Template‐Assisted Synthesis of Self‐Doped Polyaniline: Morphological Effects of Templates on the Conductivity

Self‐doped sulfonated polyaniline (PSA) has been synthesized on the surface of micellar nanoparticles made from positively charged surfactants by biocatalysis. The conformation forced by the electrostatic charge interactions between the positively charged micelle and the negatively charged PSA increases the conductivity of the PSA by three orders of magnitude. The pure PSA recovered from ion exchange, however, shows quite similar electrical properties compared with sulfonated polyanilines reported earlier. The increased conductivity of PSA complexes is as a result of the increased charge carrier concentration caused by a certain conformational locking.

     

Synthesis of Polyaniline‐Vanadium Oxide Nanocomposite Nanosheets

Summary: Polyaniline‐vanadium oxide nanocomposite nanosheets with thickness between 10 and 20 nm, and lateral dimensions in the range of hundreds of nanometers to several microns have been synthesized by in situ intercalation polymerization of aniline with layered V₂O₅ under hydrothermal conditions. The product was characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT‐IR) spectroscopy, and X‐ray diffractometer (XRD). The effects of the concentration of aniline and reaction temperature on the morphologies of polyaniline‐vanadium oxide nanocomposites have also been investigated.

SEM image of tremella‐like polyaniline‐vanadium oxide nanocomposite nanosheets.     

Is the Reduction in Tracer Diffusivity under Nanoscopic Confinement Related to a Frustrated Segmental Mobility?

We developed an experimental method for the determination of the tracer diffusivity D_tr in ultrathin polymer films, and the changes in the segmental mobility of tracer molecules while they diffuse through matrices of different thickness and get adsorbed onto a target substrate. D_tr starts decreasing already at 120–150 nm and drops to 1% of its bulk value in films as thin as 7.5 nm. We discuss the results highlighting a strong decoupling between the reduction in mass transport at the nanoscale and the increase in the glass transition temperature determined via capacitive dilatometry together with a breakdown of the Stokes–Einstein relation between orientational and translational degrees of freedom.

     

Suppression of Crazing in Polystyrene Crosslinked with a Multifunctional Zirconium Oxo Cluster Observed In Situ during Tensile Tests

The structural development of polystyrene, which was crosslinked with varying amounts of the multifunctional cluster Zr₆O₄(OH)₄(methacrylate)₁₂, was followed in situ by small‐angle X‐ray scattering at a synchrotron radiation source. It was observed that crazing strongly diminishes with increasing cluster proportion and disappears nearly completely for the material with the highest cluster proportion of 0.87 mol‐%. Accordingly, the maximum stress before failure is strongly enhanced, whereas the maximum strain decreases.

     

The Peculiar Response of DNA Hydrogel Fibers to a Salt and pH Stimulus

DNA hydrogels which are composed of an entangled network without a crosslinker are synthesized and examined in regards to their sensitivity to salt and pH changes. The DNA hydrogel fibers only exhibited a marked response – that is a fast and large change in length – under biological conditions ([Na⁺] = 0.15 M at pH = 7) and are therefore suitable materials for bio‐inspired devices.

     

Photoactive Modified Hydroxyethylcellulose

A water‐soluble polymeric photosensitizer that contains naphthalene chromophores and absorbs light in the near UV region was obtained by modification of hydroxyethylcellulose. The excitation energy migrates along the naphthalene chromophores covalently attached to the polymer chain and can be used to induce photochemical reactions such as photoinduced electron transfer.

UV‐vis absorption (○), fluorescence emission (□), and fluorescence excitation (×) spectra of HENC in water at c_HENC = 0.232 g/L, and (+) emission spectrum of the lamps used for irradiations.     

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.

