Adley Rubira - Academia.edu (original) (raw)
Papers by Adley Rubira
Journal of Thermodynamics, 2012
High pressure phase behavior experimental data have been measured for the systems carbon dioxide ... more High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) and carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) + 1-amino-2-phenoxy-4-hydroxyanthraquinone (C.I. Disperse Red 60). Measurements were performed in the pressure up to 18 MPa and at the temperature (323 to 353 K). As reported in the literature, at higher concentrations of carbon dioxide the phase transition pressure increased very steeply. The experimental data for the binary and ternary systems were correlated with good agreement using the Peng-Robinson equation of state. The amount of water in phase behavior of the systems was evaluated.
Composites Part A: Applied Science and Manufacturing, 2011
A zinc oxide (ZnO) and poly(ethylene terephthalate) (PET) composite was obtained using a supercri... more A zinc oxide (ZnO) and poly(ethylene terephthalate) (PET) composite was obtained using a supercritical fluid deposition (SCFD) approach. The zinc precursor was solubilized in supercritical carbon dioxide (scCO2) and impregnated onto PET films. The PET film impregnated zinc precursor was chemically treated using a hydrazine alcoholic solution to obtain the ZnO/PET composite. The composite was characterized by photoacoustic spectroscopy UV–Vis,
Journal of Physics D: Applied Physics, 2001
In this work we report thermal diffusivity and specific heat measurements in N,N-dimethylacrylami... more In this work we report thermal diffusivity and specific heat measurements in N,N-dimethylacrylamide modified poly (ethylene terephthalate) (PET) films for incorporating the dye blue Samaron HGS. These thermophysical properties were studied by changing the sample preparation conditions, such as the temperature and time of N,N-dimethylacrylamide treatment, and the time and temperature of dyeing. The results showed that the heat conduction
Journal of Applied Physics, Feb 15, 2001
In this article we discuss the use of the thermal lens technique for investigating the thermal pr... more In this article we discuss the use of the thermal lens technique for investigating the thermal properties of polymers as a function of temperature. It is also discussed how the experimentally determined thermal lens parameters can be used to locate the glass transition in polymers. The methodology is tested using a solution casted films of poly͑vinyl chloride͒ as a testing sample. A comparison with conventional differential scanning calorimetry data is made. It is proposed that the current transient thermal lens methodology, with minor changes in its experimental configuration, could be adapted to develop a new methodology called differential thermal lens scanning especially designed for the investigation of the phase transitions in polymers. It is shown that this new methodology could be equally used for the measurement of the thermal expansion coefficient, above and below the glass transition.
Carbohydrate polymers, Jan 15, 2018
The advances in the field of biomaterials have led to several studies on alternative biocompatibl... more The advances in the field of biomaterials have led to several studies on alternative biocompatible devices and to their development focusing on their properties, benefits, limitations, and utilization of alternative resources. Due to their advantages like biocompatibility, biodegradability, and low cost, polysaccharides have been widely used in the development of hydrogels. Among the polysaccharides studied on hydrogels preparation, chitosan (pure or combined with natural/synthetic polymers) have been widely investigated for use in biomedical field. In view of potential applications of chitosan-based hydrogels, this review focuses on the most recent progress made with respect to preparation, properties, and their salient accomplishments for drug delivery and tissue engineering.
