Studies in Cyclocopolymerization. X. Cyclocopolymerization of Tetrahydronaphthoquinone and Dimethyl Tetrahydronaphthoquinone with Divinyl Ether

Abstract

Tetrahydronaphthoquinone (THNQ) and dimethyl tetrahydronaphthoquinone (DMTHNQ) were found by UV spectroscopy to form donor-acceptor complexes with divinyl ether (DVE), the latter being the electron donor. Since the participation of such complexed species has been considered in the cyclocopolymerization of a 1,4-diene with a monoolefin such as DVE-maleic anhydride (MA) and DVE-fumaronitrile (FN) systems, radical copolymerization of THNQ and DMTHNQ with DVE was studied. It was found that these copolymers have constant 1:1 composition regardless of the feed composition. The terpolymerization of DVE-THNQ-DMTHNQ confirmed the 1:1 donor-acceptor composition in the polymer. The integration of the NMR spectrum was used in determining the copolymer composition. The spectroscopic data suggest a cyclized repeating unit in which the copolymer main chain consists of only DVE units. There is a marked difference between these copolymers and the typical cyclo-copolymers, such as DVE-MA and DVE-FN, in which the copolymer main chains consist of DVE and the comonomer alternately, with the overall composition being 1:2. These results are interpreted in terms of the steric effect by the bulky acceptor monomers and the electronic interaction between the comonomers. The competition between an acceptor monomer and the charge-transfer (CT) complex toward the cyclized DVE radical in the propagation step appears to favor the CT complex.     

Synthesis and Characterization of Water-Soluble Starch-Acrylamide Graft Copolymers

A series of water-soluble starch-polyacrylamide graft copolymers (ST-g-PAM) were prepared by Ce⁴⁺-initiated graft copolym-erizations of acrylamide (AM) onto starch (ST) dissolved in water at 30°C. The copolymers were found to contain 3-33% (wt) of ST. The structure of the copolymers, including the average number of grafts per chain and the efficiency of the initiator, was determined by acid-catalyzed degradation of the ST followed by size exclusion chromatography (SEC) analysis of the PAM chains and was found to be consistent with the presence or absence of free ST in the polymerization product prior to hydrolysis. The average number of grafts per starch molecule was found to be three or less, depending on conditions. The initiator efficiency (6–43%) was shown to decrease with increasing [Ce⁴⁺] and decreasing [AM], and this was found to be qualitatively in accord with the proposed mechanism of initiation and polymerization. The low efficiency was shown to be due, in part, to the low rate of reaction of Ce⁴⁺ compared to the polymerization rate. The copolymers were characterized by ultra-centrifugation, SEC, and viscometry.     

Heavy Metal Removal from Synthetic Solutions with Magnetic Beads Under Magnetic Field

The aim of this study is to prepare magnetic beads which can be used for the removal of heavy metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate‐vinyl imidazole) [m‐poly(EGDMA‐VIM)] beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ nano‐powder. The specific surface area of the m‐poly(EGDMA‐VIM) beads was found to be 63.1 m²/g with a size range of 150–200 µm in diameter and the swelling ratio was 85%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA‐VIM) beads was 12.4%. The maximum binding capacities of the m‐poly(EGDMA‐VIM) beads were 32.4 mg/g for Cu²⁺, 45.8 mg/g for Zn²⁺, 84.2 mg/g for Cd²⁺and 134.5 mg/g for Pb²⁺. The affinity order on mass basis is Pb²⁺>Cd²⁺>Zn²⁺>Cu²⁺. Equilibrium data agreed well with the Langmuir model. pH significantly affected the binding capacity of the magnetic beads. Binding of heavy metal ions from synthetic wastewater was also studied. The binding capacities were 26.2 mg/g for Cu²⁺, 33.7 mg/g for Zn²⁺, 54.7 mg/g for Cd²⁺ and 108.4 mg/g for Pb²⁺. The magnetic beads could be regenerated up to about 97% by treating with 0.1 M HNO₃. These features make m‐poly(EGDMA‐VIM) beads a potential candidate for support of heavy metal removal under magnetic field.     

The Fundamental Basis for Cyclopolymerization. VII. A Cyclopolymerization Study of Certain Allylcycloalkenes

The cyclopolymerization characteristics of 3-allylcyclopentene, 3 allylcyclopentene, 3-allylcyclohexene, and 4-allylohexene were studied and the extent of their cyclopolymerization by cationic initiation were compared with previously reported solvolysis results involving the same intermediate carbonium ion. The results of this study were also compared with previously reported results on 4-vinylcyclohexene and 1, 4-dimethylenecyclohexane. The allylcycloalkenes were also polymerized by metal alkyl coordination catalysts and the extent of cyclization in each case was determined. The polymers derived from these monomers invariably contained polymeric fractions (27 to 99%) which were soluble in non-polar organic solvents. Calculations based on NMR spectral data indicated the cationic polymers were 68 to 95% cyclized. The extent of cyclization was found to parallel the interolefinic separation in the monomer. Coordination polymerization yielded somewhat lower ratios of cyclizations (54 to 80%) in all cases except for 4-allylcyclohexene. 4-Allylcyclohexene gave only 5 to 54% cyclization, 4-Vinylcyclohexene, 3-allylcyclopentene, and 3-allylcyclohexene produced soluble copolymers with maleic anhydride. Elemental analysis indicated the composition of these copolymers to be 2:1 molar in maleic anhydride and diene units. A cyclic copolymerization mechanism suggested the formation of a multicyclic repeating unit. The other monomers gave crosslinked polymers since maleic anhydride could not be incorporated into a six-membered ring.     

