Determination of the reactivity ratios for the oxidative copolymerizations of indene with methyl, ethyl and butyl acrylates

Full Paper: The copolyperoxides of various compositions of indene with methyl acrylate, ethyl acrylate and butyl acrylate have been synthesized by the free-radical-initiated oxidative copolymerization. The compositions of copolyperoxide obtained from H-1 and C-13 NMR spectra have been used to determine the reactivity ratios of the monomers. The copolyperoxides contain a greater proportion of the indene units in random placement. The NMR studies have shown irregularities in the copolyperoxide chain due to the cleavage reactions of the propagating peroxide radical. The thermal analysis by differential scanning calorimetry suggests alternating peroxide units in the copolyperoxide chain. From the activation energy for the thermal degradation, it was inferred that degradation occurs via the dissociation of the peroxide (O-O) bonds of the copolyperoxide chain. The flexibility of the polyperoxides in terms of glass transition temperature (T-g) has also been examined.

Optical, electrical and dielectric properties of TiO(2)-SiO(2) films prepared by a cost effective sol-gel process

Titanium dioxide (TiO(2)) and silicon dioxide (SiO(2)) thin films and their mixed films were synthesized by the sol-gel spin coating method using titanium tetra isopropoxide (TTIP) and tetra ethyl ortho silicate (TEOS) as the precursor materials for TiO(2) and SiO(2) respectively. The pure and composite films of TiO(2) and SiO(2) were deposited on glass and silicon substrates. The optical properties were studied for different compositions of TiO(2) and SiO(2) sols and the refractive index and optical band gap energies were estimated. MOS capacitors were fabricated using TiO(2) films on p-silicon (1 0 0) substrates. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied and the electrical resistivity and dielectric constant were estimated for the films annealed at 200 degrees C for their possible use in optoelectronic applications. (C) 2011 Elsevier B.V. All rights reserved.

Nanocrystalline TiO(2) preparation by microwave route and nature of anatase-rutile phase transition in nano TiO(2)

Nanopowders of TiO(2) has been prepared using a microwave irradiation-assisted route, starting from a metalorganic precursor, bis(ethyl-3-oxo-butanoato)oxotitanium (IV), [TiO(etob)(2)](2). Polyvinylpyrrolidone (PVP) was used as a capping agent. The as-prepared amorphous powders crystallize into anatase phase, when calcined. At higher calcination temperature, the rutile phase is observed to form in increasing quantities as the calcination temperature is raised. The structural and physicochemical properties were measured using XRD, FT-IR, SEM, TEM and thermal analyses. The mechanisms of formation of nano-TiO(2) from the metal-organic precursor and the irreversible phase transformation of nano TiO(2) from anatase to rutile structure at higher temperatures have been discussed. It is suggested that a unique step of initiation of transformation takes place in Ti(1/2)O layers in anatase which propagates. This mechanism rationalizes several key observations associated with the anatase rutile transformation.

Molecular structures and antiproliferative activity of side-chain saturated and homologated analogs of 2-chloro-3-(n-alkylamino)-1,4-napthoquinone

Side chain homologated derivatives of 2-chloro-3-(n-alkylamino)-1,4-naphthoquinone {n-alkyl: pentyl; L-5, hexyl; L-6, heptyl; L-7 and octyl; L-8} have been synthesized and characterized by elemental analysis, FT-IR, H-1 NMR, UV-visible spectroscopy and LC-MS. Compounds, L-4, n-alkyl: butyl; L-4}, L-6 and L-8 have been characterized by single crystal X-ray diffraction studies. The single crystal X-ray structures reveal that L-4 and L-8 crystallizes in P2(1) space group, while L-6 in P2(1)/c space group. Molecules of L-4 and L-8 from polymeric chains through C-H center dot center dot center dot O and N-H center dot center dot center dot O close contacts. L-6 is a dimer formed by N-H center dot center dot center dot O interaction. Slipped pi-pi stacking interactions are observed between quinonoid and benzenoid rings of L-4 and L-8. Orientations of alkyl group in L-4 and L-8 is on same side of the chain and polymeric chains run opposite to one another to form zip like structure to the alkyl groups. Antiproliferative activities of L-1 to L-8{n-alkyl: methyl; L-1, ethyl; L-2, propyl; L-3 and butyl; L-4} were studied in cancer cells of colon (COLO205), brain (U87MG) and pancreas (MIAPaCa2) where L-1, L-2 and L-3 were active in MIAPaCa2 (L-1 = 1-2 > L-3) and COLO205 (L-2 = L-3 > L-1) and inactive in U87MG. From antiproliferative studies with compounds L-1 to L-8 it can be concluded that homologation of 2-chloro-3-(n-alkylamino)-1,4-napthoquinone with saturated methyl groups yielded tissue specific compounds such as L-2 (for MIAPaCa2) and L-3 (for COLO205) with optimal activity. (c) 2013 Elsevier B.V. All rights reserved.

