Role of the Anilinium Ion on the Selective Polymerization of Anilinium 2-Acrylamide-2-methyl-1-propanesulfonate

Abstract

The development of anilinium 2-acrylamide-2-methyl-1-propanesulfonate (Ani-AMPS) monomer, confirmed by 1H NMR, 13C NMR, and FTIR, is systematically studied. Ani-AMPS contains two polymerizable functional groups, so it was submitted to selective polymerization either by free-radical or oxidative polymerization. Therefore, poly(anilinium 2-acrylamide-2-methyl-1-propanesulfonic) [Poly(Ani-AMPS)] and polyaniline doped with 2-acrylamide-2-methyl-1-propanesulfonic acid [PAni-AMPS] can be obtained. First, the acrylamide polymer, poly(Ani-AMPS), favored the π-stacking of the anilinium group produced by the inter- and intra-molecular interactions and was studied utilizing 1H NMR, 13C NMR, FTIR, and UV-Vis-NIR. Furthermore, poly(Ani-AMPS) fluorescence shows quenching in the presence of Fe2+ and Fe3+ in the emission spectrum at 347 nm. In contrast, the typical behavior of polyaniline is observed in the cyclic voltammetry analysis for PAni-AMPS. The optical properties also show a significant change at pH 4.4. The PAni-AMPS structure was corroborated through FTIR, while the thermal properties and morphology were analyzed utilizing TGA, DSC (except PAni-AMPS), and FESEM.

Brush-like Polyaniline with Optical and Electroactive Properties at Neutral pH and High Temperature

“…Another signal corresponding to the methylene groups is at 1.4 ppm (H 6 , 6H). The pattern, position, and integration of signals are consistent with research previously reported by our group [ 37 ], except for the integration of protons corresponding to aromatic anilinium due to differences in synthesis methodology. In the previous work, the polymerization proceeded directly from a bifunctional monomer, including anilinium ions, while in the present research, the doping was performed post-polymerization.…”

“…Figure 5 shows the UV–Vis spectra of macro-RAFT in aqueous solution and in solid-state. In Figure 5 a, displaying the results in aqueous solution, three absorption bands are observed at 250 nm, 284 nm, and 312 nm, corresponding to the n-π* transition of N + quaternized nitrogen, the π-π* transition of anilinium ring [ 37 ], and the π-π* of C=S of CTA [ 46 ]. On the other hand, the spectrum in the solid-state has a broadband absorption between 230 and 800 nm, with a maximum at 301 nm.…”

“…At pH 6 and pH 7, it is observed that the intensity of bipolaron decreases until pH 8, whereas, at pH 9 and pH 10, the polaron broadband shows a blue shift, presenting a new band around ~600 nm characteristic of an emeraldine base structure [ 51 ]. In our previous work, the dedoping point of the PAni doping with AMPS manifested itself at pH 4.4 [ 37 ]. Similarly, the doping point of PAni utilizing sulfuric acid is 4.4 [ 52 ].…”

“…Similarly, the doping point of PAni utilizing sulfuric acid is 4.4 [ 52 ]. This phenomenon is due to the pKa of the aniline [ 37 ].…”

“…The macro-RAFT shows only an endothermic peak at 134 °C, suggesting a crystalline polymer due to the formation of the graft point generating a physical interaction between the anilinium ions. In our previous study, the poly(anilinium 2-acrylamide-2-methyl-1-propanesulfonate) exhibited a glass transition temperature of 109 °C; even so, this was obtained from an altogether different methodology [ 37 ].…”