In the last few years, nanocomposites have been a focus of attention for researchers because they frequently exhibit unexpected hybrid properties derived from synergistic reactions between nanoparticles and the polymeric matrix. However, few studies about the dispersion of inorganic clay minerals in polyamide films have been carried out to explain the process of exfoliation. The exfoliation of nanoclays in the polyamide film provides a film with better barrier properties than the intercalation of nanoclays. The present study addresses the analysis of experimental variables (pressure, temperature, processing time, feed position, etc.) involved in the production of a polyamide film with nanoparticles, in order to obtain a film with good exfoliation, barrier and mechanical properties. SEM, TEM and XRD were also evaluated as tools to determine the degree of exfoliation of nanoparticles. The technique used in production of the film, the screw employed and the mixing time were found to be of great importance in obtaining an intercalated or exfoliated final product. The variables involved in obtaining an exfoliated Cloisite 30B/polyamide film by a double screw extruder were optimized, and a film with reduced permeability to oxygen (1,000 times lower than the control film) wasobtained. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Novel polyamides were developed that can be used as cross-linking agents for proteins such as hemoglobin. Water-soluble, nonimmunogenic polyamides containing oxygen and sulfur atoms in the backbone were prepared by the polycondensation of the diacids bis(carboxymethyloxyacetyl)-1,4-diaminobutane (1a) or 3, 3'-thiodipropionic acid (1b) with diethylene glycol bis(3-aminopropyl) ether (2). The resulting alpha,omega-diacids were converted to the corresponding activated esters using any of a variety of carboxylic acid activating reagents including the novel reagent diphenyl(1-methylimidazol-2-thiyl)phosphonate (9). The resulting polyamides could be activated with a broad spectrum of groups that allow for the cross-linking and surface modification of proteins.

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Diaspirin cross-linked hemoglobin (DCLHb), a human hemoglobin that is intramolecularly cross-linked between the alpha chains (lysine 99(alpha)(1)-lysine 99(alpha)(2)), was polymerized with a number of water-soluble, nonimmunogenic polyamide cross-linking agents. The degree of polymerization and the oxygen-carrying capacity depended upon the polyamide reagent, the starting concentration of DCLHb, the molar ratio of the polyamide reagent to DCLHb used, the reaction pH, and whether oxy- or deoxy-DCLHb was used in the polymerization reaction.

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