Presence Of Free Radical Initiator Research Articles

The Synthesis and Characterization of Polyacrolein through Radical Polymerization

AbstractA radical polymerization reaction of acrolein is reported in this article. The free radical initiator which can effectively promote the free radical polymerization of acrolein is screened out. The optimal conditions of the reaction are investigated and the yield could be up to 93.67%, in which the ratio of initiator to monomer is 1:50, monomer concentration is 7.5 mol L−1, reaction temperature is 50 °C, and the reaction time is 6 h. The structure characterizations of the obtained polymers are performed using hydrogen nuclear magnetic resonance spectroscopy, fouriertransform infrared spectroscopy, and matrix‐assisted laser desorption ionization time of fligh mass spectroscopy. The results show that the structure of the polymer contains fragments generated by decomposition of the initiator, aldehyde groups, and vinyl groups. The reaction mechanism of acrolein polymerization in the presence of free radical initiator is proposed. Thus, a novel method for the preparation of polyacrolein via radical polymerization is provided in this article.

Biobased Poly-phosphonate Additives from Methyl Linoleates

Poly-dialkyl phosphonates were synthesized by reacting methyl linoleate with dimethyl, diethyl, and di-n-butyl phosphites in the presence of free radical initiator and positively identified and characterized using gas chromatography–mass spectrometry (GC-MS), nuclear magnetic resonance (NMR; 1H, 13C, 31P), and Fourier transform infrared (FTIR). Neat poly-dialkyl phosphonates and their blends in high-oleic sunflower oil (HOSuO) and polyalphaolefin (PAO-6) base oils were investigated for their physical, chemical, and tribological properties. At room temperature, the poly-dialkyl phosphonates displayed much better solubility in HOSuO than in PAO-6. Solubility in the base oils increased in the order dimethyl < diethyl < di-n-butyl. Relative to methyl linoleate, the neat poly-dialkyl phosphonates displayed higher density, higher kinematic viscosity, higher oxidation stability, and better cold flow (lower pour point and cloud point) properties. As an additive (0–10% w/w) in HOSuO, increasing concentration of poly-di-n-butyl phosphonate resulted in increasing onset and peak oxidation temperatures and decreasing cloud point. Poly-di-n-butyl phosphonate blends in HOSuO also showed lower four-ball antiwear (AW) coefficient of friction (COF) and wear scar diameter (WSD) than corresponding blends with zinc dialkyl dithiophosphate (ZDDP). As an additive (0–10% w/w) in PAO-6 base oil, poly-di-n-butyl phosphonate displayed lower four-ball antiwear COF and comparable WSD relative to similar blends of ZDDP in PAO-6. The results indicate that poly-dialkyl phosphonates are promising biobased AW additives with comparable or better performance than current petroleum-based commercial AW additives such as ZDDP.

Novel hybrid biosorbents of agar: Swelling behaviour, heavy metal ions and dye removal efficacies

Agar based hybrid biosorbents were synthesized by free radical copolymerization of acrylamide, NN′-methylenebisacrylamide (NN′MBAAm) on the agar backbone in presence of free radical initiator (ceric ammonium nitrate (CAN)) via oxidation, grafting and crosslinking reactions. The resultant hybrid materials have been characterized by FTIR spectroscopy, elemental analysis, thermal analysis (TGA/DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) taking agar as a reference. The swelling responses of hybrid materials have been extensively studied with various pH, time, temperature and ionic strength [NaCl] of the solution. These hybrid materials have been utilized for selective removal of heavy metal ions (Fe(III), Cr(III), Ni(II) and Mn(II)) and dye (methylene blue) through adsorption mechanism by formation of complex between the functional groups of biosorbent and metal ions & dye. These hybrid materials showed excellent results with their potential applications for environmental remediation from the textile effluents and heavy metal ions contaminated water bodies.

