Lauroyl Peroxide Research Articles

Sidewall functionalization of single-walled carbon nanotubes with organic peroxides.

Single-wall carbon nanotubes (SWNTs) and their fluorinated derivatives (F-SWNTs) were reacted with organic peroxides including benzoyl and lauroyl peroxide to produce phenyl and undecyl sidewall functionalized SWNTs, respectively, which were characterized by Raman, FTIR, and UV-Vis-NIR spectra as well as TGA/MS, TGA/FTIR, and TEM data.

Preparation of Nano Fe3O4/Polystyrene Composite Microspheres by in situ Polymerization

Carboxyl-functionalized magnetic microspheres were prepared by in situ polymerization of styrene and methyacrylic acid at 85°C in the presence of nano-Fe 3 O 4 in styrene, using lauroyl peroxide as an initiator. The effects of the surfactant, the weight ratio of magnetite to styrene, the amount of monomer and initiator on the polymerization reaction and microsphere properties were investigated in detail. Transmission electron microscopy showed the property of the surfactant on the surface of nano-Fe 3 O 4 determined the magnetite content and the distribution of the magnetite in the microspheres. The optimum conditions of the reaction were optimized. The adsorption result of bovine-γ IgG proves that the magnetic microspheres have a potential wide application in the biological field.

A Practical Radical Based Access to Functionalised Geminal Bisphosphonates

Xanthate derivatives of tetraalkylmethylenebisphos­phonate add efficiently to various functionalised olefins to give the corresponding adducts via a radical chain reaction initiated by a small amount of lauroyl peroxide.

A New Tin‐Free Source of Amidyl Radicals.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Dual curing of carbon fiber reinforced photoresins for rapid prototyping

AbstractPhoto‐thermal dual‐curing of a carbon fiber reinforced photoresin is reported in this study. The primary limitation of carbon fibers is that they are opaque to ultra‐violet (UV) light, and the resin present inside the carbon fiber tow remains uncured if only a photolytic mechanism is used. Therefore, a dual‐curing resin formulation was developed that consisted of acrylate ester of bisphenol A‐epoxy (primary resin), 1‐hydroxycyclohexyl phenyl ketone (a photoinitiator), and lauroyl peroxide (thermal initiator). The fibers were dispersed in the resin and photocured by UV radiation. Subsequently, the composites were thermally cured to solidify the resin present inside the fiber tow. Differential scanning calorimetry indicates that the thermal initiator activates at approximately 70°C. The dual‐cured composites, processed by a dip‐coating technique and also in a desktop photolithography unit, were tack‐free and fully solidified in the interior. Thus, it was established that by using a dualcuring resin formulation, the resin present outside and inside the carbon fiber tow could be cured to produce a carbon fiber reinforced photoresin. Such a reaction scheme has application in composite photolithography where incorporation of carbon fibers into photopolymers can enhance electrical and thermal conductivities of rapid tooling materials.

Tin-free radical sequences under acidic conditions. Convergent access to azole-containing structures.

[reaction: see text] Various xanthates add efficiently to olefins bearing [1,2,4]triazole, imidazole, or benzimidazole moieties in the presence of camphorsulfonic acid via a radical chain reaction initiated by a small amount of lauroyl peroxide. The adducts may be transformed to more complex molecules by implementing a further radical cyclization.

Amperometric Detection of Peroxides Using Peroxidase and Porphyrin Biomimetic Modified Electrodes

Biosensors designed with crosslinked redox hydrogel and horseradish peroxidase have been evaluated in aqueous and nonaqueous media. Electrodes made of a single layer of active material were prepared with Os(byp)2ClPyCH2NHPoly(allylamine) polymer, (PAA-Os), attached to the enzyme by PEG-400 bifunctional reagent with the Os sites acting as electron wires. The electrodes proved to be stable in the presence of organic solvent considering the time evolution of the redox charge and the catalytic current. However, a reasonable decrease in the enzyme response is apparent while increasing solvent content in solution for detection of hydrogen and lauroyl peroxide. As an alternative biomimetic strategy, electrodes were modified with consecutive layers of PAA-Os and electropolymerized Fe-protoporphyrin IX. The electrochemical detection of peroxides was also possible with this system, proving that the poly[Fe-protoporphyrin IX]/Osmium complex system can mimic the peroxidase activity towards hydrogen and organic peroxides. The replacement of Fe-protoporphyrin by Ni-protoporphyrin IX and PAA-Os by PAA in different experiments demonstrates that the mechanism for peroxide reduction involves both Os and Fe-protoporphyrin IX sites. The enzymatic electrodes were applied to benzoyl peroxide quantitation in a pharmaceutical product. The method validation demonstrates that a simple and rapid FIA detection can be applied.

A new tin-free source of amidyl radicals.

[reaction: see text] The readily available N-(O-ethyl thiocarbonylsulfanyl)amides are powerful amidyl radical precursors that undergo 5-exo cyclization to give pyrrolidinone derivatives via a radical-chain reaction initiated by a small amount of lauroyl peroxide.

Preparation of a sensor device with specific recognition sites for acetaldehyde by molecular imprinting technique

In order to prepare a quartz crystal microbalance (QCM) sensor device with an acetaldehyde-imprinted polymer layer, methyl methacrylate and ethylene dimethacrylate were polymerized with lauroyl peroxide in chloroform containing acetaldehyde. This resulted in the formation of a polymer layer having a recognition side for the acetaldehyde on the quartz crystal oscillator. When an acetaldehyde aqueous solution was dropped into the solution in which the sensor is immersed, good sensitivity and response were observed. The good selectivity was also proved by testing the sensor in an acetone, chloroform or trichloroethane aqueous solution.

Polymerization of methyl methacrylate in the presence of N-acetyl-ε-aminocaproic acid acetylamide

The effect of N-acetyl-e-aminocaproic acid acetylamide on radical polymerization of methyl methacrylate initiated with lauroyl peroxide was studied.

Reactivity of Hydrogenated Diamond Surface with Radical Initiators Generating Organic Oxygen Radical Species.

Reactivity of hydrogenated diamond surface was investigated with peroxide radical initiators. The radical initiators used in this study were diacyl peroxide (R-COO-OOC-R) and dialkyl peroxide (R3CO-OCR3). Hydrogen abstraction reaction of hydrogenated diamond surface was attempted in liquid phase using these radical initiators. The radical species generated from diacyl peroxide such as benzoyl peroxide and lauroyl peroxide could extract the hydrogen atoms from the diamond surface, regardless of the kind of solvent. From the results of the spectra, we presume that the functional group is related to the radical species introduced on the diamond surface. On the other hand, the radical species generated from dialkyl peroxide such as di-t-butyl peroxide and dicumyl peroxide did not fully extract the hydrogen atoms from the diamond surface, regardless of the kind of solvent. Although oxygen radicals are generated from both diacyl peroxide and dialkyl peroxide, the molecular structure of the generated radical species is different for each radical species. The radical species generated from diacyl peroxide is R-COO·, and the radical species generated from dialkyl peroxide is R3CO·. It was revealed that the reactivity of hydrogenated diamond surface with radical species depended not on the functional group in the radical initiator but on the molecular structure of the generated radical species.

Development of Conducting Composite Materials for Electrochemical Sensing in Organic Media

Several electrochemical transducers have been developed for use in organic media. These transducers are based on rigid conducting dispersed composites prepared from a mixture of graphite powder in a polymer matrix. The behavior of composites based on silicone, several epoxies, polyester and polyurethane was studied in organic solvents like acetone, acetonitrile, ethanol, chloroform and tetrahydrofuran. The composites were characterized using cyclic voltammetry and were calibrated with ferrocene. Composites with silicone or epoxy showed a high stability in organic solvents. These composites have a homogeneous surface and they show high stability and reproducibility while performing electrochemical measurements. The surface of these devices can be renewed by a simple polishing procedure using alumina paper. The plastic nature of these materials makes them modifiable, permitting the incorporation of fillers before they are cured. To test their capacity for biosensing in organic media, the matrix of one transducer was biologically modified with horseradish peroxidase (HRP) producing a graphite-epoxy-HRP biocomposite. A biosensor built with this material responded linearly to lauroyl peroxide between 10−6 and 10−5 M in acetonitrile and the enzyme remained stable in the biocomposite.

