Polyurethane coating with thin polymer films produced by plasma polymerization of diglyme

Aqueous-based polyurethane dispersions have been widely utilized as lubricants in textile, shoes, automotive, biomaterial and many other industries because they are less aggressive to surrounding environment. In this work thin films with different thickness were deposited on biocompatible polyurethane by plasma polymerization process using diethylene glycol dimethyl ether (Diglyme) as monomer. Molecular structure of the films was analyzed by Fourier Transform Infrared spectroscopy. The spectra exhibited absorption bands of O-H (3500-3200cm(-1)), C-H (3000-2900cm(-1)), C=O (1730-1650cm(-1)), C-O and C-O-C bonds at 1200-1600cm(-1). The samples wettability was evaluated by measurements of contact angle using different liquids such as water, glycerol, poly-ethane and CMC. The polyurethane surface showed hydrophilic behavior after diglyme plasma-deposition with contact angle dropping from 85(0) to 22(0). Scanning Electron Microscopy revealed that diglyme films covered uniformly the polyurethane surfaces ensuring to it a biocompatible characteristic.

NMR study of styrene-butadiene rubber (SBR) and TiO2 nanocomposites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Polymerization of photocurable commercial dental methacrylate-based composites - Photocalorimetry study

Due to their excellent aesthetics, photopolymers have been extensively used in several dentistry applications. However, several problems are reported, e.g. low mechanical and abrasion resistance, shrinkage during polymerization, etc. Properties of the final restorations are intrinsically related to the polymerization stage, which can be conveniently studied by photocalorimetry. In the present work the polymerization reaction and the filler content of different photocurable commercial dental methacrylate-based composites were studied by means of photocalorimetry and thermogravimetry, respectively. The results show that the values of curing rate, the heat of polymerization and the filler content vary significantly from one composite to another.

New layered double hydroxides intercalated with substituted pyrroles. 1. In situ polymerization of 4-(1H-pyrrol-1-yl)benzoate

The two-dimensional hybrid organic-inorganic materials Zn-2-Cr and Zn-2-Al-LDHs (Layered Double Hydroxides) containing 4-(1H-pyrrol-1yl)benzoate anions as the interlayer anions were synthesized by the co-precipitation method at constant pH followed by subsequent hydrothermal treatment for 72 h. The materials were characterized by PXRD, C-13 CP-MAS NMR, ESR, TGA, and TEM. The basal spacing found by the X-ray diffraction technique is coincident with the formation of bilayers of the intercalated anions. Solid-state C-13 NMR and ESR data strongly suggest the partial in situ polymerization of the 4-(1H-pyrrol-1yl)benzoate anions during coprecipitation. (c) 2006 Elsevier Ltd. All rights reserved.

Polymerization of ethylene by the tris(pyrazolyl)borate titanium(IV) compound immobilized on MAO-modified silicas

The immobilization of soluble catalyst {Tp(Ms)}TiCl3 (Tp(Ms*)HB(3-mesityl-pyrazolyl)(2)(5-mesityl-pyrazolyl)(-)) on silica and MAO-modified silicas containing 4.0, 8.0 and 23.0 wt.% Al/SiO2 yields active supported catalysts for ethylene polymerization. Among the supported catalysts studied by XRF spectroscopy, higher titanium content was obtained using MAO-modified silica containing 8.0 wt.% Al/SiO2 as support. For the ethylene polymerization reactions carried out in hexane at 60degreesC using a combination of triisobutylaluminum (TiBA) and methylaluminoxane (MAO) (1:1), the activities varied between 24.4 and 113.5 kg of PE/mol [Ti] h. The highest activity is reached using MAO-modified silica containing 4.0 wt.% Al/SiO2 as support. The viscosity-average molecular weights ((M) over bar (v)) of the PE's produced with the supported catalysts varying from 1.44 to 9.94 x 10(5) g/mol with melting temperatures in the range of 125-140degreesC. The use of other Lewis acid cocatalysts, including TiBA, diethylaluminium chloride (DEAC), and trimethylaluminum (TMA) resulted also in the formation of active catalysts for ethylene polymerization. However, the activities are lower than that one using a combination of TiBA and MAO. The viscosity-average molecular weights (R,) of PE's are influenced by varying the cocatalysts as well as the Al/Ti molar ratio. The supported catalyst generated in situ under ethylene atmosphere is roughly four times more active than supported one containing 4.0 wt.% Al/SiO2. (C) 2003 Elsevier B.V. All rights reserved.

Nanocomposites of Styrene-Butadiene Rubber and Synthetic Anatase Obtained by a Colloidal Route and Their Photooxidation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparison between different conditions of the chemical polymerization of polyaniline on top of PET films

Composites produced during the in situ chemical polymerization of aniline on top of a poly(ethylene terephthalate) (PET) film, in different conditions, were studied by open-circuit potential (Voc), ultraviolet-visible, and infrared spectroscopy, electrical conductivity measurements, scanning electron microscopy, and atomic force microscopy. The polymerization monitoring by Voc showed a maximum associated with the intermediate pernigraniline oxidation state and a final formation of polyaniline (PANI) in the doped emeraldine salt (ES) form. Furthermore, high electrical conductivity values were obtained for the PANI-ES coating prepared under selected conditions. A globular formation was observed for the doped PANI-ES coating with globules of sizes of the same order and same shape of the PET, demonstrating the influence of the substrate on the coating morphology.

