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Radical Initiator (radical + initiator)
Kinds of Radical Initiator Selected AbstractsSide Chain Bromination of Mono and Dimethyl Heteroaromatic and Aromatic Compounds by Solid Phase N-Bromosuccinimide Reaction Without Radical Initiator under Microwave.CHEMINFORM, Issue 49 2004Shyamaprosad Goswami Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Stereocontrol in Radical Processes Through the Exocyclic Effect: Dual Role of Triethylboron as Radical Initiator and in situ Derivatization Agent.CHEMINFORM, Issue 34 2001Jean-Pierre Bouvier Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivityELECTROPHORESIS, Issue 17 2003Michael Lämmerhofer Abstract A new chiral monomer derived from cinchona alkaloid, namely O -9-(tert -butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O -9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 ,m in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1 - co -HEMA- co -EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4 - co -HEMA- co -EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency. [source] Radical Addition of Ethers to Terminal Alkynes with High E -SelectivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 30 2009Zili Chen Abstract Direct radical additions of ethers to terminal alkynes were investigated by using Me2Zn/O2 as radical initiator to afford 2-vinyl ether derivatives with high E -selectivity, while reversed E/Z selectivity is obtained with Et3B/O2. Two competitive pathways are suggested for the formation of vinyl radical B: zinc-radical exchange (route a) followed by protonation provides E -configuration products exclusively through Zn(II) complexation. Hydrogen abstraction by vinyl radicals (route b) yields mainly Z isomers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Kinetic study on the prooxidative effect of vitamin C on the autoxidation of glycerol trioleate in micellesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2006Zai-Qun Liu Abstract Vitamin C (L -ascorbic acid) protects human health by scavenging toxic free radicals and other reactive oxygen species formed in cell metabolism. The surplus supplementation of vitamin C, however, may be harmful to health because the level of 8-oxoguanine and 8-oxoadenine in lymphocyte DNA varies remarkably. In the process of the kinetic investigation on the 2,2,-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced autoxidation of glycerol trioleate (GtH) in the micelles of cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and Triton X-100, the addition of vitamin C accelerates the autoxidation of GtH even in the absence of the free radical initiator, AAPH. The initiating rate, Ri, of vitamin C (VC)-induced autoxidation of GtH is related to the micelle charge, i.e. Ri,=,14.4,×,10,6 [VC] s,1 in SDS (anionic micelle), Ri,=,1961,×,10,6 [VC] s,1 in Triton X-100 (neutral micelle) and Ri is a maximum in CTAB (cationic micelle) when the vitamin C concentration is ,300,µM. Thus, vitamin C can initiate autoxidation of GtH in micelles, especially in the neutral one. Moreover, the attempt to explore whether ,-tocopherol (TocH) could rectify vitamin C-induced autoxidation of GtH leads us to find that the rate constant of TocH reacting with the anionic radical of vitamin C (VC.,), k,inh, is ,103M,1,s,1, which is less than that of the ,-tocopherol radical (Toc.) with vitamin C (kinh,=,,105,M,1,s,1). Thus, the equilibrium constant of the reaction Toc.+VC,,TocH+VC., is prone strongly to the regeneration of Toc. by vitamin C rather than the reverse reaction. Copyright © 2006 John Wiley & Sons, Ltd. [source] Surfactant assisted polymerization of tetrafluoroethylene in supercritical carbon dioxide with a pilot scale batch reactorJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Alberto Giaconia Abstract Chain-free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO2), at 50 °C and 121,133 bar, with tertiary -amyl-per-pivalate as a free radical initiator, using a 5-L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant-free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200,500 ,m. Quite interestingly, when the free acid surfactant was used, a clear acceleration of the polymerization rate was observed and smaller polymer particles with more regular quasi-spherical morphology were obtained. Melt fusion crystallinity of as-polymerized poly(TFE) seemed not substantially affected by the presence of the stabilizers and was rather high (80,86%) suggesting that polymerization mainly occurs at polymer particle surface. All these elements suggest that FLUOROLINK® 7004H PFPE carboxylic acid decreases coagulation of primary polymer particles leading to an increase in polymer surface area. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 257,266, 2008 [source] Synthesis of PS and PDMAEMA mixed polymer brushes on the surface of layered silicate and their application in pickering suspension polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Yongfang Yang Abstract An ammonium free radical initiator was ion exchanged onto the surface of clay layers. Polystyrene (PS) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) mixed polymer brushes on the surface of clay layers were prepared by in situ free radical polymerization. PS colloid particles armored by clay layers with mixed polymer brushes were prepared by Pickering suspension polymerization. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the structure and morphology of the colloid particles. Clay layers on the surface of PS colloid particles can be observed. Because of the cationic nature of the PDMAEMA brushes the colloid particles have positive zeta potentials at low pH values. X-ray photoelectron spectroscopy (XPS) was used to analyze the surface of the colloid particles. N1s binding energy of PDMAEMA chains on the surface of clay layers was detected by XPS. The two peaks of the N1s binding energy indicate two different nitrogen environments on the surface of clay layers. The peak with a lower binding energy is characteristic of neutral nitrogen on PDMAEMA chains, and the peak with a higher binding energy is attributed to protonated nitrogen on PDMAEMA chains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5759,5769, 2007 [source] Synthesis and characterization of poly(methyl methacrylate)/casein nanoparticles with a well-defined core-shell structureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2003Junmin Zhu Abstract Well-defined, core-shell poly(methyl methacrylate) (PMMA)/casein nanoparticles, ranging from 80 to 130 nm in diameter, were prepared via a direct graft copolymerization of methyl methacrylate (MMA) from casein. The polymerization was induced by a small amount of alkyl hydroperoxide (ROOH) in water at 80 °C. Free radicals on the amino groups of casein and alkoxy radicals were generated concurrently, which initiated the graft copolymerization and homopolymerization of MMA, respectively. The presence of casein micelles promoted the emulsion polymerization of the monomer and provided particle stability. The conversion and grafting efficiency of the monomer strongly depended on the type of radical initiator, ROOH concentration, casein to MMA ratio, and reaction temperature. The graft copolymers and homopolymer of PMMA were isolated and characterized with Fourier transform infrared spectroscopy and differential scanning calorimetry. The molecular weight determination of both the grafted and homopolymer of PMMA suggested that the graft copolymerization and homopolymerization of MMA proceeded at a similar rate. The transmission electron microscopic image of the nanoparticles clearly showed a well-defined core-shell morphology, where PMMA cores were coated with casein shells. The casein shells were further confirmed with a zeta-potential measurement. Finally, this synthetic method allowed us to prepare PMMA/casein nanoparticles with a solid content of up to 31%. Thus, our new process is commercially viable. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3346,3353, 2003 [source] Synthesis of highly crosslinked monodisperse polymer particles: Effect of reaction parameters on the size and size distributionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002J. Choi Abstract Monodisperse polystyrene particles crosslinked with different concentrations of divinylbenzene were synthesized in the 3.2,9.1 ,m size range by dispersion polymerization in an isopropyl alcohol/toluene mixed-dispersion medium with poly(N -vinylpyrrolidone) as a steric stabilizer and 2,2,-azobisisobutyronitrile as a radical initiator. The effects of the reaction parameters such as the crosslinking agent concentration, media solvency (controlled by varying the amount of toluene addition), the initiator concentration, and the stabilizer concentration on the particle size and size distribution were investigated with reference particles with a monodisperse size distribution and crosslinked by 1.5 wt % divinylbenzene. The appropriate increase in media solvency was a prerequisite for preparing crosslinked particles without coagulated and/or odd-shaped particles. The investigation of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with a monodisperse size distribution. The glass-transition temperatures of the particles increased with increasing divinylbenzene concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4368,4377, 2002 [source] Radical and cationic polymerizations of 3-ethyl-3-methacryloyloxymethyloxetaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2001Tsuneyuki Sato Abstract 3-Ethyl-3-methacryloyloxymethyloxetane (EMO) was easily polymerized by dimethyl 2,2,-azobisisobutyrate (MAIB) as the radical initiator through the opening of the vinyl group. The initial polymerization rate (Rp) at 50 °C in benzene was given by Rp = k[MAIB]0.55 [EMO]1.2. The overall activation energy of the polymerization was estimated to be 87 kJ/mol. The number-average molecular weight (M,n) of the resulting poly(EMO)s was in the range of 1,3.3 × 105. The polymerization system was found to involve electron spin resonance (ESR) observable propagating poly(EMO) radicals under practical polymerization conditions. ESR-determined rate constants of propagation (kp) and termination (kt) at 60 °C are 120 and 2.41 × 105 L/mol s, respectively,much lower than those of the usual methacrylate esters such as methyl methacrylate and glycidyl methacrylate. The radical copolymerization of EMO (M1) with styrene (M2) at 60 °C gave the following copolymerization parameters: r1 = 0.53, r2 = 0.43, Q1 = 0.87, and e1 = +0.42. EMO was also observed to be polymerized by BF3OEt2 as the cationic initiator through the opening of the oxetane ring. The M,n of the resulting polymer was in the range of 650,3100. The cationic polymerization of radically formed poly(EMO) provided a crosslinked polymer showing distinguishably different thermal behaviors from those of the radical and cationic poly(EMO)s. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1269,1279, 2001 [source] Radical Polymerisation of 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol Acrylates and Methacrylates: A New Family of Fluorinated PolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2004Ana Robert Estelrich Abstract Summary: The preparation of a new family of acrylic esters with a perfluorinated chain directly bonded to one or two conjugated triple bonds from 1H,1H,2H,2H-perfluoro-3,5-alkyldiynol and 1H,1H-perfluoro-2,4-alkyldiynol is reported. Their solution homopolymerisation was studied in the presence of a radical initiator and it was found that the polymerisation process bore more similarity to that observed with the analogous hydrocarbonated monomers containing triple bonds rather than that observed with polyfluorinated monomers without any alkyne groups. Furthermore, under the reaction conditions used, the triple bonds remained unchanged as there was no cross-linking process. The homopolymers obtained were characterised by NMR, infrared spectroscopy and gel permeation chromatography whenever possible. Structure of new fluorinated homopolymers. [source] Functionalization of LDPE by Melt Grafting with Glycidyl Methacrylate and Reactive Blending with Polyamide-6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2003Qian Wei Abstract Low-density polyethylene (LDPE) was functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed for reactive blending with polyamide-6 (PA6). The effect of the reaction procedure on the grafting degree of LDPE- g -GMA samples (0.5,12.5 wt.-% GMA) was analyzed as a function of the concentration of GMA monomer, radical initiator (BTP), and addition of styrene as co-monomer. Optimized grafting conditions were obtained when the amount of the monomer is below 10 wt.-% and that of peroxide in the range 0.2,0.4 wt.-%. Binary blends of PA6 with LDPE- g -GMA (3.5 wt.-% GMA) and with LDPE at various compositions (80/20, 67/33, 50/50 wt.