Excited State Absorption of Doped and Undoped Polyanyline

Polyaniline is a conducting polymer with appealing electrical and optical properties, arising from the -conjugation along the polymer backbone. The understanding of its excited state absorption is of prime importance for designing and fabricating optical devices. Here, we report on the study of the excited state absorption of doped and undoped PANI by using femtosecond pulses in the spectral range from 450nm up to 850nm. For undoped PANI, we observed saturation of absorption as well as reverse saturable absorption, depending on the excitation wavelength. For doped PANI, however, only saturable absorption was observed.

NMR study of slow motions of HDA hydrocarbons chains inside lamellar structures

Measurements of H-1 and C-13 Nuclear Magnetic Resonance (NMR) for the nano-composite materials formed by the intercalation of hexadecylamine (HDA) in metal oxides (TiO2, V2O5 and MoO3), are reported. The H-1 NMR spin-lattice relaxation in the rotating frame was described by using the spectral density due to Davidson and Cole, which incorporates a distribution of correlation times characterized by a width parameter epsilon. The fitting of the data was obtained for epsilon = 0.74, indicating that the correlation times are distributed over a narrow range in this system. High-resolution C-13 NMR techniques were used to resolve the NMR lines of middle-chain methylene groups in the spectra and variable contact time cross-polarization {H-1-}C-13 experiments were employed to analyze the reorientation dynamics of the CH3 and CH2 groups in the HDA chains.

The use of colloidal ferrofluid as building blocks for nanostructured layer-by-layer films fabrication

The electrostatic layer-by-layer technique has been exploited as an useful strategy for fabrication of nanostructured thin films, in which specific properties can be controlled at the molecular level. Ferrofluids consist of a colloidal suspension of magnetic grains (with only a few nanometers of diameter) with present interesting physical properties and applications, ranging from telecommunication to drug delivery systems. In this article, we developed a new strategy to manipulate ferrofluids upon their immobilization in nanostructured layered films in conjunction with conventional polyelectrolytes using the layer-by-layer technique. We investigated the morphological, optical, and magnetic properties of the immobilized ferrofluid as a function of number of bilayers presented in the films. Ferrofluid/polyelectrolyte multilayers homogeneously covered the substrates surface, and the magnetic and optical properties of films exhibited a linear dependence on the number of bilayers adsorbed.

Nuclear Magnetic Resonance Study of Hydrated Bentonite

Impedance spectroscopy and nuclear magnetic resonance (NMR) were used to investigate the mobility of water molecules located in the interlayer space of H(+) - exchanged bentonite clay. The conductivity obtained by ac measurements was 1.25 x 10(-4) S/cm at 298 K. Proton ((1)H) lineshapes and spin-lattice relaxation times were measured as a function of temperature over the temperature range 130-320 K. The NMR experiments exhibit the qualitative features associated with the proton motion, namely the presence of a (1)H NMR line narrowing and a well-defined spin-lattice relaxation rate maximum. The temperature dependence of the proton spin-lattice relaxation rates was analyzed with the spectral density function appropriate for proton dynamics in a two-dimensional system. The self-diffusion coefficient estimated from our NMR data, D similar to 2 x 10(-7) cm(2)/s at 300 K, is consistent with those reported for exchanged montmorillonite clay hydrates studied by NMR and quasi-elastic neutron scattering (QNS).

Electropolymerization studies of PAni/(poly)luminol over platinum electrodes

This work presents a cyclic voltammetry study of the polyaniline/polyluminol copolymer on platinum electrodes. The results show that under determined conditions it is possible to obtain the copolymer deposited on a metallic surface. The luminol presence clearly affects the oxidation of aniline in the nucleation process and, additionally, changes the cyclic voltammetric characteristics of the obtained material. In this aspect, the copolymer presents hybrid characteristics when compared to the polyaniline and polyluminol separately obtained and seems to present intermediary conductivity.

