Large‐Scale Synthesis of Necklace‐Like Single‐Crystalline PbTiO3 Nanowires

Summary: We show in this communication that large‐scale necklace‐like single‐crystalline tetragonal perovskite PbTiO₃ nanowires can be obtained via a simple electrospinning method. The morphology and the crystal structure are investigated by SEM, XRD, and HRTEM. The length of the necklace‐like PbTiO₃ nanowires is from tens to several tens of micrometers, the wider the diameter of it is between 100 and 200 nm and the thinner the part is between 20 and 50 nm. The necklace‐like PbTiO₃ nanowires exhibit high surface photovoltage under the action of external electric field, which is probably applicable in displaying photoelectric devices of heterojunction structure.

SEM image of the electrospinning necklace‐like PbTiO₃ nanowires.     

Combining RAFT Radical Polymerization and Click/Highly Efficient Coupling Chemistries: A Powerful Strategy for the Preparation of Novel Materials

This paper highlights the powerful combination of reversible addition–fragmentation chain transfer (RAFT) radical polymerization and various click/coupling chemistries. This is not an exhaustive review but rather an overview demonstrating the impressive possibilities that the “marriage” of these two synthetic approaches offers in modern macromolecular design and synthesis.

     

Electrostatically Dissipative Polystyrene Nanocomposites containing Copper Nanowires

Summary: A scalable synthesis of copper nanowires by alternating current electrodeposition into porous aluminium oxide was used to produce multigram quantities of 16 nm diameter by >2 µm long nanowires. Polystyrene nanocomposites were prepared by solution processing. The composites containing unpassivated nanowires were non‐uniformly dispersed and showed electrical percolation at ≈2 vol.‐% Cu loading, while the composites containing HSC₁₈H₃₇‐passivated nanowires were uniformly dispersed, but remained resistive up to at least 10 vol.‐% Cu loading.

Copper nanowires prepared by alternating current electrodeposition into porous aluminium oxide templates.     

Stepwise Self‐Assembly of P3HT/CdSe Hybrid Nanowires with Enhanced Photoconductivity

A facile approach to prepare poly(3‐hexylthiophene) (P3HT)/cadmium selenide quantum dot (CdSe QD) hybrid coaxial nanowires by a stepwise self‐assembly process is reported. P3HT nanowires of ≈20 nm diameter are first prepared by self‐assembly in a poor solvent such as cyclohexanone, and then as‐prepared CdSe QDs are deposited compactly onto the P3HT nanowires by non‐covalent interactions between P3HT and CdSe. When illuminated with white light, the hybrid nanowires show enhanced photoconductivity compared with the pristine P3HT nanowires and the blended nanocomposites.

     

Copolymers Containing Phosphorescent Iridium(III) Complexes Obtained by Free and Controlled Radical Polymerization Techniques

A methacrylate‐functionalized phosphorescent Ir(III)‐complex has been synthesized, characterized, and applied as a monomer in radical copolymerizations. Together with methyl methacrylate, the complex has been copolymerized under free radical polymerization conditions. Aiming for host‐guest‐systems, applicable e.g. in organic light emitting devices (OLEDs), the complex was further copolymerized with a methacrylate‐functionalized carbazole derivative using the atom transfer radical polymerization technique. Applying gel permeation chromatography, in combination with a photodiode array detector, could clearly prove the formation of the copolymers. The optical properties of the photoactive monomers as well as the copolymers were investigated by absorption and emission spectroscopy (in solution). For the carbazole‐copolymer, the emission originates almost exclusively from the complex. This provides evidence of an efficient intrachain energy transfer, which makes the system an interesting candidate for potential OLED applications.

     

Polysilsesquioxane Nanosheets Synthesized in Confined Environment

Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

AFM image of a polymethylsilsesquioxane nanosheet.     

RAFT Inverse Miniemulsion Polymerization of Acrylamide

RAFT inverse miniemulsion polymerization is demonstrated for the first time as an alternate way to synthesize hydrophilic polymer latexes. The kinetic behavior of inverse RAFT miniemulsion polymerization of acrylamide is similar to that observed in aqueous RAFT solution polymerization. A water‐soluble initiator provides better control than a lipophilic initiator in inverse RAFT miniemulsion polymerization under the conditions used here.

     

Optical Non‐Linearity from Montmorillonite Intercalated with a Chromophore‐Containing Dendritic Structure: A Self‐Assembly Approach

Chromophore‐containing dendritic structures (G1, G2) are utilized to intercalate layered silicates, which results in a large d‐spacing up to 126 Å. An exfoliated morphology is obtained by mixing the dendritic structure intercalated layered silicates with polyimide in N,N‐dimethylacetamide solution. The dendritic structures attached on the clay template would arrange in a non‐centrosymmetric manner. This self‐assembled arrangement brought about the electro‐optical coefficients of 5–6 pm · V⁻¹ for these relatively low chromophore‐containing organic/inorganic nanocomposites without resorting to poling. Excellent temporal stability (100 °C) is also achieved.

