Amidification of poly(styrene-co-maleic anhydride) with amines in tetrahydrofuran solution: A kinetic study

Summary

The kinetics of the reaction between a styrene-maleic anhydride copolymer (SMA) and amines was investigated in tetrahydrofuran solution between 0°C and 40°C. This reaction converts the maleic anhydride (MA) into the corresponding amide-acid, while the consecutive reaction of the generated acid with amine forming a diamide or transformation of the acid-amide into the imide was not observed. The amine reactivity follows the order: 1-octylamine> >1-methyl hexylamine> >1,1-dimethyl propylamine or dibutylamine, demonstrating that the amine reactivity depends, to a large extent, upon its steric hindrance. This reaction is reversible as shown by IR at high temperatures, but the reverse reaction was undetectable between 0 and 40°C. The overall reaction involves spontaneous and autocatalytic reactions, and the overall reaction rate can be written as:-d[MA]/dt=k₀[MA][-NH₂]+k₁[MA][-NH₀]². In the case of 1-octylamine below 0.02 M, the spontaneous reaction dominates (i.e, k₀> >k₁[-NH₂]).