Víctor M. Chapela

Meritorious Autonomous University of Puebla, Ejido Puebla, Baja California, Mexico

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Publications (53)49.33 Total impact

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    ABSTRACT: Two novel ATRP initiator (R-X): 2-bromo-2-methyl-N-(1-phenyl-ethyl)propanamide (I) and 2,2,2-trichloro-N-(1-phenylethyl)acetamide (II) were synthesized and characterized by 1H-NMR, IR, EI. Also, crystal structures of (I) and (II) are reported. Compounds (I) and (II) were used in the ATRP reaction of methyl methacrylate (MMA) and acrylamide (AAD) at 48°C, using CuBr/Me6TREN and ethanol/toluene (60:40) mixture as catalytic complex and solvent, respectively. End-group analysis by 1H-NMR was used to determinate the molecular mass of the polymers synthesized via ATRP. The Mn values for poly(MMA) using (II) were 2333 and 3952 g/mol, which is higher in comparison with the Mn values obatined for (AAD)/(II) and (AAD)/(I) systems indicating that monomers containing ester moiety in their structure, such as acrylates and methacrylates, may be good candidates to polymerize with (II) and CuBr/Me6TREN.
    Macromolecular Symposia 05/2014; 339(1).
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    ABSTRACT: The structural characterisation of the molecule 1,4-bis[2-cyano-2-(o-pyridyl)ethenyl] benzene obtained through Knoevenagel condensation is reported. The single crystals, as light brown rods, were cultured from a chloroform solution using a slow evaporation method at ambient temperature. The compound crystallised in the monoclinic system belonging to the C2/c space group with a = 26.4556(9) Å, b = 3.73562(10) Å, c = 18.4230(6) Å, β = 109.841(4)° and the asymmetric unit comprising Z = 4. The structure is ordered and the molecules of the title compound exhibited a lattice with water molecules located at sites of inversion and two-fold axial symmetries. Thus, only halves of the molecules are symmetrically independent. The lattice is reported and contrasted with X-ray single-crystal diffraction and theoretical calculations of 1,4-bis(1-cyano-2-phenylethenyl)benzene. By using density functional theory (DFT) and second order Moller-Plesset (MP2) theoretical calculations, the ground state geometry in the whole molecule at the B3LYP/6-31+G(d,p), and MP2/6-31+G(d,p) theory levels, respectively, were optimised. The DFT calculations showed a quasi-planar structure of the molecule, whereas the wave function-based MP2 method afforded a non-planar optimised structure with significant torsion angles between the pyridine and phenyl rings.
    Chemical Papers- Slovak Academy of Sciences 02/2014; · 0.88 Impact Factor
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    ABSTRACT: The effect of the ratio of oxygen to carbon atoms (O/C) on the morphology of carbon nanostructures has been studied by varying the methanol and ethanol ratio in the reaction mixtures. Notable morphological differences in the synthesized carbon nanostructures are observed as a function of the O/C ratio. At a high O/C ratio, i.e., using methanol (O/C = 1), the synthesized carbon nanoshells (CNS) are faceted. Moreover, other faceted nanostructures, such as triangular and hexagonal, are observed in this strong oxidative environment. Decreasing the O/C ratio in the mixture by adding ethanol induces changes in the CNSs morphology; they are less faceted and favor only the growth of single-walled carbon nanotubes mixed with the CNSs. The importance of the O/C ratio is corroborated by replacing ethanol (O/C = 0.5) with polyethylene glycol (O/C = 0.5) in the methanol:ethanol reaction mixture. Finally, at very low O/C ratios, i.e., methanol:octanol mixtures, CNS are obtained and no faceted nanostructures or SWCNT are found. Thus, adjusting the O/C ratio is a method for obtaining high purity samples of CNS. Moreover, the use of the alcohols during the synthetic process is a simple and green method of functionalizing CNS.
    Carbon. 01/2014; 76:292–300.
