Preparation of microporous polymers in the form of particles and a thin film from hyperbranched polyphenylenes

The use of a hyperbranched polymer as a building block for the synthesis of a microporous organic polymer was demonstrated. Hyperbranched polyphenylenes (HBPs) were prepared from (3,5‐dibromophenyl)boronic acid, which contained numerous unreacted bromophenyl end groups. Utilizing metal‐catalyzed coupling reactions between these functional groups, cross‐linked porous polymers were obtained. Although the HBPs did not show porosity, their cross‐linked polymers had highly porous structures with Brunauer–Emmett–Teller surface areas of up to 2030 m²/g. An insoluble porous thin film was fabricated by spin casting of a solution containing a HBP followed by Sonogashira cross‐coupling reaction. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2336–2342     

Fluorinated phenylated polyphenylenes with nanoporous structures and ultralow dielectric constants formed in supercritical carbon dioxide

New fluorinated bis(tetraarylcyclopentadienones) are synthesized, and their compositions and structures are investigated by elemental analysis and IR, Raman, ¹H, ¹³C, and ¹⁹F NMR spectroscopy. The fluorinated bis(tetraarylcyclopentadienones) are used to prepare a number of new fluorinated phenylated polyphenylenes that combine high thermal and mechanical characteristics and low dielectric constants (2.54?C2.74) with solubility in organic solvents. With the use of supercritical carbon dioxide, thermally stable nanoporous materials with ultralow dielectric constants (1.58?C1.97) are designed on the basis of phenylated polyphenylenes. For phenylated polyphenylenes, the described approach to the synthesis of nanoporous structures with the use of supercritical carbon dioxide is developed for the first time. This approach provides the basis for creation of new breakout technologies in the field of microelectronics.     

Phospho‐l‐tyrosine‐agarose chromatography: Adsorption of human IgG and its proteolytic fragments

The behavior of human immunoglobulin G (IgG) and antigen‐binding fragment (Fab fragment) adsorption onto phospho‐l ‐tyrosine immobilized on agarose (P‐Tyr‐agarose) was evaluated by pseudoaffinity chromatography. The effects of buffer systems MES, MOPS, Bis–Tris, Tris–HCl and sodium phosphate (NaP) and pH on IgG adsorption were studied and high purity values were obtained (96%, based on ELISA analysis of albumin, transferrin and immunoglobulins A, G and M) when IgG was purified from human plasma diluted in 10 mmol L^?1 NaP buffer at pH 6.0. The capture of IgG by the P‐Tyr‐agarose was also promising, since 91% of the IgG was adsorbed when plasma was diluted in 25 mmol L^?1 MES buffer at pH 5.5, recommending its use for IgG depletion from human plasma under this condition. The experimental data on IgG adsorption kinetics were in agreement with the pseudo‐second‐order model. The adsorption isotherm data were well described by the Langmuir–Freundlich model with the value of parameter n being <1 (0.72), indicating negative cooperativity. Selectivity was achieved on P‐Tyr‐agarose from digested human IgG in HEPES 25 mmol L^?1 buffer at pH 7.0 where Fab fragments were obtained in eluted fractions without Fc fragments (but with uncleaved IgG) with 86.2% recovery.     

New polymer materials with controlled nanoporous structure based on N-vinylpyrrolidone

The polymer networks with nanoporous structure were obtained by the crosslinking free-radical copolymerization of N-vinylpyrrolidone with triethylene glycol dimethacrylate in bulk in the presence of amphiphilic copolymer and its fractions as templates. The templating agents consisted of copolymer or their fragments with similar monomer units and different molecular weight. Macromolecular templates were shown to be removed from the polymer composite by PrⁱOH leaving the pores. The values of the specific surface areas, the total pore volumes, pore size, and pore size distribution were measured by the method of low-temperature nitrogen absorption. The maximum value of the specific surface area was calculated to be ~26 m² g^–1. The value was significantly higher than that for the usual copolymer network. The relationship between specific surface area, parameters of pores, and macromolecular structure of template has been established. It is shown by Brunauer—Emmett—Teller method that the macromolecules having a branched architecture are more effective for the preparation of the polymer network with more developed specific surface area and narrow pore size distribution.

