Holes and Ledges Created by Multilayer Assembly on Polyelectrolyte Brushes: A Novel Route for the Three‐Dimensional Nanoscale Design of Surfaces

The layer‐by‐layer (LBL) assembly of poly(diallyldimethylammonium chloride) and poly(sodium styrene sulfonate) on poly(sulfo propyl methacrylate) brushes resulted in films with nanometer‐ and micrometer‐sized holes and ledges, observed by atomic force microscopy and scanning electron microscopy. Polyelectrolyte assembly was followed by the quartz microbalance technique. The formation of ledges and holes is explained by the interaction of the brush polymers with the incoming polyelectrolytes during the LBL assembly, inducing a spatially localized and self‐organized accumulation of the assembled polymers.

     

Effects of Catalyst Isoquinoline in Polymerization Process on the Aggregation Structures of Polyimide in Solution

Summary: A thermoreversible gel or a dendritic crystal has been obtained in a novel polyimide solution at low temperature, depending on the approach taken to add the isoquinoline catalyst during the polymerization process. By adding the isoquinoline at the beginning of polymerization, two kinds of layer structures in the gel are developed. However, by adding the isoquinoline after the polymerization has been carried out for one hour, a perfect dendritic crystalline structure is gradually developed in the polymerization solution.

PLM photographs of the obtained polyimide crystals.     

Novel Superlattices via Blending of Asymmetric Triblock Terpolymers with Diblock Copolymers

The formation of superlattices in blends of a series of asymmetric BSV triblock terpolymers and symmetric SV or VC diblock copolymers is investigated with S being polystyrene, B being poly(1,2‐butadiene), V being poly(2‐vinylpyridine), and C being poly(cyclohexyl methacrylate). All of these triblock terpolymers and diblock copolymers by themselves self‐assemble into lamellae. Apart from various core shell morphologies, in these blends some new unexpected superstructures were obtained.

A TEM micrograph of a 50/50 blend of B₃₀S₅₈V with S₄₅V.     

Low‐Temperature Growth of Thick Polystyrene Brushes via ATRP

Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < T_g by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.     

Simultaneous Detection and Removal of Mercury Ions in Aqueous Solution with Fluorescent Conjugated Polymer‐Based Sensor Ensemble

A water‐soluble, sulfur‐containing fluorescent conjugated polymer exhibits a visible fluorescence color change for detection of mercury in the presence of thymine. A new concept provides the design of a sensor ensemble using a simple combination method. This strategy avoids the need for complicated design and synthesis of a recognition group, eliminating the tedious synthetic efforts for the preparation of a sensor material.

     

Step‐Growth Radical Addition‐Coupling Polymerization (RACP) for Synthesis of Alternating Copolymers

We report a new type of step‐growth radical addition‐coupling polymerization (RACP) involving consecutive addition of carbon‐centered radical derived from α,α′‐dibromo dibasic ester to NO double bond of C‐nitroso compound followed by cross‐coupling of carbon‐centered radical and in situ formed nitroxyl radical, which produces alternating copolymers with high molecular weight and unimodal molecular weight distribution from saturated and unsaturated monomers.

     

Polyurethanes Containing Indole‐Based Non‐Linear Optical Chromophores: from Linear Chromophore to H‐Type

Two new “H” type of indole‐based chromophores were designed and successfully introduced to the polymeric system, the resultant polymers demonstrated enhanced NLO effects, good processability, thermal stability and nearly excellent transparency, indicating the advantages of “H” type chromophore moieties. And they could be promising candidates for the practical applications as new photonic materials.

     

Self‐Assembly and Dispersion of Chromogenic Molecules: A Versatile and General Approach for Self‐Assessing Polymers

Summary: Self‐assessing polymer blends based on poly(ethylene terephthalate glycol) or linear low‐density polyethylene and small amounts (0.5–2% w/w) of chromogenic sensor dyes are prepared and investigated. The cyano‐substituted oligo(p‐phenylene vinylene) dyes employed in the study exhibit pronounced optical absorption changes upon self‐assembly, because of charge‐transfer interactions or conformation changes. The extent of dye aggregation (and therewith the optical absorption characteristics) in these blends is significantly influenced by exposure to external stimuli. Subjecting appropriately processed samples to either temperatures above their glass transition or mechanical deformation can significantly change the extent of aggregation, which in turn leads to a color change.

Mechano‐optical response of a 1.0% w/w LLDPE/C18‐RG blend film. Pristine films are orange due to aggregated dye molecules. Deformation leads to dispersion of the dye and irreversibly changes the color to yellow.     

pH‐Switchable Macroscopic Assembly through Host–Guest Inclusion

A novel pH‐switchable macroscopic assembly is reported using alginate‐based hydrogels functionalized with host (α‐cyclodextrin, αCD) and guest (diethylenetriamine, DETA) moieties. Since the interaction of αCD and DETA is pH sensitive, the host hydrogel and guest hydrogel could adhere together when the pH is 11.5 and separate when the pH is 7.0. Furthermore, this pH‐controlled adhesion and dissociation shows a good reversibility. The host and guest polymers have good biocompatibility; therefore, this pH‐sensitive macroscopic assembly shows great potential in biotechnological and biomedical applications.

     

Sequential Polymer Precipitation of Core–Shell Microstructured Composites with Giant Permittivity

Polymeric core–shell microstructures have been constructed through a new method, namely sequential precipitation, which is intrinsically a self‐assembly and phase separation process. High‐quality poly(vinyldene fluoride)–polycarbonate–lithium perchlorate composite films with spherical core–shell microstructures have been prepared and determined to consist of conducting cores and insulating shells. Because of the percolation effect, the resulting materials present a dielectric constant as high as 10⁴–10⁷ at the threshold.

