Permeation Chromatography (permeation + chromatography)

Distribution by Scientific Domains

Kinds of Permeation Chromatography

  • gel permeation chromatography

  • Terms modified by Permeation Chromatography

  • permeation chromatography analysis

  • Selected Abstracts

    Use of the Surfmer 11-(Methacryloyloxy) undecanylsulfate MET as a Comonomer in Polystyrene and Poly(methyl methacrylate)

    P.C. Hartmann
    Abstract The polymerizable surfactant sodium 11-(methacryloyloxy) undecanylsulfate (MET) has been synthesized with high purity, and its thermal stability and phase transitions have been studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. MET has been copolymerized in solution with methylmethacrylate (MMA) or styrene (S), initiated by azo-bis-isobutyronitrile (AIBN). The copolymers thus obtained have been studied by Gel Permeation Chromatography (GPC), Transmission Electron Microscopy (TEM), and DSC. Due to the incompatibility between the polar head of the MET units and the non polar S or MMA units, MET units organize in the amorphous polymer matrix and arrange in lamellar structures. [source]

    Some biophysical properties of castor oil esterified with some acid anhydrides

    Mona A. Saied
    Abstract A series of castor oil adducts were synthesized by esterification of castor oil with acid anhydrides: phthalic, maleic and succinic anhydrides. The chemical structure of castor oil and the prepared adducts were characterized by means of IR and 1H,NMR spectroscopy. The number-average and weight-average molecular weights were measured by gel permeation chromatography. The electrical properties were studied through the permittivity, dielectric loss and conductivity measurements, which are considered to be in the range of electrical insulation. The electrical conductivity, which describes the ionic mobility of the systems, was found to be in the range of 10,9 to 10,12,S/cm. This indicates that castor oil and its esters could be used for antistatic applications. The viscosity,, and the activation energy,E,, obtained from the dependency of viscosity on temperature using the Arrhenius equation, were found to increase with increasing molecular weight of the system. The effect of different concentrations of castor oil and its esters on the growth activities of the sugar beet pathogens R.,solani and S.,rolfsii was studied through the determination of percent germination, average length of hyphal extensions, dry mass yield and the production of sclerotia. The obtained data indicate that the esterification of castor oil with anhydrides improves the antifungal activity. [source]

    Synthesis and Optoelectronic Properties of Nonpolar Polyrotaxane Insulated Molecular Wires with High Solubility in Organic Solvents,

    Michael J. Frampton
    Abstract Hydrophilic polyanionic conjugated polyrotaxanes are readily synthesized in water by Suzuki coupling, but their high polarity and ionic nature limit the potential applications of these materials. Here, we demonstrate three methods for transforming these polar polyelectrolytes into nonpolar lipophilic insulated molecular wires. A water-soluble polyfluorene- alt -biphenylene ,-cyclodextrin (CD) polyrotaxane was converted into nonpolar derivatives by methylation of the carboxylic acid groups with diazomethane and conversion of the hydroxyl groups of the CDs to benzyl ethers, trihexylsilyl ethers, benzoyl esters, and butanoate esters to yield polyrotaxanes that are soluble in organic solvents such as chloroform and cyclohexane. Elemental analysis, NMR spectroscopy, and gel permeation chromatography (GPC) data support the proposed structures of the organic-soluble polyrotaxanes. The extents of reaction of the polyrotaxane CD hydroxyl groups were 55% for trihexylsilyl chloride/imidazole; 81% for benzyl chloride/sodium hydride; 72% for benzoyl chloride/pyridine/4-dimethylaminopyridine; and 98% butanoic anhydride/pyridine/4-dimethylaminopyridine. Alkylation, silylation, and esterification increase the bulk of the encapsulating sheath, preventing interstrand aggregation, increasing the photoluminescence efficiency in the solid state and simplifying the time-resolved fluorescence decay. The organic-soluble polyrotaxanes were processed into polymer light-emitting diodes (PLEDs) from solution in nonpolar organic solvents, thereby excluding ionic impurities from the active layer. [source]

    On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking,

    W. Zhao
    Abstract The green emission of poly(9,9,,-dioctylfluorenyl-2,7,,-diyl), end-capped by polyhedral oligomeric silsequioxanes, (PFO-POSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green-to-blue emission intensity ratio, used to assess the emission properties of thin (90,nm) films, was 3.70, 4.35, and 1.54 for an air-annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5,6,,m) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl-to-aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting. [source]

    In-line analysis of the influence of monomeric and oligomeric hindered amine on the hydrolysis of polycarbonate in a PC/ABS blend