Characterization and Biomedical Applications, 2015
Acta Scientiarum. Technology, 2003
RESUMO. O polímero poli(tereftalato de etileno)-PET-tem tido suas propriedades de superfície modi... more RESUMO. O polímero poli(tereftalato de etileno)-PET-tem tido suas propriedades de superfície modificadas, visando às mais diversas aplicações. O dióxido de carbono supercrítico (CO 2 SC) tem um grande potencial para a modificação e o processamento de polímeros sólidos, devido à sua alta difusividade e poder de solvatação. O objetivo do presente trabalho foi investigar a incorporação do corante Vermelho Dianix em filmes de PET modificados e não-modificados com N,N-dimetilacrilamida, nos processos de CO 2 SC e em meio aquoso. No processo com CO 2 SC, o tratamento dos filmes de PET modificados com N,N-dimetilacrilamida aumentou, em média, 1,6 vezes a quantidade de corante incorporado. Já em meio aquoso, a incorporação do corante nos filmes de PET modificados com N,N-dimetilacrilamida aumentou, em média, 2 vezes; no entanto, a quantidade absorvida pelo PET foi menor. A quantidade de corante incorporado em filmes de PET foi determinada por espectrofotometria UV-VIS a 520nm, usando N,Ndimetilformamida como solvente. Palavras-chave: poli (tereftalato de etileno), N-N-dimetilacrilamida, corante Vermelho Dianix. ABSTRACT. Comparison between conventional and supercritical CO 2 processes in pet films sorption with dianix red dye. The effects of modifying agents and dyeing conditions of dispersed dyes for PET films have been thoroughly studied. This research reports the dye incorporation processes in non-modified and modified N,Ndimethylacrylamide PET films with supercritical CO 2 and with conventional process. The dye uptake was increased 1,6 times, in average, with N,N-dimethylacrylamide modified films. Using a conventional process, the amount of sorbet dye in the modified PET films was 2 times higher when compared to the non-modified ones. The dye incorporated in the PET film was extracted using N,N-dimethylformamide and its amount was determined by UV-VIS spectroscopy at 520nm.
![Research paper thumbnail of PET depolymerisation in supercritical ethanol catalysed by [Bmim][BF4]](https://attachments.academia-assets.com/105949654/thumbnails/1.jpg)
](RSC Adv., 2014
Poly(ethylene terephthalate) was depolymerised under supercritical ethanol, 98 wt% of diethyltere... more Poly(ethylene terephthalate) was depolymerised under supercritical ethanol, 98 wt% of diethylterephthalate was obtained after 45 min, by adding [Bmim][BF4] as catalyst.
Polymer, 2005
Blends stand out as simple and cheap materials with unique properties. The miscibility of blends ... more Blends stand out as simple and cheap materials with unique properties. The miscibility of blends formed by bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) doped with europium (III) acetylacetonate have been studied by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and photoluminescent (PL) spectroscopy. DSC studies demonstrated that undoped PC/PMMA blends obtained by precipitation method present one glass transition temperature, evidencing their apparent miscibility. FTIR spectra revealed synergic effects in the PC/PMMA system as well as the incorporation of the Eu 3C complex. TGA analysis suggested that the Eu 3C complex remains preferably in the PC micro-phase. SEM analysis showed that europium (III) acetylacetonate is homogeneously distributed within the blend and PL spectra evidenced the photoluminescence of Eu 3C incorporated into the blend.
Polymer, 2008
A novel procedure has been developed to covalently graft multiple hydrophilic polymer ultra-thin ... more A novel procedure has been developed to covalently graft multiple hydrophilic polymer ultra-thin layers to functionalized polyethylene surface. Polyethylene films have been functionalized by two methods, chromic acid oxidation and maleic anhydride grafting, to produce surfaces containing reactive groups, carboxylic acid and anhydride, respectively. The reactive groups formed in the functionalization were used to anchor a poly(vinyl alcohol) (PVA) ultra-thin layer by thermal esterification. After anchoring PVA, a second ultra-thin layer, constituted of poly(acrylic acid) (PAA), was also anchored. The second layer was anchored by thermal esterification between PVA hydroxyl groups and PAA carboxylic acid groups. The procedure presented in this work allows the formation of an ultra-thin layer. The macromolecule anchoring reactions occur only at the interfaces, consequently, only the macromolecules in contact with the interface are anchored. The formation of the ultra-thin layer and the surface characteristics have been analyzed through XPS, ATR-FTIR, SEM, and AFM data.