     

Hybrid magnetic amphiphilic composites based on carbon nanotube/nanofibers and layered silicates fragments as efficient adsorbent for ethynilestradiol

In this work, hybrid magnetic amphiphilic composites were prepared by the catalytic growth of carbon nanotubes (CNTs) and nanofibers CNF on layered silicates fragments. SEM, TEM, Raman, XRD, Mössbauer, TG/DTA showed that CVD with CH₄ at 800 °C produced CNF and magnetic Fe cores fixed on the surface of microfragments of silicates layers. Due to the amphiphilic character, the composites can be easily dispersed in water and efficiently adsorb hydrophobic contaminant molecules. For example, the composites showed remarkable adsorption capacities for the hormone ethinylestradiol, e.g. 2–4 mg m^?2, compared to ca. 0.1 mg m^?2 obtained for high surface area activated carbon and multiwall CNT. These results are discussed in terms of a high hydrophobic exposed surface area of the CNT and CNF fixed on the layered silicates fragments surface. Moreover, the composites can be easily removed from water by a simple magnetic separation process.     

Synthesis of insulin fragments with disulfide bridges between intact chains A20-B19

The synthesis of six insulin fragments is described, in which various sequences of the two chains are linked by the disulfide bridge between A²⁰ and B¹⁹. The fragments in question are: A^20–21–B^19–21, A^20–21–B^18–21, A^20–21–B^17–21, A^19–21–B^19–21, A^16–21–B^18–21 and A^20–21–B^12–21. In order to build up the simpler fragments the disulfide bridge was established by oxidation with iodine of two S-trityl cysteine peptides in which the carboxyl and amino groups were protected by the t-butyl and t-butyloxycarbonyl residue. From the mixture obtained the unsymmetrical cystine peptide was separated in all cases from the two symmetrical ones by counter-current distribution. In the synthesis of the more complex fragments advantageous use was made of smaller unsymmetrical fragments prepared as above but having one amino group protected by the N-trityl residue. After selective elimination of this group it was possible to lengthen the peptide chain at this position. The free peptides were obtained by removal of the protecting groups with strong acids, in particular concentrated hydrochloric acid. While in this deprotecting step the disulfide bond was stable, conditions are discussed under which disproportionation was observed. None of the six synthetic insulin fragments showed activity in stimulating rat adipose tissue to convert ¹⁴C-labelled glucose to CO₂ in vitro.     

Construction of a Shape-Diverse Fragment Set: Design,Synthesis and Screen against Aurora-A Kinase

Historically, chemists have explored chemical space in a highly uneven and unsystematic manner. As an example, the shape diversity of existing fragment sets does not generally reflect that of all theoretically possible fragments. To assess experimentally the added value of increased three dimensionality, a shape-diverse fragment set was designed and collated. The set was assembled by both using commercially available fragments and harnessing unified synthetic approaches to sp³-rich molecular scaffolds. The resulting set of 80 fragments was highly three-dimensional, and its shape diversity was significantly enriched by twenty synthesised fragments. The fragment set was screened by high-throughput protein crystallography against Aurora-A kinase, revealing four hits that targeted the binding site of allosteric regulators. In the longer term, it is envisaged that the fragment set could be screened against a range of functionally diverse proteins, allowing the added value of more shape-diverse screening collections to be more fully assessed.     

Ammonolysis of magnesiothermic tantalum powders

Tantalum nitrides are synthesized by ammonolysis of a mesoporous magnesiothermic tantalum powders. The effect of specific surface area of the powders and synthesis temperature on product composition is shown. Nitrogen content in the ammonolysis product of tantalum powder with a specific surface area of 56 m² g^–1 corresponds to oxynitride TaON exposed to 600°C for 1 h. The specific surface area of the oxynitride is 35 m² g^–1.     

