Thin Films by Multilayer Build‐Up of Electron Transport Materials

We present the synthesis and the electrochemical characterization of polymeric electron transport materials, synthesized by polycondensation of substituted triazines and α,ω‐dihaloalkanes. They can be reversibly reduced with the least negative potential at −0.39 V, which is below the reduction potential of oxygen. In addition, the formation of polyelectrolyte multilayers is possible by the electrostatic self‐assembly method. This multilayer formation takes place in a very defined way up to thirty double layers.

An example of one of the polymeric triazine electron transport materials synthesized and a schematic diagram of a self‐assembled multilayer film.     

Living Radical Polymerization as a Tool for the Synthesis of Polymer‐Protein/Peptide Bioconjugates

Combinations of synthetic and natural macromolecules offer a route to new functional materials. While biological and polymer chemistry may not be natural bedfellows, many researchers are focusing their attention on the benefits of combining these fields. Recent advances in living radical polymerization have provided methods to build tailor‐made macromolecular moieties using relatively simple processes. This has led to a plethora of block copolymers, end‐functional polymers and polymers with a whole range of biological recognition abilities. This review covers work carried out until late 2006 combining living radical polymerization with proteins and peptides in the rapidly‐expanding field of bioconjugation.

     

Stabilization of Polymer Bilayers by Introducing Crosslinking at the Interface

Summary: Bisphenol A solid epoxy serves as an effective reaction compatibilizer to the bisphenol A polycarbonate (PC)/PMMA bilayer systems. Addition of epoxy to the bottom PMMA layer can retard or even prevent the dewetting of PC films by introducing crosslinking between both components at the interface. This is the first investigation of polymer bilayers stabilized by chemical reactions.

AFM topographic image of a representative dewetting hole.     

Novel Mechanism for Layered Silicate Clay Intercalation by Poly(propylene oxide)‐Segmented Carboxylic Acid

Summary: Poly(propylene oxide)‐amidoacids were used to intercalate montmorillonite clay to afford organoclays with an X‐ray basal spacing as wide as 81 Å. Differing from the ionic exchange between quaternary ammonium salts and the metal ions in clays, the intercalation mechanism involves a beta‐amidoacid chelation with sodium ions in the silicate interlayer confinement. With the end groups tethered on the silicate surface, the hydrophobic poly(propylene oxide)‐backbones self‐aggregate and consequently widen the interlayer space between neighboring silicate plates.

Postulated structure of the chelation of sodium ions by the poly(propylene oxide)‐amido acid.     

New Quenching Procedure for Preservation of Initial Polymer/Catalyst Particle Morphology in Ziegler–Natta Olefin Polymerization

Preservation of initial polymer/catalyst particle morphology under air, was examined using stopped‐flow Ziegler–Natta polymerization with various quenching conditions and post‐chemical treatments. The exposure of the initial particles to air caused the fast formation of cracks on the surface, finally leading to significant reformation of the particle shape, when polymerizing particles were washed with heptane at ?65 °C under N₂ or under CO₂. On the other hand, when the particles were washed with heptane containing an appropriate amount of tetrahydrofuran under CO₂, the particle morphology under air was almost completely maintained even after 1 h exposure. The present results are useful for various ex situ characterizations of unstable initial polymer/catalyst particles.

     

On‐Chip Alginate Microencapsulation of Functional Cells

We report the use of a PTFE‐based microfluidic device for the encapsulation of living, therapeutically‐active cells within monodisperse alginate microspheres. We present a novel microfluidic platform and a flexible experimental method for the production of alginate microspheres. Cell lines HEK293, U‐2 OS and PC12 were separately encapsulated using this method, with minimal loss of cell viability.

     

Water Soluble Star‐block Copolypeptides: Towards Biodegradable Nanocarriers for Versatile and Simultaneous Encapsulation

The synthesis of water soluble star‐block copolypeptides and their encapsulation properties are described. The star‐block copolypeptides, obtained by ring‐opening polymerization of amino acid N‐carboxyanhydrides, consist of a PEI core, a hydrophobic polyphenylalanine or polyleucine inner shell, and a negatively charged polyglutamate outer shell. The encapsulation study showed that these water soluble, amphiphilic star‐block copolypeptides could simultaneously encapsulate versatile compounds ranging from hydrophobic to anionic and cationic hydrophilic guest molecules.

     

Magnetic Molecularly Imprinted Polymer Particles Synthesized by Suspension Polymerization in Silicone Oil

Summary: Magnetic nanoparticles have been prepared by a co‐precipitation method and modified with methacryloxypropyltrimethoxysilane. Magnetic molecularly imprinted polymer particles have been prepared by suspension polymerization in silicone oil. The particles possess a high affinity to the template molecules and are rapidly separated under a magnetic field.

SEM photograph of magnetic MIP particles.     