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    ABSTRACT: The molecular structure and molecular interactions of an [small alpha],[small beta]-unsaturated nitrile, such as the interaction between adjacent molecules of (Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-2-yl)-acrylonitrile (Z-DPPyACN) throughout the 4-diphenylamino moiety with the phenyl and pyridyl rings, play an important role in the self-assembly behaviors and optical properties of its powder and single-crystal forms. The crystal packing exhibits multiple C-H[small pi] and CHHC edge-to-face interactions that contribute to the supramolecular network between adjacent molecules. The resulting molecular structure resembles a pinwheel which exhibits a strong emission intensity at three different wavelengths. The crystal belongs to the monoclinic space group P21/n, with dimensions a = 12.9551(2), b = 11.29300(15), c = 14.6992(3) A, [small beta] = 115.648(2)[degree] and Z = 4. The single-crystal compound shows three emission maxima at 533, 569, and 607 nm, whereas the powder and the molecules in an aggregated state show maximum emission intensities that are dependent on the nature of the solvent. The Z-DPPyACN dye's optical properties show a Stokes shift caused by the reorganization of the molecule in the excited state, as effected by the solvent polarity. This indicates a large change in the dipole moment of dye molecules upon excitation due to an intramolecular charge transfer interaction. From a theoretical point of view, the molecular geometry, electronic structure, and excitation energies are reported using density functional theory and compared with the experimentally determined one photon absorption and emission spectra.
    CrystEngComm 01/2014; · 3.88 Impact Factor
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    ABSTRACT: In this review paper, have been investigated three novel crystal structures of three molecules with carbazole substituents as the electron-donor group. These molecules, 2-(phenyl)-3-(N-ethyl-(3'-carbazolyl))acrylonitrile (I), 2-(3''- pyridyl)-3-(N-ethyl-(3'-carbazolyl))acrylonitrile (II), and 2-(4-pyridyl)-3-(N-ethyl-(3´-carbazolyl))acrylonitrile (III) in their structure, possess the electron-donor carbazole moiety, a -CN group attached to the double bond, and a phenyl or a pyridine function at the meta- or para-position. It was revealed with the help of single crystal diffraction X-ray analysis that there exists no difference in the crystal system, because all the compounds were crystallized in monoclinic system with space group P21/c. For determining the effect of the position of the nitrogen atom substitution on the crystal properties, has been analyzed and contrasted the molecular packing in a single crystal with that of other previously reported carbazole derivatives. The double bond bearing N-ethylcarbazole,–CN, phenyl or pyridine groups was observed to impart sufficient polarity in order to show slipped π-stacking aggregation in the solid state, affecting the compounds in the solid state and consequently affecting their fluorescence properties. The substitution at the para position was reported to exhibit more multiple C-H...π interactions as well as an interesting and unexpected short contact distance between adjacent N...N molecules those brought a conformational change resulting in an edge-to-face alignment in the molecules and affecting the best relative photoluminescence efficiency of the sample.
    Current Physical Chemistry. 01/2014; 4(1).
  • Journal of Molecular Structure. 01/2014;
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    ABSTRACT: Four (dimethylamino)arylacrylonitrile derivatives in the solid state are presented. The compounds were characterized by single crystal X-ray diffraction to investigate the effects of substituents on the resulting crystals lattices and to examine the effects of the factors controlling their solid state on photochemical behavior. The molecules included 2-(phenyl)-3-(4-dimethylaminophenyl)acrylonitrile (I) 2-(2′-pyridyl)-3-(4-dimethylaminophenyl)-acrylonitrile (II), 2-(3′-pyridyl)-3-(4-dimethyl-aminophenyl)acrylonitrile (III) and 2-(3′-pyridyl)-3-(4-dimethylaminophenyl)acrylonitrile (IV). The dimethyl-, CN groups and the position of nitrogen atom in the pyridyl groups affected the nature of the molecular packing and consequently their fluorescence properties. The lattice of each compound is compared with acrylonitriles previously reported and the effect of substitution on the crystal properties with the strongest emission in solid state is examined. Based on analyses of molecular packing in the single crystals, the differences in the fluorescence could be attributed to aggregates that showed non-classical herringbone packing with π–π overlap between neighbor molecules. Also the crystal structure studies showed that the N atom position is located anti to the CN group, giving a more planar geometry. This N-dimethyl substituent for I–IV appears to be general for more planar ground-state geometry about the nitrogen atom and consistent with an “amino conjugation effect” to obtain sufficient quinoid structures.
