Ruthenium‐catalyzed fast living radical polymerization of methyl methacrylate: The R?Cl/Ru(Ind)Cl(PPh3)2/n‐Bu2NH initiating system

A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)₂? Cl/Ru(Ind)Cl(PPh₃)₂ initiating system in the presence of n‐Bu₂NH as an additive [where (MMA)₂? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (M_n's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (M_n ～ 10⁵) and narrow MWD (M_w/M_n ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu₃N, whereas n‐BuNH₂ resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148     

Sonochemically enhanced adsorption and degradation of methyl orange with activated aluminas

Removal of Methyl orange (MO), as a model contaminants, in aqueous solution by the simultaneous application of ultrasound with the addition of porous adsorbent powders is reported. Activated alumina powders in acidic form were used as an adsorbent. Results showed that MO could be degraded by ultrasonic irradiation at 130 kHz with the first order rate constant of 8x10(-4) and 5x10(-4) sec(-1), in acidic and basic conditions, respectively, without adsorbents. Adsorption rates of MO by activated alumina mainly depended on the acidity of alumina, the pH of solution and the stirring speed. At pH=4.2 with mechanical stirring without ultrasonic radiation, acidic activated alumina (0.1 g/100 ml) removed MO at about two times more rapidly than ultrasonic irradiation. In the case of simultaneous application of ultrasound irradiation and activated alumina, MO was almost removed from the solution within 10 min, which corresponded to as a rate constant of 5x10(-3) sec(-1). This kind of synergistic enhancement of removal rate with ultrasound and adsorbents should be practically useful for the elimination of contaminants in the water treatment processes. In addition, the effects of pH and coexisting chemicals in the solution were examined for the processes. Although the adsorption process was effective in some selected conditions, ultrasonic degradation was more robust in wider range of pH and coexisting chemicals. Simultaneous application of the two processes can perform complementary.     

Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.     

Professor Fosong Wang on his 80th birthday: A great scientist and a great ambassador

It is a great pleasure for international colleagues in polymer science to celebrate Professor Fosong Wang on his 80th birthday. Professor Fosong Wang, a member of the Chinese Academy of Sciences, is a great polymer scientist, with over 300 publications and a few books. He is internationally recognized in his work on stereoregular polymers and electronically active polymers, particularly the development of     

Deformation Electron-Density Distributions of Tetraazathiapentalenes with Hypervalent S-N Bonds

Abstract

The deformation electron-density distributions of 6a-thia-1,3,4,6-tetraazapentalene derivatives (I, II) and bis(phenylthio)dibenzothiophene (III) were investigated by the X-ray diffraction method. For I and II, a structure around the hypervalent S-N bonds is a trigonal bipyramid with equatorial sp² hybrid of S-C bond and lone-pair electrons and apical polarized S-N bonds. In 111 lone-pair electron densities are observed perpendicular to the thiophene ring and the C-S-C sulfide planes.     

INTRAMOLECULAR TRAPPING OF THE NITRENE GENERATED BY PHOTOLYSIS OF S,S-DIPHENYL N-ACYLSULFILIMINE

Abstract

Various N-acyldiphenylsulfilimines (1a-k) were found to undergo photolysis in argon atmosphere, to afford the corresponding isocyanates, diphenyl sulfide and diphenyl disulfide. Attempts to trap intramolecularly the acylnitrene with olefinic linkage or sulfide afforded small amounts of the trapped products, whereas photolysis of N-mesitoyldiphenyl-sulfilimine (Ia) afforded a C–H inserted product of the nitrene in a substantial yield together with the isocyanate. Benzophenone-sensitized photolysis of Ia indicates that the nitrene generated is a singlet species.     

Synthesis of N-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide for EPR brain imaging

A scalable synthetic route for ¹⁵N-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide (¹⁵N-TEEPONE) is described. This ¹⁵N-labeled nitroxide is suitable for electron paramagnetic resonance imaging of brain, and its higher sensitivity compared with that of its ¹⁴N-counterpart is an important advantage of the labeled derivative.     

Synthesis and properties of disilanylene-containing polymers

Alternating polymers, poly[(disilanylene)ethynylene]s and poly[(1, 2-diethynylenedisilanylene)(1-silacyclopenta-2, 4-diene-3, 4-diyl)]s were prepared by the anionic ring-opening polymerization of 1, 2, 5, 6-tetrasilacycloocta-3, 7-diynes and 4, 5, 10-trisilacyclo[6.3.0]undeca-1(11), 8-diene-2, 6-diynes, respectively. Poly[(disilanylene)butenyne-1, 4-diyl]s were synthesized by the reaction of 1, 2-diethynyldisilanes with a catalytic amount of RhCl(PPh₃)₃. Photochemical and conducting properties of the polymers are described.