-%) were prepared in an internal mixer and their properties were evaluated by torque, SEM and DSC analyses. Morphological examination by SEM showed a large improvement of phase dispersion and interfacial adhesion in PA6/LDPE- g -GMA blends as compared with PA6/LDPE blends. The average diameter of dispersed polyolefin particles was about 0.4 ,m for LDPE- g -GMA contents <,50 wt.-%. A marked increase of melt viscosity was observed for the compatibilized blends depending on the concentration of grafted polyolefin, and it was accounted for by the reaction between the epoxy groups of GMA and the carboxyl/amine end-groups of PA6. The variation of torque was thus related to the molar ratio of reactive group concentration. The analysis of crystallization and melting behavior pointed out marked differences in the phase structure of the blends due to the presence of the functionalized polyolefin. Finally, the in situ formation of a graft copolymer between LDPE- g -GMA and PA6 was investigated by means of a selective dissolution method (Molau test) and by FT-IR and DSC analyses. SEM micrograph of fracture surface of PA6/LDPE- g -GMA 50/50 blend. [source] A Solvent Free Graft Copolymerization of Maleic Anhydride onto Cellulose Acetate Butyrate Bioplastic by Reactive ExtrusionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2006Arief C. Wibowo Abstract Summary: Interfacial adhesion between fibers and matrix is a crucial factor for effective stress transfer from matrix to fiber; especially in short fiber reinforced composite systems. The use of a chemical compatibilizer is an efficient means to achieve such adhesion. Maleic anhydride-grafted-cellulose acetate butyrate (CAB-g-MA) is one such compatibilizer which can be used in biocomposite fabrication, and this has been synthesized in our laboratory by utilizing a twin-screw reactive extrusion process in the presence of a free radical initiator (2,5-dimethyl-2,5-di(tert -butylperoxy)hexane). The unique feature of this process is its solvent-free approach for grafting of maleic anhydride onto CAB, without hydroxyl group protection. CAB-g-MA was characterized using FTIR as well as by a non-aqueous titration method. The effects of initiator and monomer concentrations and various processing conditions on the graft content were also investigated. The preliminary results show that by adding approximately 10 wt.-% of CAB-g-MA into a plasticized cellulose acetate butyrate (TEB)-industrial hemp fiber biocomposites system, an improvement in tensile strength (20%) and in tensile modulus (45%) were obtained. These results are promising in that they pave the way for future studies involving the use of CAB-g-MA as a suitable compatibilizer for cellulose ester-natural fiber biocomposites. [source] Inhibitory effects of Keishi-bukuryo-gan on free radical induced lysis of rat red blood cellsPHYTOTHERAPY RESEARCH, Issue 4 2002Nobuyasu Sekiya Abstract Keishi-bukuryo-gan (KBG) prevents the progression of atherosclerosis in cholesterol-fed rabbits by its antioxidative effect. The present study was to test our hypothesis that ingestion of KBG would protect red blood cell (RBC) membranes from free radical induced oxidation if polyphenolic antioxidants in KBG could be absorbed and circulated in the blood. When incubated with a RBC suspension, KBG and four of five herb medicines constituting KBG provided strong protection for RBC membranes against haemolysis induced by 2,2-azo-bis (2-amidinopropane) dihydrochloride (AAPH), an azo free radical initiator. The inhibitory effect was dose dependent at concentrations of 100,1000 ,g/mL. Furthermore, the ingestion of 200,mg of KBG was associated with a significant decrease in susceptibility of RBC to haemolysis in rats. Copyright © 2002 John Wiley & Sons, Ltd. [source] Nano-reactors for controlling the selectivity of the free radical grafting of maleic anhydride onto polypropylene in the meltPOLYMER ENGINEERING & SCIENCE, Issue 10 2006Dean Shi This paper reports on a successful application of the concept of nanoreactors to effectively controlling the selectivity of the free radical grafting of maleic anhydride (MAH) onto polypropylene (PP) in the melt, an industrially relevant process. More specifically, a free radical initiator of type ROOR was first confined into (or encapsulated by) the