2-(Phenylazo)pyridineplatinum(II) Catecholates Showing Photocytotoxicity, Nuclear Uptake, and Glutathione-Triggered Ligand Release

Platinum(II) complexes Pt(pap)(an-cat)] (1) and Pt(pap)(py-cat)] (2) with 2-(phenylazo)pyridine (pap), 4-2-(anthracen-9-ylmethylene)amino]ethyl]benzene-1,2-diol (H(2)an-cat), and 4-2-(pyren-1-ylmethylene)amino]ethyl]benzene-1,2-diol (H2py-cat) were prepared, and their photoinduced cytotoxicity was studied. The complexes were found to release catecholate ligand in the presence of excess glutathione (GSH), resulting in cellular toxicity in the cancer cells. The catecholate complex Pt(pap)(cat)] (3) was prepared and used as a control. Complex 3, which is structurally characterized by X-ray crystallography, has platinum(II) in a distorted square-planar geometry. The complexes are redox-active, showing responses near 0.6 and 1.0 V versus SCE in N,N-dimethylformamide/0.1 M tetrabutylammonium perchlorate corresponding to a two-step catechol oxidation process and at -0.3 and -1.3 V for reduction of the pap ligand. Complex 1 showed remarkable light-induced cytotoxicity in HaCaT (human skin keratinocytes) and MCF-7 (human breast cancer) cells, giving IC50 value of similar to 5 mu M in visible light of 400-700 nm and >40 mu M in the dark. The 2',7'-dichlorofluorescein diacetate (DCFDA) assay showed the generation of reactive oxygen species (ROS), which seems to trigger apoptosis, as is evident from the annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) assay. The fluorescence microscopic images showed significant nuclear localization of the complexes and free ligands. A mechanistic study revealed possible reduction of the coordinated azo bond of pap by cellular GSH, releasing the catecholate ligand and resulting in remarkable photochemotherapeutic action of the complexes.

Carfentrazone-ethyl Pond Dissipation and Efficacy on Floating Plants

Carfentrazone-ethyl (CE) is a reduced risk herbicide that is currently being evaluated for the control of aquatic weeds. Greenhouse trials were conducted to determine efficacy of CE on water hyacinth ( Eichhornia crassipes (Mart.) Solms- Laub.), water lettuce ( Pistia stratiotes L.), salvinia ( Salvinia minima Baker) and landoltia (Landoltia punctata (G. Mey.) Les & D. J. Crawford ) . CE controlled water lettuce, water hyacinth and salvinia at rates less than the maximum proposed use rate of 224 g ha -1 . Water lettuce was the most susceptible to CE with an EC 90 of 26.9 and 33.0 g ha -1 in two separate trials. Water hyacinth EC 90 values were calculated to be 86.2 to 116.3 g ha -1 , and salvinia had a similar susceptibility to water hyacinth with an EC 90 of 79.1 g ha -1 . Landoltia was not adequately controlled at the rates evaluated. In addition, CE was applied to one-half of a 0.08 ha pond located in North Central, Florida to determine dissipation rates in water and hydrosoil when applied at an equivalent rate of 224 g ha -1 . The half-life of CE plus the primary metabolite, CE-chloropropionic acid, was calculated to be 83.0 h from the whole pond, and no residues were detected in water above the limit of quantification (5 μg L -1 ) 168 h after treatment. CE dissipated rapidly from the water column, did not occur in the sediment above the levels of quantification, and in greenhouse studies effectively controlled three species of aquatic weeds at relatively low rates.(PDF contains 6 pages.)

Preparação e Avaliação da Atividade Catalítica de Polímeros de Condensação de Metilpiridinas e Tereftalaldeído em Reações de Nitroaldol e Cicloadição Heterodipolar [3+2]

Nesse estudo, foram preparadas bases poliméricas derivadas de 2,6-dimetilpiridinas e tereftaladeído utilizando a 2,4,6-trimetilpiridina como agente de reticulação. As resinas foram sintetizadas sob aquecimento convencional e purificadas por precipitação em metanol, apresentando rendimentos variando de 59 a 95%. Os copolímeros produzidos foram caracterizados por análise termogravimétrica (TGA), ressonância nuclear magnética de núcleo de hidrogênio (RMN-1H) e espectroscopia na região do infravermelho com técnica de ATR (FTIR - ATR), além de sua atividade básica. A capacidade catalítica do material produzido foi avaliada em reações nitroaldólicas, do tipo Henry, tanto em aquecimento convencional quanto com o uso de reator de micro-ondas. Não sendo observada atividade catalítica significativa para as resinas testadas, nestas reações. O material polimérico produzido também foi testado como suporte para cobre na catálise de reações de cicloadição heterodipolar do tipo [3+2] com benzilazida e propiolato de etila, para a formação de triazóis, processadas em reator de micro-ondas e sob aquecimento convencional. A reação mostrou-se regiosseletiva e processos de reciclo do catalisador se mostrou eficiente em reações consecutivas