    Journal of Molecular Structure 02/2013; 1034:238–248. · 1.40 Impact Factor
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    ABSTRACT: A combined theoretical and experimental study on the structure, infrared, UV-Vis and 1H NMR data of trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine and trans-4-(m-cyanostyryl)pyridine is presented. The synthesis was carried out with an efficient Knoevenagel condensation using green chemistry conditions. Theoretical geometry optimizations and their IR spectra were carried out using the Density Functional Theory (DFT) in both gas and solution phases. For theoretical UV-Vis and 1H NMR spectra, the Time-Dependent DFT (TD-DFT) and the Gauge-Including Atomic Orbital (GIAO) methods were used, respectively. The theoretical characterization matched the experimental measurements, showing a good correlation. The effect of cyano- and methyl- substituents, as well as of the N-atom position in the pyridine ring on the UV-Vis, IR and NMR spectra, was evaluated. The UV-Vis results showed no significant effect due to electron-withdrawing cyano- and electron-donating methyl-substituents. The N-atom position, however, caused a slight change in the maximum absorption wavelengths. The IR normal modes were assigned for the cyano- and methyl-groups. 1H NMR spectra showed the typical doublet signals due to protons in the trans position of a double bond. The theoretical characterization was visibly useful to assign accurately the signals in IR and 1H NMR spectra, as well as to identify the most probable conformation that could be present in the formation of the styrylpyridine-like compounds.
    International Journal of Molecular Sciences 01/2013; 14(2):4005-29. · 2.46 Impact Factor
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    ABSTRACT: This study examined absorption properties of 2-styrylpyridine, trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine, and trans-4-(m-cyanostyryl)pyridine compounds based on theoretical UV/Vis spectra, with comparisons between time-dependent density functional theory (TD-DFT) using B3LYP, PBE0, and LC-ωPBE functionals. Basis sets 6-31G(d), 6-31G(d,p), 6-31+G(d,p), and 6-311+G(d,p) were tested to compare molecular orbital energy values, gap energies, and maxima absorption wavelengths. UV/Vis spectra were calculated from fully optimized geometry in B3LYP/6-311+G(d,p) in gas phase and using the IEFPCM model. B3LYP/6-311+G(d,p) provided the most stable form, a planar structure with parameters close to 2-styrylpyridine X-ray data. Isomeric structures were evaluated by full geometry optimization using the same theory level. Similar energetic values were found: ∼4.5 kJ mol(-1) for 2-styrylpyridine and ∼1 kJ mol(-1) for derivative compound isomers. The 2-styrylpyridine isomeric structure differed at the pyridine group N-atom position; structures considered for the other compounds had the cyano group attached to the phenyl ring m-position equivalent. The energy difference was almost negligible between m-cyano-substituted molecules, but high energy barriers existed for cyano-substituted phenyl ring torsion. TD-DFT appeared to be robust and accurate approach. The B3LYP functional with the 6-31G(d) basis set produced the most reliable λ(max) values, with mean errors of 0.5 and 12 nm respect to experimental values, in gas and solution, respectively. The present data describes effects on the λ(max) changes in the UV/Vis absorption spectra of the electron acceptor cyano substituent on the phenyl ring, the electron donor methyl substituent, and the N-atom position on the electron acceptor pyridine ring, causing slight changes respect to the 2-styrylpyridine title compound.
    Journal of Molecular Modeling 10/2012; · 1.98 Impact Factor
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    Journal of Materials Science Research. 06/2012; 1(3):96-105.
