Syntheses and characterizations of aniline/butylthioaniline copolymers: Comparisons of copolymers prepared by the new concurrent reduction and substitution route and the conventional oxidative copolymerization method

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 ( E 0 ) and a redshifted maximum wavelength (λ max ; ultraviolet–visible) in comparison with its parent unsubstituted polyaniline (Pan). However, copolymers CP1–CP4 (obtained via the OCP method) displayed opposite behaviors, showing higher E 0 values and blueshifts in λ max 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 1 H 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.