     

N‐Alkylation of imides using phase transfer catalysts under solvent‐free conditions

N‐Alkylation of imides in the reaction of imides and alkylhalides, catalyzed by PT catalysts under solvent‐free conditions, has been developed. The reaction occurs in the presence of K₂CO₃, and in many cases it takes place spontaneously. In the N‐benzylation reaction, it has been recognized that TBAB (tetrabutylammonium bromide) and TBATFB (tetrabutylammonium tetrafluoroborate) show highest catalytic effect. Versatility and synthetic capacity of the solvent‐free alkylation has been confirmed by N‐benzylation and N‐ethylation of various imides. The developed procedure gives easy access to N‐(ω‐bromoalkyl)imides.     

Synthesis of alkyl 6‐methyl‐4‐(2‐pyridyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates for evaluation as calcium channel antagonists

The Bigenelli acid catalyzed condensation of 2‐pyridylcarboxaldehyde ( 1 ), urea ( 2 ) and an alkyl acetoacetate ( 3 ) afforded the respective alkyl (Me, Et, i‐Pr, i‐Bu, t‐Bu) 6‐methyl‐4‐(2‐pyridyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates ( 4a‐e ). The most potent calcium channel antagonist ethyl 6‐methyl‐4‐(2‐pyridyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylate ( 4b , IC₅₀ = 1.67 × 10^?5 M) wasa much weaker calcium channel antagonist than the reference drug nifedipine (Adalat®, IC₅₀ = 1.40 × 10^?8 M) on guinea pig ileal longitudinal smooth muscle (GPILSM). The alkyl 6‐methyl‐4‐(2‐pyridyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates did not show any inotropic effect on heart since no increase, or decrease, in the contractile force of guinea pig left atrium was observed. These structure activity studies show that the alkyl 6‐methyl‐4‐(2‐pyridyl)‐1,2,3,4‐tetrahydro‐2H‐pyrimidine‐2‐one‐5‐carboxylates ( 4a‐e ) are partial bioisosteres of nifedipine with respect to calcium channel antagonist activity on guinea pig ileal longitudinal smooth muscle (GPILSM).     

Convenient synthesis of some 2‐substituted 4(3H)‐quinazolinone derivatives

A series of 2‐substituted‐4(3H)‐quinazolinones 13‐20 has been synthesized in good yields using the reaction of double lithiated 2‐methylquinazolinone‐4 with a variety of aromatic aldehydes. They have been easily transformed in high yields into the corresponding 2‐substituted conjugated derivatives 21‐28 bearing terminal aryl groups by F₃CCOOH mediated dehydration.     

An Efficient Blue‐Emitting Conjugated Copolymer Based on Fluorene and Carbazole with a Peripheral Dendritic Carbazole Pendant at the 9‐Position

A new fluorene‐co‐carbazole‐based copolymer (PFCD), with a bulky peripheral dendritic carbazole pendant at the 9‐position, has been designed and synthesized through a Suzuki polycondensation reaction. The resulting copolymer exhibits desirable properties, such as excellent solubility, good thermal stability, and electrochemical properties. PFCD also shows efficient blue light‐emitting properties with excellent color purity and high photoluminescent quantum yield. The results of the photophysical properties indicate that the large side dendron with peripheral carbazole groups can not only efficiently suppress the π‐stacking of polymer chains but also raise the HOMO level of the resulting polymer material. Thus, PFCD is expected to be a promising pure blue light‐emitting material and further experiments on electroluminescent properties, film morphology, and aggregation behaviors are in progress.

     

New TRANS/CIS tetrahydroisoquinolines. 3. [1,3]‐oxazolo‐[3,2‐B]‐tetrahydroisoquinolinones having an angular aryl substituent

The parent compound 5‐oxo‐10a‐phenyl‐2,3,10,10a‐tetrahydro‐5H‐[1,3]‐oxazolo‐[3,2‐b]‐isoquinoline‐10‐carboxylic acid ( 5 ) was prepared in large scale and a good yield by reaction between homophthalic anhydride ( 3 ) and 4,5‐dihydro‐2‐phenyl‐1,3‐oxazole ( 4 ). Thus, the closure of the isoquinoline ring and fusion of the 1,3‐oxazol ring occur in one step. Trans configuration was assumed for the product. The parent acid 5 was converted in four steps to the target aminomethyl derivatives 9a‐1 . The latter contain four features that make them interesting from pharmaceutical point of view.     