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    ABSTRACT: A novel water-soluble polymer containing phosphorus poly(sodium p-methacryloylaminobenzylphosphonate) was synthesized by free radical polymerization in the presence of K2S2O8 as initiator, in water as solvent at 70°C with a 48 h reaction time. The new monomer used for the polymerization was synthesized by reaction between sodium aminobenzylphosphonate and methacryloyl chloride at 4°C in methanol with a yield of 78.3%. The compounds, monomer and polymer, were characterized by IR, 1H-NMR and potentiometric titrations. The new monomer and polymer reported here are important because they are very water-soluble and contain a versatile ligand, –PO(ONa)2, which could be used in environmental applications. The polymer possibly could be used as a metalchelating polymer or as flocculant.
    Designed Monomers & Polymers 04/2012; 10(3):273-280. · 0.88 Impact Factor
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    ABSTRACT: Nanocrystalline 2,6-distyrylpyridine (2,6-DStP)-doped TiO(2) monoliths were prepared by the sol-gel technique. Different concentrations of the 2,6-DStP doping agent were utilized. Samples were characterized by x-ray diffraction, photoacoustic spectroscopy (optical absorption), and luminescence spectroscopy. As-prepared samples showed amorphous structure and traces of the anatase crystalline phase of TiO(2) after annealing at room temperature. The samples exhibited average particle size from 6 nm to 7.5 nm for molar concentration of 2,6-DStP from 0.0% to 0.03%. The photoacoustic spectra revealed the absorption edge at wavelength around 375 nm (3.38 eV), which is attributed to TiO(2), and a gap shift varying from 1.91 eV, to 2.41 eV, to 1.86 eV with the molar concentration of 2,6-DStP. Photoluminescence spectroscopy showed three different bands around 555 nm, 607 nm, and 779 nm when the samples were excited with 407 nm, 488 nm, and 633 nm laser lines, respectively.
    Journal of Electronic Materials 12/2011; 40(12):2388-2391. · 1.64 Impact Factor
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    ABSTRACT: The present work addresses the optical and morphological properties of organic films based on low molecular weight dyes styrylpyridine derivatives 2-styrylpyridine (A), 4-chlorophenyl-2-vinylpyridine (B) and 4-fluorophenyl-2-vinylpyridine (C), embedded in a polymeric matrix poly(N-vinylcarbazole) (PVK). The films were prepared by a spin-coating technique from solutions with dye:PVK ratios of 0.25:1, 0.5:1 and 1:1. Solvents were chloroform and toluene. The molar absorption coefficient (ε) spectra for a dye:PVK mixture in solution were a combination of the absorptions of both components separately, but for the deposited films, the shape of the spectrum showed that the poly(N-vinylcarbazole) absorption dominated. However, when the same films were dissolved again in CHCl3, their spectra showed an absorption shape similar to that of the solution mixture before the deposition. Solution viscosity measurements were carried out with an Ubbelohde glass capillary viscometer to corroborate the results that showed a better mixture of the dye with the host in chloroform. The morphology of the prepared films was analyzed by atomic force microscopy and exhibited a solvent effect, with a pinhole-free, smooth surface when toluene was used and a wavy surface with chloroform. The ratio dye:matrix was the principal parameter for obtaining optical quality films; for 0.25:1 and 0.5:1 ratios, the films were of good quality, but for 1:1, the dye was expelled from the PVK and a crystallization was present over the surface of the films. Film thickness was also measured and films deposited from toluene solutions gave an average thickness of 54nm while films from chloroform solutions had an average thickness greater than 160nm that increased depending on chromophore concentration.