Optimization of hydrogen storage capacity in silica-supported low valent Ti systems exploiting Kubas binding of hydrogen

Silica-based materials grafted with low valent Ti fragments for Kubas-type binding of hydrogen were optimized for hydrogen adsorption capacity by varying the surface area, pore size, loading levels, and type of organometallic precursor. All materials were characterized by XRD, nitrogen adsorption, and XPS where appropriate. The surface area of HMS silica was optimized by varying silica-to-surfactant molar ratio, and also by tuning the pore size by varying the surfactant’s carbon chain length (C₆, C₈, C₁₀, C₁₂). Then Ti fragments originating from either benzyl, allyl, or methyl Ti precursors were grafted onto the optimal HMS surface at different loading levels to arrive at Ti grafted HMS materials with H₂ storage capacities and binding properties superior to those previously reported by our group for benzyl Ti (III) species on silica. HMS prepared with dodecylamine using a silica:surfactant ratio of 3:1 and subsequently grafted with 0.2 M equiv. of TiBz₄ had the highest H₂ adsorption at 2.45 wt% at 77 k and 60 atm, which equates to an average of 3.98 H₂ molecule per Ti metal center, just one H₂ molecule short of the theoretical saturation limit of 5 H₂/Ti predicted by the 18-electron rule. The H₂ adsorption capacities of Me₃Ti-HMS and Allyl₃Ti-HMS prepared using the same optimized sample of C₁₂-HMS silica at a 3:1 Si:surfactant ratio possessed H₂ adsorption values corresponding to 2.4 and 2.27 H₂ per Ti center, respectively, at 60 atm and 77 K. This performance level is significantly lower than that of the benzyl Ti (III) system. The binding enthalpies of the benzyl Ti (III) material increase with H₂ coverage to 23 kJ/mol, while the enthalpies for the newly synthesized Me₃Ti-HMS and Allyl₃Ti-HMS materials increase with H₂ coverage to a maximum of 2.66 and 4.17 kJ/mol, respectively. XPS studies on these materials suggested a trend in π-back donating ability on the Ti (III) centers of methyl > allyl > benzyl, opposite that observed experimentally. The reason for the diminished performance of the allyl and methyl Ti (III) systems may thus be related to the presence of THF ligands blocking coordination sites in the allyl and methyl systems. THF is not present in the benzyl system because this solvent is not required for synthesis.     

Magnetic parameters and rotational mobility of the ≡SiON(O·)CX3 nitroxides (X = H,D) grafted on silica surface

The magnetic parameters of the SiON(O^·)CX₃ nitroxides (X = H, D) grafted on an activated Aerosil surface were determined. The optimal geometry of the radicals was calculated and their rotational mobility was characterized. The activation energies to the rotation of radical fragments around various bonds were estimated.     

Electric Double‐Layer Capacitors Based on Highly Graphitized Nanoporous Carbons Derived from ZIF‐67

Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp²‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g^?1 is observed at a scan rate of 20 mV s^?1. This value is very high compared to previous works on carbon‐based electric double layer capacitors.     

Synthesis of nitrogen-containing carbon materials for solid polymer fuel cell cathodes

The following nitrogen-containing supports with various nitrogen contents and structure and texture properties were synthesized: carbon nanofibers (N-CNFs) and amorphous microporous carbon materials (N-AMCMs). It was found that the above characteristics can be regulated by varying synthesis conditions: precursor compositions and reaction temperature and time. Mesoporous nitrogen-containing CNFs with a specific surface area of 30–350 m²/g and a pore volume of 0.10–0.83 cm³/g were formed by the catalytic decomposition of a mixture of ethylene with ammonia at 450–675°C. Microporous materials (N-AMCMs) with a specific surface area of 472–3436 m²/g and a micropore volume of 0.22–1.88 cm³/g were prepared by the carbonization of nitrogen-containing organic compounds at 700–900°C. An increase in the carbonization temperature and reaction time resulted in an increase in the specific surface area and microporosity of N-AMCMs, whereas lower temperatures of 450–550°C and reaction times of 1–3 h were optimal for the preparation of N-CNFs with a developed texture. It was found that milder synthesis conditions and higher nitrogen contents of precursors were required for obtaining high nitrogen concentrations in both N-CNFs and N-AMCMs. The synthetic method developed allowed us to prepare carbon supports with nitrogen contents to 8 wt %.     