Chiral Salan Aluminium Ethyl Complexes and Their Application in Lactide Polymerization

Synthetic routes to aluminium ethyl complexes supported by chiral tetradentate phenoxyamine (salan-type) ligands [Al(OC6H2(R-6-R-4)CH2)(2){CH3N(C6H10)NCH3}-C2H5] 7: R = H ; 5, 8: R = Cl; 6, 9: R = CH3) are reported. Enantiornerically pure salan ligands 1-3 with (R,R) configurations at their cyclohexane rings afforded the complexes 4, 5, and 6 as mixtures of two diastereoisomers (a and b). Each diastereoisomer a was, as determined by X-ray analysis, monomeric with a five-coordinated aluminium central core in the solid state, adopting a cis-(O,O) and cis-(Me,Me) ligand geometry. From the results of variable-temperature (VT) H-1 NMR in the temperature range of 220-335 K, H-1-H-1 NOESY at 220 K, and diffusion-ordered spectroscopy (DOSY), it is concluded that each diastereoisomer b is also monomeric with a five-coordinated aluminium central core.

Soluble neodymium chloride 2-ethylhexanol complex as a highly active catalyst for controlled isoprene polymerization

Soluble NdCl3 center dot 3EHOH (2-ethyl hexanol) in hexane combined with AlEt3 is highly active for isoprene polymerization in hexane. The NdCl3 center dot 3EHOH/AlEt3 has higher activity than the typical binary catalyst NdCl3 center dot 3(i)PrOH (isopropanol)/AlEt3 and ternary catalyst NdV3 (neodymium versatate)/AlEt2Cl/Al(i-Bu)(2)H. The molecular weight of polyisoprenes can be controlled by variation of [Nd], [Al]/[Nd] ratio and polymerization temperature and time. The NdCl3 center dot 3EHOH/AlEt3 catalyst polymerized isoprene to afford products featuring high cis-1,4 stereospecificity (ca. 96%), high molecular weight (ca. 10(5)) and relatively narr ow molecular weight distributions (M-w/M-n = 2.0-2.8) simultaneously. More importantly, some living polymerization characteristics were demonstrated: (a) absence of chain termination; (b) linear correlation between M-n and polymer yield; (c) increment of molecular weight in the 'seeding' polymerization. Though some deviation from the typical living polymerization such as molecular weight distribution is not narrow enough and the line of M-n and polymer yield does not extrapolate to zero, controlled polymerization with the current catalyst can still be concluded.

Preparation and characterization of poly(ethyl acrylate)/bentonite nanocomposites by in situ emulsion polymerization

Transparent poly(ethyl acrylate) (PEA)/bentonite nanocomposites containing intercalated-exfoliated combinatory structures of clay were synthesized by in situ emulsion polymerizations in aqueous dispersions containing bentonite. The samples for characterization were prepared through direct-forming films of the resulting emulsions without coagulation and separation. An examination with X-ray diffraction and transmission electron microscopy showed that intercalated and exfoliated structures of clay coexisted in the PEA/bentonite nanocomposites. The measurements of mechanical properties showed that PEA properties were greatly improved, with the tensile strength and modulus increasing from 0.65 and 0.24 to 11.16 and 88.41 MPa, respectively. Dynamic mechanical analysis revealed a very marked improvement of the storage modulus above the glass-transition temperature. In addition, because of the uniform dispersion of silicate layers in the PEA matrix, the barrier properties of the materials were dramatically improved. The permeability coefficient of water vapor decreased from 30.8 x 10(-6) to 8.3 x 10(-6) g cm/cm(2)s cmHg. (C) 2002 Wiley Periodicals, Inc.

The miscibility of homopolymer random copolymer blends .1. Poly(styrene-co-acrylonitrile) poly(ethyl methacrylate) and poly(styrene-co-acrylonitrile) poly(methyl methacrylate) blends

The miscibility of blends of poly(styrene-co-acrylonitrile) (SAN) with poly(methyl methacrylate) (PMMA) or poly(ethyl methacrylate) (PEMA) has been investigated by means of NMR and DSC techniques. It is found that there are intermolecular interactions between the phenyl groups in SAN and carbonyl groups in PMMA or PEMA, and the strength of this intermolecular interaction strongly depends on the properties of ester side groups in PEMA or PMMA, composition of the blends and a certain composition of the copolymer. It is this specific interaction instead of the intramolecular repulsion force within the copolymer that plays a key role for the miscibility of SAN/PMMA and SAN/PEMA blends.

