Arrangement of Conductive Rod Nanobrushes via Conductive–Dielectric–Conductive Sandwiched Single Crystals of Poly(ethylene glycol) and Polyaniline Block Copolymers

Conductive rod nanobrushes of polyaniline (PANI) were developed via the growth of conductive–dielectric–conductive sandwiched single crystals obtained from poly­(ethylene glycol) (PEG₅₀₀₀)-<i>b</i>-PANI_<i>n</i>, PANI_<i>n</i>-<i>b</i>-PEG₆₀₀₀-<i>b</i>-PANI_<i>n</i>, and PANI_<i>n</i>-<i>b</i>-PEG₃₅₀₀₀-<i>b</i>-PANI_<i>n</i> block copolymers synthesized by interfacial polymerization fostering two different oxidants (ammonium peroxydisulfate (APS) as a weaker and potassium hydrogen biiodate (PHD) as a stronger oxidant). Based on the dispersity of the diameter of the PANI nanofibers and the various molecular weights of PEG substrates, two distinct morphologies were detected, i.e., matrix–dispersed morphology for PANI_<i>n</i>-<i>b</i>-PEG₃₅₀₀₀-<i>b</i>-PANI_<i>n</i> and dispersed–dispersed morphology for PANI_<i>n</i>-<i>b</i>-PEG₆₀₀₀-<i>b</i>-PANI_<i>n</i> and PEG₅₀₀₀-<i>b</i>-PANI_<i>n</i> single crystals. In matrix–dispersed single crystals, through an elevated crystallization temperature (<i>T</i>_c), a convergence occurred between the heights of matrix (partly stretched PANIs) and disperses (fully stretched PANIs). Because of their higher conductivity (e.g., 3 vs 10^–4 S/cm for copolymers and 84 vs 8 × 10^–3 S/cm for corresponding homopolymers), the variation in height between the matrix and disperses was lower in PHD-synthesized PANI nanofibers (e.g., height variance of 2 nm for PHD-synthesized PANI₁₈₀ vs 57 nm for APS-synthesized PANI₁₇₅ at <i>T</i>_c = 38 °C). The diameter of the dispersed PANI was inversely proportional to the crystallization temperature and was directly proportional to the PANI repeating units. Although in PEG₃₅₀₀₀-based systems PANI-dispersed diameters of up to 58 nm were detected in PANI₁₀₉-<i>b</i>-PEG₇₉₅-<i>b</i>-PANI₁₀₉ single crystals at <i>T</i>_c = 18 °C due to a scarcity in the provided surface area, the maximum diameters included in PEG₆₀₀₀ and PEG₅₀₀₀ single crystals were 9 and 7 nm, respectively. In dispersed–dispersed morphologies, having extended conformation of PANI brushes on PEG₅₀₀₀ and PEG₆₀₀₀ substrates, their substrate thickness did not vary by the lengthening of the PANI brushes, and the only effect oxidant had in these systems was on the population of grown single crystals; that is, the weaker the oxidant, the larger the population