     

A New Strategy to Exfoliate Silicone Rubber/Clay Nanocomposites

Summary: A new strategy was developed to prepare disorderly exfoliated nanocomposites, in which a soft siloxane surfactant with a weight‐average molecular weight ( ) of 1 900 was adopted to modify the clay. The modified clay slurry was then mixed with silicone rubber by hand, and exfoliation was achieved. The proposed mechanism thereof was verified by TEM and XRD. The physical entanglement of the soft siloxane surfactant plays a vital role in the diffusion and intercalation of the matrix molecules during the compounding of the slurry‐polymer mixture. This simple method is applicable to other silicone‐based materials reinforced by clay.

TEM micrograph of silicone rubber/clay‐sil nanocomposite.     

Strategy for Better Ordering in Diblock Copolymer Based Nanocomposites

A simple approach to improve the structural ordering in block copolymer/nanoparticle nanocomposites is presented. It is to blend a small molecular weight homopolymer with the composites, which can uniformly swell the preferred domain where the nanoparticles locate and increase the conformational entropy of the domain. Consequently, the interfaces between the block copolymer domains become smooth that improves the long range order in the nanocomposites. Furthermore, the uniform swelling of the preferred domain by the homopolymer will allow higher loading of nanoparticles without adversely affecting the long range order.

     

Highly Conductive Core–Shell Nanocomposite of Poly(N‐vinylcarbazole)–Polypyrrole with Multiwalled Carbon Nanotubes

In this communication, the synthesis, characterization, and properties of highly conductive core–shell nanocomposites of poly(N‐vinylcarbazole) (PNVC)–polypyrrole (PPY) copolymers with multi‐walled carbon nanotubes (MWCNTs) are described. A unique free‐radical coupling reaction between PNVC and PPY cation radicals in chloroform solvent, using feric chloride as an oxidant, in the presence of suspended MWCNTs in the reaction medium, was used for the synthesis of nanocomposite. Field‐emission scanning and transmission electron microscopy studies showed the formation of the core–shell nanocomposite. Raman spectrocopy results as well as thermogravimetric analysis supported the electron microscopic observations. The resulting PNVC–PPY copolymer‐coated MWCNTs showed an unprecedentedly increased value of direct electrical conductivity (bulk) compared to the conductivity of all samples even with pure MWCNTs.

     

The Nucleating Effect of Carbon Nanotubes on Crystallinity in R‐BAPB‐Type Thermoplastic Polyimide

Summary: The relatively high degree of crystallinity of a new thermoplastic polyimide (PI) makes it a favorable matrix candidate for fiber reinforced composites. This advantage is the result of the ability of the matrix to recrystallize during the composite manufacturing process. In this study we examine the potential nucleating effect of carbon nanotubes on a thermoplastic PI. In addition to their inherent mechanical contribution, the carbon nanotubes help recover a significant proportion of the original crystallinity.

Scanning electron micrograph of the spherulitic structure of a recrystallized carbon nanotube/polyimide film.     

Highly Efficient and Well‐Controlled Ambient Temperature RAFT Polymerization under Solar Radiation

Highly efficient and well‐controlled ambient temperature reversible addition–fragmentation chain transfer (RAFT) polymerization is readily carried out under environmentally friendly mild solar radiation. This discovery has significantly extended studies from man‐made separated‐spectroscopic‐emission UV‐vis radiation (Macromolecules 2006 , 39, 3770) to natural continuous‐spectroscopic‐emission solar radiation for ambient temperature RAFT polymerization.

     

Biomimetic Dopamine‐Diels–Alder Switches

Mussel adhesives function as tools for surface modifications of a wide variety of materials due to their remarkable adhesion properties. Herein, a combination of bioinspired mussel adhesives based on a dopamine derivative, polymer chemistry, and well‐established Diels–Alder (DA) chemistry leads to a bioinspired switchable surface system that possesses the capability of attaching and detaching specific polymers on demand. A dopaminemaleimide compound, which has been attached to a gold surface under maritime conditions undergoes DA‐ and retro‐DA‐click‐conjugations with cyclopentadiene‐carrying PEG chains. The surface attachment and the subsequent DA/rDA cycles are evidenced via XPS analysis.

     

A New Route for the Preparation of Brain‐Like Nanostructured Polyaniline

A novel approach has been explored to prepare brain‐like polyaniline (PANI) nanostructures with many convolutions (140–170 nm in average diameter) using aniline/citric acid (CA) salt as the template and chlorine gas as the oxidant by a gas/solid reaction for the first time. The method provided here differs significantly from the traditional one in which the polymerization of PANI is usually carried out in acidic solution.

     

Two‐Photon Pattern Bleaching for Characterizing Structural Changes in Polymer Films

Using two‐photon absorption, an array of spots in a dye‐doped polymer film can be bleached, creating a three‐dimensional structure that can be imaged with two‐photon or confocal microscopy. Microscopic deformations resulting from various treatments to the film can be characterized, for example, swelling or shrinking. This technique is demonstrated on dye‐doped poly(vinyl alcohol), in which the effect of swelling with the addition of water to the film is shown.

     

Preparation of Nanostructured Polyaniline and its Super‐Amphiphilic Behavior

PANI nanofibers are prepared electrochemically by template‐free method on a stainless steel electrode. Both the hydrophilicity and the lipophilicity of the modified SS surface are enhanced by the nanostructured PANI, and a super‐amphiphilic surface is obtained in this way. The influence of polymerization conditions, such as polymerization potentials, polymerization time, the acidity, and the dopants on the super‐amphiphilic property, has been systematically investigated. In addition, the mechanisms of obtaining a super‐amphiphilic surface are briefly discussed.