Journal of Applied Polymer Science, 1989
European Polymer Journal, 2005
Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studi... more Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO 2) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO 2 at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO 2 , film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.
European Polymer Journal, 2005
In this work, the thermotropic liquid crystal MBBA (N-(4-methoxybenzilidene)-4-butylaniline), ent... more In this work, the thermotropic liquid crystal MBBA (N-(4-methoxybenzilidene)-4-butylaniline), entrapped on hydrogels, based on cross-linked polyacrylamide (PAAm), was studied. The liquid crystalline phases of system were characterized by polarized optical microscopy (POM), refractive index, optical transmittance, scanning electron microscopy (SEM) and water loss. It was verified the presence of birefringence on hydrogel+liquid crystal. The dynamic of formation of such birefringence
Journal de Physique IV (Proceedings), 2005
Samples of PC/PMMA blend having proportion 6/4, 4/6 and 2/8 were doped with acetylacetonate of Eu... more Samples of PC/PMMA blend having proportion 6/4, 4/6 and 2/8 were doped with acetylacetonate of Eu(acac) 3 having concentrations of 0-16%. Through Photoacoustic Spectroscopy (PAS) the interaction of Eu 3+ with the blends was studied using the visible range 200-530 nm, monitoring a wide absorption band from 280 to 320 nm, where results pointed that 2/8 blend presents the highest absorption. Preliminary luminescent emission showed higher emission for lower Eu(acac) 3 amounts and suggests that the 2/8 blend as more efficient at 615 nm. In addition, it is presented a study of thermal diffusivity and heat capacity evolution related to the doping amount for all blend proportions. Normalized thermal diffusivity is higher for 2/8 blend (a mean~5 .64 x 10-3 cm 2 s-1) and the specific heat was almost constant (c p(mean)~ 1.66 Jg-1 K-1).
Applied Surface Science, 2006
The modification of polysulfone surface was used to obtain effective interactions between an orga... more The modification of polysulfone surface was used to obtain effective interactions between an organic polymeric surface and an inorganic specie. A previous treatment of the polymer surface with modifiers is required in order to provide adherence. Our objective was the synthesis and the surface characterization of copper sulfide coated polysulfone (CuS-PSf) films. SEM micrographs showed a homogeneous distribution of copper sulfide, which contributes to increasing electrical conductivity. Xray analysis showed a decrease in copper sulfide particles (covellite porcelain) when compared with other polymeric composites prepared under similar conditions. The measured surface conductivity of the CuS-PSf films was higher than those of other similar systems, ca. 800 S cm À1 .
Química Nova, 2002
MATERIALS CHEMISTRY IN 25 YEARS OF BRAZILIAN CHEMICAL SOCIETY. Communications on Chemistry of Mat... more MATERIALS CHEMISTRY IN 25 YEARS OF BRAZILIAN CHEMICAL SOCIETY. Communications on Chemistry of Materials topics were already presented in the first annual meetings of the Brazilian Chemical Society, dispersed throughout various meeting sections. The SBQ Materials Chemistry division was organized in 1993, attracting those members with an interest in the composition, structure and properties of materials, as related to their functions. This paper is an account of the development of Materials Chemistry research in Brazil, based on the SBQ annual meetings data.
International Journal of Molecular Sciences, 2014
Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial ... more Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.
International journal of biological macromolecules, Jan 24, 2015
Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previous... more Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previously synthesized N,N-dimethyl chitosan (DMC) (86% dimethylated by (1)H NMR spectroscopy) was complexed with HP by mixing HP and DMC aqueous solutions (both at pH 3.0). The polyelectrolyte complex (PEC) obtention was confirmed by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG) and wide-angle X-ray scattering (WAXS). In vitro controlled release assays of HP from PEC were investigated in the simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The PEC efficiently protected the HP in SGF condition in which HP is degraded. On the other hand, in SIF PEC promoted the releasing of 80±1.5% of loaded HP. The promissory results indicated that the PEC based on DMC/HP presented potential as drug-carrier matrix, since biological activity of HP was improved at pH close to physiological condition.