    Thin Solid Films 01/2011; 519(18):6015-6020. · 1.87 Impact Factor
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    ABSTRACT: The kinetics of atom transfer radical polymerization of N-(S)-α-methylbenzylmethacryloylamine (S-(-)-α-MBMA) and α-methylbenzylmethacrylate (α-MBM) monomers, as assessed by % conversion, were determined at 48 °C in a toluene/ethanol mixture (60:40) by a dilatometry method. The effect of the presence of — CONH- or — COOR- moieties on the ATRP polymerization of such monomers was investigated. Controlled polymerizations were performed with the catalyst system $$ \left[ {\hbox{M}} \right]/\left[ {{\hbox{R}} - {\hbox{X}}} \right]/\left[ {{\hbox{M}}{{\hbox{t}}^{\rm{n}}} - {\hbox{Y}}} \right]/\left[ {\hbox{L}} \right] $$ at molar ratios of 100:15:15:15; 200:15:15:15; 300:15:15:15; and 400:15:15:15, where R-X was EBIB or MCP, Mtn-Y(CuBr or CuCl) and L (Me6TREN). Also with N-S-(-)-α-MBMA, some studies used ATCA and ABPA as R-X. Plots of the ln[M]0/[M] vs t as well as from the log Rp vs log [M] showed that the ATRP processes followed a pseudo first-order kinetics with respect to the monomer concentration and that the molecular weight of the resulting polymers increased with the conversion. The ATRP results for both monomers showed a similar trend and revealed that the presence of N-S-(-)-α-MBMA (amide group) affects the polymerization, i.e. it did not react when the EBIB/CuBr/Me6TREN catalyst system was used. The Mn and Mw were determined by 1H-NMR and GPC. PDI values fell between 1.19 and 1.5, and indicated that the majority of the systems showed good control of polymerization.
    Journal of Polymer Research 01/2011; 18(4):559-568. · 2.02 Impact Factor
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    ABSTRACT: We synthesized three novel highly fluorescent compounds, 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile, and 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile by Knoevenagel condensation. The first two were synthesized without solvent in the presence of piperidine as a catalyst; the third was synthesized without a catalyst and with N,N-dimethylformamide as a solvent. In solution, the molar absorption coefficients showed absorptions at 380, 378, and 396 nm, respectively; in solid state, absorptions were at 398, 390, and 442 nm, respectively. The fluorescence emission was at 540, 540 and 604 nm, respectively, the 2-(4-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile showed a red shift in the emission of 64 nm compared to the other two compounds. The fluorescence quantum yield for the compounds in powder form showed values of 0.05, 0.14, and 0.006, respectively; compared with the value measured for the Alq3 reference, 2-(3”-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile had a lightly higher value. The third harmonic generation measurement for 2-(2’-pyridyl)-3-(N-ethyl-(3’-carbazolyl))acrylonitrile yielded a χ(3) value of 5.5 × 10−12 esu, similar to that reported for commercial polymers.
    Materials. 01/2011;
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    ABSTRACT: The Knoevenagel condensation between aldehydes and substrates with active methylene groups was applied to synthesise a series of 3-(4-substituted phenyl)-2-arylacrylonitriles (aryl = phenyl or pyridyl). Chloro-, fluoro-, or dimethylamino-substituted aryls and a cyano group attached to the double bond of acrylonitrile were studied. Previous studies showed that the condensation products were E isomers. The compounds synthesised were: 3-(4-chlorophenyl)-2-phenylacrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-(4-chlorophenyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-fluorophenyl)-2-phenylacrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-3-yl)acrylonitrile, 3-(4-fluorophenyl)-2-(pyridin-4-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-phenylacrylonitrile, 3-(4-dimethylaminophenyl)-2-(pyridin-2-yl)acrylonitrile, 3-(4-dimethylaminophenyl)-2-(pyridin-3-yl)acrylonitrile, and 3-(4-dimethylaminophenyl)-2-(pyridin-4-yl)acrylonitrile. Structures were confirmed by IR, MS, and NMR spectral data. Molar absorption coefficient, absorbance, and fluorescence emission spectra were compared in order to evaluate the effects of substituents on phenyl and the position of nitrogen in pyridine moiety on the electronic properties of acrylonitrile derivatives prepared. Keywordssolvent-free synthesis–Knoevenagel condensation–propenenitrile–4-dimethylaminophenyl derivatives–phenylpyridylacrylonitriles
