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Search Results: 1 - 10 of 597 matches for " Issa Katime "
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Swelling Properties of New Hydrogels Based on the Dimethyl Amino Ethyl Acrylate Methyl Chloride Quaternary Salt with Acrylic Acid and 2-Methylene Butane-1,4-Dioic Acid Monomers in Aqueous Solutions  [PDF]
Issa Katime, Eduardo Mendizábal
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.13026
Abstract: Hydrogels of dimethylaminoethyl acrylate methyl chloride quaternary salt (Q9) have been synthesized with different monomer ratio by copolymerization of this poorly studied monomer either with acrylic acid or with 2-methylene bu-tane-1,4-dioic acid. Hydrogel swelling was measured as a function of the composition of the hydrogel and of the crosslinking agent ratio. High values of swelling have been obtained at very high crosslinking values (< 14 wt %) and the equilibrium swelling was reached at very low time (less than 15 minutes). The swelling isotherms consisted of a steep initial portion and then levelled off as asymptotically to the equilibrium swelling limit. The experimental data suggest clearly that the swelling process obeys second-order kinetics. According to this, the kinetics rate constant and the equilibrium water content were determined at different comonomer composition and crosslinker concentration. The calculated kinetic constants ranged from 0.48 to 3.76 × 10-2 min-1 for poly (acrylic acid-co-Q9) hydrogels and from 0.68 to 4.0 × 10-2 min-1 for poly (2-methylene butane-1,4-dioic acid-co-Q9) hydrogels depending on the hydrogels composition. The diffusion process was evaluated for each hydrogel showing a non-Fickian type diffusion. In all cases was observed a considerable increase in diffusion coefficient as Q9 content increases.
Cationic Microemulsion Polymerization of Alkyl Acrylates  [PDF]
Issa Katime, Jesús Arellano, Eduardo Mendizábal, Jorge Flores
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.15043
Abstract: Here we present the polymerization of n-butyl acrylate (BA), ethyl acrylate (EA) and methyl acrylate (MA) in tri-component microemulsions, using a cationic surfactant such as dodecyl trimetyl ammonium bromide in water, as a function of temperature, initiator type and, monomer and initiator concentration. The final latexes are transparent and blue color, with particle size ranging between 20 and 60 nm determined by quasielastic light scattering (QLD) and SEC molar masses of the order of 106 g/mol. Reaction times are short and reaction rates are high with final conversions between 70 and 98% depending on the monomer and the reaction conditions.
New Family of Functionalized Monomers Based on Amines: A Novel Synthesis that Exploits the Nucleophilic Substitution Reaction  [PDF]
Lissette Agüero, Luis G. Guerrero-Ramírez, Issa Katime
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.13018
Abstract: Chemistry modifications are usually performed to introduce specific group that can increase properties and functionality of materials. In this study, we present the synthesis of six new functionalized monomers prepared by nucleophilic substitution reactions. Reaction of aliphatic and aromatic amines with acryloyl chloride at –20ºC, in presence of triethylamine allowed the synthesis of the corresponding amides. Proton nuclear magnetic resonance (1H NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and ultraviolet- visible (UV-Vis) measurements confirmed the success of the synthesis with a yield over 90%. These compounds emerged as potentially attractive monomers since they can be used to obtain stimuli-sensitive polymeric materials, due to the presence of amide and pyridine groups.
Polymeric Nanohydrogels of Poly(N-Isopropylacrylamide) Combined with Others Functionalized Monomers: Synthesis and Characterization  [PDF]
Lissette Agüero Luztonó, Yuneivy Cepero Donates, Luis Guillermo Guerrero Ramirez, Addys González Palomo, Dionisio Zaldivar Silva, Issa Katime
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2014, DOI: 10.4236/jbnb.2014.51005
Abstract:

Nanohydrogels from inverse microemulsion (w/o) polymerization, at 25°C, of N-isopropylacrylamide (NIPA) and functionalized monomers are described. The functionalized monomers were: N-(pyridine-4-ylmethyl) acrylamide (NP4MAM) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM). The polymeric nanohydrogel obtained was characterized by attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectrometry (1HNMR), while their morphology and particle size was assessed by scanning electron microscopy (SEM) and dynamic light scattering. Their thermal properties were studied by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). As a preliminary measure of biocompatibility, in vitro evaluations of the nanohydrogels were carried out by cellular toxicity (colon carcinoma cells, CT

Empleo de una sonda infrarroja in situ para monitorear reacciones de esterificación
Sánchez C.,Francisco J.; Cesteros,Carlos; Katime,Issa A.;
Ingeniería e Investigación , 2006,
Abstract: a batch reactor was employed having ph meter, ir probe and continuous operation detectors so that it could work as a cstr reactor. as esterification advanced, then ir bands corresponding to the carboxyl acid cooh group and the alcohol c-oh group decreased whilst a parallel increase was presented in the ester -coor group band which was forming. reaction progress could be observed by continuous ir spectrum registration. the ir band for hoh (water) could not be studied because it needed a completely anhydrous medium for doing so. standard solutions could be prepared for quantifying ir band peak intensity, according to a component?s composition in the mixture. however, when phase changes occurred in the reaction mixture, this method could not be employed for following the course of a particular reaction because random variation was detected in band intensity.
