Dendritic polyaniline nanoparticles synthesized by carboxymethyl chitin templating

Dendritic polyaniline (PANI) nanoparticles were synthesized via oxidative polymerization of aniline, using ammoniumperoxodisulfate as an oxidant, and CM-chitin as a template. The reaction was performed under acidic conditions and the template was removed after the polymerization was completed. Molecular characterization (including UV-vis, FTIR, TGA, and XRD) suggests that the structure of the synthesized dendritic PANI nanoparticles is identical to that of the emeraldine form of PANI, synthesized by the conventional route (without the addition of the CM-chitin template). SEM images reveal that the dendritic PANI nanoparticles have an average diameter in the nanometer range, and are globular in shape, with radially oriented PANI dendrites; in contrast, irregularly-shaped aggregates of PANI are obtained using the conventional synthesis. It was further found that the size of the dendritic PANI nanoparticles is dependent on the CM-chitin content. The higher the CM-chitin concentration, the smaller is the size of the dendritic PANI nanoparticles obtained. An interpretation of these observations and a possible formation mechanism are proposed based on self-assembly between the CM-chitin chains and the aniline monomer.     

Anomalous rheology of polypyrrole nanoparticle/alginate suspensions: effect of solids volume fraction, particle size, and electronic state

The rheology of dispersions of polypyrrole (PPY) nanoparticles (nPPY) is compared to that of micron-sized PPY particles (CPPY), each suspended in aqueous sodium alginate. With increasing PPY volume fraction, the Newtonian viscosity of the CPPY/alginate suspensions exhibits a ??normal?? increase, whereas that of the nPPY/alginate suspensions decreases to a minimum and then increases again. Enhanced elasticity, indicative of agglomerate formation via bridging interactions with the alginate, is observed only in the CPPY rheology. By comparing doped versus dedoped nPPY particles, and investigating the effect of nPPY particle size, we conclude that the negative viscosity change of the nPPY dispersions is due to adsorption of a dense layer of alginate, resulting in a decrease in bulk alginate concentration. The viscosity upturn at higher nPPY volume fractions indicates the onset of particle agglomeration via bridging interactions with alginate. The results demonstrate improved dispersability of both doped and dedoped nPPY over CPPY particles.     

Polyaniline nanoparticles with controlled sizes using a cross-linked carboxymethyl chitin template

Polyaniline (PANI) nanoparticles were chemically synthesized in the presence of a cross-linked carboxymethyl chitin (CM-chitin) acting as a template. The reaction was performed under acidic conditions and the template was removed after the polymerization of aniline was completed. The morphology of the synthesized PANI was globular with a diameter in the nanometer range. The degree of cross-linking of the CM-chitin played an important role in determining the size of the obtained PANI nanoparticles, which decreased from approximately 392 to 160 nm with increase in concentration of the cross-linking agent, glutaraldehyde, from 0 to 9 μmol, respectively. At a higher glutaraldehyde concentration (18 μmol), an aggregated PANI network was observed due to the incomplete removal of the more highly cross-linked CM-chitin. Molecular characterization (including UV-Visible, FTIR, TGA, and XRD techniques) revealed that the structure of the synthesized PANI nanoparticles is identical to that of conventional PANI. A mechanism is proposed for the formation of PANI nanoparticles in the presence of the cross-linked CM-chitin template.     

Physical and Electrical Properties of Chlorophyllin/Carboxymethyl Chitin and Chlorophyllin/Carboxymethyl Chitosan Blend Films

Blend films consisting of chlorophyllin dispersed in carboxymethyl chitin (CM-chitin) and carboxymethyl chitosan (CM-chitosan) were prepared by solution casting and characterized for their physical and electrical properties. Homogeneous films were obtained having chlorophyllin content up to 50 wt% in the CM-chitin matrix and 30 wt% in the CM-chitosan matrix. Agglomeration of chlorophyllin particles in the chlorophyllin/CM-chitosan blend was observed, when chlorophyllin content reached 50 wt%. The electrical conductivity of CM-chitosan was higher than that of CM-chitin by approximately 2 orders of magnitude due to the higher content of amino polar groups. The electrical conductivity increased with increasing chlorophyllin content. The addition of metal ion salts improved the electrical conductivity of the blend films.