    Vipin V. Rajan
    Abstract The polycarbonate/polyacrylonitrile butadiene styrene (PC/ABS) blends lose mechanical properties when exposed to outdoor conditions. This is due to the ultraviolet (UV) induced photo-oxidation of the PC phase and the polybutadiene portion of the ABS. It is known that ABS can be stabilised against terrestrial light by the use of hindered amine in combination with a UV absorber. However, such hindered amine cannot be used when PC is present in a multi component polymer blend. The hydrolysis of PC is accelerated when a small amount of hindered amine light stabilisers (HALS) is incorporated in the resin and is exposed to elevated temperature. In this article the effect of monomeric and oligomeric hindered amine on the hydrolysis of PC during the compounding of PC/ABS blend in a twin screw extruder at 240C is observed by means of in-line UV-vis spectroscopy. Tinuvin 765 was used as monomeric hindered amine and Tinuvin 622 as oligomeric hindered amine. The molecular weight of the compounded sample was determined by gel permeation chromatography (GPC) and the rheological properties were observed using an online viscometer. It was found that the extent of hydrolysis induced by the oligomeric hindered amine is less compared to monomeric amine. It was also observed that polymeric hindered amine imparts better dispersion of the ABS phase into the polymer blend. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Synthesis and characterization of temperature-sensitive block copolymers from poly(N -isopropylacrylamide) and 4-methyl-,-caprolactone or 4-phenyl-,-caprolactone

    Ren-Shen Lee
    Abstract This study synthesizes thermally sensitive block copolymers poly(N -isopropylacrylamide)- b -poly(4-methyl-,-caprolactone) (PNIPA- b -PMCL) and poly(N -isopropylacrylamide)- b -poly(4-phenyl-,-caprolactone) (PNIPA- b -PBCL) by ring-opening polymerization of 4-methyl-,-caprolactone (MCL) or 4-phenyl-,-caprolactone (BCL) initiated from hydroxy-terminated poly(N -isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct2 as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2-hydroxyethanethiol (ME) as a chain-transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), 1H-NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (Tg) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases Tg. Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA- b -PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29,2.74 mg L,1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    The substituent effects on the structure and surface morphology of polyaniline

    Mutlu Sahin
    Abstract In this work, poly(2-fluoroaniline), poly(2-chloroaniline), poly(2-methylaniline), and poly(N -ethylaniline) were prepared by a self-assembly method using an oxidizing system consisting of a dopant anion, p-toluene sulfonate with ammonium peroxydisulfate. The effects of substituents on the surface morphology, conductivity, molecular weight, spectral and thermal properties of the polymers were studied. SEM results revealed that the surface morphology of the resulting polymers changed from nanofiber to spherical structure by changing the substituent on the aniline monomers. The structure and properties of these conducting films were characterized by FTIR, UV-vis, elemental analysis, TGA, conductivity, and cyclic voltammetry. The polymer films show electroactivity in monomer free solution. Molecular weight of the polymers was determined by gel permeation chromatography. The dry electrical conductivity values of the substituted-polyanilines were found to be lower than that of PANI. The results revealed that the molecular structures of the polymers were similar to those of the emeraldine form of polyaniline. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Synthesis and characterization of a silicone resin with silphenylene units in Si-O-Si backbones

    Mengqiu Jia
    Abstract A silicone resin with silphenylene units in Si-O-Si backbones was synthesized by hydrolysis-polycondensation of 1,4-bis(hydroxydimethylsilyl)benzene (BHB) with chlorosilanes. The structure and property of this novel silicone resin were characterized by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogarvimetric analysis (TG), scanning electron microscope (SEM), and electrochemical impedance spectrum (EIS). This silicone resin could be applied as the film forming material of coating when it is prepared under the condition of R/Si, Ph/R, and the content of silphenylene units being 1.3, 0.5, and 10 mol %, respectively. GPC, IR, and NMR results show that the silphenylene units have been incorporated into the polymer of silicone resin. The TG analysis indicates that this novel silicone resin has good heat resistance with the onset degradation temperature of 500.3C and residual weight of 85.6% at 900C. SEM results demonstrate that the silicone resin with silphenylene units can form full and uniform films, and its surface morphology of clear paints were not damaged by heat below 350C. EIS analysis reveals that clear paints of the silicone resin with silphenylene units have good resistance to corrosion. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Improvement of the thermal stability of polyhydroxybutyrates by grafting with maleic anhydride by different methods: Differential scanning calorimetry, thermogravimetric analysis, and gel permeation chromatography

