Single‐Step Electrospinning of Bimodal Fiber Meshes for Ease of Cellular Infiltration

Bimodal fiber meshes with fiber diameters differing by one order of magnitude, are electrospun in a simple one‐step process, using a standard single syringe electrospin setup. The nano‐ and microfiber meshes combine the benefits of nanofibers (cell adhesion, proliferation) with those of microfibers (open structure, large pore size) and are therefore interesting as scaffolds for cellular infiltration.

     

A Novel Class of Betaine‐Type Polyampholytes with Stimuli‐Responsive and Complexing Properties

Linear and crosslinked betaine‐type polyampholytes based on ethyl 3‐aminocrotonate and unsaturated carboxylic acids have been synthesized by very fast polymerization in bulk and solution. Bulk polymerization occurred exothermically even at room temperature and without adding an initiator. The polyampholytes showed stimuli‐responsive properties with respect to pH, ionic strength, water/organic solvent mixtures, and metal ion complexation.

Temperature profile of the polymerization reaction for an equimolar mixture of CRO and AA with time in the absence of initiator.     

Direct Synthesis of Biodegradable Polysaccharide Derivative Hydrogels Through Aqueous Diels‐Alder Chemistry

A robust synthetic strategy where polysaccharide derivative precursors react through aqueous Diels–Alder chemistry without the involvement of catalysts and coupling reagents, allowing for the direct encapsulation of positive and negative proteins within biodegradable hydrogels. The results demonstrated that the aqueous Diels–Alder chemistry provides an extremely selective reaction and proceeds with high efficiency for polysaccharide bioconjugation. This synthetic approach uniquely allows for the direct fabrication of biologically functionalized gels with ideal structures, which provides a competitive alternative to conventional conjugation techniques such as click chemistry.

     

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.     

Electrospinning of Collagen Nanofiber Scaffolds from Benign Solvents

Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro‐2‐propanol. Simple binary mixtures of phosphate‐buffered saline and ethanol have been found to be highly effective for electrospinning. FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning. Crosslinking of the electrospun collagen scaffolds was achieved with standard methods.

     

Towards Chiral Microporous Soluble Polymers—Binaphthalene‐Based Polyimides

Recently, intrinsically microporous polymers have received increased interest in research. Contrary to currently commercially used microporous materials, e.g., zeolithes or polymer networks, they can be dissolved, processed and further functionalised. Microporous poly(imide)s are especially interesting, as they are chemically and thermally resistant to decomposition up to high temperatures. In this paper, we report for the first time on a chiral poly(imide) which is intrinsically microporous and soluble in common solvents. After analysing the structure of the polymer, its pore system is characterised via its ability to adsorb nitrogen, argon, hydrogen and carbon dioxide. Furthermore, the chiral polymer is compared with its racemic counterpart, illustrating the special role of an organised superstructure.

     

Novel Approach of Evaluating Polymer Nanocomposite Structure by Measurements of the Freezing‐Point Depression

Summary: A novel experimental approach based on the freezing‐point depression of a solvent in a swollen gel has been developed to characterize the structure of nanocomposites. A higher depression in the freezing point has been related with an exfoliated nanocomposite. This increased depression not only depends on the formation of a tighter network but also on the decrease of the size of the solvent cages where the nucleation takes place.

The nucleation process of unfilled and organoclay‐filled natural rubber with the same crosslinking density.     

In situ Localization of Molecules in Crosslinked Particles during Electrohydrodynamic Process: Simple Route to Produce Microcapsules and Fibers with Controlled Release

This study reports a spontaneous selective localization of molecules in crosslinked particles during electrospraying and electrospinning polymer solutions containing the particles. It provides a facile way of preparing microcapsules and fibers with controlled release. The dye molecules were phase separated from the crystalline polymer matrix during the electrohydrodynamic process and moved to the solvent‐rich crosslinked particles. The position of the particles in the microcapsules and fibers could be controlled by adjusting compatibility of the particles with the matrix polymer. The microcapsules and fibers did not show the initial burst release of the molecules and gave considerably prolonged release behavior.

     

Well‐aligned Nano‐fiberous Membranes Based on Three‐pole Electrospinning with Channel Electrode

Three‐pole electrospinning devices integrated with a blade‐cage collector were developed to fabricate well‐aligned nano‐fiberous membranes. The proposed three‐pole configuration with a channel electrode can be a powerful tool in aligning nano‐fibers with regular diameter because the generated electric field can be accurately controlled without severe fluctuation in comparison with other methods. The three‐pole electrospinning method is also valid for industrial mass production and accurate diameter control of the aligned nano‐fibers.

