Synthesis and properties of an ionic polyacetylene with norbornene moieties

New conjugated ionic polymer with the pendent norborene moieties was prepared by the activated polymerization of 2-ethynylpyridine by using 5-[(5-bromopenthoxy)methyl]-2-norborene without any additional initiator or catalyst. This polymerization proceeded well in the mild reaction condition to give a high yield of polymer (polymer yield: 90%). The chemical structure of poly{2-ethynyl-N-[(5-norborenylmethoxy)pentyl]pyridinium bromide} (PENPPB) was characterized by such instrumental methods as NMR (¹H and ¹³C), IR, UV–vis spectroscopies, and elemental analysis to have the conjugated polymer backbone bearing norbornyl moieties. The photoluminescence maximum peak of polymer was located at 519 nm, which corresponds to the photon energy of 2.39 eV. The norbornyl substituents within the polyacetylene-based polymers shifted PL maximum values because substituent size affects the molecule arrangement. The cyclovoltammograms of polymer exhibited the electrochemically stable window at ?1.6 to 2.3 V region. It was found that the kinetics of the redox process of polymer might be mainly controlled by the electron transfer process based on the experiment of the oxidation current density of polymer versus the scan rate.     

Facile synthesis of activated carbon/carbon nanotubes compound for supercapacitor application

A large number of carbon nanotubes (CNTs) have been produced commingled in activated mesocarbon microbeads (AMCMBs) activated by potassium hydroxide in a stainless steel container at 900 °C, in which an especial buried-protection method with petroleum coke powders was used to protecting the product during activation. The CNTs were found to be about 50 nm in diameter and characteristic length more than 10 μm. In addition, the AMCMBs/CNTs compound when used for electrode material of electrochemical double-layer capacitors exhibited a specific capacitance of 243 F g^?1 in 6 M KOH aqueous solution.     

A novel,conjugated polymer containing fluorene,pyridine and unsymmetric carbazole moieties: Synthesis,protonation and electrochemical properties

An optically active, conjugated polymer bearing unsymmetric pendant carbazole chromophores was prepared via the Suzuki coupling of 9,9-dioctylfluorene-2,7-diboronic acid and a novel pyridine-containing compound. The polymer had a T_g of 192 °C and T_d10 at 437 °C under a nitrogen atmosphere and exhibited absorption bands at 320–400 nm and displayed an additional absorption bands at 380–480 nm after protonation with aq. HCl solution. The photoluminescence of the polymer shifted from 360–460 nm to 460–560 nm after protonation and the photoluminescence quantum yield of the polymer in THF solution was 0.88. The emission color of the polymer film changed from blue (439 nm) to yellow (551 nm) under an applied bias voltage of 2.5 V.     

A continuous-flow electrophile scavenger prepared by a simple grafting procedure

A versatile method for grafting reactive polymer onto macroporous polymer monoliths has been developed, and this method used to prepare a monolith containing primary amines. Reactive polymer was grafted onto residual olefins within the crosslinked monoliths using free-radical polymerization, and without requiring any pre-grafting activation. Capacities of the grafted monoliths were easily controlled by altering the composition of the grafting solution. Grafting N-vinylacetamide, followed by amide cleavage using hydrazine, afforded a monolith containing primary amine groups that was used for efficient continuous-flow scavenging of isocyanates, with 92% of phenyl isocyanate removed from solution in a reaction with a residence time of 49 min. High levels of scavenging required only a small excess of polymeric amine.     

Conjugated polymers based on benzodithiophene and arylene imides: Extended absorptions and tunable electrochemical properties

Three novel conjugated polymers have been designed and synthesized via the alternative copolymerization of the electron-donating monomer benzodithiophene (BDT) and three different electron-accepting monomers: perylene diimide (PDI), naphthalene diimide (NDI), and phthalimide (PhI). All obtained copolymers show good solubility in common organic solvents as well as broader absorptions in visible region and narrower optical band gaps compared to homopolymers from BDT units. It is found that the absorptions of the copolymers are red-shifted with increasing the electron-withdrawing ability of the co-monomer. In particular, the absorption edge of P(BDT-NDI) film extends to 760 nm, whereas that of P(BDT-PhI) film is only at 577 nm. Cyclic voltammograms of the three polymers disclose that P(BDT-PDI) and P(BDT-NDI) are typical n-type materials because PDI and NDI are strong electron-accepting groups, while P(BDT-PhI) is a stable p-type material where the weak electron-withdrawing monomer (PhI) is introduced. The results suggest that the absorption range and the electrochemical properties of the conjugated polymers can be tuned by appropriate molecule-tailoring, which will help exploring ideal conducting polymers for potential applications in polymer optoelectronics, especially in polymer solar cells.     

