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

Abstract

Conductive rod nanobrushes of polyaniline (PANI) were developed via the growth of conductive–dielectric–conductive sandwiched single crystals obtained from poly(ethylene glycol) (PEG5000)-b-PANIn, PANIn-b-PEG6000-b-PANIn, and PANIn-b-PEG35000-b-PANIn 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 PANIn-b-PEG35000-b-PANIn and dispersed–dispersed morphology for PANIn-b-PEG6000-b-PANIn and PEG5000-b-PANIn single crystals. In matrix–dispersed single crystals, through an elevated crystallization temperature (Tc), 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 Tc = 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-b-PEG795-b-PANI109 single crystals at Tc = 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.