Journal of the Brazilian Chemical Society, 2014
Recentemente, foi desenvolvido em nosso grupo de pesquisas um modelo que prevê 100% do perfil de ... more Recentemente, foi desenvolvido em nosso grupo de pesquisas um modelo que prevê 100% do perfil de liberação de soluto a partir de hidrogel. Este considera os efeitos de difusão e de partição e permite obter os valores da atividade de partição, α, e da constante cinética de liberação, k R. Embora α e k R sejam dependentes de fatores diversos, a hipótese de que a razão α/k R não seja dependente do volume de fluido de intumescimento foi testada neste trabalho. Assim, foram determinados valores da razão α/k R para vitamina B 12 (VitB 12) e diclofenaco de potássio (DFK) que foram submetidos a ensaios de liberação em três temperaturas (25, 35 e 45 °C), sendo avaliados, em cada temperatura, os volumes 250, 350 e 450 mL. O hidrogel utilizado é baseado na goma arábica quimicamente modificada copolimerizada com N,N-dimetilacrilamida (AGm-DMAAm), na razão 60-40 (m/m) sendo o carregamento dos solutos feito durante o processo de gelificação. Foi verificado que a razão α/k R não depende do volume do fluido de liberação para uma determinada temperatura. Mas a temperatura é um fator importante, influenciando fortemente o processo de liberação destes solutos. A variação da temperatura de 25 para 35 °C afeta mais a liberação de DFK do que a liberação de VitB 12. Isso foi atribuído a interações eletrostáticas entre os grupos (R-COO-) contidos nesse soluto e a grupos positivamente carregados na matriz. Foram calculados os valores de tempo de meia vida de liberação, t 1/2 , e a energia de ativação, Ea R , do processo de liberação dos solutos. Recently, a model predicting whole profile solute release from a hydrogel was developed. In such model, the partition activity, α, and release kinetic constant, k R , can be obtained. Although α and k R depend on many factors, the hypothesis that α/k R ratio does not depend on external fluid volume was tested in the present study. Thus, α/k R values for two distinct solutes, vitamin B 12 (VitB 12) and diclofenac potassium (DFK), were obtained at 25, 35 and 45 °C using 250, 350 and 450 mL of external fluid. The hydrogel used in the experiments was obtained by the copolymerization of N,N-dimethylacrylamide-modified Arabic gum (AGm-DMAAm), at wt% ratio of 60-40. It was verified that α/k R ratio is not volume dependent, at a certain temperature, but the temperature strongly influences the α/k R ratio for both solutes. Changing temperature from 25 to 35 °C affected DFK release much more than VitB 12 release. This was attributed mainly to electrostatic interactions between (R-COO-) from DFK and the positively charged groups in the GAm-DMAAm matrix. Additionally, the values for the half-life time release, t 1/2 , equilibrium time release, t eq , as well as the activation energy for releasing, Ea R , were determined and discussed in light of the partition-diffusion model.
Journal of Thermodynamics, 2012
High pressure phase behavior experimental data have been measured for the systems carbon dioxide ... more High pressure phase behavior experimental data have been measured for the systems carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) and carbon dioxide (CO2) + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) + 1-amino-2-phenoxy-4-hydroxyanthraquinone (C.I. Disperse Red 60). Measurements were performed in the pressure up to 18 MPa and at the temperature (323 to 353 K). As reported in the literature, at higher concentrations of carbon dioxide the phase transition pressure increased very steeply. The experimental data for the binary and ternary systems were correlated with good agreement using the Peng-Robinson equation of state. The amount of water in phase behavior of the systems was evaluated.
Composites Part A: Applied Science and Manufacturing, 2011
A zinc oxide (ZnO) and poly(ethylene terephthalate) (PET) composite was obtained using a supercri... more A zinc oxide (ZnO) and poly(ethylene terephthalate) (PET) composite was obtained using a supercritical fluid deposition (SCFD) approach. The zinc precursor was solubilized in supercritical carbon dioxide (scCO2) and impregnated onto PET films. The PET film impregnated zinc precursor was chemically treated using a hydrazine alcoholic solution to obtain the ZnO/PET composite. The composite was characterized by photoacoustic spectroscopy UV–Vis,
Journal of Physics D: Applied Physics, 2001
In this work we report thermal diffusivity and specific heat measurements in N,N-dimethylacrylami... more In this work we report thermal diffusivity and specific heat measurements in N,N-dimethylacrylamide modified poly (ethylene terephthalate) (PET) films for incorporating the dye blue Samaron HGS. These thermophysical properties were studied by changing the sample preparation conditions, such as the temperature and time of N,N-dimethylacrylamide treatment, and the time and temperature of dyeing. The results showed that the heat conduction
Journal of Applied Physics, Feb 15, 2001
In this article we discuss the use of the thermal lens technique for investigating the thermal pr... more In this article we discuss the use of the thermal lens technique for investigating the thermal properties of polymers as a function of temperature. It is also discussed how the experimentally determined thermal lens parameters can be used to locate the glass transition in polymers. The methodology is tested using a solution casted films of poly͑vinyl chloride͒ as a testing sample. A comparison with conventional differential scanning calorimetry data is made. It is proposed that the current transient thermal lens methodology, with minor changes in its experimental configuration, could be adapted to develop a new methodology called differential thermal lens scanning especially designed for the investigation of the phase transitions in polymers. It is shown that this new methodology could be equally used for the measurement of the thermal expansion coefficient, above and below the glass transition.
Carbohydrate polymers, Jan 15, 2018
The advances in the field of biomaterials have led to several studies on alternative biocompatibl... more The advances in the field of biomaterials have led to several studies on alternative biocompatible devices and to their development focusing on their properties, benefits, limitations, and utilization of alternative resources. Due to their advantages like biocompatibility, biodegradability, and low cost, polysaccharides have been widely used in the development of hydrogels. Among the polysaccharides studied on hydrogels preparation, chitosan (pure or combined with natural/synthetic polymers) have been widely investigated for use in biomedical field. In view of potential applications of chitosan-based hydrogels, this review focuses on the most recent progress made with respect to preparation, properties, and their salient accomplishments for drug delivery and tissue engineering.
Characterization and Biomedical Applications, 2015
Acta Scientiarum. Technology, 2003
RESUMO. O polímero poli(tereftalato de etileno)-PET-tem tido suas propriedades de superfície modi... more RESUMO. O polímero poli(tereftalato de etileno)-PET-tem tido suas propriedades de superfície modificadas, visando às mais diversas aplicações. O dióxido de carbono supercrítico (CO 2 SC) tem um grande potencial para a modificação e o processamento de polímeros sólidos, devido à sua alta difusividade e poder de solvatação. O objetivo do presente trabalho foi investigar a incorporação do corante Vermelho Dianix em filmes de PET modificados e não-modificados com N,N-dimetilacrilamida, nos processos de CO 2 SC e em meio aquoso. No processo com CO 2 SC, o tratamento dos filmes de PET modificados com N,N-dimetilacrilamida aumentou, em média, 1,6 vezes a quantidade de corante incorporado. Já em meio aquoso, a incorporação do corante nos filmes de PET modificados com N,N-dimetilacrilamida aumentou, em média, 2 vezes; no entanto, a quantidade absorvida pelo PET foi menor. A quantidade de corante incorporado em filmes de PET foi determinada por espectrofotometria UV-VIS a 520nm, usando N,Ndimetilformamida como solvente. Palavras-chave: poli (tereftalato de etileno), N-N-dimetilacrilamida, corante Vermelho Dianix. ABSTRACT. Comparison between conventional and supercritical CO 2 processes in pet films sorption with dianix red dye. The effects of modifying agents and dyeing conditions of dispersed dyes for PET films have been thoroughly studied. This research reports the dye incorporation processes in non-modified and modified N,Ndimethylacrylamide PET films with supercritical CO 2 and with conventional process. The dye uptake was increased 1,6 times, in average, with N,N-dimethylacrylamide modified films. Using a conventional process, the amount of sorbet dye in the modified PET films was 2 times higher when compared to the non-modified ones. The dye incorporated in the PET film was extracted using N,N-dimethylformamide and its amount was determined by UV-VIS spectroscopy at 520nm.
