st.
Preparation of a novel functionalized magnetic nanobiocomposite as a carrier for protein adsorption
(TAYLOR & FRANCIS INC, 2020) Metin, Aysegul Ulku; Dogan, Mustafa; Erdem, Umit; Babacan, Taner; Gungunes, Hakan
This study aims the synthesis of a novel functionalized magnetic nanocarrier based on xanthan gum biopolymer. Glycidyl methacrylate was grafted on xanthan gum chains by radical polymerization reaction using two types of initiators: ammonium persulfate and benzoyl peroxide. Characterization studies of the magnetic nanocarrier were performed using several instruments such as Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy-Dispersive-X-Ray Spectroscopy, X-Ray Diffraction Spectroscopy, Transmission Electron Microscopy, Mossbauer Spectroscopy, and Vibrating Sample Magnetometer. According to the Vibrating Sample Magnetometer data and Mossbauer analysis, Fe atoms were incorporated successfully in the polymer chains in Fe3+ state and magnetic nanocarrier has super-paramagnetic behavior, respectively. Epoxy groups on magnetic nanoparticles were converted to carboxylic acid groups using iminodiacetic acid and then tested to usability as a carrier for immobilization of proteins such as albumin, lipase and cytochrome c. The adsorption of albumin and lipase on magnetic nanoparticles were pH-dependent while cytochrome c was immobilized in a wide range of pH value. The calculated maximum experimental immobilization capacity of magnetic nanoparticles was 65.10 mg g(-1), 62.0 mg g(-1) and 188.0 mg g(-1) for albumin, lipase and cytochrome c, respectively. Experimental data fitted to Langmuir isotherm better than Freundlich. The rate of cytochrome c adsorption followed the pseudo-second-order kinetic. Results showed that the functionalized magnetic nanoparticles can be effectively used as a carrier for protein separations, especially for cytochrome c. Moreover, the functionalized magnetic nanocarrier had high affinity to Cytochrome c protein even in multiple protein systems.
The chemical synthesis and characterizations of silver-doped polyaniline: role of silver-solvent interactions
(SPRINGER, 2020) Tas, Recep; Can, Muzaffer; Sari, Hayati
In this work, we successfully synthesized silver-doped polyaniline (NPANI-Ag-X; X represents I- and BF4- dopants,) by using chemical oxidation polymerization in various solvent media, which are deionized water, dimethylformamide, acetonitrile, 1,4-dioxane, tetrahydrofuran and acetone to give new features into polyaniline (PANI). Then, the solvent effects on the formation of NPANI-Ag-X were investigated. Most of the solvents used in the syntheses show ligand properties and form complexes with metal ions. According to their stability, these complexes can inhibit the reactions of metal ions. Polymer samples were characterized by using scanning electron microscopy, X-ray diffractions, energy-dispersive X-ray analysis, Fourier transform infrared spectrometry, atomic absorption spectrometer, ultraviolet-visible spectrophotometers, thermal analysis (TGA, DTA) and electrical conductivity measurements. The experimental results obtained show that some properties such as crystallinity, conductivity, metal contents and surface area of PANI polymers have changed with the addition of silver to the polymer. Studies have also shown that these properties can be controlled by the exchange of metal ions and solution media. It was observed that the solvents were effective in adding metal to the polymer and the amount of metal in the synthesized polymers varied depending on the solvent used.
Investigation on phenol degradation capability of Scenedesmus regularis: influence of process parameters
(TAYLOR & FRANCIS LTD, 2020) Basaran Kankilic, Gokben; Metin, Aysegul Ulku; Aluc, Yasar
Phenol removal from environmental solutions has attracted much attention due to phenol's high toxicity, even at low concentrations. This study aims to reveal the phenol biodegradation capacity of Scenedesmus regularis. Batch system parameters (pH, amount of algal cell, phenol concentration) on biodegradation were examined. After 24 h of treatment, 92.16, 94.50, 96.20, 80.53, 65.32, 52 and 40% of phenol were removed by Scenedesmus regularis in aqueous solutions containing 5, 10, 15, 20, 30, 40 and 50 mg/L of phenol, respectively. To describe the correlation between degradation rate and phenol concentration, the Michaelis-Menten kinetic equation was used where V-max and K-m are 0.82 mg phenol g algea(-1) h(-1) and 24.97 ppm, respectively. Phenol remediation ability of S.regularis can enable the usage of the spent biomass as biofuel feedstock and animal feed makes it a 'green' environmental sustainable process.