Microparticle‐Supported Conjugated Polyelectrolyte Brushes Prepared by Surface‐Initiated Kumada Catalyst Transfer Polycondensation for Sensor Applications

A ‘grafting‐from’ approach to synthesize microparticle‐supported conjugated polyelectrolyte brushes is presented. Poly(3‐bromohexylthiophene) is selectively grown from monodisperse organosilica microparticles by surface‐initiated Kumada catalyst‐transfer polycondensation (SI‐KCTP) and then ionizable amino groups are introduced by a two‐step polymer analogous transformation. Optical properties of the resulting microparticle‐supported conjugated polyelectrolyte brushes were found to be dependent on the surrounding chemical environment and thus the particles are promising materials for sensor applications.

     

Facile Synthesis of Self‐Assembled Polyaniline Nanodisks

Polyaniline nanodisks have been synthesized successfully by the chemical oxidation polymerization of aniline by a self‐assembly process without the use of any acid. The thickness and lateral dimensions of the polyaniline nanodisks are in the range of 20–30 nm and 1–2 µm, respectively. The influence of synthetic parameters, such as the concentration of ammonium peroxydisulfate and pH, on the morphologies of polyaniline nanostructures have been investigated.

     

On the Incorrectness of the Factor 2 in the Radical Termination Equation

The IUPAC recommended factor 2 preceding rate coefficients in the radical termination kinetic equations is claimed to be incorrect and confusing. This recommendation can lead to incorrect analysis of experimental data, especially while applying kinetic Monte Carlo simulations. The statement is based on the derivation of the corresponding relationships.

     

Fabrication and Characterization of an Organic‐Inorganic Gradient Surface made by Polymethylsilsesquioxane (PMSQ)

Summary: A simple method for the fabrication of a chemical composition gradient from organic to inorganic by the pyrolysis of a polymethylsilsesquioxane (PMSQ) thin film in a gradient temperature field is reported. The resultant chemical gradient surface demonstrates gradual changes in wettability, and slight microstructural changes are observed along the substrate.

FT‐IR spectra of gradient PMSQ surface along the length from the unheated side to the heated side.     

Ethylene and Ethylene/Propylene Polymerization Behavior of Bis(phenoxy‐imine) Zr and Hf Complexes with Perfluorophenyl Substituents

The catalytic properties of bis(phenoxy‐imine) Zr and Hf complexes incorporating perfluorophenyl groups with methylaluminoxane were investigated. The fluorinated complexes produced far higher‐molecular‐weight polyethylenes and ethylene/propylene copolymers with increased activities compared with the non‐fluorinated congeners. Moreover, the fluorinated complexes displayed a higher incorporation ability for propylene.

Structures of complexes 1 – 4 .     

Polyelectrolyte Multilayer Microspheres as Carriers for Bienzyme System: Preparation and Characterization

Summary: Polyelectrolyte multilayer microspheres were prepared by alternating adsorption of dextran sulfate and protamine on melamine formaldehyde cores followed by the partial decomposition of the core. Peroxidase and glucose oxidase were immobilized in the prepared microspheres. Retention of enzymatic activity of the peroxidase/glucose oxidase system incorporated into the microspheres was demonstrated. Applicability of the bienzyme system immobilized in the microspheres for kinetic glucose assay was shown.

SEM image of the polyelectrolyte multilayer microsphere.     

Synthesis of Novel Biomimetic Zwitterionic Phosphorylcholine‐Bound Chitosan Derivative

Summary: Water‐soluble biomimetic chitosan derivative conjugating zwitterionic phosphorylcholine was efficiently prepared through Atherton‐Todd reaction under the mild conditions, and the possible formation mechanism of zwitterionic product was related to the nucleophilic attack of adjacent 3‐hydroxyl on the D ‐glucosamine residue to phosphorus with the help of base. UV absorption and melting behaviors of DNA/phosphorylcholine‐bound chitosan derivative showed that the phosphorylcholine‐bound chitosan derivative could be a new carrier for long‐circulating macromolecular drug delivery.

Structure of zwitterionic PC‐chitosan.     

Chemical Dual‐Responsive Wettability of Superhydrophobic PANI‐PAN Coaxial Nanofibers

PANI‐PAN coaxial nanofibers have been prepared by electro‐spinning during polymerization. The surface of the resulting nanofibers is superhydrophobic with a water contact angle up to 164.5°. Conductivity of the PANI‐PAN nanofibers is about 4.3 × 10⁻² S · cm⁻¹. The superhydrophobic nanofibers show a chemical dual‐responsive surface wettability, which can be easily triggered by changing pH value or redox properties of the solution. A reversible conversion between superhydrophobicity and superhydrophilicity can be performed in a short time. The strategy used here may provide an easy method to control the wettability of smart surfaces by using properties of low‐cost functional polymers.

     

Urease‐Catalyzed Carbonate Precipitation inside the Restricted Volume of Polyelectrolyte Capsules

A new biomimetic approach for performing CaCO₃ synthesis exclusively inside micron‐sized polyelectrolyte capsules, based on the fermentative formation of a precipitative agent (CO₃²⁻ anion) by urease‐catalyzed urea hydrolysis, was developed. Precipitated CaCO₃ completely fills the interior capsule volume and has a metastable vaterite phase.

     

Layer‐by‐Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition

Enzyme‐loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer‐by‐layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery.