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Benzoyl Peroxide (benzoyl + peroxide)
Selected AbstractsSynthesis of Polypyrrole Using Benzoyl Peroxide as a Novel Oxidizing AgentMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2006Chandrasekaran Saravanan Abstract Summary: Benzoyl peroxide is used as an oxidizing agent for the first time in the synthesis of conducting polypyrrole. Synthesis of polypyrrole is commonly performed by chemical oxidative polymerization using water-soluble oxidizing agents. In this work, polypyrrole was prepared using organic solvent-soluble benzoyl peroxide as an oxidizing agent in the presence of p -toluenesulfonic acid (p -TSA) and sodium lauryl sulfate (SLS) surfactant via the inverted-emulsion-polymerization technique. During polymerization, SLS is converted to dodecyl hydrogensulfate (DHS) and incorporated on to polypyrrole along with p -TSA dopant, indicating SLS is acting as emulsifier as well as dopant. The influence of synthesis conditions such as the duration of the reaction, the temperature, the concentration of the reactants, etc., on the properties of polypyrrole was investigated to determine the optimum conditions for the synthesis of polypyrrole salt. Polypyrrole was obtained in a reaction time of 1 h with high yield (154 wt.-% with respect to pyrrole used) and good conductivity (2 S,·,cm,1). The conductivity of polypyrrole-salt was found to be nearly the same even after seven months of storage at ambient temperature (1.7 S,·,cm,1). [source] Polycarbonate particles and dye-labeled particles by miniemulsion polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2004Frédéric Tronc Abstract We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4-vinyl-1,3-dioxan-2-one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil-soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water-soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999,2009, 2004 [source] Synthesis of Polypyrrole Using Benzoyl Peroxide as a Novel Oxidizing AgentMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2006Chandrasekaran Saravanan Abstract Summary: Benzoyl peroxide is used as an oxidizing agent for the first time in the synthesis of conducting polypyrrole. Synthesis of polypyrrole is commonly performed by chemical oxidative polymerization using water-soluble oxidizing agents. In this work, polypyrrole was prepared using organic solvent-soluble benzoyl peroxide as an oxidizing agent in the presence of p -toluenesulfonic acid (p -TSA) and sodium lauryl sulfate (SLS) surfactant via the inverted-emulsion-polymerization technique. During polymerization, SLS is converted to dodecyl hydrogensulfate (DHS) and incorporated on to polypyrrole along with p -TSA dopant, indicating SLS is acting as emulsifier as well as dopant. The influence of synthesis conditions such as the duration of the reaction, the temperature, the concentration of the reactants, etc., on the properties of polypyrrole was investigated to determine the optimum conditions for the synthesis of polypyrrole salt. Polypyrrole was obtained in a reaction time of 1 h with high yield (154 wt.-% with respect to pyrrole used) and good conductivity (2 S,·,cm,1). The conductivity of polypyrrole-salt was found to be nearly the same even after seven months of storage at ambient temperature (1.7 S,·,cm,1). [source] Benzoyl peroxide,p -acetylbenzylidenetriphenyl arsoniumylide initiated copolymerization of citronellol and styrenePOLYMER INTERNATIONAL, Issue 8 2001K Srivastava Abstract Alternating copolymers, containing styrene and citronellol sequences, have been synthesized by radical polymerization using benzoylperoxide (BPO),p -acetylbenzylidenetriphenyl arsoniumylide (pABTAY) as initiator, in xylene at 80,±,1,°C for 3,h under inert atmosphere. The kinetic expression is Rp , [BPO]0.88 [citronellol]0.68 [styrene]0.56 with BPO and Rp , [pABTAY]0.27 [citronellol]0.76 [styrene]0.63 with pABTAY, ie the system follows non-ideal kinetics in both cases, because of primary radical termination and degradative chain transfer reactions. The activation energy with BPO and pABTAY is 94,kJ,mol,1 and 134,kJ,mol,1, respectively. Different spectral techniques, such as IR, FTIR, 1H NMR and 13C NMR, have been used to characterize the copolymer, demonstrating the presence of alcoholic and phenyl groups of citronellol and styrene. The alternating nature of the copolymer is shown by the product of reactivity ratios r1 (Sty),=,0.81 and r2 (Citro),=,0.015 using BPO and r1 (Sty),=,0.37 and r2 (Citro),=,0.01 using (pABTAY), which are calculated by the Finemann,Ross method. A mechanism of copolymerization is proposed. © 2001 Society of Chemical Industry [source] New and emerging treatments in dermatology: acneDERMATOLOGIC