Antibacterial coating on in-line suction respiratory catheter to inhibit the bacterial biofilm formation using renewable cardanyl methacrylate copolymer

Health-care materials associated with infections are very common in hospital admitted patients. There are generally infected by contact with the catheter or other multipurpose devices which are contacted with microbes. The respiratory infections associated with the pathogens having strong biofilm forming ability on catheter surface, causes life-threatening in every year. Therefore, a catheter coating material is of great interest which inhibits the biofilm formation of pathogens on a catheter to prevent respiratory infections. In this study, we synthesized cardanol containing copolymers as antimicrobial healthcare material via radical polymerization of cardanyl methacrylate (CMA) with styrene (St) monomer in presence of free radical initiator. The rate of polymerization was drastically reduced with the increase of feeding CMA monomer in copolymer. The thermal and mechanical properties were found to increase with incorporation of cardanol moiety in brittle and hard polystyrene. This soft copolymer was grafted onto polyvinyl chloride respiratory catheter which showed high antibacterial activity, inhibit the biofilm formation and also prevent bacterial adhesion. Therefore, the developed coating material on respiratory catheter surface is effective way to control the respiratory catheter-associated nosocomial infections.

Photo Polymerization Of Methyl Methacrylate In Homogeneous Aqueous Medium By Host-Guest Complexation With Β- Cyclodextrin

Photo polymeruization of Methyl Methacrylate (MMA) by host-guest complexation with β-cyclodextrin was investigated in homogeneous aqueous medium. Vinyl monomers like MMA, Styrene etc. become water soluble due to complexation with β-CD and can easily be polymerized in aqueous solution in the presence of free radical initiator. Polymerization was also carried out with uncomplexed monomer and in presence of organic solvent. A systematic study of the kinetics of photosensitized polymerization of MMA with dye (acriflavin) , reducing agent(ascorbic acid) under buffered condition (Na2HPO4 – citric acid) in presence of β-CD in aqueous solution has been made against the different variables like concentration of monomer, dye, ascorbic acid, time and temperature. Presence of β-CD showed obviously effects on the polymerization, so as to increase the rate of polymerization and percentage conversion of monomer, increase of molecular weight of polymer. The mechanism of polymerization and kinetic scheme proposed was examined in the light of the experimental results. Thermal degradation pattern of the polymer sample was studied by thermo gravimetric analysis.

2-Acrylamido-2-methyl-1-propanesulfonic Acid Grafted Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Acid-/Oxidative-Resistant Cation Exchange for Membrane Electrolysis.

For developing acid-/oxidative-resistant aliphatic-polymer-based cation-exchange membrane (CEM), macromolecular modification of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) was carried out by controlled chemical grafting of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). To introduce the unsaturation suitable for chemical grafting, dehydrofluorination of commercially available PVDF-co-HFP was achieved under alkaline medium. Sulfonated copolymer (SCP) was prepared by the free radical copolymerization of dehydofluorinated PVDF-co-HFP (DHPVDF-co-HFP) and AMPS in the presence of free radical initiator. Prepared SCP-based CEMs were analyzed for their morphological characteristics, ion-exchange capacity (IEC), water uptake, conductivity, and stabilities (mechanical, chemical, and thermal) in comparison with state-of-art Nafion117 membrane. High bound water content avoids the membrane dehydration, and most optimal (SCP-1.33) membrane exhibited about ∼2.5-fold high bound water content in comparison with that of Nafion117 membrane. Bunsen reaction of iodine-sulfur (I-S) was successfully performed by direct-contact-mode membrane electrolysis in a two-compartment electrolytic cell using different SCP membranes. High current efficiency (83-99%) confirmed absence of any side reaction and 328.05 kJ mol-H2(-1) energy was required for to produce 1 mol of H2 by electrolytic cell with SCP-1.33 membrane. In spite of low conductivity for reported SCP membrane in comparison with that of Nafion117 membrane, SCP-1.33 membrane was assessed as suitable candidate for electrolysis because of its low-cost nature and excellent stabilities in highly acidic environment may be due to partial fluorinated segments in the membrane structure.