Synthesis, characterization and swelling performance of a temperature/pH-sensitive kappa-carrageenan graft copolymer
(ELSEVIER, 2020) Geyik, Gulcan; Isiklan, Nuran
A binary graft copolymerization of dimethylaminoethyl methacrylate (DMAEMA) and acrylic acid (AA) onto kappa-carrageenan (CG) was performed by using microwave irradiation in the presence of 4A'-Azobis(4-cyanovaleric acid) (ACVA). The structure of the CG-g-P(DMAEMA/AA) copolymers was confirmed using C-13 NMR, MR, DSCTFGA and XRD. The effects of the DMAEMA/AA ratio, the microwave power and irradiation duration, and the concentrations of CG and ACVA on grafting yield and grafting efficiency were all investigated, and the best values of them were found to be 150% and 85%, respectively. The lower critical solution temperatures (LCST) for CG-g-P(DMAEMA/AA) copolymers at various pH conditions were determined, and when the pH value of the medium was increased from 12 to 10, the LCST of the copolymer decreased from 53 degrees C to 39 degrees C. Moreover, swelling performance of the copolymers under various pH conditions was examined, and it was observed that the swelling ratio of the copolymer increased with a decrease in the pH value of the medium. (C) 2020 Elsevier B.V. All rights reserved.
Synthesis and biological evaluation of novel urea, thiourea and squaramide diastereomers possessing sugar backbone
(ELSEVIER SCI LTD, 2020) Isilar, Ozer; Bulut, Adnan; Yaglioglu, Ayse Sahin; Demirtas, Ibrahim; Arat, Esra; Turk, Mustafa
A series of novel chiral 14 urea, thiourea and squaramide stereoisomers possessing carbohydrate backbones as well as amide functional groups was synthesized and characterized by their, H-1 NMR, C-13 NMR, FT-IR, HRMS, optical rotation, and melting points. Their antiproliferative activities were investigated against HeLa and PC3 cell lines. The compounds 9, 11 and 12 showed better activities at 25 mu M against PC3 cell line with respect to the standard 5-fluorouracil (5-FU). Especially, the compounds 9 and 11 showed higher activities than the standard 5-FU even at low concentration (5 mu M) against HeLa cell line. IC50 results also confirm these activities. The compounds 9, 10 and 11 have the IC50 values of 1.10 mu M, 1.51 mu M and 1.02 mu M, respectively while 5-FU has 2.51 mu M. Moreover, their cytotoxicity tests have proven that their viabilities were in between 50% and 100%.
Methylene blue adsorption on magnetic alginate/rice husk bio-composite
(ELSEVIER, 2020) Alver, Erol; Metin, Aysegul Ulku; Brouers, Francois
Magnetic alginate/rice husk (m-ALG/RH) bio-composite beads prepared with ionotropic gelation method and used for methylene blue (MB) removal. Structural analysis of magnetic alginate/rice husk composite beads was performed using FTIR, SEM-EDS and TGA techniques. The accomplishment of magnetic alginate/rice husk composite beads as an adsorbent for the removal methylene blue was investigated from aqueous solution. Maximum experimental adsorption capacity of the bio-composite beads was calculated as 274.9 mg/g. The various process parameters such as pH, temperature and initial MB concentration optimized. It was determined that pH no significant effect on dye removal efficiency of beads while temperature and ionic strength caused a decrease on removal efficiency. The various isotherm models were applied for determine the adsorption mechanism and Freundlich isotherm model is more compatible with the experimental data. The kinetic studies showed that the adsorption of methylene blue can be well described by the fractal Brouers-Sotolongo kinetic model. The thermodynamic calculations indicated that methylene blue adsorption was a spontaneous and exothermic nature. The results showed that the magnetic alginate/rice husk bio-composite as low-cost and eco-friendly adsorbent can be effectively used for cationic dye removal steps in the environmental engineering applications. (C) 2020 Elsevier B.V. All rights reserved.