THERAPY, Issue 2 2008A. Katsambas ABSTRACT:, Topical retinoids, benzoyl peroxide, azelaic acid, and topical and oral antibiotics remain the milestone of treatment for mild to moderate acne vulgaris. Oral isotretinoin is useful for the treatment of severe nodular acne, treatment-resistant acne, and acne with a risk of physical or psychological scarring. Hormonal treatment in female acne is useful in resistant or late-onset acne. With increasing concerns regarding teratogenicity of isotretinoin and increasing antibiotic resistance, there is a clear need for therapeutic alternatives to these long-used treatments. Research in the pathogenesis of acne has allowed for new therapies and future perspectives regarding acne to evolve. They include low-dose long-term isotretinoin regimens, insulin-sensitizing agents, 5,-reductase type 1 inhibitors, topical photodynamic therapy, new combination formulations, dietary interventions, and antiinflammatory agents such as lipoxygenase inhibitors. [source] Free radical graft copolymerization of poly(n -butyl methacrylate) and poly(butyl acrylate) onto chlorinated rubber: Characterization and mechanical properties,ADVANCES IN POLYMER TECHNOLOGY, Issue 2 2004Shanaz Ahmed Abstract Graft copolymerization of n -butyl methacrylate and butyl acrylate onto chlorinated rubber was carried out in solution medium (xylene) using benzoyl peroxide as initiator. The chlorinated rubber-g-(n -butyl methacrylate- co -butyl acrylate) (CR-g-nBMA- co -BA) was isolated from the copolymerization mixture by extracting with isopropyl ether. Infrared (FT-IR) spectra, proton nuclear magnetic resonance (1H NMR) and thermogravimetric analysis of the graft copolymer showed the occurrence of grafting. Percent grafting and grafting efficiency calculated under different experimental conditions are discussed. The mechanical properties of the grafted CR films were studied under different strain rates. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 103,110, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20003 [source] Synthesis and physical properties of low-molecular-weight redistributed poly(2,6-dimethyl-1,4-phenylene oxide) for epoxy resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Hann-Jang Hwang Abstract Low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with 4,4,-isopropylidenediphenol (bisphenol A) with benzoyl peroxide as an initiator in toluene. The redistributed PPO was characterized by proton nuclear magnetic resonance, mass spectra, and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with terminal phenolic hydroxyl groups and low molecular weights (weight-average molecular weight = 800,4000) were used in the modification of a diglycidyl ether of bisphenol A/4,4,-diaminodiphenylmethane network system. The curing behaviors were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of molecular weight and the amount of redistributed PPO oligomers incorporated into the network on the physical properties of the resulting systems were investigated. The thermal properties of the cured redistributed PPO/epoxy resins were studied by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetric analysis, and dielectric analysis. These cured redistributed PPO/epoxy resins exhibited lower dielectric constants, dissipation factors, coefficients of thermal expansion, and moisture absorptions than those of the control diglycidyl ether of bisphenol A based epoxy. The effects of the composition on the glass-transition temperature and thermal stability are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis by a single-step swelling process and characterization of micrometer-sized polychloromethylstyrene/poly(butyl methacrylate) hemispherical composite particles of narrow size distributionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Sigal Baruch-Sharon Abstract Polychloromethylstyrene (PCMS) micrometer-sized particles of narrow size distribution were prepared by the dispersion polymerization of chloromethylstyrene in a mixture of ethanol and dimethyl sulfoxide. Micrometer-sized PCMS/poly(butyl methacrylate) hemispherical composite particles of narrow size distribution were prepared by a single-step swelling process of the uniform PCMS template particles with emulsion droplets of butyl methacrylate (BMA) containing benzoyl peroxide, followed by the polymerization of BMA at 73°C within the swollen template particles. The effects of various polymerization parameters, for example, BMA volume, initiator type and concentration, and toluene as the swelling solvent, on the properties (size and size distribution, morphology, polymerization yield, and composition) of the hemispherical composite particles were elucidated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal and dynamic mechanical properties of organic,inorganic hybrid composites of itaconate-containing poly(butylene succinate) and methacrylate-substituted polysilsesquioxaneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008Takenori Sakuma Abstract Itaconate-unit-containing poly(butylene succinate) (PBSI) was synthesized by the reaction of 1,4-butanediol, succinic acid, and itaconic acid in a molar ratio of 2.0 : 1.0 : 1.0, and the obtained PBSI was reacted with methacryl-group-substituted polysilsesquioxane (ME-PSQ) in the presence of benzoyl peroxide (BPO) at 130°C to produce PBSI/ME-PSQ hybrid composites. The thermal and dynamic mechanical properties of the PBSI/ME-PSQ hybrid composites were investigated in comparison with those of PBSI cured at 130°C in the presence of BPO. As a result, the hybrid composites showed a much higher thermal degradation temperature and storage modulus in the rubbery state than the cured PBSI (C-PBSI). The thermal degradation temperature and storage modulus of the hybrid composites increased with increasing ME-PSQ content. The glass-transition temperature, measured by dynamic mechanical analysis of the hybrid composites, somewhat increased with increasing ME-PSQ content. However, the glass-transition temperatures of all the hybrid composites were lower than that of C-PBSI. Although the IR absorption peak related to CC groups was not detected for C-PBSI, some olefinic absorption peaks remained for all the hybrid composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis, characterization, and cure reaction of methacrylate-based multifunctional monomers for dental compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Mousa Ghaemy Abstract The synthesis of 2,2-bis[(4-(2-hydroxy-3-methacryloxyethoxy)phenyl]propane (BHEP) and (1-methacryloxy-3-ethoxymethacryloxy-2-hydroxy)propane (MEHP) for use as the monomer phase in dental composites are reported. The monomers were prepared by the reaction of 2-hydroxyethyl methacrylate (HEMA) with diglycidyl-ether of bisphenol A (DGEBA) and with glycidyl methacrylate (GMA), respectively. The progress of the reaction was followed by measuring the disappearance of the epoxide group peak using FTIR and the structure of the monomers was characterized by 1H-NMR. BHEP and MEHP have lower viscosity because of the presence of long aliphatic spacer on both sides of the aromatic ring in BHEP and the absence of aromatic rings and the presence of only one hydroxyl group in each molecule of MEHP. Thermal curing of the monomers was conducted in a DSC using benzoyl peroxide as an initiator. Photopolymerization of the monomers was also conducted with the visible light using camphorquinone and N,N -dimethylaminoethyl methacrylate as the photoinitiating system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] BEHAVIOR OF AVIRULENT YERSINIA PESTIS IN LIQUID WHOLE EGG AS AFFECTED BY STORAGE TEMPERATURE, ANTIMICROBIALS AND THERMAL PASTEURIZATIONJOURNAL OF FOOD SAFETY, Issue 3 2010JOSHUA B. GURTLER ABSTRACT Yersinia spp. are psychrotrophic bacteria capable of growth at temperatures as low as ,2C, known to contaminate shell eggs and liquid eggs in the U.S.A. and South America. A study was performed to determine the thermal sensitivity of avirulent Yersinia pestis in liquid whole egg (LWE), evaluate the growth pattern of the bacterium in LWE at temperatures of 4,22C and assess the ability of 10 antimicrobial compounds to inhibit the growth of attenuated Y. pestis in LWE. The estimated decimal reduction values of avirulent Y. pestis in LWE at 54C (D54) were 1.39,1.58 min, and D60 values were 13.8 and 11.4 s by the addition of 0 and 965 IU of nisin (MP Biomedicals, LLC, Solon, OH), respectively. Low molecular weight chitosan (0.5%) and an activated lactoperoxidase system (2.18 U/mL) were ineffective at inhibiting growth of Y. pestis, while 500 IU/mL of nisin inhibited populations by up to 1 log cfu/mL at 4, 10 and 15C when compared with the control. Allyl isothiocyanate, diacetyl, diethyl dicarbonate, ethylenediaminetetraacetic acid, methylparaben, monolaurin and benzoyl peroxide inhibited the growth of attenuated Y. pestis when added at high levels. PRACTICAL APPLICATIONS The genus Yersinia does not currently pose a problem in pasteurized liquid egg products, although it has been isolated from eggs in the U.S.A. and Argentina. Yersiniae, which are psychrotrophic bacteria, can grow at temperatures as low as ,2C; therefore, incidental or intentional contamination of liquid whole egg (LWE) with Yersinia spp. could result in multiplication to high populations, even when stored under refrigeration (ca. 4C). We have shown that avirulent Yersinia pestis is able to multiply to populations of >2, 5 and 8 log cfu/mL in LWE at 4C within 6, 