Counting the number of active centers in MgCl2-supported Ziegler–Natta catalysts by quenching with 2-thiophenecarbonyl chloride and study on the initial kinetics of propylene polymerization

Using 2-thiophenecarbonyl chloride (TPCC) as a quenching agent, the number of active centers in propylene polymerization with MgCl₂-supported Ziegler–Natta catalysts were determined by measuring the sulfur content of the quenched polymer. Under suitable conditions, the thiophenecarbonyl-labeled polymer chains were stable in the reaction system when TPCC/Al > 1. The number of active centers was found to increase in the first 5 minutes of propylene polymerization, accompanied by rapid decrease of the propagation rate constant k_p. Diffusion barrier from the polymer covering the catalyst fragments is thought as the main reason of the rapid decay of k_p in the initial stage.     

Electro-optical and electrochemical properties of an ionic polyacetylene derivative with azobenzene anisole moieties

An ionic polyacetylene derivative with azoanisole moieties was prepared by the activated polymerization of 2-ethynylpyridine by using 4-[4-(9-bromononyloxy)phenylazo]anisole without any additional initiator or catalyst in high yield. The chemical structure of poly[2-ethynyl-N-(p-methoxyphenylazophenyl)oxynonylpyridinium bromide] (PEMPB) was characterized by instrumental methods such as NMR (¹H and ¹³C), IR, UV–vis spectroscopies to have a conjugated polymer backbone system with the designed azobenzene moieties as substituents. This polymer was completely soluble in organic solvents and well processible. The electrochemical and electro-optical properties of PEMPB were studied. The cyclovoltammograms of this polymer exhibited the irreversible electrochemical behaviors between the oxidation and reduction peaks. The oxidation current density of PEMPB versus the scan rate is approximately linear relationship in the range of 30 mV/s–120 mV/s. The exponent of scan rate, x value of PEMPB, is found to be 0.6. The absorption spectrum starts around 700 nm and shows a characteristic absorption band at visible region of 464 nm due to the π → π* interband transition of the polymer backbone, which is a peak of the conjugated polyene backbone. The photoluminescence spectrum showed that the PL peak is located at 539 nm corresponding to the photon energy of 2.30 eV.     

Influence of nanoparticle diameter on conjugated enzyme activity

Lactase conjugated to nanomaterials represents an area of significant potential to the food processing as a means to produce novel value-added products, reduce waste, and enable diagnostics. While it is recognized that, in general, matter exhibits unique properties when manipulated at the nanoscale, little is known about how reducing the size of the carrier to the nanoscale effects attached lactase. The purpose of this work is to investigate the influence of particle size on activity retention of lactase (Aspergillus oryzae) covalently conjugated to magnetic nanoparticles of varying sizes. Lactase was attached to carboxylic acid functionalized magnetic nanoparticles 18 nm, 50 nm, and 200 nm in diameter using carbodiimide chemistry. After attachment, activity retention was 73%, 39%, and 14% compared to the free enzyme for the 18 nm, 50 nm, and 200 nm conjugates, respectively. The apparent K_m was not significantly different as a function of particle size while the apparent k_cat decreased with increasing particle size. Reducing the particle size of magnetic nanoparticles can increase the activity retention of conjugated lactase. This work provides improved understanding of enzyme-nanoparticles systems and allows for enhanced design of lactase-conjugated materials.     

Synthesis and properties of ionic conjugated polymer with spiroxazine moiety

A noble conjugated ionic polymer with photochromic spiroxazine moiety, poly[2-ethynyl-N-hexyloxyspiroxazine pyridinium bromide] (PEHSPB) 6 was prepared by the activated polymerization of 2-ethynylpyridine 5 with 1,3,3-trimethyl-6′-bromohexyloxyspiro[2H]-indol-2,3′-[3H]-naphth[2,1-b][1,4]oxazine 4 without any additional initiator or catalyst. The polymerization reaction was performed in DMF solvent at the temperature of 120 °C. As the polymerization proceeded, the reaction solution became more viscous and black in colour. The polymer yield and inherent viscosity were 75% and 0.15 dL/g, respectively. The instrumental analysis data on the chemical structure of PEHSPB 6 indicated that the present PEHSPB 6 have a conjugated polymer backbone system with the spiroxazine-hexyl substituents. X-ray diffraction analyses of the polymers indicated that the present polymers are mostly amorphous. The photoluminescence peak is located at 515 nm corresponding to the photon energy of 2.41 eV. Upon UV irradiation, closed spiroxazine form is transformed into the open merocyanine form that reverts back to the colourless spiro form in dark.     