Pre-column derivatization of amines with 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl chloroformate followed by LC-fluorescence and LC-APCI-MS

A pre-column derivatization method for the sensitive determination of amines using the labeling reagent 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl chloroformate (BCIC-Cl) followed by high-performance liquid chromatography with fluorescence detection has been developed. Identification of derivatives is carried out by high performance liquid chromatography/atmospheric pressure chemical ionization (LC-APCl-MS-MS). The chromophore of 2-(9-carbazole)-ethyl chloroformate (CEOC) reagent is replaced by 1,2-benzo-3,4-dihydrocarbazole-9-isopropyl functional group, which results in a sensitive fluorescence derivatizing reagent BCIC-Cl. BCIC-Cl can easily and quickly label amines. Derivatives are stable enough to be efficiently analyzed by high-performance liquid chromatography and show an intense protonated molecular ion corresponding m/z [MH](+) under APCl in positive-ion mode. The collision-induced dissociation of protonated molecular ion formed a product at m/z 260 corresponding to the cleavage of CH2-OCO bond. Studies on derivatization demonstrate excellent derivative yields over the pH 9.0-10.0. Maximal yields close to 100% are observed with a 3 to 4-fold molar reagent excess. In addition, the detection responses for BCIC derivatives are compared with those obtained using CEOC and FMOC as derivatization reagents. The ratios of l(BCIC)/l(CEOC) and l(BCIC)/l(FMOC) are, respectively, 1.23-3.14 and 1.25-3.08 for fluorescent (FL) responses (here, l is relative fluorescence intensity). Separation of the derivatized amines had been optimized on reversed-phase Eclipse XDB-C-8 column. Detection limits are calculated from 1.0 pmol injection, at a signal-to-noise ratio of 3, are 10.6-37.8 fmol. The mean interday accuracy ranges from 94 to 105% for fluorescence detection with the largest mean %CV < 7.5. The mean interday precision for all standards is < 6.0% of the expected concentration. Excellent linear responses are observed with coefficients of > 0.9997.

2-(2-Phenyl-1H-phenanthro-[9,10-d]imidazole-1-yl)-acetic acid (PPIA) and its application for determination of amines by high performance liquid chromatography with fluorescence detection and identification with mass spectroscopy/atmospheric pressure chemical ionization

A simple, sensitive, and mild method for the determination of amino compounds based on a condensation reaction with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC-HCI) as the dehydrant with fluorescence detection has been developed. Amines were derivatized to their acidamides with labeling reagent 2-(2-phenyl-1H-phenanthro-[9,10-d]imidazole-1-yl)-acetic acid (PPIA). Studies on derivatization conditions indicated that the coupling reaction proceeded rapidly and smoothly in the presence of a base catalyst in acetonitrile to give the corresponding sensitively fluorescent derivatives with an excitation maximum at lambda(ex) 260nm and an emission maximum at lambda(em) 380nm. The labeled derivatives exhibited high stability and were enough to be efficiently analyzed by high-performance liquid chromatography. Identification of derivatives was carried out by online post-column mass spectrometry (LC/APCI-MS/MS) and showed an intense protonated molecular ion corresponding m/z [MH](+) under APCI in positive-ion mode. At the same time, the fluorescence properties of derivatives in various solvents or at different temperature were investigated. The method, in conjunction with a gradient elution, offered a baseline resolution of the common amine derivatives on a reversed-phase Eclipse XDB-C-8 column. LC separation for the derivatized amines showed good reproducibility with acetonitrile-water as mobile phase. Detection limits calculated from 0.78 pmol injection, at a signal-to-noise ratio of 3, were 3.1-18.2 fmol. The mean intra- and inter-assay precision for all amine levels were < 3.85% and 2.11%, respectively. Excellent linear responses were observed with coefficients of > 0.9996. The established method for the determination of aliphatic amines from real wastewater and biological samples was satisfactory. (c) 2006 Elsevier B.V. All rights reserved.

Simple derivatization method for sensitive determination of fatty acids with fluorescence detection by high-performance liquid chromatography using 9-(2-hydroxyethyl)-carbazole as derivatization reagent

A simple and sensitive method for the determination of short and long-chain fatty acids using high-performance liquid chromatography with fluorimetric detection has been developed. The fatty acids were derivatized to their corresponding esters with 9-(2-hydroxyethyl)-carbazole (HEC) in acetonitrile at 60 degreesC with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters of C-1-C-20 fatty acids was completely separated within 38 min in conjunction with a gradient elution on a reversed-phase C-18 column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (lambda (ex) 335 nm). Studies on derivatization conditions indicate that fatty acids react proceeded rapidly and smoothly with HEC in the presence of EDC and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility for fatty acids derivatives. The R.S.D. (n = 6) for each fatty acid derivative are <4%. The detection limits are at 45-68 fmol levels for C-14-C-20 fatty acids and even lower levels for