Empleo de una sonda infrarroja in situ para monitorear reacciones de esterificación Using an infrared probe for in situ monitoring of esterifying reactions
Sánchez Castellanos Francisco José,Cesteros Carlos,Katime Issa A
Ingeniería e Investigación , 2006,
Abstract: Se empleó un reactor batch (por lotes), dotado de tres detectores: pH, Sonda IR y operación en continuo, de tal forma que puede operarse como un reactor CSTR. En la medida en que la esterificación procede, decrecen las bandas correspondientes al grupo -COOH del ácido carboxIlico y la del grupo C-OH del alcohol, presentándose al mismo tiempo incremento en la banda del grupo -COOR del ester que se está formando. El progreso de la reacción se puede seguir por el registro continuo de los espectro IR. La banda correspondiente a H-O-H del agua no se puede seguir ya que se requiere de un ambiente absolutamente anhidro para hacerlo. De otro lado, por aparte pueden prepararse soluciones patrones para poder cuantificar la intensidad de los picos en el espectro IR, segün la composición del componente en la mezcla. Sin embargo, cuando se presentan cambios de fase en la mezcla reactiva, este metodo no puede emplearse para seguir el curso de una reacción, ya que se presenta una variación muy aleatoria en la senal de intensidad de los picos. A batch reactor was employed having pH meter, IR probe and continuous operation detectors so that it could work as a CSTR reactor. As esterification advanced, then IR bands corresponding to the carboxyl acid COOH group and the alcohol C-OH group decreased whilst a parallel increase was presented in the ester -COOR group band which was forming. Reaction progress could be observed by continuous IR spectrum registration. The IR band for HOH (water) could not be studied because it needed a completely anhydrous medium for doing so. Standard solutions could be prepared for quantifying IR band peak intensity, according to a component’s composition in the mixture. However, when phase changes occurred in the reaction mixture, this method could not be employed for following the course of a particular reaction because random variation was detected in band intensity.
Síntesis de mono y diitaconatos de alquilo y arilo
Sánchez Francisco J.,Katime Issa A.,Meaurio Emilio
Ingeniería e Investigación , 1997,
Abstract: Se presenta una técnica para la síntesis en laboratorio de mono y diitaconatos y la separación de los mismos por extracción selectiva con solventes orgánicos. La pureza de los productos se determina por cromatografía en capa fina y por espectroscopia infrarroja.
Influência do comon?mero e do método de polimeriza??o na cinética de libera??o de fenobarbitona a partir de hidrogéis
Barcellos, Ivonete O.;Katime, Issa A.;Soldi, Valdir;Pires, Alfredo T. Nunes;
Polímeros , 2000, DOI: 10.1590/S0104-14282000000200013
Abstract: the release of water-soluble drugs from initially hydrated hydrogels matrices generally involves the simultaneous water absorption and drug desorption through a swelling-controlled diffusion mechanism. the diffusional behaviour of phenobarbitone from a hydrogel formed by a 2-hydroxyethylmethacrylate (hema) and methyl monoitaconate (mmi) copolymer was reported. the drug release into water was performed by high pressure liquid cromatography and the results showed that the phenobarbitone release from the hydrogels studies, considering the diffusion coefficient values did not change with the temperature and the polymerization method. the activation energy values suggested a more favorable phenobarbitone release from the hydrogels p(hema-co-mmi) polymerized in mass and bulk solution.
Influência do comon mero e do método de polimeriza o na cinética de libera o de fenobarbitona a partir de hidrogéis
Barcellos Ivonete O.,Katime Issa A.,Soldi Valdir,Pires Alfredo T. Nunes
Polímeros , 2000,
Abstract: A libera o de drogas solúveis em água a partir de matrizes de hidrogéis hidratados, geralmente envolve simultaneamente a absor o de água e a libera o da droga via mecanismo de difus o controlada. Foi analisado o comportamento difusional da fenobarbitona no hidrogel do copolímero 2-hidroxietil metacrilato (HEMA) e monoitaconato de metila (MMI). A libera o da droga no meio aquoso foi acompanhada por cromatografia líquida de alta press o e os resultados mostraram que a libera o da fenobarbitona a partir dos hidrogéis estudados, considerando-se os valores dos coeficientes de difus o, n o variou com a temperatura e com o método de polimeriza o. Os valores de energia de ativa o sugerem um favorecimento na libera o da fenobarbitona a partir dos hidrogéis de p(HEMA-co-MMI) polimerizados em massa e em solu o.
Obtención de hidrogeles derivados del ácido itacónico
Sánchez Francisco J.,Novoa Rosa M.,Díaz de Apodaca Helena,Katime Issa A.
Ingeniería e Investigación , 1996,
Abstract: Se presenta una técnica para la obtención de hidrogeles de acrilamida, empleando comonámeros monoésteres del ácido itacántco. A estos hidrogeles se les determina su cinética de hinchamiento a pH neutro y 20°C.
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