RSC Adv., 2014
Poly(ethylene terephthalate) was depolymerised under supercritical ethanol, 98 wt% of diethyltere... more Poly(ethylene terephthalate) was depolymerised under supercritical ethanol, 98 wt% of diethylterephthalate was obtained after 45 min, by adding [Bmim][BF4] as catalyst.
Polymer, 2005
Blends stand out as simple and cheap materials with unique properties. The miscibility of blends ... more Blends stand out as simple and cheap materials with unique properties. The miscibility of blends formed by bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) doped with europium (III) acetylacetonate have been studied by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and photoluminescent (PL) spectroscopy. DSC studies demonstrated that undoped PC/PMMA blends obtained by precipitation method present one glass transition temperature, evidencing their apparent miscibility. FTIR spectra revealed synergic effects in the PC/PMMA system as well as the incorporation of the Eu 3C complex. TGA analysis suggested that the Eu 3C complex remains preferably in the PC micro-phase. SEM analysis showed that europium (III) acetylacetonate is homogeneously distributed within the blend and PL spectra evidenced the photoluminescence of Eu 3C incorporated into the blend.
Polymer, 2008
A novel procedure has been developed to covalently graft multiple hydrophilic polymer ultra-thin ... more A novel procedure has been developed to covalently graft multiple hydrophilic polymer ultra-thin layers to functionalized polyethylene surface. Polyethylene films have been functionalized by two methods, chromic acid oxidation and maleic anhydride grafting, to produce surfaces containing reactive groups, carboxylic acid and anhydride, respectively. The reactive groups formed in the functionalization were used to anchor a poly(vinyl alcohol) (PVA) ultra-thin layer by thermal esterification. After anchoring PVA, a second ultra-thin layer, constituted of poly(acrylic acid) (PAA), was also anchored. The second layer was anchored by thermal esterification between PVA hydroxyl groups and PAA carboxylic acid groups. The procedure presented in this work allows the formation of an ultra-thin layer. The macromolecule anchoring reactions occur only at the interfaces, consequently, only the macromolecules in contact with the interface are anchored. The formation of the ultra-thin layer and the surface characteristics have been analyzed through XPS, ATR-FTIR, SEM, and AFM data.
Journal of Applied Polymer Science, 1989
European Polymer Journal, 2005
Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studi... more Free-radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) films has been studied using supercritical carbon dioxide (SC-CO 2) as a solvent and a swelling agent. As the reaction temperature was below the melting point, PP was modified in the solid phase. The PP film was first soaked with the monomer GMA and benzoyl peroxide (BPO) as an initiator using SC-CO 2 at different experimental conditions of pressure, temperature, and thermal treatment time. After releasing CO 2 , film GMA molecules were grafted onto PP in different times. Using this method, the degree of grafting and the morphology could be controlled through the combination of pressure, temperature, and soaking time. FTIR spectra confirmed that GMA had been grafted onto PP and that polypropylene-graft-glycidyl methacrylate (PP-g-GMA) presented a high surface reactivity for conductive polyaniline anchoring. DSC measurements and TG analyses showed that the thermal profiles of the graft copolymer and virgin PP are quite similar and that the graft PP does not exhibit changes in terms of thermal degradation profile and melting temperature, respectively. X-ray data showed that a high degree of grafting leads to a lower degree of crystallinity of polypropylene.
