Synthesis of 2‐(9H‐carbazole‐9‐yl)ethyl methacrylate: Electrochemical impedance spectroscopic study of poly(2‐(9H‐carbazole‐9‐yl)ethyl methacrylate) on carbon fiber

In this contribution, 2‐(9H‐carbazol‐9‐yl) ethyl methacrylate (CzEMA) monomer was chemically synthesized. The monomer characterization was performed by FT‐IR, ¹H‐NMR, ¹³C‐NMR, and melting point analysis. The electropolymerization of CzEMA was studied onto carbon fiber microelectrodes (CFMEs) as an active electrode material in 0.1M sodium perchlorate (NaClO₄)/acetonitrile (ACN) solution. The electropolymerization experiments were done from 1 mM to 10 mM. The detailed characterization of the resulting electrocoated Poly (CzEMA)/CFME thin films was studied by various techniques, i.e., cyclic voltammetry (CV), Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The effects of initial monomer concentrations (1, 3, 5, and 10 mM) during the preparation of modified electrodes were examined by EIS. Capacitive behaviors of modified CFMEs were defined via Nyquist, Bode‐magnitude, and Bode‐phase plots. Variation of capacitance values by initial monomer concentration and specific capacitance values are presented. The highest specific capacitance value electrocoated polymer thin film by CV method in the initial monomer concentration of 5 mM with a charge of 52.74 mC was obtained about 424.1 μF cm^?2. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphological and impedance studies on electropolymerized 3,4-(2,2-dibenzylpropylenedioxy)thiophene nanostructures on micron sized single carbon fiber

Micron sized single carbon fibers were cyclovoltammetrically coated with poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] resulting in a nanofiber network at the surface. The method provides conjugated polymer nanostructures covalently and uniformly bound to micron sized substrates. When the electropolymerization is carried out with different electrolytes in acetonitrile the dopant influences the structure of the coating layer what is proved by electrochemical impedance spectroscopy and electron microscopy. Electrodes based on poly[3,4-(2,2-dibenzylpropylenedioxy)thiophene] on single carbon fiber microelectrodes (SCFMEs) prepared in Bu₄NPF₆/ACN show the best capacitance performance due to their higher surface area. The improvement is attributed to the formed nanofiber network structure which results in a more efficient charge transport and collection.     

Synthesis and characterization of mid-chain macrophotoinitiator of poly(ε-caprolactone) by combination of ROP and click chemistry

Well-defined mid-chain functional macrophotoinitiator of poly(ε-caprolactone) (PCL-PI-PCL) was synthesized by combination of ring-opening polymerization (ROP) and click chemistry strategy. Dibromo functional photoinitiator (Br–PI–Br) was prepared by the condensation of 2-bromopropanoyl bromide with 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl propan-1-one (PI). Subsequently, terminal bromo groups in Br–PI–Br were converted to azido groups to form diazido functional photoinitiator (N₃–PI–N₃) using NaN₃. Well-defined precursor alkyne-functionalized PCL (alkyne-PCL) was prepared by ROP of ε-CL in the presence of propargyl alcohol as the initiator and stannous-2-ethylhexanoate (Sn(Oct)2) as the catalyst. Finally, the alkyne-functionalized PCL was coupled with N₃–PI–N₃ with high efficiency by click chemistry. The spectroscopic studies showed that low-polydispersity PCL with desired photoinitiator functionality in the middle of the chain was obtained.     