Mn3O4/p(DCPD)HIPE nanocomposites as an efficient catalyst for oxidative degradation of phenol
(SPRINGER, 2020) Yesil, Rabia; Cetinkaya, Sevil
The increase in the amount of wastewater containing organic pollutants in various industrial processes creates serious problems for the environment. Sulfate radical-based advanced oxidation process (AOP) is an effective route to remove pollutants from wastewater. However, designing a new nano-based catalyst to generate sulfate radicals is an important factor for the AOP. For this vision, porous trimanganese tetraoxide-polydicyclopentadiene (Mn3O4/pDCPD) nanocomposite, having an open-cell structure, was successfully designed via high internal phase emulsion (HIPE) and ring-opening metathesis polymerization (ROMP) approaches. The effect of Mn(3)O(4)nanoparticle concentration on the structure was investigated, and the resulting Mn3O4/p(DCPD)HIPE nanocomposites were fully characterized by FT-IR, XRD, FE-SEM, TEM, solid-state(13)C CPMAS NMR, DSC, and TGA analysis. The selected nanocomposite containing 5 wt% of Mn(3)O(4)was used as a model catalyst to mediate the heterogeneous oxidation of phenol in the presence of oxone. It is concluded that Mn3O4/p(DCPD)HIPE nanocomposite is a highly active catalyst to generate sulfate radicals for phenol degradation. Complete removal of 25 mg/L phenol was achieved in 30 min under the conditions of [catalyst] = 0.8 g/L, [oxone] = 2 g/L, andT = 25 degrees C. The phenol degradation followed the pseudo-first-order kinetic model, and the highest kinetic constant of 0.0611 min(-1)was achieved. No significant loss in the activity of the catalyst was determined after four consecutive cycles. Graphical abstract
pH/temperature-responsive poly(dimethylaminoethyl methacrylate) grafted kappa-carrageenan copolymer: Synthesis and physicochemical properties
(WILEY, 2020) Geyik, Gulcan; Isiklan, Nuran
kappa-Carrageenan-graft-poly(dimethylaminoethyl methacrylate) (CRG-g-PDMA) was synthesized via free-radical copolymerization under microwave irradiation.C-13-Nuclear magnetic resonance spectroscopy (C-13-NMR), fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods were used for characterization of the CRG-g-PDMA structure. The effect of reaction variables including the concentrations of the initiator and dimethylaminoethyl methacrylate (DMA) as well as the microwave irradiation time and power on graft ratio and conversion was investigated, and their highest values were obtained to be 179 and 76%, respectively. The lower critical solution temperatures (LCSTs) of the CRG-g-PDMA copolymers were determined at various pH conditions, and their value in distilled water was found as 47 degrees C. Besides, the swelling capacity of the copolymers under different pH levels was investigated and it was seen that the swelling capacity of the copolymer increased with the decrease in the pH value of the medium. The CRG-g-PDMA copolymer exhibited excellent swelling performance in acidic pH conditions and possessed responsiveness to pH and temperature stimuli.
Increasing Photocatalytic Stability and Photocatalytic Property of Polyaniline Conductive Polymer
(SPRINGER INTERNATIONAL PUBLISHING AG, 2020) Dogan, Deniz; Tas, Recep; Can, Muzaffer
This study aims to enhance the photocatalytic properties and stability of polyaniline (PANI) by preparing polyaniline-metal oxide composites. Polyaniline and polyaniline-metal oxide composites were synthesized via chemical polymerization method and characterized by using scanning electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray analysis, and Fourier transform infrared spectrometry. The morphological characteristics of the polymers synthesized in media with and without metal oxide are quite different from each other. These differences are due to the presence of metal oxides in the polymer structure, and the interactions between PANI-metal oxides, as mentioned in the XRD interpretations. The photocatalytic properties of polyaniline and each polyaniline-metal oxide composite were investigated using methylene blue (MB) under UV light and in the dark. (MB is one of the pollutant dyes found in wastewater.) The findings showed that photocatalytic property and stability of polyaniline can be enhanced by preparing the polyaniline-metal oxide composites. TheE(g)values of the selected metal oxides are around 3 eV values. The metal oxides, having the 3 eV energy bandgap range, exhibit better photocatalytic properties. Graphic It was aimed to investigate the photocatalytic properties and to increase the photocatalytic properties of polyaniline with the metal oxide. Polyaniline-metal oxide composites were synthesized and characterized. And their photocatalytic properties of each oxide composite were investigated by degradation of methylene blue under UV light and in dark media.