14 and 26 days, respectively. This study provides information that will be helpful in determining thermal and nonthermal means of controlling yersiniae in LWE products. [source] Photoreactive nanomatrix structure formed by graft-copolymerization of 1,9-nonandiol dimethacrylate onto natural rubberJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2010Yoshimasa Yamamoto Abstract Formation of photoreactive nanomatrix structure was investigated by graft-copolymerization of an inclusion complex of 1,9-nonandiol dimethacrylate (NDMA) with ,-cyclodextrin (,-CD) onto natural rubber particle using potassium persulfate (KPS), tert -butyl hydroperoxide/tetraethylenepentamine (TBHPO/TEPA), cumene hydroperoxide/tetraethylenepentamine (CHPO/TEPA), and benzoyl peroxide (BPO) as an initiator. The graft copolymer was characterized by 1H NMR and FTIR after coagulation. The conversion of NDMA and the amount of residual methacryloyl group were found to be 58.5 w/w % and 1.81 w/w %, respectively, under the suitable condition of the graft-copolymerization. The morphology of the film specimen, prepared from the graft copolymer, was observed by transmission electron microscopy (TEM) after staining the film with OsO4. Natural rubber particle of about 1.0 ,m in diameter was dispersed in poly(NDMA) matrix of about 10 nm in thickness. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2418,2424, 2010 [source] Room-temperature RAFT copolymerization of 2-chloroallyl azide with methyl acrylate and versatile applications of the azide copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010Guang Li Abstract A new vinyl azide monomer, 2-chlorallyl azide (CAA), has been synthesized from commercially available reagent in one step. The reversible addition fragmentation chain transfer (RAFT) copolymerization of CAA with methyl acrylate (MA) was carried out at room temperature using a redox initiator, benzoyl peroxide (BPO)/N,N -dimethylaniline (DMA), in the presence of benzyl 1H -imidazole-1-carbodithioate (BICDT). The polymerization results showed that the process bears the characteristics of controlled/living radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow, and a linear relationship existing between ln([M]0/[M]) and the polymerization time. Chain extension polymerization was performed successfully to prepare block copolymer. Furthermore, the azide copolymers were functionalized by CuI -catalyzed "click" reaction with alkyne-containing poly(ethylene glycol) (PEG) to yield graft copolymers with hydrophilic PEG side chains. Surface modification of the glass sheet was successfully achieved via the crosslinking reaction of the azide copolymer under UV irradiation at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1348,1356, 2010 [source] Nanometer-scale surface modification by polymerization of tetrafluoroethylene on polymer substrates in supercritical fluoroformJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008Toshiaki Mori Abstract Surface penetrated polymerization of tetrafluoroethylene (TFE) was carried out on a polycarbonate (PC) plate in supercritical fluoroform (scCHF3). Since the high diffusiveness is one of peculiar features of supercritical fluids, TFE monomers and initiators (perfluorinated benzoyl peroxide) could penetrate into the surface of polymer substrates and be photo-polymerized. After washing physisorbed homopolymers on the surface, polytetrafluoroethylene (PTFE) was found to penetrate into 50,800 nm depth from the surface and covered the PC surface in the proportion of 85%. The surface coverage density and the penetration depth could be controlled by adjusting of the pressure of scCHF3. The TFE-penetrated polymerization could be applied for various polymer plates such as polyethylene, polystyrene, polypropylene, poly(ethylene terephthalate), and polyimide. In addition to polymer plates, this technique could be applied to a cellulose paper, a nylon textile, and a porous PC membrane. The PTFE-penetrated nylon textile showed a high resistance for washing test with detergents, compared with the commercial fluoropolymer-sprayed nylon textile. The PTFE-penetrated porous PC membrane showed high oxygen permeability (P/P = 5.2), compared with that of the untreated PC membrane (P/P = 3.5) in gas permeation experiments of O2 and N2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1577,1585, 2008 [source] Novel UV-induced photografting process for preparing poly(tetrafluoroethylene)-based proton-conducting membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2007Masaharu Asano Abstract A novel process comprising the UV-induced photografting of styrene into poly(tetrafluoroethylene) (PTFE) films and subsequent sulfonation has been developed for preparing proton-conducting