    Shinn-Gwo Hong
    Abstract The crystallization and thermal degradation behaviors of polyhydroxybutyrate (PHB) grafted with maleic anhydride (MA) by different techniques were analyzed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The results of DSC, TGA, and GPC analyses indicated that the grafting method could affect the crystallization rate, crystallinity, and thermal stability of PHB because of changes in the molecular weight of PHB and the amount of MA grafted during the reaction. The reduction of the molecular weight of PHB that reacted during the processing followed this order of methods: melt grafting > solvent grafting > mechanical grafting. However, the grafting ratio of MA followed this order of methods: melt grafting > mechanical grafting > solvent grafting. All three grafting methods significantly improved the thermal stability, therefore increasing the crystallization rate and melting temperature of the as-received PHB. A grafting ratio of MA as low as 0.07 wt % could result in a significant improvement in the heat resistance of PHB. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Polymerization of itaconic acid initiated by a potassium persulfate/N,N -dimethylethanolamine system

    S. J. Veli
    Abstract The synthesis and characterization of poly(itaconic acid) (PIA) with a novel initiator/activator system is presented. The initiator in this system was potassium persulfate, whereas the activator was N,N -dimethylethanolamine (DMEA). PIA was synthesized in distilled water and in 0.1M HCl at 40C with reaction times of 72 and 96 h. PIA was investigated with differential scanning calorimetry, gel permeation chromatography, and pulse gradient spin echo-NMR and compared to the same polymer synthesized in dioxane with 2,2,-azobisisobutyronitrile as the initiator. It was shown that, despite the fact that some residual DMEA remained in the system, the properties of the PIA polymerized in the aqueous phase were very similar to the dioxane-synthesized polymer, which will enable a faster, cheaper, and environmentally more acceptable polymerization of itaconic acid. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis and characterization of high thermally-stable and good soluble PVK-based polymers with perylene moiety

    Jianli Hua
    Abstract Three new poly(N -vinylcarbazole) (PVK)-based copolymers containing N -(n -butyl)- N -ethyl-1,6,7,12-tetra-(4- tert -butyl-phenoxy)-3,4,9,10-perylene tetracarboxylic bisimides were successfully synthesized by partially formylated by the standard Vilsmeier reaction, and the formyl groups of high reactivity are condensed with cyanoacetylated perylene to afford PVK-based polymers. The copolymers containing different percentage of perylene were obtained through the percentage of cyanoacetylated perylene unit being controlled by the initial feed ratio. The structures and properties of three copolymers were characterized and evaluated by FT-IR, NMR, UV,vis, FL spectroscopy, gel permeation chromatography, and thermogravimetric analysis measurements. The polymers were highly soluble in conventional solvents such as toluene, CHCl3, THF, DMF etc., and they were thermally stable up to 442,445C. Three copolymers have emission spectra with characteristic features of the perylene unit, and fluorescence quantum yields of polymers are higher than that of perylene bisimide, which may be caused by singlet,singlet energy transfer from PVK backbone to perylene in the polymers. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Study of epoxy toughened by in situ formed rubber nanoparticles

    Jun Ma
    Abstract The effect of rubber nanoparticles on mechanical properties and fracture toughness was investigated. Rubber nanoparticles of 2,3 nm were in situ synthesized in epoxy taking advantage of the reaction of an oligomer diamine with epoxy. The chemical reaction was verified by gel permeation chromatography (GPC) and 1HNMR, and the microstructure was characterized by transmission electron microscope. The rubber nanoparticles caused much less Young's modulus deterioration but toughened epoxy to a similar degree in comparison with their peer liquid rubber that formed microscale particles during curing. Fifteen wt % of rubber nanoparticles increased fracture energy from 140 to 840 J/m2 with Young's modulus loss from 2.85 to 2.49 GPa. The toughening mechanism might be the stress relaxation of the matrix epoxy leading to larger plastic work absorbed at the crack tip; there is no particle cavitation or deformation; neither crack deflection nor particle bridging were observed. The compound containing rubber nanoparticles demonstrates Newtonian liquid behavior with increasing shear rate; it shows lower initial viscosity at low shear rate than neat epoxy; this provides supplementary evidence to NMR and GPC result. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Unsymmetrical ,-diimine nickel (II) complex with rigid bicyclic ring ligand: Synthesis, characterization, and ethylene polymerization in the presence of AlEt2Cl