Fabrication of copper coated polymer foam and their application for hexavalent chromium removal

The polymer foam coated with zero-valent copper (Cu⁰) was designed and prepared for the removal of hexavalent chromium (Cr(VI)) in water. Firstly, porous poly(tert-butyl acrylate) was fabricated by concentrated emulsion polymerization and then acrylic acid groups were generated on the surface of foam by hydrolysis reaction. Secondly, with the help of the large amount reactive carboxylic acid groups, polyethyleneimine (PEI) were chemically grafted onto the surface by the reaction between amine group and acrylic acid group. Finally, zero-valent copper was reduced by sodium borohydride (NaBH₄) and coated on the surface of polymer foam. Thus the copper functionalized porous adsorbent (Cu⁰–PEI–PAA) was constructed, and then applied for removing Cr(VI) from aqueous solution. The removal mechanism of Cr(VI) involved redox reaction by zero-valent copper and adsorption by amine groups, simultaneously. As a result, 99.5% of Cr(VI) could be removed within 2 h, and the maximum removal capacity for Cr(VI) of Cu⁰–PEI(1800)–PAA was 9.16 mg/g. Furthermore, the effect of initial concentration of Cr(VI), pH value, and temperature on the Cr(VI) removal was investigated. Therefore, the as-prepared zero-valent copper-loaded polymer foam could be an efficient and promising remediation material to remove Cr(VI) from wastewater.     

Amorphization of pharmaceutical compound by co-precipitation using supercritical anti-solvent (SAS) process (Part I)

The aim of this work is to investigate the feasibility of using supercritical anti-solvent (SAS) co-precipitation process to influence the crystallinity or amorphous character of a crystalline non-steroidal anti-inflammatory drug (NSAID), indomethacin (IDMC) for solubility enhancement. Co-precipitations of IDMC and the water-soluble polymer excipient poly(vinylpyrrolidone) (PVP) have been prepared by SAS. The SAS co-precipitates with drug to polymer ratios of 85:15, 50:50 and 20:80 were generated using supercritical carbon dioxide as anti-solvent. The untreated and SAS powders (before and after storage) were characterised using scanning electron microscopy (SEM, morphology), powder X-ray diffractometry (PXRD, crystallinity), USP dissolution tester and thermogravimetric analysis. In addition, stability stress tests on SAS co-precipitates on open pans were carried out at 75% RH and room temperature or 40 °C in order to evaluate their physical stability. SAS co-precipitates with PVP contents more than 50 wt.% were X-ray amorphous and remained stable after 7 months storage at 75% RH and room temperature or 40 °C. It was demonstrated that the drug to polymer ratio influenced amorphous content of the SAS co-precipitates. By using different polymer ratios, the morphologies of a drug–polymer composite can be varied. TGA analyses revealed that the composition of SAS co-precipitates were consistent with the experimentally designed composition. Amorphous form of IDMC produced by SAS has improved dissolution properties as compared to the crystalline form. This form is also stable under stress test conditions compared as with spray-dried amorphous indomethacin. It is suggested that PVP excipient could be a suitable “amorphous inducing and stabilizing” agent for SAS process.     

Porosity control of porous silicon carbide ceramics

Porous SiC ceramics were fabricated by the carbothermal reduction of polysiloxane-derived SiOC containing polymer microbeads followed by sintering. The effect of the SiC powder:polysiloxane-derived SiC (SiC:PDSiC) ratio on the porosity and flexural strength of the porous SiC ceramics were investigated. The porosity generally increased with decreasing SiC:PDSiC ratio when sintered at the same temperature. It was possible to control the porosity of porous SiC ceramics within a range of 32–64% by adjusting the sintering temperature and SiC:PDSiC ratio while keeping the sacrificial template content to 50 vol%.The flexural strengths generally decreased with increasing porosity at the same SiC:PDSiC ratio. However, a SiC:PDSiC ratio of 9:1 and a sintering temperature of 1750 °C resulted in excellent strength of 57 MPa at 50% porosity. Judicious selection of the sintering temperature and SiC:PDSiC ratio is an efficient way of controlling the porosity and strength of porous SiC ceramics.     