Tribological Properties of Limonene Bisphosphonates

Limonene was chemically modified by reacting it with dialkyl phosphites of varying alkyl structures under inert atmosphere in the presence of free radical initiators. The reaction gave a mixture of mono- and di-adduct products and was optimized to produce only the di-adduct product limonene bisphosphonate by forcing both limonene double bonds to react completely. The product mixture was carefully characterized using a combination of gas chromatography–mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance spectroscopy (1H, 13C, 31P). The bisphosphonates were investigated for their physical and tribological properties. The alkyl bisphosphonates displayed density and viscosity that was a function of the alkyl structure (methyl, ethyl, n-butyl) and much higher than the values for the unreacted limonene. They also displayed improved oxidation stability but lower viscosity index and solubility in polyalphaolefin (PAO6) and high-oleic sunflower oil (HOSuO) base oils. Tribological characterization of the neat modified oils on a four-ball tribometer showed improved extreme-pressure weld point by all three di-adducts and improved anti-wear coefficient of friction (COF) and wear scar diameter (WSD) by the n-butyl di-adduct only. The limonene bisphosphonates also displayed improved COF and WSD as additives in PAO6 and HOSuO base oils at low concentrations. The effects of chemical modifications on physical and tribological properties can be explained in terms of increased polarity of the modified products, insertion of heavy atoms (from PO3) into the limonene structure, and complete absence of unsaturation in the modified products.

Fluorogenic α-Tocopherol Analogue for Monitoring the Antioxidant Status within the Inner Mitochondrial Membrane of Live Cells

We report here the preparation of a lipophilic fluorogenic antioxidant (Mito-Bodipy-TOH) that targets the inner mitochondrial lipid membrane (IMM) and is sensitive to the presence of lipid peroxyl radicals, effective chain carriers in the lipid chain autoxidation. Mito-Bodipy-TOH enables monitoring of the antioxidant status, i.e., the antioxidant load and ability to prevent lipid chain autoxidation, within the inner mitochondrial membrane of live cells. The new probe consists of 3 segments: a receptor, a reporter, and a mitochondria-targeting element, constructed, respectively, from an α-tocopherol-like chromanol moiety, a BODIPY fluorophore, and a triphenylphosphonium cation (TPP). The chromanol moiety ensures reactivity akin to that of α-tocopherol, the most potent naturally occurring lipid soluble antioxidant, while the BODIPY fluorophore and TPP ensure partitioning within the inner mitochondrial membrane. Mechanistic studies conducted either in homogeneous solution or in liposomes and in the presence of free radical initiators show that the antioxidant activity of Mito-Bodipy-TOH is on par with that of α-tocopherol. Studies conducted on live fibroblast cells further show the antioxidant depletion in the presence of methyl viologen (paraquat), a known agent of oxidative stress and source of superoxide radical anion (and indirectly, a causative of lipid peroxidation) within the mitochondria matrix. We recorded a ca. 8-fold emission enhancement with Mito-Bodipy-TOH in cells stressed with methyl viologen, whereas no enhancement was observed in control studies with untreated cells. Our findings underscore the potential of the new fluorogenic antioxidant Mito-Bodipy-TOH to study the chemical link between antioxidant load, lipid peroxidation and mitochondrial physiology.

Functionalization of Low Density Polyethylene with Ethyl Crotonate and Ethyl Salicylate in the Presence of Free Radical Initiator: FTIR-RI Kinetics Study

Functionalization of Low Density Polyethylene with Ethyl Crotonate and Ethyl Salicylate in the Presence of Free Radical Initiator: FTIR-RI Kinetics Study

Identification and optimization of novel pyrimido-isoxazolidine and oxazine as selective hydride donors

Two novel carbon skeletons (3S,3a′R)-6′-(methylthio)-5′,7a′-dihydro-1′H-spiro[indoline-3,3′-isoxazolo[3,4-d]pyrimidine]-2,4′(3a′H)-dione (11a) and 3-(methylthio)-4a,5,7,11c-tetrahydropyrimido[4′,5′:3,4][1,2]oxazino[6,5-b]indol-1(2H)-one (12a) are characterized as hydride donors. The generation of these hydride sources during the spiroannulation reaction between isatin (4) and pyrimidine (5) through the free radical mechanism, was confirmed by (i) the increase in the stoichiometric yields of 11 and 12 when the same reaction was carried out in the presence of free radical initiators (e.g., mCPBA) and (ii) the formation of oxazepine (14) when AIBN was used as free radical initiator. The PKIE [KH/KD] values 4.5 and 4.9 obtained when deuterated 11a (d) was used in the presence of TFA and TFA-d, respectively, suggest the hydride transfer step to be the rate determining step. These hydrides donors selectively reduce aldehyde in the presence of other reducible groups.