Carbothermic reduction synthesis of calcium hexaboride using PVA-calcium hexaborate mixed gels

In this study, PVA-CaB₆O₁₀·5H₂O precursor mixtures were prepared by coating the ceramic powders with PVA to synthesize CaB₆ via carbothermal reduction. Boron loss, the main problem in the synthesis of borides, was reduced by the use of metastable CaB₆O₁₀ as a transitional phase which is stable until the critical temperature ranges where the boron sub-oxides have higher volatilities. To minimize boron loss, due to the high hydrophilicity and ability to form cross-linked PVA-borate gels, PVA was used as a carbon source and carbon coating process was carried out via pyrolysis of the PVA - CaB₆O₁₀·5H₂O mixed gels. The effect of the molecular weight of PVA on the CaB₆ synthesis was also studied. Because of highly efficient interaction of CaB₆O₁₀·5H₂O with the PVA60-water solution, PVA60 was found to be the optimal carbon source. The CaB₆O₁₀·5H₂O-PVA60 composite powder was characterized by using Fourier transform infrared spectroscopy (FTIR) and the effect of molecular weight of the PVA’s on the thermal characteristics of mixed powders were analyzed by using simultaneous thermal analysis (STA). The effect of carbothermic reduction temperature and dwell time on the phase formation were examined via x-ray diffractometer (XRD) and scanning and transmission electron microscopy (SEM and TEM) techniques. The optimum synthesis conditions were determined for the formation of CaB₆ as 1450ºC for 12 h under an Argon flow by using the CaB₆O₁₀·5H₂O-PVA60 mixed precursor.     

Synthesis of the intermetallic clathrate Na2Ba6Si46 by oxidation of Na2BaSi4 with HCl

A new preparation route to the intermetallic clathrate-I compound Na₂Ba₆Si₄₆ is introduced, which allows one to make large amounts of product with standard laboratory equipment. The precursor Na₂BaSi₄ is oxidized with gaseous HCl at 673 K to Na₂Ba₆Si₄₆, NaCl and BaCl₂. Full-profile refinement of the crystal structure from the X-ray powder diffraction data revealed a composition close to Na₂Ba₆Si₄₆ (Na_1.94(1)Ba_6.06(1)Si₄₆, space group , a=10.281(1) Å). Differential scanning calorimetry showed an exothermic effect at 874 K, indicating that Na₂Ba₆Si₄₆ is metastable. The product was additionally characterized by scanning electron microscopy. The electronic structure of Na₂Ba₆Si₄₆ was investigated by a first-principles, all-electron full-potential method, predicting metallic conductivity. Na₂Ba₆Si₄₆ obtained by oxidation with HCl shows Pauli paramagnetism; no bulk superconductivity was found down to 1.8 K in a magnetic field of 20 Oe.     

Formation kinetics of radiolytic lipid products in model food–lipid systems with gamma irradiation

Irradiation processes can change the lipid composition of foods. The major lipid radiolysis products are known to be 2-alkylcyclobutanones and hydrocarbons, the formation kinetics of which is determined by the chemical nature of the inherent lipids. This information can be used to evaluate the irradiation history of lipid-rich foods. A solid-phase microextraction (SPME)-assisted gas chromatography–mass spectrometry (GC–MS) technique was used to study the formation of volatile hydrocarbons and 2-dodecylcyclobutanone (2-DCB), a cyclobutanone formed from the esters of palmitic acid, in irradiated (0–50 kGy) tripalmitin and chicken fat. Thirty-three volatile compounds (hydrocarbons, aldehydes, ketones) increased with irradiation dose to varying extents. Six major lipid radiolysis products were selected to analyze their formation kinetics: tridecane, 1-tetradecene, tetradecane, 1-pentadecene, pentadecane, and 2-DCB. The concentration of the selected compounds increased linearly with irradiation dose following zeroth-order kinetics, except for tridecane and tetradecane in tripalmitin, formation of which followed first-order kinetics. The formation rate of hydrocarbons was higher in tripalmitin than in chicken fat (5× higher for pentadecane), while 2-DCB formed faster (3.5×) in chicken fat than in tripalmitin. This difference was related to the diversity in the natural fatty acid composition of chicken fat as compared to the homogeneous structure of tripalmitin. The results of this study indicate that the concentrations of palmitic acid radiolysis products linearly increase with irradiation dose in general to offer potential to back-trace irradiation dose in lipid-rich foods.