Influence of Reaction Conditions on Synthesis of PAni/MnO(2) Composites

An investigation of the parameters as aniline: MnO(2) and temperature on synthesis of polyaniline/MnO(2) composites was performed. The composites were chemically prepared in H(2)SO(4) media using different aniline: MnO(2) ratios at 0 degrees C. After the ratio optimization, the syntheses were performed at 20 degrees C. The polyaniline/MnO(2) composites were characterized by scanning electron microscopy (SEM), ultraviolet-visible, near infrared and infrared spectroscopic techniques. Composites obtained with a uniform, homogeneous and thicker coating of polyaniline films under oxide was considered as the best condition for synthesis.

Thermodynamics and Lithium Intercalation in CeO(2)-TiO(2) Thin Film

The kinetics and the thermodynamics of electrochemical intercalation of lithium into CeO(2)-TiO(2) films prepared by the sol-gel process were studied by galvanostatic intermittent titration technique (GITT) as function of the depth of lithium intercalation. The open-circuit-potential versus x in Li(x)(CeO(2)-TiO(2)) curve consists of two straight lines with different slopes, one in the range of 0.03 <= x <= 0.09 and the other of 0.09 < x <= 0.15. The standard Gibbs energy for lithium intercalation Delta G(1)(0) was 6kJ/mol for x = 0.09 in Li(x)(CeO(2)-TiO(2)) at room temperature. The chemical diffusion coefficient value, D(Li+), of lithium intercalation into thin film oxide was 2.14.10(-11) cm(2)/s at x = 0.15, and the value of the component diffusion coefficient D(Li+),(k) was about one order of magnitude lower than the coefficient of chemical diffusion.

Electrochemical Behaviour of the AA2024 Aluminium Alloy Modified with Self-Assembled Monolayers/Polyaniline Double Films

The electrochemical characteristics of the AA2024 aluminium alloy modified with octadecyltrimethoxysilane (ODTMS) + polyaniline (PANi) and propiltrimethoxysilane (PTMS) + (PANi) were studied in the present work. The results show that the different protective coatings shift the values of corrosion and pit potentials to more positive values making the system nobler and indicate that the double film ODTMS + PANi present the best protection against corrosion characteristics, that is probably due to the two contributions: anodic protection associated with the barrier effect.

Synthesis and characterization of mono and polymeric cyclopalladated compounds: Crystal and molecular structure of [{Pd(dmba)(ONO(2))}(2)(mu-pz)] center dot H(2)O (pz = pyrazine)

In the treatment of cyclometallated dimer [Pd(dmba)(mu-Cl)](2) (dmba = N,N-dimethylbenzylamine) with AgNO(3) and acetonitrile the result was the monomeric cationic precursor [Pd(dmba)(NCMe)(2)](NO(3)) (NCMe=acetonitrile) (1). Compound 1 reacted with m-nitroaniline (m-NAN) and pirazine (pz), originating [Pd(dmba)(ONO(2))(m-NAN)] (2) and [{Pd(dmba)(ONO(2))}(2)(mu-pz)] center dot H(2)O (3), respectively. These compounds were characterized by elemental analysis, IR and NMR spectroscopy. The IR spectra of (2-3) display typical bands of monodentade O-bonded nitrate groups, whereas the NMR data of 3 are consistent with the presence of bridging pyrazine ligands. The structure of compound 3 was determined by Xray diffraction analysis. This packing consists of a supramolecular chain formed by hydrogen bonding between the water molecule and nitrato ligands of two consecutive [Pd(2)(dmba)(2)(ONO(2))2(mu-pz)] units. (c) 2008 Elsevier Ltd. All rights reserved.

LDPE/EVA Composites for Antimicrobial Properties

Composites with antimicrobial activity are of great interest nowadays and the development of titanium dioxide with these functional properties presents interest in academic and industrial sectors.An approach to develop PE composite containing silver microparticles to have an antimicrobial effect is presented. To obtain such antimicrobial composites, LDPE/EVA were processed with Ag particles on TiO2 particles as inorganic carrier substance. Titanium dioxide nanoparticles (P-25) were covered with silver particles using Turkevich Method or citrate reduction method. The Ag/TiO2 particles were dispersed at concentration of 0,8 wt% and 1% wt% in LDPE/ethylene vinyl acetate copolymer (EVA)-(50% w/w) at the melt state in a Haake torque Rheometer. Silver microparticles were characterized with UV-Vis Spectroscopy. The composites thus prepared were characterized through XRD, Ares Rheometer, Scanning Electronic Microscopy (SEM) and JIS Z 2801 antimicrobial tests to study the effects of the addition of particles on rheological properties, morphological behavior and antimicrobial properties. The results showed that incorporation of silver/titanium dioxide particles on composites obtained systems with differents dispersions. The Ag/TiO2 particles showed uniform distribution of Ag on TiO2 particles as observed by SEM-EDX and antimicrobial tests according to JIS Z 2801 shows excellent antimicrobial properties.

