Direct Writing of Conducting Polymers

Described herein is a new printing method—direct writing of conducting polymers (CPs)—based on pipette‐tip localized continuous electrochemical growth. A single barrel micropipette containing a metal wire (Pt) is filled with a mixture of monomer, supporting electrolyte, and an appropriate solvent. A droplet at the tip of the pipette contacts the substrate, which becomes the working electrode of a micro‐electrochemical cell confined to the tip droplet and the pipette. The metallic wire in the pipette acts as both counter and reference electrode. Electropolymerization forms the CP on the working electrode in a pattern controlled by the movement of the pipette. In this study, various width poly(pyrrole) 2D and 3D structures are extruded and characterized in terms of microcyclic voltammetry, Raman spectroscopy, and scanning electron microscopy.

     

Orientation in Nematic Liquid Crystals Doped with Orange Dyes and Effect of Carbon Nanoparticles

Some properties of nematic liquid crystal E7 doped with two disperse orange dyes used together and effect of addition of carbon nanoparticles (single walled carbon nanotube or fullerene C₆₀) on them were studied. Two dyes (disperse orange 11 and 13) having high solubility and order parameter were used as co-dopants. A notable increase in order pa-rameter was obtained comparing to that of liquid crystal doped with single dye. When carbon nanoparticles were used as dopant, a decrease in order parameter was observed at low temperatures while it increased at high temperatures. When applied voltage changed, the order parameter abruptly increased in its threshold value and saturated in higher voltages as expected. An appreciable change in textures was not observed with addition of dopants. This addition gave rise to an increase in nematic-isotropic phase transition temperatures compared with that of pure liquid crystal.     

Rubbery wound closure adhesives. I. design,synthesis, characterization,and testing of polyisobutylene‐based cyanoacrylate homo‐ and co‐networks

Novel rubbery wound closures containing various proportions and molecular weights of polyisobutylene (PIB) and poly(2‐octyl cyanoacrylate) [P(OctCA)] for potential clinical use were designed, synthesized, characterized, and tested. Homo‐networks were prepared by crosslinking 3‐arm star‐shaped PIBs fitted with terminal cyanoacrylate groups, [Ø(PIB‐CA)₃], and co‐networks by copolymerizing Ø(PIB‐CA)₃ with OctCA using N‐dimethyl‐p‐toluidine (DMT). Neat Ø(PIB‐CA)₃, and Ø(PIB‐CA)₃/OctCA blends, upon contact with initiator, polymerize within seconds to optically transparent strong rubbery co‐networks, Ø(PIB‐CA)₃‐co‐P(OctCA). Homo‐ and co‐network formation was demonstrated by sol/gel studies, and structures and properties were characterized by a battery of techniques. The T_g of P(OctCA) is 58 °C by DSC, and 75 °C by DMTA. Co‐networks comprising 25% Ø(PIB‐CA)₃ (M_n = 2400 g/mol) and 75% P(OctCA) are stronger and more extensible than skin. Short and long term creep studies show co‐networks exhibit high dimensional stability and <6% creep strain at high loading. When deposited on porcine skin co‐networks yield hermetically‐adhering clear rubbery coatings. Strips of porcine skin coated with co‐networks could be stretched and twisted without compromising membrane integrity. The co‐network is nontoxic to L‐929 mouse fibroblasts. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1640–1651     

Design of multiple-target chemoprobe: “naked-eye” colorimetric recognition of Fe3+ and off–on fluorogenic detection for Hg2+ and its on-site applications

A novel multiple-target chemoprobe (E)-N′-((9-pentyl-9H-carbazole-3-yl)methylene)thiophene-2-carbohydrazide (CTH) was designed, successfully synthesized and employed for the detection of Hg²⁺ and Fe³⁺ ions as off–on fluorometric and colorimetric responses, respectively, in H₂O/DMF (10/90, v/v, Britton–Robinson buffer, pH 7) medium. The chemoprobe CTH demonstrated high sensitivity towards Hg²⁺ and Fe³⁺, among wide range of competitive cations with low recognition limits of 5.1 nM and 5.89 µM, respectively. The complexes of the chemoprobe CTH were synthesized and characterized by ¹H-NMR titration, FT-IR and MALDI-TOF MS techniques, which confirmed the binding stoichiometries and the possible sensing mechanisms, were suggested based on the hydrolysis reaction of C=N group. The practical utility of the chemoprobe CTH was revealed in quantification of the trace amounts of Hg²⁺ and Fe³⁺ in water samples. Also, a silica-coated test paper was used for the fluorescent monitoring of Hg²⁺, providing a novel approach for the quantitative and on-site detection in real samples. More excitingly, a smartphone application was employed for the visual detection of Fe³⁺ by recognizing the RGB (red/green/blue) of the chemoprobe CTH solution.

Graphical abstract

     

Ligated anionic block copolymerization of methyl methacrylate with n-butyl acrylate and n-nonyl acrylate as promoted by lithium 2-(2-methoxyethoxy) ethoxide/diphenylmethyllithium

Poly(methyl methacrylate-b-n-butyl acrylate) (PMMA-b-Pn-BuA) and poly(methyl methacrylate-b-n-nonyl acrylate) (PMMA-b-Pn-NonA) diblock copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and the n-alkyl acrylate (n-BuA or n-NonA), in a 90/10 toluene/tetrahydrofuran (THF) mixture at −78°C. When diphenylmethyllithium (DPMLi) ligated with lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM) is used as the initiator, the polymerization of each block appears to be living. Molecular weight and composition of block copolymers can be predicted from the monomer over initator molar ratio and the molecular weight distribution is narrow. Size exclusion chromatography (SEC) supports that no homo-PMMA contaminates the final copolymer. Although the reverse polymerization sequence Pn-NonA-b-PMMA always results in some contamination by homo-Pn-NonA, it has no really significant effect on the final product characteristics. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1543–1548, 1997