membranes. Although under UV irradiation the initial radicals were mainly generated on the surface of the PTFE films by the action of photosensitizers such as xanthone and benzoyl peroxide, the graft chains were readily propagated into the PTFE films. The sulfonation of the grafted films was performed in a chlorosulfonic acid solution. Fourier transform infrared and scanning electron microscopy were used to characterize the grafted and sulfonated membranes. With a view to use in fuel cells, the proton conductivity, water uptake, and mechanical properties of the prepared membranes were measured. Even through the degree of grafting was lower than 10%, the proton conductivity in the thickness direction of the newly prepared membranes could reach a value similar to that of a Nafion membrane. In comparison with ,-ray radiation grafting, UV-induced photografting is very simple and safe and is less damaging to the membranes because significant degradation of the PTFE main chains can be avoided. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2624,2637, 2007 [source] Cp2TiCl-catalyzed living radical polymerization of styrene initiated from peroxidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2006Alexandru D. Asandei Abstract The effects of the reaction conditions and nature of the initiator were investigated in the Cp2Ti(III)Cl-catalyzed living radical polymerization of styrene initiated by benzoyl peroxide (BPO), tert -butyl peroxide (TBPO), tert -butyl peroxybenzoate (TBPOB), dicumyl peroxide (CPO), and tert -butylperoxy 2-ethylhexyl carbonate (TBPOEHC). The reversible termination of the growing chains with Cp2Ti(III)Cl affords a linear dependence of molecular weight on conversion over a wide range of temperatures (60,120 °C) with an optimum in polydispersity (Mw/Mn < 1.2) for St/BPO/Cp2TiCl2/Zn = 100/1/3/6 at 60,90 °C. The similarity of the kinetic parameters from polymerizations initiated by peroxides with vastly different half-life times (t = 1 h, t = 543 h) and the minimum peroxide/Ti = 1/2 ratio required for a living process indicate that initiation occurs primarily by the redox reaction of the peroxide with Cp2Ti(III)Cl rather than peroxide thermal decomposition. This is consistent with one Ti equivalent consumed in the redox initiation and the second one utilized in the reversible termination of the growing chains. Qualitatively, based on the livingness of the process, these initiators ranked as BPO > TBPOB , TBPO > CPO > TBPOEHC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1106,1116, 2006 [source] Synthesis and characterization of electrically conducting poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004P. Savitha Abstract A series of poly(o -/m -toluidine- co - o -/m -aminoacetophenone) copolymers combining the features of high conductivity and processibility are synthesized and characterized by a number of techniques including 1H NMR; thermogravimetry; IR, Raman, and UV,visible spectroscopy; scanning electron microscopy; and X-ray diffraction. The copolymers are synthesized by the emulsion and inverse emulsion methods using conventional ammonium persulfate and a new oxidant, benzoyl peroxide, respectively. The influence of the polymerization conditions such as the monomer feed ratios, solvent, and the nonsolvent is investigated. The composition of the resulting copolymers is determined by 1H NMR analysis. The conductivity of the copolymers varies with the aminoacetophenone content in the feed and the polymerization conditions. It is interesting that the conductivity of the copolymers is higher than that of the corresponding homopolymers. The results are rationalized on the basis of the effect of the COCH3 substituent on the polymer structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4300,4310, 2004 [source] Polycarbonate particles and dye-labeled particles by miniemulsion polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2004Frédéric Tronc Abstract We describe the synthesis of several different polycarbonate particles by miniemulsion polymerization. The monomers were allylmethyl carbonate (AlMeC), di(ethylene glycol) bisallylcarbonate (DBAC), and 4-vinyl-1,3-dioxan-2-one [vinyl ethylene carbonate (VEC)]. For these polymerizations, higher monomer conversions were obtained with oil-soluble initiators (azobisisobutyronitrile and benzoyl peroxide) than with a water-soluble initiator (potassium persulfate). Benzoyl peroxide was particularly effective in yielding particles with a narrow size distribution. Although increasing amounts of a surfactant (sodium dodecyl sulfate) led to smaller particles, the choice of the monomer was the major determinant. For example, in polymerization reactions carried out at 85 °C with benzoyl peroxide as the initiator and with otherwise identical recipes, we obtained particle sizes of 181 nm with AlMeC, 296 nm with VEC, and 203 nm with DBAC. Fluorescent particles were synthesized with comonomers based on the benzothioxanthene nucleus. Because the dyes had poor solubility in the monomers, it was necessary to include typically 20 wt % bromobenzene or dichlorobenzene based on the monomer in the miniemulsion reaction mixture. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1999,2009, 2004 [source] Benzoyl peroxide-initiated copolymerization of citronellol and vinyl acetateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2002Prachi Pandey Abstract The radical copolymerization of citronellol with vinyl acetate (VA) in xylene at 60 ± 0.1 °C for 90 min in the presence of benzoyl peroxide follows ideal kinetics and results in the formation of an alternating copolymer as demonstrated by the values of the reactivity ratios [r1 (VA) = 0.02 and r2 (citronellol) = 0.0002], which have been calculated with the Kelen,Tüdos method. The overall activation energy is computed to be 75 kJ/mol. The IR spectrum of the copolymer shows the presence of bands at 3400 cm,1 due to an alcoholic group and 1750 cm,1 due to a ,CO group. The values of the Mark,Houwink constants for this copolymer system have been determined with gel permeation chromatography to be , = 0.375 and K = 2.4 × 10,4. The glass-transition temperature, determined with differential scanning calorimetry, is 68.32 °C. The mechanism has been elucidated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1243,1252, 2002 [source] Copolymerization of (2-phenyl-1,3-dioxolane-4-yl)methyl methacrylate with alkyl methacrylates: Reactivity ratios and copolymer characterizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2002Mehmet Co Abstract The radical copolymerizations of (2-phenyl-1,3-dioxolane-4-yl-)methyl methacrylate (PDMMA) with methyl methacrylate (MMA), ethyl methacrylate (EMA), and butyl methacrylate (BMA) were studied in dioxane at 60 °C with benzoyl peroxide as an initiator. The glass-transition temperatures of poly(PDMMA- co -MMA), poly(PDMMA- co -EMA), and poly(PDMMA- co -BMA) varied from 130 to 138 °C, from 100 to 134 °C, and from 63 to 122 °C, respectively, depending on the copolymer composition. Along with some physicochemical properties and thermal stability investigations of the copolymers, the monomer reactivity ratios were also determined with the conventional Finemann,Ross and Kelen,Tüdös linearization methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1184,1191, 2002 [source] Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two-dimensional nuclear magnetic resonance spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2001A. S. Brar Abstract Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from 1H NMR spectra, and comonomer reactivity ratios were determined by the Kelen,Tudos (KT) method and the nonlinear least-squares error-in-variable method (EVM). The reactivity ratios obtained from KT and EVM were rG = 37.4 ± 12.0 and rV = 0.036 ± 0.019 and rG = 35.2 and rV = 0.03, respectively. Complete spectral assignments of 13C and 1H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two-dimensional 13C,1H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051,4060, 2001 [source] Monitoring the synthesis of new polymer nanocomposites based on different polyhedral oligomeric silsesquioxanes using Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 11 2009Nicoleta Mihaela Sulca Abstract The kinetic behavior of the urethane dimethacrylate (UDMA) copolymerized and reinforced by different concentrations of polyhedral oligomeric silsesquioxane (POSS) with methacrylic groups was studied through Raman spectroscopy. UDMA-POSS networks have been synthesized with three different types of POSS, two monofunctional POSS (1-propylmethacrylate)-heptaisobutyl substituted (HISO-POSS) and heptacyclopentyl-octasiloxan-1-yloxy) dimethylsilyl] propyl methacrylate (CPENTYL-POSS) and one octafunctional POSS-methacryl substituted (MA-POSS). In order to show the influence of POSS on the final conversion, the hybrid systems were cured using three types of initiators which decompose at different temperatures: azobisisobutyronitrile (AIBN) (65 °C), benzoyl peroxide (BP) (80 °C) and di- tert -butyl peroxide (DTBP) (120 °C). The structure of the hybrid's surface was investigated by X-ray photoelectron spectroscopy (XPS) and the Tg values were calculated from dynamic mechanical analysis (DMA) tests. Copyright © 2009 John Wiley & Sons, Ltd. [source] Prospective, open-label, comparative study of clindamycin 1%/benzoyl peroxide 5% gel with adapalene 0.1% gel in Asian acne patients: efficacy and tolerabilityJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 