Microwave‐Assisted Synthesis of Associative Hydrogels

In the present paper, the microwave (MW)‐assisted synthesis of hydrogel forming polymers based on poly(acrylic acid) ( 1 ) is described. The polymer analogous condensation reaction between adamantyl moieties bearing free amino groups and poly(acrylic acid) ( 1 ) was carried out simply by mixing both components and subsequent use of MW protocol. The mixture was irradiated for 20 min without the addition of solvents or coupling agents. Aqueous solutions of the sodium salts of the obtained hydrophobically modified poly(acrylic acid)s showed a very high viscosity due to the intermolecular association of the hydrophobic side chains and the resulting formation of physical networks. By the addition of randomly methylated β‐cyclodextrin (RAMEB), the rheology of these systems could be influenced significantly.

     

Molecularly Imprinted Multi‐Layer Core‐Shell Nanoparticles – A Surface Grafting Approach

Surface initiated living‐radical polymerization (SIP) based on dithiocarbamate iniferters has been used to create molecularly imprinted core‐shell (CS) nanoparticles. Using this approach, propranolol, morphine and naproxen have been successfully imprinted in particle shells (the latter could not be imprinted using conventional aqueous‐based CS methods). Rebinding properties of the imprinted particles appear to be similar to those made by alternative methods. The living radical initiation mechanism makes it possible to build complex multi‐layer particles sequentially. As a demonstration, multi‐layer propranolol‐imprinted particles were generated. Two additional functional shells were grown over the imprinted shell, while the propranolol binding was retained, albeit at a reduced level.

     

Reactivity of the A-CH=N=NR-CX-B System. 1,3,4-thiadiazoles and Δ2 -thiadiazolines

The reactivity of the - system towards ferric chloride has been investigated. The cyclo-oxidation reaction led to the formation of 2-amino-5-thenoyl-1,3,4-thiadiazoles and 4-methyl-5-imino-2-thenoyl-Δ²-1,3,4-thiadiazolines. Their structures were proven spectro-scopically and chemically (nucleophilic attack and formation of the related 2-amino-1,3,4-thiadiazoles and 4-methyl-5-imino-Δ²-1,3,4-thiadiazolines).     

Supramolecular Nanoscaled Self‐Assembly of Bifunctional Cyclodextrin and Trifunctional Melamine Precursors

A new type of guest–core supramolecular networks via inclusion complexation of nanoscaled building blocks such as bifunctional cyclodextrin (CD) derivatives and trifunctional melamine derivatives were prepared. By using AFM and an adoption of the cryo‐TEM technique under high acceleration voltage the nanoscale supramolecular network structure, nexus units, and CD molecules could be visualized. In addition to the 2‐D ¹H NMR rotating frame Overhauser effect spectroscopy (ROESY) experiments, theoretical studies on the molecular docking of the CDs and the melamine derivative have been conducted to elucidate the thermodynamic properties by the two‐layered integrated molecular orbital and molecular mechanics (ONIOM) method, which combines both quantum mechanics and molecular mechanics (QM/MM) calculations.

     

Study on Effects of Polydispersity on the Form Factor and Depletion Interaction in Colloid‐Polymer Mixtures with Laser Distribution

Summary: We investigate the influence of the polydispersity of colloidal particles and polymer, respectively, on the form factor and depletion interaction by using the laser distribution for parallel plates immersed in a solution of nonadsorbing polymers. For colloidal particles, we show that the measurement of scattering intensity of a polymer‐colloid mixture can be described qualitatively in terms of the parameters K and M of the laser distribution. The form factor of the monodisperse system varies considerably, but generally stays close to the average value that corresponds to the form factor of polydisperse system. By using the laser distribution in the chain length of polymers, we present the complex polymer segment density of polymer chain between particles with the product‐function approximation comprehensively and accurately. In particular, we find that for small values of parameter M, the change of values of parameter K has no effect on depletion interaction.

Predicted form factor for polydisperse core‐shell particles.