Novel nanocomposites of polyaniline dispersed with ␥-Fe 2 O 3 nanoparticles were prepared by the in situ polymerization of aniline in the presence of ammonium peroxysulfate as an oxidizing agent. Dielectric constants of the derived composites varied with the composition of ␥-Fe 2 O 3 present in the matrix. A maximum dielectric constant of ϳ5500 was achieved when 10 mass % ␥-Fe 2 O 3 nanoparticles were present. Nanocomposites were characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and thermal analytical techniques. Conductivity increased marginally by increasing the amount of ␥-Fe 2 O 3 in the matrix. Dielectric constants increased 100 -150 times compared to plain polyaniline matrix and were 20 -40 times higher than that of ␥-Fe 2 O 3 nanoparticles.

Blend membranes of a natural polymer, chitosan, with a synthetic polymer, poly(vinyl alcohol) (PVA), were prepared by solution casting and crosslinked with a urea formaldehyde/sulfuric acid (UFS) mixture. Chitosan was used as the base component in the blend system, whereas PVA concentration was varied from 20 to 60 wt %. Blend compatibility was studied by differential scanning calorimetry, and Fourier transform infrared spectroscopy was used to study membrane crosslinking. Membranes were tested for pervaporation dehydration of isopropanol and tetrahydrofuran (THF) at 308C in close proximity to their azeotropic compositions. Membrane performance was assessed by calculating flux and selectivity. Swelling experiments performed in water þ organic mixtures at 308C were used to explain the pervaporation results. The blend membrane containing 20 wt % PVA when tested for 5 and 10 wt % watercontaining THF and isopropanol feeds exhibited selectivity of 4203 and 17,991, respectively. Flux increased with increasing concentration of water in the feed. Selectivity was highest for the 20 wt % PVA-containing blend membrane. The results of this study are unique in the sense that the crosslinking agent used-the UFS mixture-was novel.

Six novel polyureas were prepared from benzimidazolin-2-one and benzimidazolin-2-thione, which acted as hard segments, with two aromatic diisocyanates (4,4Ј-diphenylmethane diisocyanate and toluene 2,4-diisocyanate) and one aliphatic diisocyanate (hexamethylene diisocyanate). The polymers that formed were fully characterized with Fourier transform infrared spectroscopy, 13 C-NMR cross-polarization/magic-angle spinning, differential scanning calorimetry, and thermogravimetry. X-ray diffraction revealed that the polymers contained crystalline and amorphous regions that varied with the nature of the backbone structures. All the polyureas were insoluble in common organic solvents, and this made it difficult to investigate their solution properties.

Stringent environmental regulation has endowed dispersible coatings with excellent property profiles in industrial applications. In this aspect, aqueous polyurethane dispersions (PUDs) are of special interest. The present study reports on the synthesis of hydroxylated polyester (HP) based polyurethane polyols containing internal carboxyl group with different diisocyanates. These polyurethane polyols were partly acetoacetylated with ethyl acetoacetate to incorporate ␤-ketoester in the polyurethane polyol backbone. The synthesized polyols were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. Polyurethane polyols and their acetoacetylated cousins were used to develop PUDs. Particle size of the reactive PUDs was evaluated by a particle size analyzer. PUDs were crosslinked with hexamethoxy methyl melamine and their film properties were studied by dynamic mechanical and thermal analyzers and thermogravimetric analyses. The effects of different diisocyanate and acetoacetylation on the stability of reactive dispersion and properties of the crosslinked films were evaluated.

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