Syntheses, antitumour activities and antiangiogenesis of 1,2,3-tris(ethoxycarbonyl)-2-propyl acrylate and its polymers

A new monomer, 1,2,3-tris(ethoxycarbonyl)-2-propyl acrylate (TPA), was synthesized by reaction of acryloyl chloride and triethyl citrate. The homopolymer of TPA and its copolymers with acrylic acid (AA), vinyl acetate (VAc) and maleic anhydride (MAH) were prepared by polymerization using lauroyl peroxide (LPO) at 70 °C for 24 h. The structures of TPA and its polymers were identified by FTIR, 1H NMR, 13C NMR spectroscopies, and elemental analysis. The number average molecular weights and polydispersity indices of the synthesized polymers determined by GPC were in the range 4200–23 000 g mol−1 and 1.1–2.1, respectively. The IC50 values of the synthesized samples against cancer cell lines were greater than those of 5-fluorouracil (5-FU). The percentage inhibition values of SV40 DNA replication were 82.2 for TPA, 34.3 for poly (TPA), 81.9 for poly(TPA-co-AA), 82.0 for poly(TPA-co-VAc), 35.6 for poly(TPA-co-MAH) and 12.7 for 5-FU. The inhibitions of SV40 DNA replication and antiangiogenesis for the synthesized TPA and its polymers are much greater than those of the control. © 2001 Society of Chemical Industry

Polyether-Modified Poly(acrylic acid): Synthesis and Applications

Poly(acrylic acid) (PAA) copolymers modified with block-copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) are inherently attractive for medicinal applications as their components are considered pharmaceutically safe. The laboratory-scale synthesis of poly(acrylic acid) bonded onto a PEO−PPO−PEO triblock (Pluronic) backbone via dispersion polymerization is reported. Initial optimization of the synthesis defines appropriate levels of initial loading of acrylic acid and Pluronic, with a mixture of 2,2‘-azobis(2,4-dimethylpentanenitrile) and lauroyl peroxide as an initiator system. The synthesis results in a copolymer with low residual monomer content and a very high degree of bonding between Pluronic and PAA. Diluted aqueous solutions of Pluronic-g-PAA exhibit rapid thermogelation. Rheological parameters of the copolymers urge on their ophthalmic applications.

Investigation of dual-staged polymerization and secondary forming of photopultruded, fiber-reinforced, methacrylate-copolymer composites.

To develop a dual-curing monomer system for the photopultrusion of reformable (soft) composites, a microhardness assay showed that in a blend with 2,2-Bis[4-2-hydroxy-3-methacryloxypropoxy)phenyl] propane (Bis-GMA), the substitution of methyl methacrylate (MMA) for triethylene glycol dimethacrylate (TEGDMA) delayed the onset of gelation during photopolymerization. Adding lauroyl peroxide permitted the completion of polymerization thermally. This system was used to form silicate-glass-fiber-reinforced composites, with varying degrees of conversion, by photopultruding over a range of pulling speeds. Sol-gel extractions demonstrated both fully soluble and insoluble matrices. For the soluble material, gel permeation chromatography elucidated a trimodal distribution of molecular weights that corresponded to MMA, Bis-GMA, and polymeric molecules with molecular weights in the tens of thousands. Composites with matrix solubilities above about 10% wt could be swaged after photopultrusion to change the cross section from circular to rectangular before thermal processing. The effect on the final elastic modulus was small (-44GPa, as measured in flexure for 57% vol-reinforced composites); but the final flexure strength was reduced by approximately 25% to a constant of about 1.2 GPa. Morphological characteristics that were seen in the circular-sectioned precursors were observed in the swaged rectangular products as well, including flaws when swaging was conducted at matrix solubilities above about 75%.

