Studies on chemical oxidative copolymerization of aniline and o-alkoxysulfonated anilines II. Mechanistic approach and monomer reactivity ratios

The copolymerization of aniline (An) with o-alkoxysulfonated anilines, i.e. 1-(o-amino)-propane-3-sulfonic acid (APPrS) and 1-(o-amino)-butane-4-sulfo nic acid (APBuS), was a new way to produce water-soluble and self-doped pol yaniline derivatives. Poly(An-co-APPrS) and poly(An-co-APBuS) were synthesi zed, in H2SO4 acidic medium, by chemical oxidation using ammonium persulfat e. The mechanistic study showed that, during their copolymerization, anilin e and alkoxysulfonated-derivatives exhibit two opposite behaviors towards t he initial mechanism of dimerization and the following growing process. Bec ause of the steric hindrance of the bulky alkoxysulfonated groups, the dime rization process involved at least one molecule of aniline. On the contrary , in the course of the propagation step, due to the electron-donating effec t of the substituent, both alkoxysulfonated anilines exhibited much greater reactivity than aniline and hence were easily incorporated into the growin g polymer chains. The comonomer reactivity ratios, computed by using the ex tended Kelen-Tudos method, were as follows: r(An) = 0.04 +/- 0.01, Y-APPrS = 27 +/- 9 and r(An) = 0.04 +/- 0.01, r(APBuS) = 12 +/- 6. These findings s trongly suggest the formation of block copolymers. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.