Production of reinforced composites with natural fibers for industrial applications - Extrusion and injection WPC

The aim of this work is to study the replacement of currently used thermoplastics by composites reinforced with vegetable fibers with several advantages, mainly better mechanical properties, low weight and competitive cost compared to its counterparts. Extrusion and injection molding processes were studied using polypropylene (PP) matrix. The raw materials used were sugar cane bagasse, elephant grass, wood, milk cartons and recycled polypropylene. The composites were tested for bending, tension, hardness and impact resistance, following ASTM standards. The results obtained were extremely positive since they proved that natural fibers as reinforcement can be an important alternative to replace talc and other fillers.

Efeito da adição de diatomita no comportamento reológico e mecânico de argamassas colantes

The mortar is a type of adhesive products used in large scale in construction, it is a function of its variety and ease of application . Although industrialized product and endowed with technology in its production is very frequent occurrence of the same pathology , which causes frequent damage and losses in the construction industry. Faced with this real market situation , the technical and scientific study of the effects of the addition of diatomite on the rheological and mechanical behavior of adhesive mortars are needed. This work back as a suggestion the use of diatomite as a mineral additive in formulations of adhesive mortars for partial replacement of cellulose based additives . The choice of using this mineral occurs through physical, chemical and rheological properties that justify its use in this product line , and is a raw material abundant in our region and can thus contribute positively to the minimization of direct costs cellulose -based additives . Industrial adhesive mortar used for comparison , was type AC1 . Formulations of adhesive mortar with diatomite held constant dosed quantities of sand, cement and the water / cement (w / c ) , or adhesive mortar formulations were developed with levels 10, 20, 30 and 40% of diatomite substituting part of the cellulose -based additives . These mortars were subjected to the following tests that define and evaluate the rheological and mechanical behavior of this type of mortar. The results attest the best performance of the adhesive mortar type AC1 with partial replacement of 30 % of the cellulose-based additive for diatomite

Panels Produced from Thermoplastic Composites Reinforced with Peach Palm Fibers for Use in the Civil Construction and Furniture Industry

In order to cooperate in minimizing the problems of the current and growing volume of waste, this work aim at the production of panels made from industrial waste -thermoplastic (polypropylene; polyethylene and acrylonitrile butadiene styrene) reinforced with agro-industrial waste - peach palm waste (shells and sheaths). The properties of the panels like density, thickness swelling, water absorption and moisture content were evaluated using the ASTM D1037; EN 317; and ANSI A208.1 standards regarding particle boards. Good results were obtained with formulations of 100% plastic waste; 70% waste plastics and 30% peach palm waste; and 60% waste plastics and 40% peach palm waste.

Rheological, Mechanical and Adhesive Properties of Surfactant-Containing Systems Designed as a Potential Platform for Topical Drug Delivery

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

Microemulsões e fases líquidas cristalinas como sistemas de liberação de fármacos

A mistura de tensoativos com água, em determinadas proporções, na ausência ou na presença de substâncias lipofílicas pode formar diferentes tipos de agregados, entre os quais agregados polimorfos representados pelas microemulsões (ME) e mesofases liotrópicas - os cristais líquidos (LC), que estão intimamente ligados com a proporção e a natureza dos componentes da mistura. Nesse trabalho, foi discutido o papel desses sistemas na incorporação de fármacos com diferentes propriedades físico-químicas, influenciando fortemente a liberação, assim como a biodisponibilidade dos fármacos. Aspectos sobre a formação e a caracterização de microemulsões e cristais líquidos também foram discutidos. A análise da literatura indicou que, dependendo da polaridade do fármaco, o efeito da ME ou LC pode ser usado para otimizar o efeito terapêutico por meio do controle da velocidade ou do mecanismo de liberação do fármaco.