     

Green Nanocomposites from Renewable Resources: Biodegradable Plant Oil‐Silica Hybrid Coatings

Green nanocomposite coatings based on renewable plant oils have been developed. An acid‐catalyzed curing of epoxidized plant oils with 3‐glycidoxypropyltrimethoxysilane produced transparent nanocomposites. The hardness and mechanical strength improved by incorporating the silica network into the organic polymer matrix, and good flexibility was observed in the nanocomposite. The nanocomposites showed high biodegradability.

     

New Approach in Modeling of Metallocene‐Catalyzed Olefin Polymerization Using Artificial Neural Networks

A new approach for the estimation of kinetic rate constants in olefin polymerization using metallocene catalysts is presented. The polymerization rate has been modeled using the method of moments. An ANN has been used and trained to behave like the mathematical model developed before, so that it gets polymerization rate at different reaction times and predicts reaction rate constants. The network was trained using modeling results in desired operational window. The polymerization rates were normalized to make the network work independent of operational conditions. The model has also been applied to real polymerization rate data and the predictions were satisfactory. This model is specially useful in comparing different new metallocene catalysts.

     

1,1‐Diphenyl Ethylene‐Mediated Radical Polymerisation: A General Non‐Metal‐Based Technique For The Synthesis Of Precise Core Cross‐Linked Star Polymers

This communication details the successful synthesis of low polydispersity core cross‐linked star (CCS) polymers via DPE‐mediated polymerisation. We demonstrate the ability to produce poly(methyl methacrylate) and poly(acrylonitrile) CCS polymers that are currently inaccessible via the two most common non‐metal‐based controlled radical polymerisation techniques (NMP and RAFT polymerisations).

     

A Highly Selective,Colorimetric, and Fluorometric Multisignaling Chemosensor for Hg2+ Based on Poly(p‐phenyleneethynylene) Containing Benzo[2,1,3]thiadiazole

A novel colorimetric and fluorometric chemosensor for Hg²⁺ detection based on poly(p‐phenyleneethynylene) (PPE) containing benzo[2,1,3]thiadiazole (BDT) has been developed. A highly Hg²⁺‐selective fluorescence quenching property in conjunction with a visible colorimetric change from yellow to violet can be observed, which indicates that PPE‐BDT can serve as a sensitive ‘naked‐eye’ indicator for Hg²⁺.

     

Oxazolidines versus schiff bases

The formation of oxazolidines from propionaldehyde and aliphatic β-aminoalcohols is complicated by the appearance of appreciable amounts of unsaturated Schiff bases. The simple Schiff base, often the dominant species when aromatic aldehydes react with amines, could not be detected in the present aliphatic systems. We conclude that in aliphatic systems the order of stability is and . The gem-dimethyl group α to nitrogen stablizes the heterocyclic ring remarkably.     

New Azo Chromophore‐Containing Conjugated Polymers: Facile Synthesis by Using “Click” Chemistry and Enhanced Nonlinear Optical Properties Through the Introduction of Suitable Isolation Groups

A new series of azobenzene‐containing polyfluorenes have been successfully prepared through polymer reactions by the utilization of “click” chemistry. All the polymers were well characterized and soluble in common solvents. By the application of the concept of “suitable isolation group”, the macroscopic nonlinear optical (NLO) properties of the polymers could be boosted to as large as three times that of the polymer without isolation moieties. Also, all the polymers were thermally stable, and demonstrated good procesability, coupled with improved optical transparency. Thus, they are good candidates for the practical applications as new photonic materials.

     

Synthesis of Poly(ethylene oxide)s Bearing Functional Groups along the Chain

Well‐defined poly(ethylene oxide)s (PEOs) bearing reactive sites regularly distributed along the chain have been synthesized by the polycondensation of PEO containing a central tertiary amino group with dichloromethane, followed by quaternization with suitable reagents to obtain polyzwitterionic or cationic PEOs with alkyl, allyl, or fluorocarbon pendant groups. The pendant allyl groups have been converted into primary amino groups by reaction with 2‐aminoethanethiol hydrochloride to obtain polyamino‐functionalized PEO.

Polyfunctional PEOs bearing different pendant groups.