Chemical and Photoluminescence Properties of Purified Poly(2-methoxyaniline-5-sulfonic acid) and Oligomer

Abstract

Both the chemical and the electrochemical synthesis of poly(2-methoxyaniline-5-sulfonate) (PMAS) in aqueous media have been found to give two distinct polymer fractions with molecular weights of approximately 8-10 and 2 kDa, respectively. It is now possible to isolate the pure high molecular weight (HMWT) PMAS and low molecular weight (LMWT) PMAS oligomer and to study their individual and combined photochemistry and redox chemistry. The HMWT PMAS fraction was confirmed to be an emeraldine salt by its characteristic redox and pH switching behavior, in contrast to the oligomeric LMWT PMAS, which was inert under the same conditions. Mixtures of these two fractions exhibit photoluminescence arising from the oligomeric LMWT PMAS fraction. The observed LMWT PMAS emission was modulated by the presence of the conducting HMWT PMAS emeraldine salt via a static resonant energy transfer arising from quenching at 460 nm when excited at 355 nm. The nonlinear fluorophore-quencher behavior suggests that the two PMAS fractions are strongly associated. The behavior fitted the static Perrin quenching model in which the oligomeric LMWT PMAS fluorophore is diffusionally restricted by the presence of HMWT PMAS quencher.

Electrochemical synthesis and characterisation of polyaniline/poly(2-methoxyaniline-5-sulfonic acid) composites

“…600 nm [38][39][40]. In contrast, treating PMAS with aqueous NaOH solution is reported to result in replacement of the initial bands by two bands at 350-390 and 750 nm, consistent with a compact coil conformation of PMAS emeraldine salt [30,31,40], i.e. a conformational change occurs rather than de-doping of the polymer.…”

“…These characteristics are believed to indicate a partially to largely extended coil conformation of polyaniline chains [34][35][36]. The UV-vis spectrum of PMAS exhibits a characteristic band at 473 nm which is assigned as a low wavelength polaron band as well as a free carrier tail in the NIR indicative of an extended coil conformation [30,37]. The UV-vis spectrum of a PAn/PMAS film deposited potentiodynamically on ITO-Pt-coated glass is compared to that of PAn/HCl in Fig.…”

“…It has been recently demonstrated that PMAS has two distinct fractions which exhibit different physical properties [29,30]. The higher molecular weight PMAS fraction (M w > 10 kDa) is conductive, electroactive and non-fluorescent.…”

The influence of poly(2-methoxyaniline-5-sulfonic acid) on the electrochemical and photochemical properties of a highly luminescent ruthenium complex

“…This observation is surprising given that the excited state lifetime of the [Ru(bpy) 3 ] 2+ moiety is approximately three times longer than the [Ru(bpy) 2 PVP 10 ] 2+ luminophore. This behaviour may arise due to the strong absorbance by the PMAS at the excitation wavelength of 355 nm [38]. Alternatively, the PMAS may act as an electron transfer quencher of the ruthenium excited state.…”

Low-potential facile electrosyntheses of free-standing poly(5-methoxyindole) film with good fluorescence properties

“…Such theoretical studies mentioned above showed that all the pyrrolic atoms of radical-cations of 5MIn were not active and the coupling reaction cannot occur indeed, leading to no polymeric material obtained. Up to date, there was no reports on electrosyntheses of high-quality P5MIn films, although poly(3-methoxythiophene) [29,30], poly(2-methoxyaniline) [31][32][33][34][35] and polymethoxybenzene [36,37] had been studied. Based on the above, it is still a challenge to prepare high-quality P5MIn film.…”