A new type of highly conductive self-doping polyaniline, MPS-Pan, containing a sulfonic acid moiety covalently bonded to the polymer backbone through an electron-donating propylthio linkage has been successfully prepared via a novel concurrent reduction and substitution route. At a similar self-doping level, the resultant MPS-Pans displayed much higher conductivity than the corresponding sulfonated polyaniline (S-Pan). Furthermore, for fully doped samples, contrary to the trend of decreasing conductivity with the sulfonation degree in S-Pan, the conductivity of MPS-Pan was found to increase with its substitution degree. These results agreed with the expectation that electron-deficient charge carriers (e.g. semiquinone radical cations) on acid-doped polyaniline chains will be better stabilized by the electron-donating alkylthio substituent. Surprisingly, TG and XPS studies showed that MPS-Pan was thermally much more stable than S-Pan, with S-Pan starting to lose its sulfonic acid dopant at 185 °C, while MPS-Pan remained intact up to ∼260 °C.

Highly conductive new aniline copolymers containing butylthio substituent have been first prepared from unsubstituted polyaniline, utilizing a concurrent reduction and substitution reaction performed in the solid-state matrix of polyaniline. The resultant copolymer film after one reaction treatment cycle was found to contain ca. 38 mol % of butylthio group and was as conductive (3-4 S/cm) as its parent polyaniline film (2-3 S/cm). Most surprisingly, copolymers containing butylthio group as high as 91 and 121 mol % (based on atomic ratio S/N measured by XPS) can also be easily prepared and still displayed a conductivity as high as 1 and 0.6 S/cm, respectively, despite the presence of the large amount of bulky butylthio substituent. All these new butylthioaniline copolymers are highly soluble in THF, dioxane, 2-methoxyethyl ether, and 2-methoxyethanol, which are nonsolvents for the parent polyaniline. The results suggest that the concurrent reduction and substitution route is a better way, as compared with the conventional copolymerization method, for preparing aniline copolymers with a more conjugated and regular backbone structure.

New highly solution‐processable aniline/butylthioaniline copolymers were prepared via oxidative copolymerization (OCP) and by concurrent reduction and substitution (CRS). Butylthio‐substituted polyaniline obtained via the CRS route (Pan‐SBu), being in line with the expected property changes after the addition of an electron‐donating substituent to an aromatic ring, displayed a lowered redox potential (E0) and a redshifted maximum wavelength (λmax; ultraviolet–visible) in comparison with its parent unsubstituted polyaniline (Pan). However, copolymers CP1–CP4 (obtained via the OCP method) displayed opposite behaviors, showing higher E0 values and blueshifts in λmax than the unsubstituted Pan. The results suggested that CP1–CP4 had shorter conjugation lengths than the unsubstituted Pan, possibly because of their chain conjugation defects (e.g., 1,3‐ring linkage structures), as evidenced by IR studies. The results of 1H NMR studies also indicated that Pan‐SBu had much higher structural homogeneity than copolymer CP4. Because the CRS synthetic route involved no backbone alternations, the resultant copolymer (Pan‐SBu) should have maintained the same backbone structure and hence the high conductivity of the parent unsubstituted Pan. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1767–1777, 2005

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