    Ting Li
    Abstract Unsymmetrical ,-diimine ligand 1 was successfully synthesized via condensation of trimethylaluminum (TMA) metalated 2-methyl-6-isopropyl-aniline with rigid bicyclic aliphatic diketone camphorquinone. Syn- and anti-stereoisomers were detected by 13C NMR in the condensation product. The corresponding ,-diimine nickel (II) complex 1 was prepared from the exchange reaction of (DME)NiBr2 with the ligand 1, and displayed high activity for ethylene polymerization in the presence of diethylaluminum chloride (AlEt2Cl). The resultant polymers were confirmed by gel permeation chromatography and 13C NMR characterization to be broad molecular weight distribution polyethylene with various branches, and high degree of branching, even at low polymerization temperature ,10C. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis, characterization, and antimicrobial properties of novel quaternary amine methacrylate copolymers

    Supriya Punyani
    Abstract A novel amine methacrylate monomer trimethylolpropane trimethacrylate,piperazine,ethyleneglycol dimethacrylate (TMPTMA-PPZ-EGDMA) was synthesized by amination of trimethylolpropane trimethacrylate (TMPTMA) with excess of piperazine (PPZ) followed by reaction with ethyleneglycol dimethacrylate (EGDMA). Copolymerization of TMPTMA-PPZ-EGDMA with 2-hydroxyethyl methacrylate (HEMA) was carried out by free radical polymerization using ammonium persulfate (APS) and N,N,N,,N,-tetramethyl ethylenediamine (TEMED) as a redox initiator. The copolymers obtained were then quaternized with 1-iodooctane. The monomers were characterized by FTIR and 1H NMR spectral studies. The molecular weights and polydispersity values of the monomers were determined with gel permeation chromatography. Quaternized copolymers containing more than 20% amine methacrylate monomer showed microporosity in the range of 9.9,10.4 ,m. The antibacterial activity of the quaternized copolymers against Escherichia coli and Staphylococcus aureus was studied using UV,vis spectrophotometer and scanning electron microscopy. Quaternized copolymers showed broad-spectrum contact-killing antibacterial properties without releasing any active agent as checked by iodide selective ion meter. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Graft copolymerization of methyl methacrylate with an N -substituted maleimide,liquid-crystalline copolymer by atom transfer radical polymerization

    T. ak
    Abstract The synthesis of novel copolymers consisting of a side-group liquid-crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine-functional copolymers 6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate and (2,5-dioxo-2,5-dihydro-1H -pyrrole-1-yl)methyl 2-bromopropanoate were synthesized by free-radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by 1H-NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis, characterization, and comparison of properties of novel fluorinated poly(imide siloxane) copolymers

    Anindita Ghosh
    Abstract Four new poly(imide siloxane) copolymers were prepared by a one-pot solution imidization method at a reaction temperature of 180C in ortho -dichlorobenzene as a solvent. The polymers were made through the reaction of o -diphthaleic anhydride with four different diamines,4,4,-bis(p -aminophenoxy-3,3,-trifluoromethyl) terphenyl, 4,4,-bis(3,-trifluoromethyl- p -aminobiphenyl ether)biphenyl, 2,6-bis(3,-trifluoromethyl- p -aminobiphenyl ether)pyridine, and 2,5-bis(3,-trifluoromethyl- p -aminobiphenylether)thiopene,and aminopropyl-terminated poly dimethylsiloxane as a comonomer. The polymers were named 1a, 1b, 1c, and 1d, respectively. The synthesized polymers showed good solubility in different organic solvents. The resulting polymers were well characterized with gel permeation chromatography, IR, and NMR techniques. 1H-NMR indicated that the siloxane loading was about 36%, although 40 wt % was attempted. 29Si-NMR confirmed that the low siloxane incorporation was due to a disproportionation reaction of the siloxane chain that resulted in a lowering of the siloxane block length. The films of these polymers showed low water absorption of 0.02% and a low dielectric constant of 2.38 at 1 MHz. These polyimides showed good thermal stability with decomposition temperatures (5% weight loss) up to 460C in nitrogen. Transparent, thin films of these poly(imide siloxane)s exhibited tensile strengths up to 30 MPa and elongations at break up to 103%, which depended on the structure of the repeating unit. The rheological properties showed ease of processability for these polymers with no change in the melt viscosity with the temperature. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Unexpected fluorescence emission of poly(,,,- L -malic acid) in aqueous medium