Silica sol-gel immobilized amperometric enzyme electrode for peroxide determination in the organic phase

Abstract An amperometric enzyme electrode for peroxide determination in non-aqueous media has been constructed by the silica sol-gel immobilization of horseradish peroxidase (HRP) on a carbon paste electrode. Peroxides have been detected in the presence of ferrocene as the mediator in the organic phase to transfer electrons between the electrode surface and peroxides. The fabrication procedure of the enzyme electrode based on a sol-gel thin film derived from tetramethoxysilane has been optimized. The effect of operational parameters, such as different organic solvents, the amount of aqueous buffer in the organic solvent, mediator concentration and holding potential have been explored for the optimum analytical performance of the electrode. The electrode prepared using this immobilization technique has an excellent stability in some organic solvents, including methanol, acetonitrile and 2-propanol. The trend in the sensitivity of different peroxides is as follows: H 2 O 2 >lauroyl peroxide>butanone peroxide>tertbutyl-hydroperoxide. The apparent Michaelis–Menten constants ( K m app ) of the electrode in methanol for the above peroxides have been calculated. Applicability of the enzyme electrode for the measurement of hydrogen peroxide in real samples has been demonstrated. The results obtained by this electrode corroborate very well with the classical iodometric titration method for the determination of hydrogen peroxide.

Lauroyl Peroxide as a Cosurfactant in Miniemulsion Polymerization

Miniemulsion polymerizations have been carried out using only an oil-soluble initiator (lauroyl peroxide) as the cosurfactant. Diffusional instability was reduced to the point where nucleation in the monomer droplets and polymerization could be carried out before significant diffusional degradation of the droplets took place. The polymerization behavior was that expected in miniemulsion polymerization with more conventional cosurfactants.

A new synthesis of α-tetralones

α-tetralones 8a-j can be prepared by radical cyclisation, in the presence of stoichiometric amounts of lauroyl peroxide, of xanthates 5a-j obtained by an intermolecular addition of substituted S-phenacyl xanthates 4a-c to various olefins.

Functionalization of isotactic poly(propylene) with maleic anhydride in the solid phase

AbstractThe influence of temperature and type of initiator on the grafting efficiency of maleic anhydride onto isotactic poly(propylene) powder under solid‐state reaction conditions was investigated. The level of bonded maleic anhydride was found to be about 20% higher using aliphatic peroxide, such as lauroyl peroxide, in contrast to dibenzoyl peroxide, dicumyl peroxide, 2,5‐dimethyl‐2,5‐di‐tert‐butylperoxyhexane or tert‐butyl perbenzoate as initiator.The higher grafting efficiency of maleic anhydride onto polyethylene when compared with poly(propylene) is accounted for by a higher kinetic length of the addition‐transfer chain reactions.

Ferrocene-Conjugated Polyaniline-Modified Enzyme Electrodes for Determination of Peroxides in Organic Media

The development and characteristics of a reagentless amperometric organic phase enzyme electrode (OPEE) employing covalently attached horseradish peroxidase and an electrochemically deposited ferrocene-modified polyaniline film on a glassy carbon electrode is reported. The covalent attachment of ferrocene to an electrochemically deposited insoluble polymer film provided a mechanism of preventing the leaching of ferrocene into the predominantly organic solvents, required for construction of reagentless OPEE. Hydrodynamic voltammetry studies showed that the response of the OPEE to hydrogen peroxides increased at higher cathodic potentials; however, interference due to molecular oxygen also increased. Interference of molecular oxygen was minimized when the OPEE was operated at an applied potential of -50 mV (or less negative) vs Ag/AgCl. The cathodic response of the OPEE was found to increase steeply when the aqueous buffer content of the acetonitrile was increased from 0% to 5 and then plateau with no further increase when the buffer content was increased to 30%. The dynamic properties of this enzyme electrode were exploited for the detection of micromolar concentrations of different peroxides in flow injection analysis were the sensitivity trend was lauroyl peroxide>hydrogen peroxide>2-butanone peroxide>cumene hydroperoxide>tert-butyl hydroperoxide. Applicability of the enzyme electrode for measurement of peroxide in real sample was demonstrated