European Polymer Journal, 2005
In this work, the thermotropic liquid crystal MBBA (N-(4-methoxybenzilidene)-4-butylaniline), ent... more In this work, the thermotropic liquid crystal MBBA (N-(4-methoxybenzilidene)-4-butylaniline), entrapped on hydrogels, based on cross-linked polyacrylamide (PAAm), was studied. The liquid crystalline phases of system were characterized by polarized optical microscopy (POM), refractive index, optical transmittance, scanning electron microscopy (SEM) and water loss. It was verified the presence of birefringence on hydrogel+liquid crystal. The dynamic of formation of such birefringence
Journal de Physique IV (Proceedings), 2005
Samples of PC/PMMA blend having proportion 6/4, 4/6 and 2/8 were doped with acetylacetonate of Eu... more Samples of PC/PMMA blend having proportion 6/4, 4/6 and 2/8 were doped with acetylacetonate of Eu(acac) 3 having concentrations of 0-16%. Through Photoacoustic Spectroscopy (PAS) the interaction of Eu 3+ with the blends was studied using the visible range 200-530 nm, monitoring a wide absorption band from 280 to 320 nm, where results pointed that 2/8 blend presents the highest absorption. Preliminary luminescent emission showed higher emission for lower Eu(acac) 3 amounts and suggests that the 2/8 blend as more efficient at 615 nm. In addition, it is presented a study of thermal diffusivity and heat capacity evolution related to the doping amount for all blend proportions. Normalized thermal diffusivity is higher for 2/8 blend (a mean~5 .64 x 10-3 cm 2 s-1) and the specific heat was almost constant (c p(mean)~ 1.66 Jg-1 K-1).
Applied Surface Science, 2006
The modification of polysulfone surface was used to obtain effective interactions between an orga... more The modification of polysulfone surface was used to obtain effective interactions between an organic polymeric surface and an inorganic specie. A previous treatment of the polymer surface with modifiers is required in order to provide adherence. Our objective was the synthesis and the surface characterization of copper sulfide coated polysulfone (CuS-PSf) films. SEM micrographs showed a homogeneous distribution of copper sulfide, which contributes to increasing electrical conductivity. Xray analysis showed a decrease in copper sulfide particles (covellite porcelain) when compared with other polymeric composites prepared under similar conditions. The measured surface conductivity of the CuS-PSf films was higher than those of other similar systems, ca. 800 S cm À1 .
Química Nova, 2002
MATERIALS CHEMISTRY IN 25 YEARS OF BRAZILIAN CHEMICAL SOCIETY. Communications on Chemistry of Mat... more MATERIALS CHEMISTRY IN 25 YEARS OF BRAZILIAN CHEMICAL SOCIETY. Communications on Chemistry of Materials topics were already presented in the first annual meetings of the Brazilian Chemical Society, dispersed throughout various meeting sections. The SBQ Materials Chemistry division was organized in 1993, attracting those members with an interest in the composition, structure and properties of materials, as related to their functions. This paper is an account of the development of Materials Chemistry research in Brazil, based on the SBQ annual meetings data.
International Journal of Molecular Sciences, 2014
Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial ... more Chitosan, which is derived from a deacetylation reaction of chitin, has attractive antimicrobial activity. However, chitosan applications as a biocide are only effective in acidic medium due to its low solubility in neutral and basic conditions. Also, the positive charges carried by the protonated amine groups of chitosan (in acidic conditions) that are the driving force for its solubilization are also associated with its antimicrobial activity. Therefore, chemical modifications of chitosan are required to enhance its solubility and broaden the spectrum of its applications, including as biocide. Quaternization on the nitrogen atom of chitosan is the most used route to render water-soluble chitosan-derivatives, especially at physiological pH conditions. Recent reports in the literature demonstrate that such chitosan-derivatives present excellent antimicrobial activity due to permanent positive charge on nitrogen atoms side-bonded to the polymer backbone. This review presents some relevant work regarding the use of quaternized chitosan-derivatives obtained by different synthetic paths in applications as antimicrobial agents.
