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Oxidation state and proton doping level in copolymers of 2‐aminobenzoic acid and 2‐methoxyaniline
Author(s) -
Mav Ida,
Žigon Majda,
Vohlídal Jiří
Publication year - 2004
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200450835
Subject(s) - protonation , copolymer , triethylamine , doping , polymer chemistry , polymer , carboxylate , solvent , materials science , chemistry , organic chemistry , ion , optoelectronics
Abstract UV‐vis spectra of homopolymers and copolymers of 2‐aminobenzoic acid (OAB) and 2‐methoxyaniline (OMA) were analyzed in order to obtain information about the oxidation state and proton doping level of these polymers. Dimethyl sulfoxide (DMSO) was used as a solvent in which protonated forms of polyanilines are preserved and a mixture of N ‐methyl‐2‐pyrrolidone and triethylamine (0.5 %) as a solvent (NMP/TEA) in which polyanilines are assumed to be non‐protonated. Polymers were prepared in the emeraldine salt form, externally doped with HCl. It was found that only external doping is eliminated in NMP/TEA while internal doping by carboxylate groups bound in OAB units remains operative. Since doped quinoid units do not contribute to the quinoid band (Q‐band at 630 nm), the intensity ratio of the Q‐band and benzenoid band (B‐band at 320 nm) cannot be simply correlated with the oxidation state of poly(OMA‐ co ‐OAB) copolymers in contrast to poly(OMA) and polyaniline. Spectra of copolymers with less than 60 % of OMA units as well as those of poly(OAB) in DMSO and NMP/TEA are almost identical due to internal doping, which is proposed to lead to structures in which main‐chain protons are coulombically bound with immobile carboxylate anions. In the spectra of copolymers with less than 60 % of OMA units, a well‐resolved band occurs at 500 nm, which can be ascribed to alternating or close‐to‐alternating sequences of OMA and OAB units.