Morphology variation as a function of composition for blends of PVDF and a polyaniline derivative

Blends of poly(vinylidene fluoride), PVDF, and poly(o-methoxyaniline), POMA doped with toluene sulfonic acid, TSA, were prepared by casting at various compositions and studied by scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The blend composition has a great influence on the morphology obtained. As the concentration of POMA-TSA is increased in the blend an interconnecting fibrillar-like morphology is formed and the spherulites characteristic of pure PVDF are destroyed. The variation of blend morphology is further discussed based on X-ray diffraction and differential scanning calorimetry analysis. (C) 1998 Elsevier B.V. Ltd. All rights reserved

Doping of polyaniline by corona discharge

In the present article it is shown that a corona discharge can be employed to dope thin films of polyaniline (PANI) coated on poly(ethylene terephthalate) films, allowing the electrical conductivity to be tuned within the range 10(-10) to 0.3 S cm(-1). A study of the effect of different corona conditions, namely corona treatment for positive and negative polarities, air humidity, treatment time, corona current, and the geometry of the corona triode, on the electrical conductivity of the polyaniline is presented. The results indicate that the corona discharge leads to protonic doping of polyaniline similar to that which occurs in conventional protonic acid solution doping. Atomic force microscopic analysis shows that, as the PANI is exposed to the corona discharge, its globular morphology is disrupted leading to the appearance of droplet-like features and a significant decrease in the average height and surface roughness. Doping by corona discharge presents several advantages over the conventional solution method namely that it is a dry process which does not require use of chemicals reagents, and which is both rapid and avoids dopant migration. The latter can be important for applications of PANI in microelectronic devices. (C) 2000 American Institute of Physics. [S0021-8979(00)01608-X]

Interaction mechanism of poly (o-ethoxyaniline) and collagen blends

Blend films of poly (o-ethoxyaniline) (POEA) and collagen were fabricated by casting under optimized conditions and characterized by Raman scattering and UV-vis absorption spectroscopies. The UV-vis spectra showed that the addition of collagen in the aqueous solution of POEA promotes a dedoping of the POEA. This effect was also observed for the blend films as supported by Raman scattering and a mechanism for the chemical interaction between POEA-collagen is proposed. The influences of different percentage of collagen as well as the pH of stock solutions during the fabrication process of the blend films were also investigated. It was found that the preparation method plays an important role in the flexibility and freestanding properties of the films. Complementary, the surface morphology was studied by atomic force microscopy and the conductivity by dc measurements. (C) 2003 Elsevier Ltd. All rights reserved

Correlation between human panel and electronic tongue responses on the analysis of commercial sweeteners

In this work, the taste characteristics of 11 different formulations of commercial sweeteners in mineral water are evaluated by a group of trained human judges (human panel) and an electronic tongue (ET) system. The ET is comprised by 5 chemical sensors made of nanostructured conducting polymer films deposited onto gold interdigitated microelectrodes, whose electrical capacitances are measured with them immersed in sweetener solutions. It is verified that the ET exhibits sensitivity to the sweeteners in a large range of frequency (0-10(6) Hz), and its response can be reasonably correlated to the human panel evaluation.4440340

Synthesis of Hollow-Structured Nano- and Microspheres from Pectin in a Nanodroplet Emulsion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Hollow-structured nano- and microspheres with diameters ranging from 24 mu m to 160 nm were successfully produced from chemically modified pectin (Ma-Pec) through a two-step synthesis. In a first step, the Pec was modified with glycidyl methacrylate (GMA) in a heterogeneous phase system, indeed consisting of water-soluble Pec and water-insoluble GMA, via an interfacial reaction at the interface of the GMA-water phase system after 12 h under continuous stirring of 1000 rpm at 60 degrees C. In a second step, the spheres were prepared in a water-in-benzyl alcohol nanodroplet emulsion at 12000 rpm under a bubbling stream of nitrogen in the presence of sodium persulfate, as initiator, and TEMED, as catalytic agent. FT-IR spectra revealed that the vinyl groups (C=C) coming from the GMA were attached onto backbone of the polysaccharide. (13)C-CP/MAS NMR spectra demonstrated that the spheres were formed via carbon-carbon pi-bonds on Ma-Pec in the water phase, for the duration of the dispersion stage. The dark center (an empty core) and edge of the hollow spheres could be easily identified by SEM micrographs. This type of polymer structure represents a class of unique material with particular importance in terms of state-of the-art applications in both nano- and microencapsulation of drugs, for example, protection shields of biologically active agents.25424732478Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundagdo de Amparo a Pesquisa do Estado de Sao Paulo [06/50952-4]Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundagdo de Amparo a Pesquisa do Estado de Sao Paulo [06/50952-4

Synthesis and characterization of a starch-modified hydrogel as potential carrier for drug delivery system

Synthesis and characterization of a new hydrogel were. carried out using a chemically modified starch (starch-M) consisting of coupling C=C bounds coming from glycidil methacrylate (GMA) onto the polysaccharide structure. C-13 NMR, H-1 NMR, and FT-IR spectroscopies were used to confirm the incorporation of such groups onto the starch-M. The hydrogel was prepared by a crosslinking polymerization of starch-M using sodium persulfate as an initiating agent. The starch-M hydrogel shows morphology clearly different from that of the raw starch film due to the presence of, voids on its surface. The swelling process of the starch-M hydrogel was not significantly affected by changes on the temperature or on pH of the surrounding liquid, indicating the such behavior can be then understood by a diffusional process, resulting from its physical-chemical interactions with the solvent. The values of the diffusional exponent n were on the order of 0.45-0.49 for the range of pHs investigated, demonstrating that the water transport mechanism of starch-M hydrogel is more dependent on Fickian diffusion, that is, controlled by water diffusion. Such starch-M hydrogel is a promising candidate to be used in transporting and in preserving acid-responsive drugs, such as con ticoids, for the treatment of colon-specific diseases, for example, Crohn's disease. (C) 2008 Wiley Periodicals, Inc.4672567257

Exploiting the versatility of taste sensors based on impedance spectroscopy

The versatility of sensor arrays made from nanostructured Langmuir-Blodgett (LB) and layer-by-layer (LBL) films is demonstrated in two ways. First, different combinations of sensing units are employed to distinguish the basic tastes, viz. sweet, sour, bitter, and salty tastes, produced, respectively, by small concentrations (down to 0.01 g/mol) of sucrose, HCl, quinine, and NaCl solutions. The sensing units are comprised of LB and/or LBL films from semiconducting polymers, a ruthenium complex, and sulfonated lignin. Then, sensor arrays were used to identify wines from different sources, with the high distinguishing ability being demonstrated in principal component analysis (PCA) plots. Particularly important was the fact that the sensing ability does not depend on specific interactions between analytes and the film materials, but a judicious choice of materials is, nevertheless, required for the materials to respond differently to a given sample. It is also shown that the interaction with the analyte may affect the morphology of the nanostructured films, as indicated with scanning electron microscopy. For instance, in wine analysis these changes are not irreversible and the original film morphology is retrieved if the sensing unit is washed with copious amounts of water, thus allowing the sensor unit to be reused