F. L. Baines

A study of the kinetics of polymerization of aniline using proton NMR spectroscopy

Abstract The polymerization of aniline has been studied by monitoring monomer depletion using proton NMR spectroscopy. For precipitation polymerization at 298 K using Na 2 S 2 O 8 as oxidant an induction period of several minutes was observed, followed by relatively rapid polyaniline formation. In contrast, much slower polymerization was found using KIO 3 as oxidant. In both cases there is a significant residual NMR signal, even though a stoichiometric amount of oxidant was used. This was attributed to soluble aniline oligomers rather than unreacted aniline monomer. At 278 K the rate of polymerization is markedly slower for both oxidants. No significant differences were observed between the rates of precipitation polymerization and dispersion polymerization using a reactive poly(ethylene oxide)-based stabilizer. Faster reactions were observed when aniline was polymerized in the presence of ultrafine 20 nm silica particles to form polyaniline-silica colloidal nanocomposites. Polymerization was slower when aniline was polymerized in the presence of surfactant micelles to form surfactant-stabilized polyaniline particles; this is probably due to the high viscosity of the reaction solution.

Use of quaternised methacrylate polymers and copolymers as catalysts and structure directors for the formation of silica from silicic acid

A range of quaternised tertiary amine methacrylate-based homopolymers and copolymers were synthesised as mimics of the biopolymers implicated in biosilica formation. These synthetic polymers were evaluated for their ability to catalyse and direct the structure of silica formed by condensation of silicic acid in aqueous solution and at neutral pH. Homo- and co-polymers of differing degrees of quaternisation were studied, while some of the homopolymers also differed in their chain length. All polymers acted as catalysts for the condensation reaction, but at different rates according to their architecture and degree of quaternisation. The resulting silica–polymer hybrids were characterised fully, as were pure silicas obtained by calcination of the hybrids. Some crystallites were present in the hybrids and differences in crystal structure were observed in the calcined silicas, depending on the structure of the polymer, indicating that the polymers exert a structure-directing effect during initial silica formation. The work provides some new insights into structural factors affecting silica growth catalysed by synthetic cationic polymers.

Some observations on the preparation of colloidal polyaniline - silica composites

Abstract We report further investigations into the use of silica and other inorganic oxides in the preparation of colloidal polyaniline composites.