    Yaofeng Fan
    Abstract Unexpected fluorescence of poly(,,,- L -malic acid) (,,,-PMA) without traditional fluorophore was observed firstly. This fluorescent polymer was synthesized via melt polycondensation of L -malic acid. The polymer was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetry (TG), Fourier transform infrared spectroscopy (IR), Fourier transform Raman spectroscopy (Raman), and X-ray powder diffractometry (XRD). The high molecular weight ,,,-PMA was synthesized by the optimum polycondensation at 130C for 15 h, followed by fractional precipitation with diethyl ether and petroleum ether. The degree of branching of ,,,-PMA was from 10% to 20% according to the reaction condition. Terminal group of ,,,-PMA was mainly hydroxycarboxylic group companied with a few CHCHCOOH groups owing to dehydration of a normal terminal during the melt polycondensation. A fluorescence emission maximum of ,,,-PMA in water appeared at 420 nm when it was excited at 340 nm. Further study indicated that the fluorescence intensity was concentration-dependent, pH-dependent, and molecular-weight-dependent. The fluorescence formation may result from multichain aggregations, which was formed readily in aqueous solution due to intermolecular hydrogen bonds between branched ,,,-PMA. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    The synthesis of poly(3-hydroxybutyrate)- g -poly(methylmethacrylate) brush type graft copolymers by atom transfer radical polymerization method

    Hlya Arslan
    Abstract Brush type of poly (3-hydroxy butyrate), PHB, copolymer synthesis has been reported. Natural PHB was chlorinated by passing chlorine gas through PHB solution in CHCl3/CCl4 mixture (75/25 v/v) to prepare chlorinated PHB, PHB-Cl, with the chlorine contents varying between 2.18 and 39.8 wt %. Toluene solution of PHB-Cl was used in the atom transfer radical polymerization (ATRP) of methyl methacrylate, MMA, in the presence of cuprous bromide (CuBr)/2,2,-bipyridine complex as catalyst, at 90C. This "grafting from" technique led to obtain poly (3-hydroxybutyrate)-g-poly(methylmethacrylate) (PHB- g -PMMA) brush type graft copolymers (cylindrical brush). The polymer brushes were fractionated by fractional precipitation methods and the , values calculated from the ratio of the volume of nonsolvent to volume of solvent of brushes were ranged between 2.8 and 9.5 depending on the molecular weight, grafting density, and side chain length of the brushes, while the , values of PHB, PHB-Cl, and homo-PMMA were 2.7,3.8, 0.3,2.4, and 3.0,3.9, respectively. The fractionated brushes were characterized by gel permeation chromatography, 1H-NMR spectrometry, thermogravimetric analysis (TGA), and differential scanning calorimetry techniques. PHB- g -PMMA brush type graft copolymers showed narrower molecular weight distribution (mostly in range between 1.3 and 2.2) than the PHB-Cl macroinitiator (1.6,3.5). PHB contents in the brushes were calculated from their TGA thermograms and found to be in range between 22 and 42 mol %. The morphologies of PHB- g -PMMA brushes were also studied by scanning electron microscopy. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Novel adamantane-containing epoxy resin

    Xiaoming Su
    Abstract A novel adamantane-containing epoxy resin diglycidyl ether of bisphenol-adamantane (DGEBAda) was successfully synthesized from 1,3-bis(4-hydroxyphenyl)adamantane by a one-step method. The proposed structure of the epoxy resin was confirmed with Fourier transform infrared, 1H-NMR, gel permeation chromatography, and epoxy equivalent weight titration. The synthesized adamantane-containing epoxy resin was cured with 4,4,-diaminodiphenyl sulfone (DDS) and dicyandiamide (DICY). The thermal properties of the DDS-cured epoxy were investigated with differential scanning calorimetry and thermogravimetric analysis (TGA). The dielectric properties of the DICY-cured epoxy were determined from its dielectric spectrum. The obtained results were compared with those of commercially available diglycidyl ether of bisphenol A (DGEBA), a tetramethyl biphenol (TMBP)/epoxy system, and some other associated epoxy resins. According to the measured values, the glass-transition temperature of the DGEBAda/DDS system (223C) was higher than that of the DGEBA/DDS system and close to that of the TMBP/DDS system. TGA results showed that the DGEBAda/DDS system had a higher char yield (25.02%) and integral procedure decomposition temperature (850.7C); however, the 5 wt % degradation temperature was lower than that of DDS-cured DGEBA and TMBP. Moreover, DGEBAda/DDS had reduced moisture absorption and lower dielectric properties. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Synthesis and enantioselectivities of soluble polymers incorporating optically active binaphthyl and binaphthol