3 2009H-C Ko Abstract Background, Used as individual agents, topical antibiotics and benzoyl peroxide are known to be effective in treatment of acne. Clindamycin phosphate 1% with benzoyl peroxide 5% (CDP/BPO) is a new combination gel, made by rationale, in that combination drug is more effective than either ingredients used alone. Adapalene 0.1% (ADA) is the third-generation retinoid, shown to be as effective as other topical retinoid with well tolerability. Objectives, To compare the efficacy and tolerability in combination of CDP/BPO in comparison with ADA in Asian patients with mild to moderate acne vulgaris. Methods, Total of 69 patients, including 31 patients for CDP/BPO group and 38 for ADA group, with mild to moderate acne vulgaris were enrolled for a 12-week prospective, randomized, open-label comparative study of topical agents. Efficacy was assessed by lesion counts, acne grading system, and global improvement. Adverse events were also evaluated in scale of 0 (none) to 3 (severe). Results, Both CDP/BPO and ADA were effective in reducing lesion counts and acne severity scale and showed significant global improvement. However, CDP/BPO offered greater efficacy against inflammatory lesions than ADA. Both drugs were well tolerated with minimal adverse drug reactions. Conclusion, Combination formulation of CDP/BPO and ADA were shown to be both effective in decreasing total, inflammatory, and non-inflammatory lesion counts along with well tolerability in Asian patients with mild to moderate acne vulgaris. Conflicts of interest None declared [source] Synthesis of Polypyrrole Using Benzoyl Peroxide as a Novel Oxidizing AgentMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2006Chandrasekaran Saravanan Abstract Summary: Benzoyl peroxide is used as an oxidizing agent for the first time in the synthesis of conducting polypyrrole. Synthesis of polypyrrole is commonly performed by chemical oxidative polymerization using water-soluble oxidizing agents. In this work, polypyrrole was prepared using organic solvent-soluble benzoyl peroxide as an oxidizing agent in the presence of p -toluenesulfonic acid (p -TSA) and sodium lauryl sulfate (SLS) surfactant via the inverted-emulsion-polymerization technique. During polymerization, SLS is converted to dodecyl hydrogensulfate (DHS) and incorporated on to polypyrrole along with p -TSA dopant, indicating SLS is acting as emulsifier as well as dopant. The influence of synthesis conditions such as the duration of the reaction, the temperature, the concentration of the reactants, etc., on the properties of polypyrrole was investigated to determine the optimum conditions for the synthesis of polypyrrole salt. Polypyrrole was obtained in a reaction time of 1 h with high yield (154 wt.-% with respect to pyrrole used) and good conductivity (2 S,·,cm,1). The conductivity of polypyrrole-salt was found to be nearly the same even after seven months of storage at ambient temperature (1.7 S,·,cm,1). [source] A Facile Method for Grafting Polymerisation of Acrylonitrile onto LDPE Film with High Grafting EfficiencyMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2006Jianwu Zhu Abstract Summary: A facile and effective surface grafting polymerisation method was designed and investigated to graft acrylonitrile (AN) onto low-density polyethylene (LDPE) film using benzoyl peroxide (BPO) as an initiator. This method consisted of two steps. In the first step, BPO was adsorbed on the surface of LDPE film by immersing LDPE film in BPO solution; in the second step, grafting polymerisation of AN onto LDPE film was carried out under heat. Because the grafting polymerisation was carried out with AN in vapour phase and the concentration of AN was very low, the homopolymerisation of AN could be effectively suppressed and therefore the grafting efficiency was very high (approaching 100%). Grafting percent (Gp) could be controlled from 0 to 118% by adjusting reaction conditions in the first step and/or in the second step respectively. A possible model was proposed to interpret the experimental results. Schematic procedure and chemistry for grafting polymerisation of AN on LDPE film. [source] Effect of different types of peroxides on properties of vulcanized EPDM + PP blendsPOLYMER COMPOSITES, Issue 10 2010Witold Brostow Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [source] Maleated polypropylene film and wood fiber handsheet laminates,POLYMER COMPOSITES, Issue 12 2009Sangyeob Lee The grafting effect of maleic anhydride (MA) as an interfacial bonding agent and its influence on the tensile strength properties of thermomechanical pulp handsheet-isotactic polypropylene (iPP) film laminates was studied. For the MA treated with benzoyl peroxide (BPO) as an