    Chemical Papers- Slovak Academy of Sciences 01/2011; 65(1):42-51. · 0.88 Impact Factor
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    ABSTRACT: A modified system of atom transfer radical polymerization was used to perform polymerization of sodium o-methacryloylaminophenylarsonate (o-MAPHA-Na). The reaction was carried out without ligand at 48°C for 45h with methyl 2-chloro-propionate (MCP) as the initiator, copper bromide (CuBr) as the metal, and different mixtures of polar solvents, including: dimethylformamide (DMF):H2O (60:40), dimethylsulfoxide (DMSO):H2O (20:80), and DMSO. The 1H NMR spectra showed that MCP was covalently attached as end group of the resulting polymers. Unexpectedly, we found that o- and p-MAPHA-Na could polymerize in the presence of alkyl halides without any initiation method to produce free radicals from alkyl halide. Further experiments suggested that radicals could be generated from the used monomer by initiation methods such ultraviolet radiation of environmental light or temperature. Thus, it was possible that the monomer generated phenyl radicals by breaking its C-As bond. Reactions of o-MAPHA-Na and o-MAPHA with MCP and different ratios of H2O:DMF and H2O:Metanol (MeOH) showed that water was necessary for polymerization to proceed. Finally, we found that o-MAPHA underwent self-initiated polymerization when water was present in the reaction media. KeywordsAtom transfer radical polymerization– o- and p-methacryloylaminophenylarsonic acid–Sodium o- and p-methacryloylaminophenylarsonate–Free radical polymerization–Polar solvents–Functionalized monomers
    Journal of Polymer Research 01/2011; 18(4):601-613. · 2.02 Impact Factor
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    ABSTRACT: Optically active polymers were prepared using reversible addition-fragmentation chain transfer polymerization (RAFT) of N-(S)-α-methylbenzylmethacryloylamine (N-(S)-α-MBMA), a functional optically active monomer. RAFT polymerizations were carried out at 70 °C in ethanol using AIBN as a thermal initiator and benzyl or (1-phenyl)ethyl dithiobenzoate (BDB and PEDB, respectively) as the RAFT agents. The kinetic study was performed by dilatometry. Plots of conversion vs time indicated that the polymerizations followed first order kinetics. 1H NMR, IR, and UV–vis spectrophotometric studies confirmed the presence of thiocarbonylthio moieties (−SCS-) in the polymer chains. The molecular weight distributions (MWDs) were moderately narrow with polydispersity indices between 1.3 and 1.6, which indicated that the control of the reaction was not completely achievement using BDB or PEDB as RAFT agents. The optical activity [α]D25 measurements of synthesized polymers by RAFT did not show a noticeably linear increase dependence with respect to molecular weight, as was previously reported for another controlled free radical polymerization (CRP) system.
    Journal of Polymer Research 01/2011; · 2.02 Impact Factor
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    ABSTRACT: Copolymers of sodium o-methacryloylaminophenylarsonate (o-MAPHA-Na) 1 and p-methacrylolylaminophenylarsonate (p-MAPHA-Na) 2 with sodium acrylate (AA-Na) 3, sodium methacrylate (AM-Na) 4 and acrylamide (AAD) 5 were prepared by free radical polymerization in aqueous media at 70°C using potassium persulfate (K2S2O8) as the initiator. The total monomer concentration was carried out at 0.5M and the feed ratio (M1 : M2) was varied from 10 : 90 to 90 : 10 mol%. The kinetic study was carried out by dilatometric method. The copolymer compositions were calculated by arsenic content in the copolymers. The As content (ppm) was determined by atomic absorption spectrometry (AAS). The reactivity ratios (r1, r2) were estimated by the Kelen-Tüdös linearization method as well as error-in-variables method using the computer program RREVM®. In all cases, r1 < 1 and r2 > 1, indicating a tendency to form random copolymers. The values suggest that the copolymers contain a larger proportion of comonomer (i.e., AA-Na, AM-Na, or AAD). Weight-average molar masses (Mw) of copolymers were determined by multi-angle light scattering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
    Journal of Applied Polymer Science 06/2010; 118(5):2849 - 2858. · 1.40 Impact Factor
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    Macromolecular Reaction Engineering 03/2010; 4(3‐4):222 - 234. · 1.64 Impact Factor