Free Radical Initiation Copolymerization of Glucose-with MMA and Analysis of its Thermal Stability

D-glucose was used to react with methyl methacrylate (MMA) (and methyl acrylate(MA) as comparison) to generate new biomass-based materials in presence of free radical initiator. Potassium peroxydisulfate was used as free-radical initiator in the reaction. The final chemical structure and thermal stability were analyzed by FT-IR and TGA. The results showed that the Glucose-co-MMA (G-MMA) and Glucose-co-MA (G-MA) copolymers had better thermal performance than PMMA and PMA.

Low protein fouling polypropylene membrane prepared by photoinduced reversible addition‐fragmentation chain transfer polymerization

AbstractIn this study, 2‐hydroxyethyl methacrylate and N‐isopropyl acrylamide was block grafted onto the polypropylene macroporous membrane surface by photo‐induced reversible addition‐fragmentation chain transfer (RAFT) radical polymerization with benzyl dithiobenzoate as the RAFT agent. The degree of grafting of poly(2‐hydroxyethyl methacrylate) on the membrane surface increased with UV irradiation time and decreased with the chain transfer agent concentration increasing. The poly(2‐hydroxyethyl methacrylate)‐ grafted membranes were used as macro chain transfer agent for the further block graft copolymerization of N‐isopropyl acrylamide in the presence of free radical initiator. The degree of grafting of poly(N‐isopropyl acrylamide) increased with reaction time. Furthermore, the poly(2‐hydroxyethyl methacrylate)‐ grafted membrane with a degree of grafting of 0.48% (wt) showed the highest relative pure water flux and the best antifouling characteristics of protein dispersion. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A Preliminary Study on Ultraviolet Radiation-Cured Unsaturated Polyester Resin Based on Palm Oil

Unsaturated polyester resins (UPR) based on palm oil were synthesized from various ratios of monoglyceride/maleic anhydride using polycondensation technique. The chemical structures of MG as well as the resulting polymer matrices were confirmed by spectral FTIR. The ultraviolet (UV) curing behaviours of the resulting UPR with styrene were carried out in the presence of free radical initiator using UV machine. Preliminary studies of the UPR were evaluated by measuring their iodine number test, gel content, pendulum hardness and mechanical properties. From the results, the tensile strength of the cured polyester increased to a threshold value, after which it decreased.

Development of a novel RAFT-UV grafting technique to modify polypropylene membrane used for NOM removal

Surface modification of polypropylene microporous membrane was conducted by reversible addition-fragmentation chain transfer (RAFT) polymerization under UV irradiation. Dibenzyltrithiocarbonate was used as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy and filed emission scanning electron microscopy were used to characterize the structural and morphological changes on the membrane surface. The degree of grafting of poly(acrylic acid) (PAAc) on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. Surface-initiated block graft copolymerization with acrylamide was carried out on the PAAc modified membrane surface in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. The degree of grafting of polyacrylamide (PAAm) increased with the reaction time. These results demonstrated that block graft copolymer of PAAc and PAAm on the membrane surface was accomplished by the combination of UV irradiation and the surface-initiated RAFT method. The pure water flux through the PAAc grafted membranes increased with the degree of grafting up to 0.67 wt.%, and then it decreased. The membrane filtration of natural organic matter from the Yangtze River showed that the degree of grafting played a very important role. Reduction from pure water flux was lower, the flux recoveries after water and caustic cleaning and flux ratios after fouling were higher for the modified membrane than those of the unmodified membrane. The PAAc grafted PPMM with a degree of grafting of 2.51 wt.% possessed the best antifouling characteristics. The high hydrophilicity, high permeability, and low fouling character of the modified membranes make microporous polypropylene membranes desirable for water treatment.

Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversible addition–fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl acrylamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) and poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The grafting chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membranes containing macro-chain transfer agents, or the living membrane surfaces were further functionalized via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc grafted membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT method could be accomplished under UV irradiation and the process possessing the living character. The PPMMs with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability to aqueous media.