initiator, tensile strength properties increased 76% with PP film over untreated laminates. The optimal strength properties were obtained with a MA and BPO ratio of 2:1. A strong correlation was observed between the number of fibers in the web and tensile strength properties for both handsheet drying conditions. The R2 values were 0.95 for air-dry conditions and 0.94 from oven-dry conditions. Scanning electron microscopy images also showed the effectiveness of MA loading on the surface of thermomechanical pulp fibers due to increased fiber failure, which occurred without fiber being pulled out from the PP matrixes. Crystallinity and heat flow were determined using differential scanning calorimetry (DSC) and increased as expected as the ratio of MA and BPO increased from 0:0 to 2:1. These results were also in accordance with the morphological observations at the fracture surface, Fourier transform infrared spectra, and thermal analysis. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Investigation of redox initiators for free radical frontal polymerizationPOLYMER INTERNATIONAL, Issue 8 2009Huan Yu Abstract BACKGROUND: The reaction temperature for frontal polymerization (FP) initiated by redox initiators can be greatly decreased compared with FP initiated by peroxide initiator and disulfide initiator. We report the synthesis of poly(hydroxyethyl acrylate)s via free radical FP using benzoyl peroxide (BPO)/N,N -dimethylaniline (DMA) and ammonium persulfate (APS)/N,N,N,,N,-tetramethylethylenediamine (TMEDA) couples as redox initiators at ambient pressure. RESULTS: The results show that unlike the phenomenon of bubbles and ,fingers' when using BPO alone, a self-sustaining and stable front can be obtained when the [DMA]/[BPO] ratio is higher than 1 (mol/mol). A slight increase of the DMA (or TMEDA) reductant concentration causes a marked decrease of front temperature to 53 °C (or 61 °C). CONCLUSION: We investigated the effects of the ratio of the oxidant to the reductant and the initiator and monomer concentrations on certain parameters of FP: formation of bubbles, front velocity and front temperature. This opens the way to the potential development of FP using more appropriate monomers with low boiling points. Copyright © 2009 Society of Chemical Industry [source] Novel AB crosslinked polymer networks based on 1-vinylimidazole- terminated polyurethane and poly(methyl methacrylate)POLYMER INTERNATIONAL, Issue 11 2006Sriram Venkataramani Abstract 1-Vinylimidazole-terminated telechelic polyurethanes were prepared from 1-vinylimidazole and bromine-terminated polyurethane. This vinyl-terminated telechelic polyurethane (VTPU) and methyl methacrylate were polymerized in the presence of benzoyl peroxide to prepare novel AB crosslinked polymer networks (ABCPs). These were characterized by spectral, thermal and mechanical studies. The absence of the characteristic peak of vinyl group in infrared spectra of ABCP films confirms the occurrence of crosslinking. Static mechanical testing showed that the tensile strength of ABCP increases with increasing poly(methyl methacrylate) content. Dynamic mechanical studies revealed that ABCPs, at equal compositions of VTPU and methyl methacrylate, show good damping properties. Copyright © 2006 Society of Chemical Industry [source] Modification of polystyrene properties through grafting with N -vinylcarboxamido-2-methylpropane sulfonic acid monomerPOLYMER INTERNATIONAL, Issue 12 2004A Aggour Abstract Polystyrene (PS) possesses good mechanical properties, but its surface is relatively inert and hydrophobic. Grafting of N -vinylcarboxamido-2-methylpropane sulfonic acid (VCMP) is useful to hydrophilize the PS surface. Grafting was performed using benzoyl peroxide (BPO) as an initiator in toluene:methanol solvent mixture (3:1 volume ratio). The influence of the main factors on grafting, such as temperature, time, concentrations of initiator, PS and VCMP, has been studied. The results show that the initial rate of polymerization and percentage of grafting are enhanced by increased temperature. Furthermore, the specific rate constants of the first order reaction/are determined, and the activation energy of the grafting reaction is estimated. The grafting parameters are established and a suitable mechanism of the reaction is proposed. The grafted PS is to characterized through infrared spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential gravimetric analysis (DTG). The kinetics of thermal degradation and the order of the thermal stabilities are given. Also the decomposition activation energies of the thermal degradation are determined, and confirm the thermal stabilities of the polymers used. © 2004 Society of Chemical Industry [source] | ||||||||||||||||