Electronic structure and related properties for quasi-binary (GaP)1−x (ZnSe) x crystals

The results of pseudopotential calculations of the band structure and related electronic and optical properties of quasi-binary (GaP)_1?x (ZnSe) _x crystals in the zinc blende structure are presented. Trends in bonding and ionicity are discussed in terms of electronic charge densities. Moreover, the composition dependence of the refractive index and dielectric constants are reported. The computed values are in reasonable agreement with experimental data. The results suggest that for a proper choice of the composition x, (GaP)_1?x (ZnSe) _x could provide more diverse opportunities to achieve the desired electronic and optical properties of the crystals which would improve the performances of devices fabricated on them.     

Palladium on Carbon-Catalyzed Cross-Coupling of Aryl Halides with Potassium p-Tolyltrifluoroborate in Air

Palladium supported on carbon (Pd/C) has been shown to be an effective catalyst for the cross-coupling of potassium p-tolyltrifluoroborate with a variety of aryl bromides and iodides. Yields ranging from moderate to good were obtained using Pd/C in ethanol/water mixtures with potassium carbonate as base at 50 °C under an air atmosphere.     

Diverted total synthesis of falcitidin acyl tetrapeptides as new antimalarial leads

We report not only the convergent total synthesis of falcitidin, a natural inhibitor of falcipain-2 from myxobacterium Chitinophaga, but also its diversification into a new antimalarial class of N-acyl tetrapeptides (Acyl-His-Ile-Val-Pro-NH₂). Despite the lack of whole-cell activity of falcitidin itself, our study led to the identification of a trifluoromethyl (CF₃) analogue displaying sub-micromolar IC₅₀ activity against Plasmodium falciparum 3D7 in a standard blood-cell assay, but only when N-tritylated on its histidine (imidazole) residue.     

Novel microwave plasma‐assisted CVD reactor for diamond delta doping

We report on building a novel chemical vapor deposition (CVD) reactor for diamond delta‐doping. The main features of our reactor are: a) the use of rapid gas switching system, (b) the reactor design providing the laminar gas flow. These features provide the creation of ultra‐sharp interfaces between doped and undoped material and minimize the prolonged ”tails” formation in the doping profile. It is proved by optical emission spectroscopy that gas switching time is not more than 10 seconds. Using the novel reactor we have grown the nanometer‐thin layers of boron doped diamond. The FWHM of boron concentration profile is about 2 nm which is proved by SIMS. It is shown that the both single delta‐layer and multiple delta‐layers could be grown using the novel CVD reactor. In principle, the reactor could be used for diamond delta doping with other dopants, like nitrogen, phosphorus etc. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Parallel single-cell optical transit dielectrophoresis cytometer

In this work, we present an optical transit DEP flow cytometer for parallel single-cell analysis. Each cell's dielectric property is inferred from velocity perturbations due to DEP actuation in a microfluidic channel. Dual LED sources facilitate velocity measurement by producing two transit shadows for each cell passing through the channel. These shadows are detected using a 256-pixel linear optical array detector. Massively parallel analysis is possible as each pixel of the detector can independently analyze the passing cells. A wide channel (∼18 mm) was employed to carry many particles simultaneously, and the system was capable of detecting the velocity of over 200 cells simultaneously. We have achieved analysis rates for 10 µm diameter polystyrene spheres response exceeding 250 per second. With appropriate calibration, this DEP cytometer can quantitatively measure the dielectric response. The dielectric response (Clausius–Mossotti factor) of viable CHO cells was measured over the frequency range of 100 kHz to 6 MHz, and the obtained response matches the previously measured values by our group. The DEP cytometer uses simple modular components to achieve high throughput label-free single-cell dielectric analysis and can begin analyzing particles within 10 s after starting to pump the sample into the channel.     

Matching extension in the powers of n-connected graphs

Let G be a graph on p vertices. Then for a positive integer n₁ G is said to be n-extendible if (i) n < p/2, (ii) G has a set of n independent edges, and (iii) every such set is contained in a perfect matching of G. In this paper we will show that if p is even and G is n-connected, then G^k is -extendible for every integer k ≥ 2 such that . © 1996 John Wiley & Sons, Inc.