Tuning the activity of alternative Ru-based initiators for ring-opening metathesis polymerization of norbornene and norbornadiene by the substituent in 4-CH2R-piperidine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese e caracterização de esferas monodispersas de látex e sua utilização no preparo de filmes de cristais coloidais tridimensionais

Esferas de poliestireno foram obtidas através da polimerização do estireno sem a presença de emulsificante. A suspensão foi caracterizada por Espalhamento de Luz e Microscopia Eletrônica de Transmissão apresentando monodispersidade com tamanho em torno de 463 nm. O método de deposição vertical foi utilizado para preparar filmes em substratos de vidro a partir da suspensão de esferas. Filmes de opalas de alta qualidade foram obtidos e caracterizados por Espectroscopia de Reflectância, Microscopia Eletrônica de Varredura e Microscopia Óptica.

Effect of Flasking and Polymerization Techniques on Tooth Movement in Complete Denture Processing

Purpose: The purpose of this study was to compare the artificial tooth positional changes following the flasking and polymerization of complete dentures by a combination of two flasking methods and two polymerization techniques using computer graphic measurements.Materials and Methods: Four groups of waxed complete dentures (n = 10) were invested and polymerized using the following techniques: (1) adding a second investment layer of gypsum and conventional water bath polymerization (Control), (2) adding a second investment layer of gypsum and polymerization with microwave energy (Gyp-micro), (3) adding a second investment layer of silicone (Zetalabor) and conventional polymerization (Silwater), and (4) adding a second investment layer of silicone and polymerization with microwave energy (Silmicro). For each specimen, six segments of interdental distances (A to F) were measured to determine the artificial tooth positions in the waxed and polymerized stages using software program AutoCad R14. The mean values of the changes were statistically compared by univariate ANOVA with Tukey post-hoc test at 5% significance.Results: There were no significant differences among the four groups, except for segment D of the Silmicro group (-0.004 +/- 0.032 cm) in relation to the Gypwater group (0.044 +/- 0.031 cm) (p < 0.05), which presented, repectively, expansion and shrinkage after polymerization.Conclusions: Within the limitations of this study, it was concluded that although the differences were not statistically significant, the use of a silicone investment layer when flasking complete dentures resulted in the least positional changes of the artificial teeth regardless of the polymerization technique.

Influence of cerium (IV) ions on the mechanism of organosilane polymerization and on the improvement of its barrier properties

In this work, the effect of cerium (IV) ammonium nitrate (CAN) addition on the polymerization of bis-[triethoxysilyl]ethane (BTSE) film applied on carbon steel was studied. The electrochemical characterization of the films was carried out in 0.1 mol L(-1) NaCl solution by open-circuit potential measurements, anodic and cathodic polarization curves and electrochemical impedance spectroscopy (EIS). Morphological and chemical characterization were performed by atomic force microscopy (AFM), contact angle measurements, infrared-spectroscopy, nuclear magnetic resonance and thermogravimetric analysis. The results have clearly shown the improvement on the protective properties of the Ce(4+) modified film as a consequence of the formation of a more uniform and densely reticulated silane film. A mechanism is proposed to explain the accelerating role of Ce(4+) ions on the cross-linking of the silane layer. (C) 2008 Elsevier Ltd. All rights reserved.

Comparison of the nanoparticles performance in the photocatalytic degradation of a styrene-butadiene rubber nanocomposite

Much has been talking about the advantages of polymeric nanocomposites, but little is known about the influence of nanoparticles on the stability of these materials. In this sense, we studied the influence of both oxides of zirconium and titanium, known to have photocatalytic properties, as well as the influence of synthetic clay Laponite on the photodegradation of styrene-butadiene rubber (SBR). SBR nanocomposites were prepared by the colloidal route by mixing commercial polymer lattices and nanometric anatase TiO2, monoclinic ZrO2 or exfoliated Laponite clays colloidal suspensions. To better understand the degradation mechanisms that occur in these nanocomposites, the efficiency of different photocatalysts under ultraviolet radiation was monitored by FT-IR and UV-vis spectroscopies and by differential scanning calorimetric. It was observed that TiO2 and ZrO2 nanoparticles undoubtedly acted as catalysts during the photodegradation process with different efficiencies and rates. However, when compared to pure SBR samples, the polymer degradation mechanism was unaffected. Unlike studies with nanocomposites montmorillonite, exfoliated laponite clay effectively acts as a photostabilizer of polymer UV photodegradation. Copyright © 2012 Wiley Periodicals, Inc.

Color stability of the artificial iris button in an ocular prosthesis before and after acrylic resin polymerization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of ion concentration of ionomer in electron injection layer of polymer light-emitting devices

Polymer light-emitting devices (PLEDs) with poly(2-methoxy-5-hexyloxy)-p-phenylenevinylene (OC1OC6-PPV) as the emissive layer were studied with an electron injection layer of ionomers consisting of copolymers of styrene and methylmethacrylate (PS/PMMA) with 3, 6 and 8 mol% degree of sulfonation. The ionomers were able to form very thin films over the emissive layer, with less than 30 nm. Additionally, the presence of ion pairs of ionomer suppresses the tendency toward dewetting of the thin film of ionomer (similar to 10 nm) which can cause malfunction of the device. The effect of the ionomers was investigated as a function of the ion content. The devices performance, characterized by their current density and luminance intensity versus voltage, showed a remarkable increase with the ionomer layer up to 6 mol% of ionic groups, decreasing after that for the 8 mol% ionomer device. The study of the impedance spectroscopy in the frequency range from 0.1 to 10(6) Hz showed that the injection phenomena dominate over the transport in the electroluminescent polymer bulk. (c) 2006 Elsevier B.V. All rights reserved.