H-1 NMR study of the kinetics of substituted aniline polymerization. II. Copolymerization of 2-methoxyaniline and 3-aminobenzenesulfonic acid

We investigated the kinetics of the oxidative chemical copolymerization of 2-methoxyaniline (OMA) and 3-aminobenzenesulfonic acid (MA) by monitoring m onomer depletion with H-1 NMR spectroscopy. We adapted a semiempirical kine tic model, previously used for OMA homopolymerization, for the consumption of both OMA and MA monomers with a large difference in their reactivities. The OMA polymerization rate and end conversion showed a similar dependence on the reaction conditions, as described in the first part of this series, for its homopolymerization. Generally, the MA comonomer had an inhibition e ffect on the OMA polymerization rate. However, an increase in the initial M A concentration resulted in an increased OMA initiation rate. Because of th e higher reactivity of OMA compared with that of MA, the OMA conversion beg an before the MA conversion, and both the initiation and propagation rates were higher than those for MA. The molar ratios of the converted monomers ( MA/OMA) were always significantly lower than the corresponding MA/OMA feed fractions. They depended on the reaction conditions used for the copolymeri zation. In particular, higher oxidant or MA concentrations, higher temperat ures, and a I M DCl concentration favored MA conversion, that is, its inser tion into the copolymer. The MA end conversion was much smaller than that o f OMA, only up to 23%; for a low oxidant concentration (oxidant/monomer-def icient molar ratio), it was only 6%. (C) 2001 John Wiley & Sons, Inc.