Phragmites australis as a new cellulose source: Extraction, characterization and adsorption of methylene blue
(ELSEVIER, 2020) Kankilic, Gokben Basaran; Metin, Aysegul Ulku
The aim of this study was to investigate potential use of Phragmites australis in the production of cellulose microfibrils with chemical extraction process. Characterization of the natural P. australis and extracted fibrils were examined by FT-IR, XRD, FE-SEM, TGA, zeta potential and particle size distribution analyses indicating that amorphous polymer parts have been successfully moved away from the plant structure and cellulose content of P. australis was increased from 39.92% +/- 0.78% to 91.45 +/- 0.49%. Extracted cellulose samples showed microfibrillar structure based on FESEM images. The usability of cellulose microfibrils extracted from P. australis as an adsorbent was investigated in dye removal studies due to its abundant, eco-friendly and low-cost properties. Therefore, Methylene blue (MB) removal capacity of cellulose microfibrils from aqueous solution was tested and the effects of adsorption process parameters were evaluated in a controlled batch system. Maximum adsorption capacity (qm(max)) was found to be 54.9 mg/g and the microfibrils allowed MB removal over a wide pH range. Experimental data fit the both Langmuir and Freundlich isotherm models indicating multilayer adsorption. The adsorption process was better described with pseudo second-order kinetic model. In conclusion, P. australis is a good candidate in high purity cellulose microfibrils production as a natural material. Cellulose microfibrils are a potential alternative source which can be used as an adsorbent for wastewater treatment especially for cationic dye removal. Moreover, it can be used for production of cellulose microfibrils in various industrial applications. (C) 2020 Elsevier B.V. All rights reserved.
Designing of a stable and selective glucose biosensor by glucose oxidase immobilization on glassy carbon electrode sensitive to H2O2 via nanofiber interface
(SPRINGER, 2020) Temocin, Zulfikar
The integration of the enzymes on the solid electrode surfaces is an indispensable step for the construction of the bioelectrochemical electrode. In the current work, the blend nanofibers consisting of poly (vinyl alcohol) and poly(ethyleneimine) were deposited by the electrospinning method on an H2O2-sensitive modified glassy carbon electrode. Glucose oxidase was immobilized on the glutaraldehyde-activated blend nanofibers. Bioelectrochemical electrode displayed a good linear response to the glucose concentration ranges with two separate calibration curves, from 2 to 8 mmol L-1 and from 10 to 30 mmol L-1. Besides, it showed a high anti-interference performance against ascorbic and uric acids as well as long-term storage stability over 63 days. Moreover, analysis results in a diluted human serum sample showed that the prepared bioelectrochemical electrode has the ability to measure glucose in real samples.
Synthesis and characterization of thermo/pH-sensitive pectin-graft-poly (dimethylaminoethyl methacrylate) coated magnetic nanoparticles
(ELSEVIER, 2020) Isiklan, Nuran; Polat, Sevim
Herein, thermo- and pH-sensitive pectin-graft-poly(dimethylaminoethyl methacrylate) copolymer-coated magnetic nanoparticles were synthesized via a green and rapid synthetic approach based on microwave irradiation. Firstly, a novel thermo- and pH-sensitive pectin-graft-poly(dimethylaminoethyl methacrylate) copolymer (Pec-g-PolyDMAEMA) was synthesized and then, Pec-g-PolyDMAEMA based magnetic nanoparticles (Pec-g-PolyDMAEMA@Fe3O4) were produced via microwave-assisted co-precipitation method. The thermo/pH/magnetic field multi-sensitive hybrid nanoparticle was characterized by techniques like TEM, VSM, FT-IR, and TGA/DSC. In vitro release studies of 5-Fluorouracil (FL) were carried out by altering the temperature (37 and 44 degrees C), pH (5.5 and 7.4) and presence of an AMF. The FL release of Pec-g-PolyDMAEMA@Fe3O4@FL exhibited pH-sensitive behavior. They showed thermo/pH-sensitive FL release features with the greatest release of FL at 37 degrees C (56%) than at 44 degrees C (40%) and at pH of 7.4 (63%) than at pH of 5.5 (45%) within 48 h. The FL release was also significantly increased (100%) with the presence of a 50 mT magnetic field. These results indicate that the developed Pec-g-PolyDMAEMA@Fe3O4 nanoparticles are promising in the application of multi-stimuli-sensitive delivery of drugs. (C) 2020 Elsevier B.V. All rights reserved.