galleries of an organically modified montmorillonite (o-MMT) whose interdistance was 2.4 nm. Primary free radicals (RO ·) formed inside the o-MMT galleries had to diffuse out before they could react with the PP backbone. The controlled release of the primary free radicals significantly increased the grafting degree of MAH onto PP and greatly reduced the level of the chain scission of the latter. Those results were better understood by electron spin resonance studies on model systems and by Monte Carlo simulations. POLYM. ENG. SCI. 46:1443,1454, 2006. © 2006 Society of Plastics Engineers. [source] Preparation, characterization, and thermal properties of hydrophilic copolymers: p -chlorophenylmaleimides with hydroxylethyl methacrylate and ,-methyl itaconatePOLYMER INTERNATIONAL, Issue 9 2007Guadalupe del C Pizarro Abstract This work describes the synthesis, characterization, and thermal behavior of copolymers of p -chlorophenylmaleimide (Cl-PhMI) with ,-methyl itaconate (,-MHI) and 2-hydroxyethyl methacrylate (HEMA). Copolymerization was carried out with a radical initiator by varying the feed mole fraction of Cl-PhMI from 0.25 to 0.75. The copolymer composition was determined from the N/C ratio based on elemental analysis data and with 1H NMR spectroscopy for poly(Cl-PhMI- co -HEMA) using a proton signal attributed to the CH3 of HEMA (, = 0.7,1.4 ppm) and the area of aromatic ring protons (, = 7.2,7.8 ppm), where the proton/area relationship confirmed the copolymer compositions calculated by elemental analysis. The monomer reactivity ratios r1 and r2 were determined using the Kelen,Tüdös method. These values demonstrated that copolymerization produced random copolymers with an alternation tendency. The molecular weight and polydispersity were also determined. The thermal behavior can be correlated with the copolymer composition. An increase of the thermal decomposition temperature occurred when the content of Cl-PhMI increased. The glass transition temperature and thermal stability of poly(,-MHI) or poly(HEMA) increased with an increasing amount of Cl-PhMI in the polymer backbone. Copyright © 2007 Society of Chemical Industry [source] Copolymerization of bromophenylmaleimide with ethyl or butyl methacrylatePOLYMER INTERNATIONAL, Issue 7 2003HF Naguib Abstract N - p -Bromophenylmaleimide (BrPMI) does not polymerize in solution by conventional free radical mechanism. However, it readily polymerized in bulk when mixed with a free radical initiator and heated in a microwave oven for 7,8 min. Copolymerization of ethyl methacrylate or butyl methacrylate with BrPMI was conducted in dioxane. The copolymers were characterized by IR and 1H NMR spectroscopy and gel permeation chromatography. The monomer reactivity ratios were calculated by a non-linear least-square analysis. Thermal analysis indicated a great improvement in thermal stability of the copolymers compared with the methacrylate homopolymers. BrPMI was also polymerized in bulk in the DSC pan, which allowed the calculation of the activation energy of its polymerization. Copyright © 2003 Society of Chemical Industry [source] Reaction kinetics of graft copolymerization and thermochemical studies of the degradation of poly(vinyl alcohol) graft copolymerPOLYMER INTERNATIONAL, Issue 3 2001Yassin A Aggour Abstract Poly(vinyl alcohol) (PVA) is a water-soluble and biomedical polymer. 2-Acrylamido-2-methyl-1-propanesulfonic acid was grafted onto PVA using ammonium persulfate as radical initiator. The influences of synthesis conditions such as temperature, concentrations of initiator, PVA and monomer were investigated. Both the initial rate of grafting and the final percentage of grafting were increased by an increase in reaction temperature. The reaction kinetics were studied to determine the rate constants of the first-order reactions. An activation energy of 16.3,kJ,mol,1 was found for the grafting reaction. The graft copolymers were characterized by IR and intrinsic viscosity measurements. A proposed mechanism of the grafting reaction is discussed. Kinetics of the thermal degradation were studied using a thermogravimetric method and the order of thermal stabilities are given. The apparent activation thermodynamic parameters, Ea, ,H*, ,S* and ,G* were determined and correlated to the thermal stabilities of the homo- and grafted polymers. © 2001 Society of Chemical Industry [source] Removal of dyes from water by poly(vinyl pyrrolidone) hydrogel,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2006Bahire Filiz Senkal Abstract The interaction between polymer and dye leading to polymer-dye complex formation exhibits many interesting and important practical features. For this purpose, a hydrogel was prepared by crosslinking copolymerization of vinyl pyrrolidone with tetraallyl ammonium bromide in aqueous solution, using K2S2O8 as a radical initiator. Dye extraction experiments were carried out simply by contacting wetted gel samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye contents. The hydrogel swelled in water showing that reasonable high dye sorption capacity (0.71,1.13,g per gram of gel) was achieved. This material is also able to remove the anionic dyes completely even from highly diluted aqueous dye solutions. No trace absorbance was detected in the visible range, after processing. Copyright © 2006 John Wiley & Sons, Ltd. [source] ChemInform Abstract: Titanocene(III) Chloride Mediated Reductive Cleavage of Arylcyclopropyl Ketones.CHEMINFORM, Issue 38 2010M. Paira Abstract The first reductive cleavage of arylcyclopropyl ketones using TiCl(Cp)2 as a radical initiator is described. [source] Preparation of Core-shell Microspheres by ATRP Synthesized MacromonomerCHINESE JOURNAL OF CHEMISTRY, Issue 10 2008Hong CHU Abstract Poly(tert -butyl methacrylate) macrointermediates (PtBMA-Br) with an end of bromine atom were synthesized by atom transfer radical polymerization using ethylbromopropionate as an initiator in bulk in the presence of N,N,N,,N,,,N,, -pentamethyl diethylenetriamine (PMDETA) as a single ligand. A new macromonomer (MAA- PtBMA) was successfully prepared via end-group nucleophilic substitution with methacrylic acid to attain a high efficiency of C=C incorporation. The molecular weights of MAA-PtBMA macromonomers were controllable from 5400 to 11000 g/mol, and the molecular weight distribution was narrow (,1.20). Then, the PtBMA graft polystyrene (PtBMA-g-PSt) microspheres were prepared by dispersion copolymerization of MAA-PtBMA macromonomers with styrene using 2,2,-azobisisobutyronitrile as a free radical initiator in ethanol. The resulting PtBMA-g-PSt microspheres were regulated in diameter on a micron scale. [source] Protective Effects of Resveratrol and its Analogues against Free Radical-Induced Oxidative Hemolysis of Red Blood Cells,CHINESE JOURNAL OF CHEMISTRY, Issue 11 2002Jian-Guo Fang Abstract The in vitro oxidative hemolysis of human red blood cells (RBCs) was used as a model to study the free radical-induced damage of biological membranes and the protective effect of resveratrol (3,5,4,-trihydroxy-trans-stilbene, 1) and its analogues, i. e., 4-hydroxy- trans -stilbene (2), 3, 5- dihydroxytrans -stilbene (3), 3,4-dihydroxy- trans -stilbene (4), 4,4,-dihydroxy- trans -stilbene (5) and 2, 4, 4,-trihydroxy- trans -stilbene (6). The hemolysis of RBCs was induced by a water-soluble free radical initiator 2, 2,-azobis (2-amidinopropane hydrochloride) (AAPH). It was found that addition of AAPH at 37 °C to the suspension of RBCs caused fast hemolysis after a short period of inhibition period, and addition of 1,6 significantly suppressed the hemolysis. Compound 4 which bears an ortho -dihydroxyl functionality showed much more effective anti-hemolysis activity than that of resveratrol and the other analogues. [source] Free radical polymerization of methyl methacrylate initiated by the diphosphine Mo(0) complexesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2006Ayfer Mente Abstract The polymerization of methyl methacrylate MMA catalyzed by [Mo(CO)4L2] [L2 = diphenylphosphinomethane (dppm), diphenylphosphinoethane (dppe) or diphenylphosphinopropane (dppp)] has been studied. The activity of these single-component catalysts depends on the length of the (CH2)n bridge of diphosphine ligand. Thus, the dppm derivative displays higher activity than dppe or dppp ligands. These complexes, as free radical initiators, afforded the methyl methacrylate polymerization in chlorinated solvents. The mechanism of the polymerization was discussed and a radical mechanism was proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||