Neodymium oxide-assisted melt free-radical grafting of maleic anhydride on isotactic-polypropylene by reactive extrusion

Rare earth oxide, neodymium oxide (Nd2O3), -assisted melt free-radical grafting of maleic anhydride (MAH) on isotactic-polypropylene (i-PP) was carried out by reactive extrusion. The experimental results reveal that the addition of Nd2O3 into reactive system leads to an enhancement of the grafting degree of MAH, along with an elevated degradation of i-PP matrix. When Nd2O3 content is 4.5 mmol %, the increment of the grafting degree of MAH (maximally) is up to about 30% compared with that of the related system without adding Nd2O3, while the severest degradation of i-PP matrix simultaneously occurs. On the basis of the reaction mechanism of PP-g-MAH proposed before, the sequence of beta-scission and grafting reaction is discussed in detail. It is found that, for the reactive system studied, most tertiary macroradicals first undergo beta-scission, and then, grafting reaction with MAH takes place at the new radical chain ends. The imported Nd2O3 has no effect on the aforementioned reaction mechanism, whereas it enhances the initiating efficiency of the initiator, dicumyl peroxide (DCP).

Synthesis of eight-arm polystyrene by atom transfer radical polymerization

A new initiator for atom transfer radical polymerization (ATRP), (Cl2HCCOOCH2)(4)C(TDCAP) was designed and successfully synthesized. The initiator was,used to initiate,the polymerization of styrene via ATRP to method yield an eight-arm polystyrene with functional end-group chlorides. The different polymers could be prepared via ATRP of different monomers at 130 degrees C using TDCAP/CuCl/bPy as the initiating system. The initiator and eight-armed polymer were characterized by means of H-1 NMR, FTIR and GPC.

Reverse atom transfer radical polymerization of (-)-menthyl methacrylate

The reverse atom transfer radical polymerization(RATRP) of (-)-menthyl methacrylate ((-)-MnMA) with AIBN(AIBN/CuCl2/bipyridine(bipy) or (-)sparteine((-)Sp) =1/2/4) initiating system in THF has been studied. The dependence of the specific rotation on molecular weight was investigated.

Surface plasmon resonance studies on the electrochemical doping/dedoping processes of anions on polyaniline-modified electrode

The combination of in situ surface plasmon resonance (SPR) with electrochemistry was used to investigate the electrochemical doping/dedoping processes of anions on a polyaniline (PAn)-modified electrode. Electrochemical SPR characteristics of the PAn film before and after doping/dedoping were revealed. The redox transformation between the insulating leucoemeraldine, and the conductive emeraldine, corresponding to the doping/dedoping of anion, can lead to very distinct changes in both the resonance minimum angle and the shape of SPR curve. This is ascribed to the swelling/shrinking effect, and the change of the PAn film in the imaginary part of the dielectric constant resulted from the transition of the film conductivity. In situ recording the time evolution of reflectance change at a fixed angle permits the continuous monitoring of the kinetic processes of doping/dedoping anions. The size and the charge of anions, the film thickness, as well as the concentration of anions are shown to strongly influence the rate of ingress/egress of anions. The time differential of SPR kinetic curves can be well applied in the detecting electroinactive anion by flow injection analysis. The approach has higher sensitivity and reproducibility compared with other kinetic measurements, such as those obtained by amperometry.

Interactions of thiamine monophosphate (TMP) with one- and two-dimensional polymeric halogenomercurate anions. Crystal structures of (TMP)(Hg2Br5)center dot 0.5H(2)O and (TMP)(2)(Hg3I8)

An investigation into the interactions between thiamine monophosphate (TMP) and anions has resulted in the preparation and X-ray characterization of the compounds (TMP)(Hg2Br5).0.5H(2)O (1) and (TMP)(2)(Hg3I8) (2). In each compound the TMP molecule exists as a monovalent cation in the usual F conformation. The halogenomercurate anions occur in two-dimensional (2-D) network in 1 or one-dimensional (1-D) chain in 2. In both 1 and 2, the structures consist of alternating cationic sheets of the hydrogen-bonded TMP molecules and anionic sheets of the polymeric halogenomercurate anions. The TMP molecule binds to the polymeric anions through the characteristic 'anion bridge I', C(2)-H..X...pyrimidinium (X = Br in 1 and 1 in 2), and electrostatic interactions between electropositive S(1) and halogen atoms. The 'anion bridge II' of the type N(4'1)-H...X...thiazolium (X = phosphate group) plays a role in stabilizing the molecular conformation. The biological implication of the host-guest-like complexation between TMP and polymeric anions is discussed.

Sol-gel-derived ceramic carbon composite electrode containing isopolymolybdic anions

A new class of polyoxomelalate (POM)-modified electrodes is fabricated by the sol-gel technique and demonstrated for nitrite sensing. The electrode material comprises an interconnected dispersion of graphite powder and a uniform dispersion of isopolymolybdic anions (Mo8O26) in a porous methylsilicate matrix. The chemically modified electrodes showed well-defined cyclic voltammograms with three reversible redox couples in acidic aqueous solutions because of the good physicochemical compatibility of Mo8O26 and the carbon ceramic matrix. The Mo8O26-modified electrodes show good stability and reproducibility, especially the renewal repeatability by simple polishing in the event of surface fouling. (C) 2000 Elsevier Science Ltd. All rights reserved.

Synthesis and free-radical ring opening polymerization of macrocyclic aryl thioether ether ketone (sulfone) oligomers

Two kinds of novel macrocyclic aryl thioether ether oligomers were synthesized by nucleophilic condensation reaction in high yields under pseudo-high-dilution condition. A combination of H-1 NMR, GPC and MALDI-TOF MS analyses unambiguously confirmed the cyclic nature and their distributions, Macrocyclic thioether ether ketone oligomers can undergo facile melt ring opening polymerization(ROP) initiated by thiyl radical to give a high molecular weight polymer.

Electrochemical behavior of heteropoly acid anions adsorbed in electrodes modified with mesoporous molecular sieve silica

Heteropoly acid H4SiW12O48 (denoted as SiW12) was assembled with the mesoporous materials MCM-41 modified with 3-aminopropyltriethoxysilane (APTES) (denote MCM-41((m))). The electrochemical behavior of SiW12/MCM-41((m)) complexes-based electrode indicated SiW12 anion was adsorbed by MCM-41((m)). In MCM-41((m)) electrode, large voltammetric waves, showing that the electrostatic bound ions adsorbed in MCM-41((m)) were electrochemically active. The potential application as amperometric sensors for nitrite is anticipated.

Novel macrocyclic aryl thioether ester oligomers: structure characterization and free-radical ring opening polymerization

Novel macrocyclic aryl thioether ester oligomers have been synthesized in high yield from phthaloyl dichloride and 4,4'-thiodiphenol under pseudo high dilution conditions. The cyclic nature was unambiguously confirmed by a combination of MALDI-TOF MS, gel permeation chromatography and NMR analyses. Single-crystal X-ray diffraction of cyclic ester dimer reveals no severe strain on the cyclic structure. The free-radical ring opening polymerization (ROP) of the macrocyclic oligomers was achieved to give high molecular weight polymers via a transthioetherification reaction. The molecular weight of the polymer resulting from ROP decreases as the conversion of cyclic oligomers increases after a polymerization period of 30 min.

A mechanistic study of electrochemical oxidation processes of (OEP)Mg(II) in the presence of anions

In the presence of F-, OH-, Cl-, electrochemical redox of (OEP)Mg(II) [2,3, 7,8,12,13,17,18 octaethyl-21H, 23H-porphine magnesium (II)] are investigated in DCE/0.1 mol/L solution by cyclic voltammetry and spectroelectrochemistry, In the presence of anions, anions are axially coordinated to (OEP)Mg(II) generate (OEP)Mg(II)Y, the E-1/2 of (OEP)MS(II)Y oxidation are negatively shifted. A chemical reaction following the second oxidation step is observed, the E-1/2 of the reaction product is obtained. Mechanism of (OEP)Mg(II) in the halogen and OH- anions titration process has been proposed.

Interactions of thiamine with anions: (Hthiamine)(thiamine) heptaiododimercurate dihydrate and its dimethanol monohydrate

In the title compounds, 3-[(4-amino-2-methyl-5-pyrimidinio)methyl] -5-(2-hydroxyethyl)-4-methylthiazolium(2+) 3-[(4-amino-2-mcthyl-5-pyrimidinyl)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium( 1+) heptaiododimercurate dihydrate, (C12H18N4OS)(C12H17N4OS)[Hg2I7]. 2H(2)O, (I), and its dimethanol monohydrate, (C12H18N4OS)(C12H17N4OS)[Hg2I7]. 2CH(3)OH . H2O (2), a crystallographic centre of symmetry in (1) or a twofold axis in (2) is imposed between the protonated and deprotonated thiamine molecules, resulting in a statistically half-occupied proton attached at N1' of the pyrimidine ring. The Hg2I73- anion, residing on the centre of symmetry in (1) or on the twofold axis in (2), interacts with two thiamine molecules, each through a C2-H ... I ... pyrimidine-ring interaction. This bridging interaction is a characteristic of thiamine in the F conformation.

Electrocatalytic reduction of nitrite using Dawson-type tungstodiphosphate anions in aqueous solutions, adsorbed on a glassy carbon electrode and doped in polypyrrole film

The electrochemical behavior of Dawson-type P2W18O626- adsorbed on a glassy carbon electrode and doped in a polypyrrole film electrode was described. These modified electrodes all display catalytic activity for nitrite reduction, either in acid solutions or in pH > 4.0 solutions.

An ESR study on (OH)-O-center dot-radical scavenging activity of water-soluble fullerenols

Water-soluble polyhydroxylated fullerene derivatives (fullerenol) were synthesized, and their scavenging ability for (OH)-O-.-radical was studied by the combination of ESR spectroscopy and spin-trapping technique with phenyl-t-butyl-nitrone. It was found that fullerenols showed an excellent efficiency in eliminating (OH)-O-. free radicals generated by UV photolysis of H2O2. At an applied fullerenol concentration of 0, 3 mg/mL in the final solution, a radical scavenging efficiency of approximate 95% was achieved, revealing the potential use of these compounds as novel potent free radical scavengers in biological systems.

Reactions of C-60 with R(3)SnH: A new synthetic route to C-60(RH)(n) and the property of C-60 to catalyze radical reactions

A new method for the preparation of polyalkyl and polyarenefullerene derivatives C-60(RH)(n)(R=Bu,n=1-3; R=Ph,n=1-10) by the reaction of C-60 with organotin hydride in toluene is described. Another series of products of stannanes R(a)Sn(b)H(c) (R=Bu, a=3-8, b=1-4, c=0-3 R=Ph, a=3-11, b=1-5, c=0-4) were also obtained, which shows that C-60 can catalyze polymerization of organic-tin. These products were determined by mass and infrared spectrometry. And the possible reaction mechanisms are discussed.