Comparison of pre-irradiation and mutual grafting of 2-chloroacrylonitrile on cellulose by gamma-irradiation

Radiation-induced graft polymerization is one of the best methods for obtaining materials with new properties. In this work, radiation grafting of 2-chloroacrylonitrile to cellulose by mutual and pre-irradiation grafting methods was investigated. The grafting yield was enhanced by applying the emulsion grafting method. The grafting yield determined in the above systems was observed as 27% at highest and 6% at lowest. The effects of concentration of monomer, reaction time and reaction temperature on grafting yield were studied. Evidence of grafting has been based on the comparative studies of cellulose and grafted cellulose by infrared spectroscopy, thermal analysis and contact angle measurement. Grafting enhances thermal stability of cellulose backbone.     

Determination of Total Antioxidant Capacity by a New Spectrofluorometric Method Based on Ce(IV) Reduction: Ce(III) Fluorescence Probe for CERAC Assay

A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized acidic sulphate medium (i.e., 0.3 M H₂SO₄ and 0.7 M Na₂SO₄) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10⁻⁷–1.0 × 10⁻⁵ M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox, quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine. The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those found by reference methods such as ABTS and CUPRAC.     

Synthesis and Spectroscopic Characterization of Fluorescent Boron Dipyrromethene-Derived Hydrazones

Derivatives of 4,4-difluoro-4-bora-3a,4a,diaza-s-indacene (BODIPY? or BDP) that possess a hydrazine substituent on position 5 are potential "turn-on" fluorophores for labeling aldehydes The unnatural amino acid L-3-formyltyrosine can be incorporated into a protein or peptide; thus, these hydrazines are potentially site specific labels for such polymers. In this work, model compounds were synthesized to assess whether the photochemical properties of the BDP-hydrazone would be suitable for protein labeling. Hydrazones were synthesized from the fluorophore 3-chloro-5-hydrazino-BDP and different aldehydes, and the absorption and emission spectra of the products were compared. The hydrazone of an unsubstituted aromatic aldehyde displays absorption and emission maxima (531 nm and 559 nm, respectively in dioxane) that are red shifted relative to those of a hydrazone from an aliphatic aldehyde (513 nm and 543 nm, respectively, in dioxane) and an increased quantum yield (0.21 vs. 0.11, respectively, in dioxane). The presence of a hydroxyl group ortho- to the aldehyde produces a hydrazone in which the absorption and emission maxima are slightly red shifted (528 nm and 564 nm, respectively in dioxane) from the unsubstituted aromatic hydrazone, but the quantum yields of the two hydrazones are equivalent. Thus, an ortho-hydroxy substituted aromatic aldehyde is a suitable electrophile for "turn on" protein labeling using the hydrazino-BDP. The specificity of this labeling reaction for the unnatural amino acid was demonstrated through fluorescent labeling of just the 3-formyltyrosine-containing α-subunit of α,β-tubulin.     

Enhanced optical absorption in nanopatterned silicon thin films with a nano-cone-hole structure for photovoltaic applications

In this paper, the optical properties of the silicon nano-cone-hole (NCH) structure array are studied. The ultimate efficiency of the optimized NCH array is enhanced by 23.11% compared to an optimized nanohole array of the same thickness. The absorptance enhancement of the NCH arrays is attributed to its lowered reflectance, more supported resonant modes, and enhanced mode interaction. The angular dependence of ultimate efficiency is also investigated.     

Optimizing the Simplon railway corridor

This paper presents a case study of a railway timetable optimization for the very dense Simplon corridor, a major railway connection in the Alps between Switzerland and Italy. The key to deal with the complexity of this scenario is the use of a novel aggregation-disaggregation method. Starting from a detailed microscopic representation as it is used in railway simulation, the data is transformed by an automatic procedure into a less detailed macroscopic representation, that is sufficient for the purpose of capacity planning and amenable to state-of-the-art integer programming optimization methods. This macroscopic railway network is saturated with trains. Finally, the optimized timetable is re-transformed to the microscopic level in such a way that it can be operated without any conflicts among the train paths. Using this micro-macro aggregation-disaggregation approach in combination with integer programming methods, it becomes for the first time possible to generate a profit maximal and conflict free timetable for the complete Simplon corridor over an entire day by a simultaneous optimization of all trains requests. In addition, this also allows us to undertake a sensitivity analysis of various problem parameters.     

Palladium(II)?NHC complexes containing benzimidazole ligand as a catalyst for C?N bond formation

The reaction of 2‐(2‐bromoethyl)‐1,3‐dioxane with 1‐alkylbenzimidazole derivatives results in the formation of the new benzimidazolium salts (1). The reaction of Pd(OAc)₂ with 1,3‐dialkylbenzimidazolium salts (1a–c) yields palladium N‐heterocyclic carbene (NHC) complexes (2a–c). All synthesized compounds were characterized by ¹H NMR, ¹³ C NMR, IR and elemental analysis techniques which support the proposed structures. As catalysts, these new palladium complexes offer a simple and efficient methodology for the synthesis of triarylamines and secondary amines from anilines and amines and in a single step with potassium tertiary butoxide as a base. Copyright © 2010 John Wiley & Sons, Ltd.     

Urea dimethacrylates functionalized with bisphosphonate/bisphosphonic acid for improved dental materials

Incorporation of bisphosphonate/bisphosphonic acid groups in dental monomer structures should increase interaction of these monomers with dental tissue as these groups have strong affinity for hydroxyapatite. Therefore, new urea dimethacrylates functionalized with bisphosphonate (1a, 1b) and bisphosphonic acid (2a, 2b) groups are synthesized and evaluated for dental applications. Monomers 1a and 1b are synthesized from 2‐isocyanatoethyl methacrylate (IEM) and two bisphosphonated amines (BPA1 and BPA2), prepared as reported elsewhere. Selective dealkylation of the bisphosphonate ester groups of 1a and 1b using trimethylsilyl bromide (TMSBr) gives monomers (2a and 2b) with bisphosphonic acid functionality. X‐ray diffractometer (XRD), Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS) analyses of monomer‐treated HAP particles show that 2a induces formation of stable monomer‐calcium salts, similar to 10‐methacryloyloxydecyl dihydrogen phosphate (MDP), with higher chemical interaction than 2b. The photopolymerization studies indicate good copolymerizability with commercial dental monomers. In vitro studies on NIH 3T3 mouse embryonic fibroblast cells have clearly shown that the tested monomers (1b and 2b) are not toxic according to the MTT standards. All these properties make these monomers suitable as biocompatible cross‐linkers/adhesives for dental applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3195–3204     

Synthesis and characterization of a methacrylate polymer with side chain ketone and its derivatives

A new type of methacrylate monomer,2-(4-benzoylphenoxy)-2-oxoethyl methylacrylate(BOEMA) was synthesized.The radical homopolymerization of BOEMA was performed at 65℃in a 1,4-dioxane solution with benzoyl peroxide as an initiator.The oxime and thiosemicarbazone derivatives of poly[2-(4-benzoylphenoxy)-2-oxoethyl methylacrylate]poly(BOEMA) were prepared with hydroxylamine hydrochloride,and thiosemicarbazone hydrochloride, respectively.The monomer and its homopolymer were characterized with Fourier transform infrared and NMR techniques. The thermal stabilities of poly(BOEMA) and its derivatives were investigated with thermogravimetric analysis and differential scanning calorimetry.The ultraviolet stability of the polymers was compared.The antibacterial and antifungal effects of the monomer and the polymer and its derivatives were also investigated on various bacteria and fungi.The activation energies of the thermal degradation of the polymers were calculated with the Ozawa and Kissinger methods.