Highly efficient and scale-up synthesis of propargylamines catalyzed by graphene oxide-supported CuCl2 catalyst under microwave condition

An efficient, green and practical approach was developed to synthesize propargylamines using recyclable GO-CuCl₂ via a one-pot multicomponent aldehyde–alkyne–amine (A³) coupling reaction. The propargylamines are readily obtained in good to excellent yields (85–96%) and on multi-gram scale (88%, 150 mmol) under microwave irradiation. GO-CuCl₂ could be easily recovered through filtration and reused at least five recycles with no significant decreases in the yields.     

Preparation of pressure-sensitive adhesives from tung oil via Diels-Alder reaction

In this study, tung oil was polymerized with a dimaleimide (4,4’-methylene-bis(N-phenylmaleimide) (MPMI) and two diacrylates (poly(propylene glycol) diacrylate (PPGDA) and bisphenol A glycerolate diacrylate (BPAGDA) via Diels-Alder reaction (DA reaction) to prepare pressure-sensitive adhesives (PSAs). On the one hand, the polymer of tung oil and MPMI was readily prepared however it was too rigid to serve as a PSA. On the other hand, the polymerization of tung oil with PPGDA or BPAGDA resulted in PSAs with peel strengths ranging from 0.1 to 0.2 N cm⁻¹ and loop tacks ranging from 0.4 to 0.5 N. Nevertheless, tung oil reacted readily with acrylic acid to form adducts (TOAA) with lower content of conjugated diene groups than those of tung oil. The use of TOAAs instead of tung oil to polymerize PPGDA failed to increase the peel strength of the resulting PSAs. However, polymerizations of TOAAs with BPAGDA resulted in PSAs with much higher peel strengths and much higher loop tacks than the polymerization of tung oil with BPAGDA. In addition, the introduction of a small amount of MPMI in the polymerization of TOAA and PPGDA significantly shortened the curing time.     

π-conjugated polymers containing pendant Mn12 cluster: Synthesis and physical properties

In this paper two conjugated polymers containing polyfluorene chain with pendant carboxyl group (P1 and P2) are synthesized via Suzuki reaction, and then two corresponding polymers containing the pendant Mn₁₂ cluster core (Mn₁₂-P1 and Mn₁₂-P2) are obtained through exchange of the pendant carboxyl group in the polymers with acetate ligand of Mn₁₂-Ac. All the polymers show similar UV–vis absorption spectra with maximum peak at 388 nm and fluorescence emission spectra with maximum peak at 419 nm and a shoulder at 443 nm that can be attributed to the polyfluorene chain. The cyclic voltammetry measurement indicates that Mn₁₂-P1 or Mn₁₂-P2 exhibit similar electrochemical behavior to that of the corresponding P1 or P2. These indicate that the introduction of Mn₁₂ cluster at the side-chain of the conjugated polymers has little influence on the photophysical and electrochemical properties of the conjugated main-chain. However, compared with pristine Mn₁₂-Ac the magnetic properties of the modified Mn₁₂ cluster has been changed after substitution of acetate group by the pendant carboxyl group of the polymer. Both of the Mn₁₂ clusters modified by the conjugated polymer (Mn₁₂-P1 and Mn₁₂-P2) show paramagnetism in the range of 2–300 K, and no SMM magnetic behavior is observed at low temperature.     

New phenomenon in competitive hydrogenation of binary mixtures of activated ketones over unmodified and cinchonidine-modified Pt/alumina catalyst

Competitive hydrogenations of eight binary mixtures of ethyl pyruvate (EP), methyl benzoylformate (MBF), ketopantolactone (KPL), pyruvic aldehyde dimethyl acetal (PA) and trifluoroacetophenone (TFAP) on platinum/alumina catalysts unmodified (racemic hydrogenation) and modified by cinchonidine (chiral hydrogenation) were studied under the experimental conditions of the Orito reaction. Reaction rates of chiral and racemic hydrogenations were determined and relative adsorption coefficients were calculated. In the competitive chiral hydrogenation of EP + MBF, EP + TFAP and KPL + MBF binary mixtures a new phenomenon was observed: namely the EP and KPL are hydrogenated faster than MBF and TFAP, whereas in racemic one the MBF and TFAP are hydrogenated faster than EP or KPL. Effects of the activated ketones structure on their reactivity and the stability of the surface complexes are discussed. It was found that differences in rate enhancement are caused by the differences both in the adsorptivity and in the reactivity of adsorbed substrates and adsorbed intermediate complexes.     