    Xiaowei Zou
    Abstract A polymer (P-1) was synthesized through the polymerization of (S)-6,6,-dibromo-3,3,-dibutyl-1,1,-binaphthol with (S)-2,2,-dioctoxy-1,1,-binaphthyl-6,6,-boronic acid in a Pd-catalyzed Suzuki reaction, and another polymer (P-2) was synthesized through the polymerization of (S)-6,6,-dibromo-3,3,-dibutyl-1,1,-binaphthol with (S)-6,6,-diethynyl-2,2,-dioctoxy-1,1,-binaphthyl in a Pd-catalyzed Sonogashira reaction. The two polymers showed good solubility in some common solvents and were characterized with NMR, Fourier transform infrared, gel permeation chromatography, and circular dichroism spectroscopy. The application of the chiral monomers and polymers in the asymmetric addition of diethyl zinc to benzaldehyde was studied. The results indicated that P-1, P-2, and the monomer (S)-3,3,-dibutyl-1,1,-binaphthol were efficient ligands in the asymmetric addition of diethyl zinc to benzaldehyde. The chiral polymer ligands P-1 and P-2 were more efficient than their monomeric version, (S)-3,3,-dibutyl-1,1,-binaphthol, and could be easily recovered and reused without a loss of catalytic activity or enantioselectivity. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    Synthesis and characterization of copolythiophene

    Jie He
    Abstract Copolythiophenes (Co-PTs), poly(3-hexylthiophene- co -3-thiophene carboxylic acid) (P3HT-TCa), poly(3-hexyloxylthiophene- co -3-thiophene carboxylic acid) (P3HOT-TCa), and poly(3-phenylthiophene- co -3-thiophene carboxylic acid) (P3PhT-TCa), were synthesized by chemical oxidized polymerization to investigate the effect of copolymerization on the properties of polythiophenes (PTs). Gel permeation chromatography showed that the molecular weight (MW) of Co-PT was lower than that of homopolythiophene. Fourier transform infrared (FTIR) spectra indicated that the copolymerization was successful between the monomers. The ,max of Co-PTs gave a "blue shift" in ultraviolet-visible (UV-VIS) spectra. Photoluminescence (PL) spectra showed that the PL intensity of Co-PT became weaker than that of homopolythiophene and the disappearance of PL had been observed in P3HOT-TCa. The thermal stability of Co-PT was influenced by the carboxyl for its low decomposition temperature. Furthermore, the copolymerization between multi-wall carbon nanotube containing thiophene ring (MWNT-Th) and 3-hexyloxylthiphene could also take place successfully. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Synthesis of a linear polyethylene macromonomer and preparation of polystyrene- graft -polyethylene copolymers via grafting-through atom transfer radical polymerization,

    Hiromu Kaneyoshi
    Abstract A vinyl-terminated linear polyethylene (number-average molecular weight = 1800, weight-average molecular weight/number-average molecular weight = 1.7, functionality = 92%) prepared by ethylene coordination polymerization was transformed into a monohydroxy-terminated linear polyethylene by hydroalumination of the vinyl group with diisobutylaluminum hydride and subsequent oxidation and hydrolysis. This monohydroxy-terminated linear polyethylene was quantitatively converted into a linear polyethylene macromonomer with a terminal ,-methacrylate group through esterification followed by dehydrobromination. A grafting-through atom transfer radical polymerization of the ,-methacrylate-terminated polyethylene and styrene was performed to yield a well-defined polystyrene- graft -polyethylene copolymer. The number-average molecular weight of the graft copolymers, measured by gel permeation chromatography, was lower than the predetermined number-average molecular weight, presumably because of the intramolecular aggregation of polyethylene side chains. The ,-methacrylate-terminated polyethylene content and number-average molecular weight of polystyrene- graft -polyethylene were determined by 1H-NMR. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 3,13, 2007 [source]

    Fabrication, structures, and properties of acrylonitrile/methyl acrylate copolymers and copolymers containing microencapsulated phase change materials

    Na Han
    Abstract The polyacrylonitrile-methyl acrylate (AN/MA mole ratio 100/0,70/30) copolymers and copolymers (AN/MA mole ratio 85/15) containing up to 40 wt % of microencapsulated n -octadecane (MicroPCMs) are synthesized in water. The MicroPCMs were incorporated at the step of polymerization. The effect of the MA mole ratio and MicroPCMs content on structures and properties of the copolymers were studied by using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TG), gel permeation chromatography (GPC), and X-ray diffraction (XRD). The feeding ratio agreed well with the composition of the AN/MA copolymers. The copolymers are synthesized in the presence of MicroPCMs. The melting point moves to lower temperature (206C), while the decomposition temperature moves to higher temperature (309C) with increasing of the MA mole ratio and microcapsules content. The number,average molecular weight of the copolymer is ,30,000. The crystallinity of the copolymer decreases with increasing of the MA mole ratio and microcapsules content. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2776,2781, 2007 [source]