Effect of both silane‐grafted and ion‐exchanged organophilic clay in structural, thermal, and mechanical properties of unsaturated polyester nanocomposites

AbstractUnsaturated polyester (UPE) resin including styrene monomer was mixed with organophilic montmorillonite (MMT) clay and its crosslinking polymerization reaction was done in the presence of free‐radical initiator. MMT clay was modified with cetyl trimethly ammonium bromide and trimethoxy vinyl silane. The nanocomposites were characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), thermogravimetric and dynamic mechanical analyses (TGA and DMA). The exfoliated nanocomposite structure was obtained when the MMT clay was modified in the presence of both modifiers, whereas individual modifications all resulted in intercalated structures. The exfoliated UPE nanocomposite exhibited better thermal and dynamic mechanical properties when compared with pure UPE and other composites, even with 3 wt% clay loading. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Highly Efficient Ambient‐Temperature Copper‐Catalyzed Atom‐Transfer Radical Addition (ATRA) in the Presence of Free‐Radical Initiator (V‐70) as a Reducing Agent

Copper can do it! Highly efficient ambient-temperature copper-catalyzed ATRA of polyhalogenated compounds to alkenes in the presence of free-radical initiator 2,2′-azobis(4-methoxy-2,4-dimethyl valeronitrile) (V-70) is reported. V-70 has been shown to be a very effective reducing agent, enabling selective formation of the ATRA product with α-olefins and highly active monomers, such as methyl acrylate, methyl methacrylate, and vinyl acetate, by using as little as 0.002 mol % of copper (see figure).

Methyl acrylate/1‐octene copolymers: Lewis acid‐mediated polymerization

AbstractCopolymerization of methyl acrylate (MA) with 1‐octene (1‐Oct) was conducted in the presence of free radical initiator, 2,2′‐azobis(2‐methylpropionitrile) (AIBN) using heterogeneous Lewis acid, acidic alumina. The polymers obtained were transparent and highly viscous liquids. The copolymer composition calculated from 1H NMR showed alkene incorporation in the range of 10–61%. The monomodal nature of chromatographic curves corresponding to the molecular weight distribution in gel permeation chromatography (GPC) further confirmed that the polymers obtained are true copolymers. The number–average molecular weights (Mn) of the copolymers were in the range of 1.1 × 104–1.6 × 104 with polydispersity index of 1.75–2.29. The effects of varying the acidic alumina amount, time of polymerization, and monomer infeed on the incorporation of 1‐Oct in the polymer chain were studied. Increased 1‐Oct infeed led to its higher inclusion in the copolymer chain as elucidated by NMR. DEPT‐135 NMR spectral analysis was used to explicate the nature of arrangement of monomer sequences in the copolymer chain. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Grafting of glycidyl methacrylate onto high-density polyethylene with reaction time in the batch mixer

The melt grafting of glycidyl methacrylate (GMA) onto high-density polyethylene (HDPE) in the presence of free radical initiators was investigated in the batch mixer. The graft content was determined with the titration and FTIR spectroscopy. The graft content increased with the increase of peroxide and initially introduced GMA concentration. Increase of the grafted GMA content resulted in decrease of the melt index. Interestingly, there was a sudden drop of GMA grafting content with the reaction time. It is assumed that depolymerization of GMA have taken place over the ceiling temperature. The crystallinity of the prepared glycidyl methacrylate grafted high density polyethylene (HDPE-g-GMA) was determined by the measurement of the heat of fusion. GMA grafted site acted as defect and crystallinity of the HDPE-g-GMA decreased with the increase of grafting reaction.

Development and characterization of vinylated polyesteramide from non-edible seeds oils

Annona squamosa- and Pongamia glabra-based polyesteramides (ASPEA and PGPEA) have been reported as corrosion protective coatings. To improve their film properties such as curing, physico-mechanical and anticorrosive properties further, post-vinylation of these resins with styrene and vinyl acetate monomer in varying ratio (4:1, 3:1 and 2:1) was carried out in the presence of free radical initiator (benzoyl peroxide). The incorporation of styrene and vinyl acetate in ASPEA/PGPEA was confirmed by FTIR and 1H NMR spectral techniques. Physico-chemical, physico-mechanical and anticorrosive properties were studied by standard methods. Thermal stability and curing behaviour of vinylated ASPEA/PGPEA was studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. It has been observed that vinylation of these resins improves the curing, physico-mechanical and anticorrosive performance of ASPEA/PGPEA films. Among all 2:1 ASPEA/PGPEA:styrene/vinyl acetate ratio exhibited best results.