Novel magnetic gel beads based on ionically crosslinked sodium alginate and polyanetholesulfonic acid: Synthesis and application for adsorption of cationic dyes
(ELSEVIER SCIENCE SA, 2020) Metin, Ayşegül Ülkü; Doğan, Deniz; Can, Muzaffer
This study offers novel magnetic gel beads as an adsorbent containing bifunctional groups for cationic dye removal. The bifunctional composite gel beads were prepared from polyanetholesulfonic acid, alginate and magnetic zeolite (m-ALG/PESA), and characterized by FESEM-EDS, XRD, VSM, and TGA-FTIR. The adsorption capability of m-ALG/PESA beads was described using methylene blue (MB) and malachite green (MG). The maximum adsorption capacities of MB and MG onto m-ALG/PESA gel beads were 400 mg/g and 164 mg/g, respectively. Regeneration and reusability studies showed that both dyes were successfully desorbed from mALG/PESA gel beads with removal percentages approximately 90 in the first cycle and magnetic gel beads maintained their shapes after 10 times adsorption/desorption cycles in highly acidic conditions. It was also observed that MG was degraded during the desorption process. Therefore, the magnetic gel beads can be considered as a regenerable adsorbent making to the adsorption process is cost-effective and it is also biodegradable and environment-friendly material when used in pilot-scale applications.
Crystal Structure of Tertiarybutyl Ammonium Bis[(naphthalene-2,3-diolato)borate] Dimethyl Sulfoxide Solvate
(Japan Soc Analytical Chemistry, 2019) Tombul, Mustafa
The structure of tertiarybutyl ammonium bis[naphthalene-2,3-diolato)borate] dimethyl sulfoxide solvate was determined by X-Ray crystallography. The compound crystallized in a triclinic system, and was characterized to be in the space group P-1, with cell parameters a = 9.6282(9)angstrom, b = 11.0221(9)angstrom, c = 13.0273(12)angstrom, alpha = 91.050(4)(0), beta = 109.419(4)(0), gamma = 94.574(2)(0), Z = 2, and V = 1298.2(2)angstrom(3). The crystal packing is governed by intermolecular and intramolecular N-H center dot center dot center dot O hydrogen bonds. The B atom takes a distorted tetrahedral geometry with four O atoms of naphthalene-2,3-diolato ligands.
Development and characterization of dual sensitive poly(N,N-diethyl acrylamide) grafted alginate microparticles
(Elsevier Science Bv, 2019) Isiklan, Nuran; Altinisik, Zeynep
Temperature and pH dual sensitive materials have attracted much interest in the fields of tissue engineering and drug delivery. In this study, a novel temperature and pH dual sensitive poly(N,N-diethyl acrylamide) grafted alginate (A-g-PDEA) microparticles were developed for 5-fluorouracil (5-FU) delivery. The structures of 5-FU loaded A-g-PDEA microparticles were characterized by FTIR, DSC, SEM, and XRD analyses. The effect of PDEA grafting percentage, temperature and pH on the swelling ratio and the release of 5-FU was explored. The obtained results displayed that the 5-FU release was controlled by both the temperature and pH of the medium. Furthermore, A-g-PDEA microparticles demonstrated a sustained release of 5-FU compared to free 5-FU. Moreover, the 5-FU release and swelling ratio of A-g-PDEA microparticles decreased with the increase in grafting percentage, crosslinking time and 5-FU/copolymer ratio. All the results indicated that A-g-PDEA microparticles are promising candidates for the sustained and controlled delivery of drugs.