     

Synthesis of Highly Hydrophilic Polyaniline Nanowires and Sub‐Micro/Nanostructured Dendrites on Poly(propylene) Film Surfaces

Summary: Polyaniline (PANI) nanowires and sub‐micro/nanostructured dendrites are synthesized and immobilized on PP‐g‐PAA film surfaces via routine oxidative polymerization of aniline under different conditions, where grafting poly(acrylic acid) (PAA) served as a template and dopant, and SDS as a surfactant. The immobilized PANI enhances the surface hydrophilicity of the poly(propylene) (PP) films, and a superhydrophilic surface is obtained in this way. The mechanism of forming different morphologies of PANI and of correspondingly obtaining a superhydrophilic surface are briefly discussed.

FESEM image shows the PANI sub‐micro/nanostructured dendrites immobilized on the surfaces of PP films. The modified surface is highly hydrophilic with a water contact angle of 3°.     

Monodispersed Magnetic Polystyrene Beads with Excellent Colloidal Stability and Strong Magnetic Response

Monodispersed polystyrene beads incorporated with Fe₃O₄ nanoparticles are prepared via dispersion polymerization. The resultant magnetic beads present well‐defined composite structures, excellent colloidal stability, and strong magnetic response. The formation mechanism for the monodispersed composite beads, incorporated with preformed Fe₃O₄ nanocrystals, was investigated. The potential applications of the monodispersed magnetic beads in bacteria capturing were demonstrated. After being coated with anti‐Salmonella CSA‐1 antibody, the magnetic beads show capturing efficiencies of >99.4% in isolating Salmonella sp.

     

Describing the Structure of a Randomly Hyperbranched Polymer

This paper describes random branching theory, a model for the solution structure of hyperbranched polymers. In this model, the hyperbranched polymer is assumed to be composed of units whose structure is simpler than the resulting polymer. These simple units can have any structure of chemical functionality, from monomers to linear chains or spherical particles. This paper outlines how this theory is constructed, describes the underlying assumptions and parameters, and summarizes the most basic form. It is shown how variations in the parameters change the behavior of the model, and described how to fit an experimental data series. This demonstrates how the model can be used to fit other data series, and how it can be used as a test for whether a polymer is randomly hyperbranched.

     

Quantum Chemical Mapping of Initialization Processes in RAFT Polymerization

Summary: We present the first ab initio simulation of a reversible addition fragmentation chain transfer (RAFT) polymerization. Using ab initio molecular orbital theory, we calculate the equilibrium constants for the first eight addition–fragmentation steps in the cyanoisopropyl dithiobenzoate‐mediated polymerization of styrene. We then simulate the concentration profiles for the RAFT agent, and its unimeric and dimeric adducts, assuming standard experimental parameters for styrene homopolymerization and the addition of the styryl radical to the RAFT agent. The simulated data show excellent agreement with published experimental data, highlighting the accuracy of quantum chemistry. In contrast, the currently used chain‐length independent models fail to describe even the qualitative trends in the data, regardless of whether the fragmentation reaction is assumed to be fast or slow. The calculated chain‐length dependent equilibrium constants are large, in agreement with the earlier proposed slow fragmentation model.

Ab initio kinetic modelling of concentration profiles during the RAFT initialization period.     

A Novel Photopolymerization Initiating System Based on an Iridium Complex Photocatalyst

The use of a photocatalyst (tris(2‐phenylpyridine)iridium [Ir(ppy)₃]) being able to generate both radicals and cations to initiate free radical polymerization and ring opening polymerization is presented. Remarkably, under soft irradiations (fluorescence bulb, sunlight), excellent cationic polymerization profiles and final conversions are obtained. The involved mechanisms are investigated by ESR experiments.

     

Metallo‐Polymerization/‐Cyclization of a C16‐Bridged Di‐Terpyridine Ligand and Iron(II) Ions

Summary: The coordinative polymerization/cyclization of a flexible monodisperse di‐terpyridine ligand with iron(II ) chloride is reported. Matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) investigations showed the preferred formation of a [2 + 2] macrocycle, but also larger aggregates (cycles or linear oligomers) with up to 10 monomer units were found. Because of its C₁₆‐spacer, the solubility is sufficient for performing viscosity experiments in CHCl₃/MeOH solution. A viscosity titration revealed a maximum in viscosity at the 1‐to‐1 ratio of iron(II ) ions to di‐terpyridine‐ligands, which indicates the formation of extended oligomers, polymers, catenanes and/or cycles at that ratio.

Schematic representation of intra‐ and intermolecular metallo‐macrocycles.     

The “Precursor Approach” to Patterned Fluorescence Images in Polymer Films

In contrast to the conventional two‐step method, which involves the generation of reactive functional groups followed by incubation in a dye solution (a wet developing process), the “precursor approach” enables the rapid and cost‐effective generation of patterned images in one step, without the need for an additional wet process. By using the “precursor approach”, the fluorescence of precursor molecules in polymer films can be effectively manipulated by: (1) photoinduced removal of transient protecting groups; (2) photoinduced protonation or intramolecular proton transfer; (3) photochromism; (4) photoinduced formation of fluorophores; (5) photoinduced oxidative degradation or molecular orientation.