Some new polymeric semiconductors

This paper deals with some new methods for synthesis of the polymeric semiconductors by conjugated reactions and also with electrophysical properties of the polymers. Elimination of hydrogen halides from α,β-dihalo derivatives by bases (calcium oxide or tertiary amines) yields polymers with conjugated bonds. The reaction proceeds at 200–300°C. under atmospheric or elevated pressures, acetylenes being the intermediates. α,β-Dihalo compounds with calcium carbide above 150°C. produce polyacetylenic copolymers by elimination of two moles of hydrogen halide, also by generating acetylene from calcium carbide. The identical reaction (elimination of water) was observed between carbonyl compounds and calcium carbide. Elimination of water from monoand bifunctional phenols in the presence of zinc chloride under pressure above 200°C. yields polyphenylenes and polyhydroxyphenylenes, dehydrobenzene (benzyne) and hydroxybenzyne being intermediates. The polyhydroxyphenylenes prepared have a degree of polymerization from 4–5 to several thousand and are of interest as intermediates for thermostable resins, inhibitors etc. Linear polycyanamide and polycyanic acid were first prepared by polycondensation of urea with ammonium bicarbonate in the presence of zinc chloride. Analogous polymers were obtained from the ring-opening polymerization of melamine and cyanuric acid. The polymers show good semiconductor and ion-exchange properties. Polycondensation of ketones with ammonium bicarbonate also gave conjugated polymers. Thus, organometallic polymers were prepared from acetyl- and diacetyl ferrocene. We have also studied electrophysical, magnetic, and catalytic properties of the conjugated polymers prepared by the new methods. The electrical conductivity of the best specimens ranged from 10^?3 to 10^?6 ohm^?1 cm.^?1; the number of electrons unpaired was 10¹⁸–10¹⁹ spins/g.     

Top‐down mass spectrometry of intact phosphorylated β‐casein: Correlation between the precursor charge state and internal fragments

Phosphorylated proteins play essential roles in many cellular processes, and identification and characterization of the relevant phosphoproteins can help to understand underlying mechanisms. Herein, we report a collision‐induced dissociation top‐down approach for characterizing phosphoproteins on a quadrupole time‐of‐flight mass spectrometer. β‐casein, a protein with two major isoforms and five phosphorylatable serine residues, was used as a model. Peaks corresponding to intact β‐casein ions with charged states up to 36⁺ were detected. Tandem mass spectrometry was performed on β‐casein ions of different charge states (12⁺, and 15⁺ to 28⁺) in order to determine the effects of charge state on dissociation of this protein. Most of the abundant fragments corresponded to y, b ions, and internal fragments caused by cleavage of the N‐terminal amide bond adjacent to proline residues (Xxx‐Pro). The abundance of internal fragments increased with the charge state of the protein precursor ion; these internal fragments predominantly arose from one or two Xxx‐Pro cleavage events and were difficult to accurately assign. The presence of abundant sodium adducts of β‐casein further complicated the spectra. Our results suggest that when interpreting top‐down mass spectra of phosphoproteins and other proteins, researchers should consider the potential formation of internal fragments and sodium adducts for reliable characterization.     

Hybrid azobenzene-doped nanoporous polymers derived from cubic octavinylsilsesquioxane

A series of novel hybrid porous polymers (HPPs) with high specific surface areas were first prepared by one-step ternary cross-linking copolymerization of octavinylsilsesquioxane (OVS), 1,3,5-tribromobenzene, and 4,4´-dibromoazobenzene via the Heck reaction. The porosities and the CO₂ uptake capacities of resulting azobenzene-doped porous polymers could be tuned by modulating the molar percentage of the azo units. At 273 K and 101 kPa, the sample with the specific surface area of ~700 m² g^–1 (data of Brunauer—Emmett—Teller (BET) surface area analysis) showed the highest CO₂ uptake of 5.45 wt.% (1.20 mmol g^–1) among the fabricated HPPs.