Preparation of poly(glycidyl methacrylate) grafted sulfonamide based polystyrene resin with tertiary amine for the removal of dye from water

Poly(glycidyl methacrylate) was grafted onto crosslinked poly(styrene) beads through the 2-chloroethyl sulphonamide (CSA) groups present in the resin using ATRP polymerization method. A beaded polymer with a poly(glycidyl methacrylate) surface shell was prepared in three steps, starting from poly(styrene-DVB) (10% crosslinking) based beads with a particle size of 420–590 μm, according to the synthetic protocol; chlorosulfonation, sulfamidation with 2-chloroethylamine hydrochloride and grafting reaction of poly(glycidyl methacrylate).The polymeric resin was prepared with 147.8% of grafted glycidyl methacrylate and subsequent modified with diethyl amine to introduce tertiary amine groups. This resin has also been demonstrated to be an efficient dye sorbent, able to remove dye from water even at ppm levels. The dye sorption capacity under non-buffered conditions is around 0.90 g dye/g resin.     

Oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran with molecular oxygen in the presence of N-hydroxyphthalimide

Catalytic system Cu(NO₃)₂/NHPI can be successfully used for the mild oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran with molecular oxygen. The oxidation reaction takes place at 50 °C and 1 atm O₂ and selectively converts the primary hydroxymethyl group of HMF to the aldehyde one. The selective formation of aromatic aldehyde is observed because of the higher rate of hydrogen abstraction from primary alcohols by the phthalimide-N-oxyl radical, as compared to the rate of the hydrogen abstraction from the aldehydes.     

Synthesis and structure study of copolymers from thiadiazole fused indolocarbazole and dithienosilole

We report synthesis and characterization of two D-A polymers (PSDT-C12 and PSDT-EH) with different side chains. Both polymers are based on alternate 12,13-dioctyl-indolo[2,3-a][1,2,5]thiadiazolo[3,4-c]carbazole (TDZIC) and dithienosilole derivative units in polymer main chain. We used TDZIC to enlarge the 2D conjugated plane of acceptor monomers by fusing benzothiadiazole (BT) unit with an indole unit having alkyl groups. PSDT-C12 exhibited 10 nm redshift compared to PSDT-EH in solid films, while their absorption spectra were almost identical in solutions. Since the backbone and side chains on the indolocarbazole group are the same, the redshift on PSDT-C12 could be resulted from the dodecyl (C12) side chain on the dithienosilole unit and different molecular weight between these two polymers. PSDT-C12 has a larger molecular weight than PSDT-EH. Therefore possibly both side chains and molecular weight contributed to the difference in the absorption spectra in solid films. The straight C-12 side chain has less steric hindrance than the branched EH side chain in solid films. PSDT-C12 has a longer main chain (larger molecule weight) than PSDT-EH, which can favour a more extended main chain interaction. The vibronic peak at 519 nm and shoulder at 563 nm in the PSDT-C12 film further confirmed stronger main chain interaction. Geometry optimization showed that head–tail (HT)-PSDT had a more twisting conjugated backbone with larger dihedral angle between dithienosilole unit and thiadiazole-fused ring compared to head–head/tail–tail (HH/TT)-PSDT.     

Preparation of nano-size ZrB2 powder by self-propagating high-temperature synthesis

Preparation of nano-size ZrB₂ powder by SHS has been investigated. Zr and B elemental powders were mixed with 10–50 wt.% NaCl, and prepared pellets were reacted under argon. Adiabatic temperatures were calculated by HSC software. Increasing NaCl content led to a continuous decrease in adiabatic temperatures and reaction wave velocity. Products were subjected to XRD, SEM and FESEM analyses. Average crystallite size of ZrB₂, which was 303 nm without NaCl, decreased to 32 nm with 40% NaCl addition. Distinct decrease in ZrB₂ particle size was also observed from SEM analyses. 30% NaCl addition was found to be optimum for ensuring a stable SHS reaction and providing the formation of nano-size ZrB₂ particles. It was revealed from particle size distribution measurements that ZrB₂ powder obtained by 30 wt.% NaCl addition contained particles mostly finer than 200 nm. A mechanism, similar to solution-precipitation was proposed for the particle size refining effect of NaCl.