Development of thermo/pH-responsive chitosan coated pectin-graft-poly(N, N-diethyl acrylamide) microcarriers
(Elsevier Sci Ltd, 2019) Isiklan, Nuran; Tokmak, Seyma
Pectin based micro/nanocarriers display promising properties for biomedical applications. In this study, thermo/pH-responsive chitosan coated pectin-graft-poly(N,N-diethyl acrylamide) (Pec-g-PDEAAm/CS) microcarriers containing 5-Fluorouracil (5-FU) as a model drug were developed. The structure, thermal stability and surface morphology of 5-FU-loaded microcarriers were investigated using FTIR, XRD, DSC and SEM. Microcarrier formulations were fabricated by varying grafting yield, drug/copolymer ratio, chitosan, and crosslinking agent concentrations. The effect of these parameters on swelling degree and 5-FU release was explored. It was observed that the grafting of pectin with poly(N,N-diethyl acrylamide) ensured sustained/controlled and thermo/pH responsive release of 5-FU. Besides, in vitro cytotoxicity results displayed that Pec-g-PDEAAm/CS microcarriers had good biocompatibility. Results illustrated that 5-FU release and swelling degree of the microcarriers were greatly controlled by especially chitosan shell, 5-FU/copolymer ratio and crosslink density. Therefore, based on the findings the developed thermo/pH-responsive Pec-g-PDEAAm/CS microcarriers might be considered as a promising carrier for controlled drug delivery.
Highly porous NiO/poly(DVB)HIPE nanocomposites for asphaltene removal: synthesis, kinetics, and thermodynamic studies
(Springer, 2019) Ozker, Taner; Cetinkaya, Sevil
Asphaltene precipitation is one of the most important problems of the petroleum industry. Asphaltene collapses during petroleum processing and extraction from the well, blocking the pipes and causing many problems. For this reason, asphaltene should be removed from heavy crude oils to improve the quality of oil and prevent asphaltene deposition. In this study, for the first time, highly porous new polyHIPE nanocomposites containing NiO nanoparticles (NPs) have been prepared for asphaltene removal. The open-celled new poly(DVB)HIPE nanocomposites were synthesized by the polymerization of monomers in the external phase of water-in-oil emulsions containing NiO NPs in the organic phase. The highest surface area was obtained at 5 wt% of NiO NP loading (367 m(2)/g). The adsorption of asphaltenes from toluene solutions onto NiO/poly(DVB)HIPE nanocomposite was investigated in detail. Maximum adsorption was obtained as 384.6 mg/g at a temperature of 298 K for NiO/poly(DVB)HIPE nanocomposite. The Freundlich, Langmuir, and Temkin isotherm models were used to correlate the adsorption data of asphaltenes on NiO/poly(DVB)HIPE nanocomposite and adsorption constants of these models were calculated. The Freundlich and Langmuir gave better results at different temperatures. The pseudo-second-order kinetic model provided the best correlation with the experimental data (R-2 >= 0.997). The results of the thermodynamic experiments showed that the adsorption was spontaneous and exothermic. It is concluded that the polyHIPE nanocomposites are important for the oil industry owing to having potential use as an adsorbent.
Efficient Two Step Synthesis for Trimethylsiloxy-Functionalized New Polymers
(Springer, 2019) Cetinkaya, Sevil; Yasar, Emine
We have presented an efficient strategy for the synthesis of trimethylsiloxy end-functionalized new polymers using ring-opening metathesis polymerization with ruthenium initiator, [(PCy3)(2)Cl2Ru=CHPh]. The key steps for the new silicon containing end-capped polymers are: In the first step, direct end-capping is carried out by adding cis-2-butene-1,4-diol to the ring-opened norbornene dicarboximides. In the second step, the reaction of hydroxy-functionalized polymers with trimethylsilyl chloride gives trimethylsiloxy-functionalized polymers. The best results for the end group introduction are achieved by reacting the living chains with an excess of the terminating agent. The molecular and structural features of the obtained polymers were confirmed by NMR and GPC analyzes, and their thermal properties were investigated by DSC. End-functionalization efficiency values were determined by NMR spectroscopy.

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