     

Supercritical CO2 antisolvent precipitation of polymer networks of l-PLA,PMMA and PMMA/PCL blends for biomedical applications

A supercritical carbon dioxide (SCCO₂) antisolvent technique was used for the precipitation of several biopolymers into fibers organized in a three-dimensional network. The work was first focused on separately processing either a biodegradable (polycaprolactone or polylactic acid) or a non-biodegradable (polymethylmetacrylate) homopolymer. Second, we established that the antisolvent supercritical technique can be also used to make fibrous networks of blends constitute by non-biodegradable and biodegradable polymers (polymethylmetacrylate/polycaprolactone). The influence of several operating variables (e.g., liquid solution concentration or flow rate and nozzle design) on the polymers morphology and properties was evaluated. For all studied systems, fibers with a rough textured surface and an extremely high surface area in the order of 100–400 m² g^?1 were precipitated. Prepared materials have potential applications in tissue engineering, since they have intrinsic advantages from a biomimetic approach.     

Fabrication of hollow SiO2 and Au (core)–SiO2 (shell) nanostructures of different shapes by CdS template dissolution

Core–shell silica (SiO₂) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO₂@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO₂ matrix (NPSM), hollow SiO₂ nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO₂@CdS with 2 M HNO₃. These SiO₂ nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m² g^?1) of NPSM and HSNS is found to be larger than the surface area (29–51 m² g^?1) of SiO₂@CdS composites indicating hollow SiO₂ morphology. Silica coated Au (SiO₂@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO₂ shell (SiO₂@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.     

Adsorption of β-carotene on modified magnesium silicate

Modified flocculation magnesium silicate is prepared by a hydrothermal process at 120°C for 18 h after adding Al₂(SO₄)₃ into the magnesium silicate gel. Compared with standard magnesium silicate with 328.116 m² g^–1 surface area, this modified magnesium silicate has a bigger BET surface area of 536.803 m² g^–1 and a lower interlayer water content. Modified magnesium silicate exhibits high β-carotene adsorption with a maximum adsorption capacity of 364.96 mg g^–1. It is shown that when suspended in organic solvent, this material can be used effectively for carotenoid separation. Furthermore, our results suggest that modified magnesium silicate may be a promising candidate as an absorbent in the decoloring of oil.     

Synthesis of titanium nitride and carbonitride nanopowders in confined-jet flow plasma reactor

The synthesis of titanium nitride and carbonitride nanopowders from titanium tetrachloride vapor in a stream of hydrogen–nitrogen plasma, generated by an arc torch, in confined-jet flow reactor has been experimentally studied. Single-phase nanopowders with a NaCl-type cubic crystal lattice as assemblies of preferably cube-shaped nanoparticles of a 20–150 nm size and aggregates based on them have been obtained in the experiments. By varying the synthesis parameters, it has been possible to prepare titanium nitride nanopowders with a specific surface area in the range of 11–39 m²/g containing 18.8–22.5 wt % nitrogen, which corresponds to the empirical formula TiN_0.79–TiN_0.99. The titanium carbonitride nanopowders had a specific surface area of 13–23 m²/g and carbon and nitrogen contents of 7.5–13.6 and 13.5–5.1 wt %, respectively.     

New proton-conducting phenyl-substituted polyphenylenes with phosphonate groups in side chain

A new method for the synthesis of polyphenylenes with phenylphosphonate side groups was developed. The method is based on transformations of p-bromophenyl-substituted polyphenylenes via the substitution of the diethyl phosphonate group for bromine in the presence of a palladium catalyst and the hydrolysis of this group giving polymers with free phosphonic acid groups.