    Enzymatic degradation of poly(L -lactic acid) fibers: Effects of small drawing

    Hideto Tsuji
    Abstract The enzymatic degradation of poly(L -lactic acid) (PLLA) fibers with different low draw ratios (1.0, 1.2, and 1.4 times) was investigated in tris-HCl buffer solution (pH = 8.6) with proteinase K by the use of gravimetry, scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and tensile testing. Surprisingly, even the small drawings (1.2 and 1.4 times) disturbed the proteinase K catalyzed enzymatic degradation of the PLLA fibers. This should have been because the enzyme could not attach to the extended (strained) chains in the amorphous regions of the uniaxially oriented PLLA fibers or could not catalyze the cleavage of the strained chains. The accumulation of crystalline residues formed as a result of selective cleavage, and removal of the amorphous chains was not observed, even for as-spun PLLA fibers. This indicated the facile release of formed crystalline residues from the surface of the as-spun PLLA fibers during enzymatic degradation. Such release may have been because the crystalline regions of the as-spun PLLA fibers were oriented with their c axis parallel to the machine direction, as reported for biaxially oriented PLLA films. Gravimetry, SEM, and tensile testing could trace the enzymatic degradation of the PLLA fibers, although the enzymatic degradation of the PLLA fibers was untraceable by GPC and DSC. 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2064,2071, 2007 [source]


    ABSTRACT Bacteriocin from Weissella paramesenteroides DFR-8 isolated from cucumber (Cucumis sativus) was purified by using only two steps, viz., pH-mediated cell adsorption,desorption method and gel permeation chromatography. A single peak observed in the purity check by analytical Reverse Phase-High Performance Liquid Chromatography (Waters 600 analytical HPLC system, Milford, MA) and a single band (molecular weight,3.74 kDa) shown on SDS-PAGE analysis strongly indicated the homogeneity of the bacteriocin preparation. Treatment with proteolytic enzymes abolished the antimicrobial activity indicating the proteinaceous nature of bacteriocin. The purified bacteriocin exhibited a broad inhibitory spectrum against foodborne pathogens and spoilage microorganisms, including gram-negative bacteria such as Salmonella typhimurium, Vibrio parahaemolyticus, Aeromonas hydrophila and Listeria monocytogenes. Response surface methodology was employed to study the interactive effect of temperature and pH on bacteriocin activity, and a regression equation was developed. The bacteriocin retained full activity after storage at,20C for 90 days, while partial and complete activity loss was observed when stored at 4 and 37C, respectively. PRACTICAL APPLICATION In recent years, bacteriocins of lactic acid bacteria have gained much attention as food biopreservatives because of their origin from generally regarded as safe organisms. In spite of various bacteriocins studied worldwide, studies on bacteriocins of Weissella paramesenteroides remain rare. The present work involves the purification of bacteriocin up to absolute homogeneity from W. paramesenteroides, an isolate first time reported from cucumber (Cucumis sativus). The purified bacteriocin (molecular weight ,3.74 kDa) was found to inhibit a large number of foodborne pathogens, including Listeria monocytogenes, which is resistant to commercially available bacteriocin, i.e., nisin. The application of central composite rotatable design enabled us to design a regression equation from which the residual activity of bacteriocin can be predicted at any given conditions of temperature and pH within the experimental domain. The broad inhibitory spectrum and thermostability of bacteriocin suggest its potential application in food preservation. [source]


    The high molecular weight (HMW) material (> 12,000 Da) of ten raw cane sugars from seven countries and two U.S. states was isolated by dialysis and analyzed by gel permeation chromatography (GPC). Simultaneous detection of colorant polymers and polysaccharides was accomplished by using two detectors in series , UV at 214 nm for colorant polymers and refractive index (RI) for carbohydrate polymers. The monosaccharide composition of the nondialyzable raw sugar fraction (the tenate) was determined by hydrolysis with trifluoroacetic acid and with oxalic acid. Aconitic acid was associated with the tenate. The raw sugars were categorized into two types according to their GPC patterns and aconitic acid content. Hydrolysis of individually collected GPC peaks demonstrated that one particular peak contained most of the aconitic acid. [source]

