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ABSTRACT: Solutions of chitin in Li(+)/N,N-dimethylacetamide systems were studied via viscometry, using LiCl concentrations of 3% and 5% (m/v) and chitin concentrations ranging from 0.075 to 0.375 gL(-1). The reduced viscosity number versus concentration plot showed a minimum that was related to the formation of Li(+)-OC complex moieties along chitin macromolecular chains. Viscosity behavior was affected by temperature according to the Eyring model: concentration dependence of flow enthalpy of activation was correlated to polymer-polymer interactions and flow entropy of activation to the stiffness of the complexed chitosan macromolecular chain.
Carbohydrate research 01/2011; 346(5):614-8. · 2.03 Impact Factor
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ABSTRACT: Particulate systems composed of polyelectrolyte complexes (PEC) based on chitosan and poly(methacrylic acid) were obtained via template polymerization. The resultant particles were characterized as having regions with different charge densities: chitosan predominating in the core and poly(methacrylic acid) at the surface, the particles being negatively charged, as a consequence. Albumin was adsorbed on these particles (after cross-linking with glutardialdehyde), and pH was controlled to obtain two conditions: (i) adsorption of positively charged albumin and (ii) adsorption of albumin at its isoelectric point. Adsorption isotherms and zeta-potential measurements showed that albumin adsorption was controlled by hydrogen bonding/van der Waals interactions and that brush-like structures may enhance the adsorption of albumin on these particles. It was also found that shearing can induce desorption of albumin from the PEC surface, depending on the continuous phase albumin concentration.
Langmuir 08/2007; 23(14):7687-94. · 4.19 Impact Factor
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ABSTRACT: Layer-by-layer (LbL) films have been produced with poly(o-ethoxyaniline) (POEA), chitosan and chitosan-poly(methacrylic acid) (CS-PMAA) nanoparticles. Because the adsorption of LbL films depends on ionic interactions and H-bonding, optimized conditions had to be established for the growth of multilayer films. Unusually thick films were obtained for POEA and CS-PMAA, thus demonstrating the importance of using chitosan in the form of nanoparticles. These nanostructured films were deposited on chromium electrodes to form a sensor array (electronic tongue) based on impedance spectroscopy. This system was used to detect copper ions in aqueous solutions
IEEE Transactions on Dielectrics and Electrical Insulation 11/2006; · 1.09 Impact Factor
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ABSTRACT: Chitosan/poly(methacrylic acid) complexes, CS/PMAA, were prepared via dropwise addition of a solution of PMAA to a solution of chitosan in acetic acid 2 wt %. The increase in molecular weight of PMAA inhibited the formation of insoluble complexes, while the increase in ionic strength first favored the formation of the complex followed by inhibiting it at higher concentrations. These observations were related to a description of polyelectrolyte complexation that was strongly dependent on macromolecular dimensions, both in terms of molecular weight and of coil expansion/contraction driven by polyelectrolyte effect.
Biomacromolecules 05/2006; 7(4):1245-52. · 5.48 Impact Factor
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ABSTRACT: Layer-by-layer (LbL) films have been produced with poly(o-ethoxyaniline) (POEA), chitosan and chitosan-poly(methacrylic acid) (CS-PMAA) nanoparticles. Because the adsorption of LbL films depends on ionic interactions and H-bonding, optimized conditions had to be established for the growth of multilayer films. Unusually thick films were obtained for POEA and CS-PMAA, thus demonstrating the importance of using chitosan in the form of nanoparticles
Electrets, 2005. ISE-12. 2005 12th International Symposium on; 10/2005
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ABSTRACT: The stabilities of alumina dispersions were studied as a function of poly- and low molecular weight electrolyte concentration, using viscometry of the dispersing phase, and zeta potential measurements. The relation of polyelectrolyte adsorption to polymer concentration (at different low molecular weight electrolyte concentrations) was found to depend upon the dimensions of the polymer (which were a priori known to decrease with increasing poly- and low molecular weight electrolyte concentration). The occurrence of flocculation and bridging in the destabilization mechanism of the alumina dispersions was also characterized.
Colloid and Polymer Science 12/2004; 283(4):413-420. · 2.33 Impact Factor
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ABSTRACT: Hard segment hydrogen bonding interactions in a particular polyurethane segmented copolymer have been analysed through a viscometric approach to determine the behaviour of polyurethane solutions with different solvent compositions. Analysis of log ηspversus log c[η] master curves (solely comprising dilute and semidilute regimes) showed that these systems could be differentiated by the slope of the first part of the curve (dilute regime), the characteristic reduced concentration c*[η], and the slope of the second part of the curve (semidilute regime), differences which were related to a possible occurrence of polymer aggregates. Experiments with solutions in the concentrated regime, at different temperatures, were used to relate non-Newtonian behaviour to hydrogen bonding.© 2001 Society of Chemical Industry
Polymer International 12/2001; 51(1):69 - 74. · 1.90 Impact Factor
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ABSTRACT: The rheology of starch–DMSO–water solutions was studied as a function of water content and temperature. A correlation between flow regime, temperature, and water content was presented so as to characterize amylose conformation change in a novel way. Rheological behavior was characterized using an empirical equation to classify fluids under study as Newtonian, pseudoplastic, or dilatant. The temperature effect was analyzed through the determination of the apparent activation energy and preexponential constant. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1285–1290, 2001
Journal of Applied Polymer Science 03/2001; 80(8):1285 - 1290. · 1.29 Impact Factor
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ABSTRACT: Chitosan membranes were manufactured and used in the study of diffusion of aqueous potassium chloride solution. Diffusion was found to be outside the Fickian regime, this deviation being correlated with possible changes in the membrane structure during the experiments as well as to the occurrence of osmosis.© 2001 Society of Chemical Industry
Polymer International 01/2001; 50(3):309 - 312. · 1.90 Impact Factor
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ABSTRACT: Magnetic particles are very important systems with potential use in drug delivery systems, ferrofluids, and effluent treatment. In many situations, such as in biomedical applications, it is necessary to cover inorganic magnetic particles with an organic material, such as polymers. In this work, latices based on magnetite covered by poly(ethyl methacrylate-co-methacrylic acid) were obtained via miniemulsion polymerization. The resultant latices had particles in the nanometric range and presented a pronounced superparamagnetic behavior.
Polymer. 47(22):7646-7652.
