Different ionic liquids (ILs) have been used as dopants in conducting polymer aqueous dispersion (PEDOT:PSS) leading to films of PEDOT:PSS/IL with enhanced electrical conductivity (up to 136 S cm-1). After the addition of the ILs, AFM images of the films show a three-dimensional conducting network of highly conducting PEDOT exhibiting preferred paths for charge carrier transport.
Summary: A wide range of epoxidized styrene‐block‐butadiene block copolymers were synthesized using hydrogen peroxide in the presence of an in situ prepared methyltrioctylammoniumtetrakis(diperoxotungstate)phosphate as the catalyst system in a water/dichloroethane biphasic system. 1H NMR and FT‐IR spectra revealed that the epoxidation procedure led mainly to 1,4‐epoxidized butadiene units. GPC analysis showed that epoxidation changed the copolymer architecture into stars with fewer arms. The copolymers showed two glass transition temperatures in accordance with the phase separation for block copolymers and, as revealed in AFM images, the self‐assembly takes place on a nanometer scale. Moreover, epoxidized styrene‐butadiene (SB) copolymers showed improved miscibility with epoxy monomers leading to self‐assembled nanostructures in the uncured state. This allows them to be used as templates for nanostructured resins.TM‐AFM phase images for: a) 40 mol‐% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.‐% DGEBA in 50 mol‐% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.imageTM‐AFM phase images for: a) 40 mol‐% epoxidized copolymer (scale bar = 300 nm); b) uncured blend containing 50 wt.‐% DGEBA in 50 mol‐% epoxidized copolymer (scale bar = 1 μm), after annealing at 80 °C in vacuum for 3 h.
Novel nanostructured thermosetting materials have been prepared by modification of an epoxy resin with a semifluorinated diblock copolymer, poly(heptadecafluorodecyl acrylate)-b-poly(caprolactone), PaFb-PCL. In a first step, the phase behavior and linear viscoelasticity of PaF-b-PCL were investigated. According to the segregation regime, no order-order transitions were detected, being the order-disorder transition temperature beyond the degradation temperature. Atomic force microscopy (AFM) images of the block copolymer after different thermal treatments revealed that self-assembly takes place into spherical nanodomains, which is consistent with the copolymer composition. This block copolymer was further used to prepare a nanostructured thermoset blend with an epoxy resin. DSC and DMA analysis reveals microphase separation of PaF block from the epoxy-rich phase after curing. The PaF block self-assembled into wormlike and spherical micelles in the thermoset system. This nanostructured blend presented unique surface properties showing high hydrophobicity (υ ) 109°) and low surface energy (17 mN/m).
A new technique for the modification of lamellar domain sizes in polymeric ionic liquid block copolymers has been proposed. Anion exchange in polymeric ionic liquids opens new ways to modify the sizes of lamella domains without modifying the ratio between the two different blocks of the neat copolymer. This study focuses on the influence of quaternization of poly(2-vinylpyridine) in poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) and the effect of anion exchange in the nanostructured phases for thin films. The resulting materials obtained from the quaternization modification technique of the block copolymers and the anion exchange of the polymeric ionic liquid were characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR). Furthermore, morphological characterization of the initial block polymer and several polymeric ionic liquid block copolymers has been carried out by atomic force microscopy (AFM) in order to analyze the influence of the anion in the nanostructures of these block copolymers.
A new method toward vertically oriented poly(3,4ethylenedioxythiophene) (PEDOT) nanotube arrays on transparent conductive oxide substrates is presented. The approach is based on the use of ZnO nanowire arrays as templates for the electropolymerization of PEDOT. Robust arrays of vertically oriented PEDOT nanotubes with different lengths and wall thicknesses were obtained by modifying the ZnO nanowire length and charge density passed during the electropolymerization, respectively. Furthermore, PEDOT nanotubes with dif-ferent morphologies (top-closed and mushroom-like) were successfully designed by varying the PEDOT electropolymerization kinetics or monomer diffusion or both. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4648][4649][4650][4651][4652][4653] 2010
Here we present the concept of metallophilic hydrogels, supramolecular systems in which the gelator species are metal-thiolates that self-assemble through metallophilic attractions. The principle is applied for a small drug, the mucolytic agent N-acetyl-l-cysteine (NAC), which readily forms hydrogels in the presence of Au(iii), Ag(i) and Cu(ii) salts. The resulting transparent hydrogels present pH induced sol/gel transition. Scanning electron microscopy (SEM) measurements reveal a microporous structure in form of flakes for the three of them. The low pH at which these hydrogels are formed (pH < 4) limits their direct use as drug-delivery systems, but still this system constitutes a novel method for easy and fast conversion of small drugs into potent hydrogelators. Future developments will help to fully develop the idea in order to create a new class of supramolecular drug-delivery systems.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.