    Properties of Arrowroot Starch Treated with Aqueous HCl at Ambient Temperature

    J.K. John
    Arrowroot starch was acid-treated using 2.2 M HCl at 29 to 30 C for durations of 0 to 72 h, and properties of the control and modified samples were compared. Increasing length of acid treatment produced a progressive decline in amylose blue value, intrinsic viscosity, and swelling power, as well as an increase in free sugars and solubility. Differential scanning calorimetry (DSC) studies highlighted changes effected by acid-treatment in the gelatinization behavior of the starch samples. Gel permeation chromatography (GPC) studies on 32- and 72-h acid-treated samples indicated a greater proportion of dextrins with a higher percentage of reducing sugars, compared to the control. While X-ray diffraction data suggested minor changes in the crystal phase impacted by acid-treatment, in vitro digestibility of both control and acid-treated samples did not show any appreciable change in overall patterns. [source]

    Solubility and degradation of polyhydroxyalkanoate biopolymers in propylene carbonate

    AICHE JOURNAL, Issue 6 2010
    Christopher W. J. McChalicher
    Abstract New biobased materials and chemicals require different processing strategies than petroleum-derived commodities. The extraction and recovery of polyhydroxyalkanoate (PHA) biopolymers from the residual cellular biomass is particularly difficult because the polymer is accumulated within the cell. PHAs have low solubility in many classical polymer solvents and are most often dissolved using undesirable chlorinated solvents. The solubility kinetics is greatly diminished when these polymers are highly crystalline. Here, 1,2-propylene carbonate is used to dissolve highly crystalline polyhydroxybutyrate at ambient pressures and moderate temperatures. We have used kinetic studies of the dissolution of the crystalline material to determine the energy barrier for dissolution of the system. Further, the degradation of polyhydroxybutyrate and similarly prepared PHA block copolymers were studied during this extraction process using molecular weight characterization by gel permeation chromatography. Finally, we have used these findings to extract PHA block copolymers from dried biomass at the bench scale. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

    Distributed midpoint chain scission in ultrasonic degradation of polymers

    AICHE JOURNAL, Issue 9 2004
    G. Sivalingam
    Abstract The ultrasonic degradation of poly(bisphenol A carbonate), poly(,-caprolactone), and poly(vinyl acetate) was investigated with various solvents such as benzene, monochlorobenzene, and dichlorobenzene. The time evolution of molecular weight was determined using gel permeation chromatography. A limiting molecular weight was observed for all the systems and was a function of solvent properties. The degradation rates increased with increase in viscosity and decrease in vapor pressure. The polydispersity reached a maximum before reaching a constant value at longer times. The experimental data indicate that the breakage of the polymer is around midpoint, with a distribution rather than an ideal midpoint scission. A continuous distribution model with a stoichiometric kernel based on Lorentzian probability distribution function was developed to satisfactorily model the experimental data. 2004 American Institute of Chemical Engineers AIChE J, 50: 2258,2265, 2004 [source]

    Antibody response to aggregated human interferon alpha2b in wild-type and transgenic immune tolerant mice depends on type and level of aggregation

    Suzanne Hermeling
    Abstract The aim of this study was to determine the sensitivity of transgenic immune tolerant mice for the type and level of aggregation of recombinant human interferon alpha2b (rhIFN,2b). RhIFN,2b was aggregated by metal-catalyzed oxidation or by incubation at elevated temperature and various pHs. Native rhIFN,2b was mixed with oxidized rhIFN,2b at different ratios to obtain samples with different aggregation levels. The preparations were characterized by UV and fluorescence spectroscopy, gel permeation chromatography (GPC), dynamic light scattering (DLS), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS,PAGE) and Western blotting, and ELISA. The immunogenicity was evaluated in wild-type mice and transgenic mice immune tolerant for hIFN,2. Sera were analyzed by ELISA for the presence of rhIFN,2b-specific antibodies. The oxidized and aged preparations widely differed regarding the level and nature of aggregates. All preparations containing aggregates increased the immune response in the wild-type mice as compared to native rhIFN,2b and were able to break the tolerance of the transgenic mice. The more native-like the conformation of the aggregated proteins, the more immunogenic the preparations were in the transgenic mice. The native-like aggregates prepared via metal catalysis induced a dose-dependent loss of tolerance in the transgenic mice. In conclusion, the transgenic mouse model can be used to screen rhIFN,2b formulations for low levels of immunogenic aggregates obtained under accelerated storage conditions. 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:1084,1096, 2006 [source]