International journal of biological macromolecules, Jan 24, 2015
Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previous... more Polysaccharide-based device for oral delivery of heparin (HP) was successfully prepared. Previously synthesized N,N-dimethyl chitosan (DMC) (86% dimethylated by (1)H NMR spectroscopy) was complexed with HP by mixing HP and DMC aqueous solutions (both at pH 3.0). The polyelectrolyte complex (PEC) obtention was confirmed by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG) and wide-angle X-ray scattering (WAXS). In vitro controlled release assays of HP from PEC were investigated in the simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The PEC efficiently protected the HP in SGF condition in which HP is degraded. On the other hand, in SIF PEC promoted the releasing of 80±1.5% of loaded HP. The promissory results indicated that the PEC based on DMC/HP presented potential as drug-carrier matrix, since biological activity of HP was improved at pH close to physiological condition.
Journal of the Brazilian Chemical Society, 2014
Recentemente, foi desenvolvido em nosso grupo de pesquisas um modelo que prevê 100% do perfil de ... more Recentemente, foi desenvolvido em nosso grupo de pesquisas um modelo que prevê 100% do perfil de liberação de soluto a partir de hidrogel. Este considera os efeitos de difusão e de partição e permite obter os valores da atividade de partição, α, e da constante cinética de liberação, k R. Embora α e k R sejam dependentes de fatores diversos, a hipótese de que a razão α/k R não seja dependente do volume de fluido de intumescimento foi testada neste trabalho. Assim, foram determinados valores da razão α/k R para vitamina B 12 (VitB 12) e diclofenaco de potássio (DFK) que foram submetidos a ensaios de liberação em três temperaturas (25, 35 e 45 °C), sendo avaliados, em cada temperatura, os volumes 250, 350 e 450 mL. O hidrogel utilizado é baseado na goma arábica quimicamente modificada copolimerizada com N,N-dimetilacrilamida (AGm-DMAAm), na razão 60-40 (m/m) sendo o carregamento dos solutos feito durante o processo de gelificação. Foi verificado que a razão α/k R não depende do volume do fluido de liberação para uma determinada temperatura. Mas a temperatura é um fator importante, influenciando fortemente o processo de liberação destes solutos. A variação da temperatura de 25 para 35 °C afeta mais a liberação de DFK do que a liberação de VitB 12. Isso foi atribuído a interações eletrostáticas entre os grupos (R-COO-) contidos nesse soluto e a grupos positivamente carregados na matriz. Foram calculados os valores de tempo de meia vida de liberação, t 1/2 , e a energia de ativação, Ea R , do processo de liberação dos solutos. Recently, a model predicting whole profile solute release from a hydrogel was developed. In such model, the partition activity, α, and release kinetic constant, k R , can be obtained. Although α and k R depend on many factors, the hypothesis that α/k R ratio does not depend on external fluid volume was tested in the present study. Thus, α/k R values for two distinct solutes, vitamin B 12 (VitB 12) and diclofenac potassium (DFK), were obtained at 25, 35 and 45 °C using 250, 350 and 450 mL of external fluid. The hydrogel used in the experiments was obtained by the copolymerization of N,N-dimethylacrylamide-modified Arabic gum (AGm-DMAAm), at wt% ratio of 60-40. It was verified that α/k R ratio is not volume dependent, at a certain temperature, but the temperature strongly influences the α/k R ratio for both solutes. Changing temperature from 25 to 35 °C affected DFK release much more than VitB 12 release. This was attributed mainly to electrostatic interactions between (R-COO-) from DFK and the positively charged groups in the GAm-DMAAm matrix. Additionally, the values for the half-life time release, t 1/2 , equilibrium time release, t eq , as well as the activation energy for releasing, Ea R , were determined and discussed in light of the partition-diffusion model.