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Selected AbstractsMolecular weight and humification index as predictors of adsorption for plant- and manure-derived dissolved organic matter to goethiteEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007T. Ohno Summary Sorptive retention of organic matter is important in maintaining the fertility and quality of soils in agricultural ecosystems. However, few sorption studies have been conducted that use dissolved organic matter (DOM) characteristic of agricultural amendments. We investigated the sorption to goethite (,-FeOOH) of DOM extracted from: (i) above-ground biomass of wheat straw (Triticum aestivum L.), maize residue (Zea mays L.), soybean residue (Glycine max (L.) Merr.), and hairy vetch residue (Vivia billosa L.); (ii) below-ground biomass from maize, soybean, canola (Brassica napus L.), and green bean (Phaseolus vulgaris L.); and (iii) beef, dairy, poultry, and pig animal manures. The apparent molecular weight (MWAP) of the DOM was measured by high performance-size exclusion chromatography and ranged from 312 to 1074 g mol,1. The carboxyl-group content of the DOM measured by potentiometric titration ranged from 4.84 to 21.38 mmol(,) g,1 carbon. The humification index (HIX) determined by fluorescence spectrometry varied from 1.15 to 4.33. Sorption was directly related to both MWAP and HIX values of the DOM. Molecular weight analysis of the solution prior to and after sorption indicated that the DOM molecules > 1800 g mol,1 were preferentially sorbed, resulting in fractionation of the DOM upon reaction with goethite. The multiple regression equation, based only on MWAP and HIX parameters, explained 76% of the variance in amount of DOM sorbed. The results indicate that MWAP and HIX are important factors in controlling the sorption of DOM to mineral surfaces. Amendment with materials that release DOM of higher molecular weight and greater humification will result in enhanced initial sorption of DOM to soil solids, thereby contributing to accumulation of a larger soil organic C pool. [source] Temperature-Resolved Local and Macroscopic Charge Carrier Transport in Thin P3HT Layers,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Patrick Pingel Abstract Previous investigations of the field-effect mobility in poly(3-hexylthiophene) (P3HT) layers revealed a strong dependence on molecular weight (MW), which was shown to be closely related to layer morphology. Here, charge carrier mobilities of two P3HT MW fractions (medium-MW: Mn,=,7,200 g mol,1; high-MW: Mn,=,27,000 g mol,1) are probed as a function of temperature at a local and a macroscopic length scale, using pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) and organic field-effect transistor measurements, respectively. In contrast to the macroscopic transport properties, the local intra-grain mobility depends only weakly on MW (being in the order of 10,2 cm2 V,1 s,1) and being thermally activated below the melting temperature for both fractions. The striking differences of charge transport at both length scales are related to the heterogeneity of the layer morphology. The quantitative analysis of temperature-dependent UV/Vis absorption spectra according to a model of F. C. Spano reveals that a substantial amount of disordered material is present in these P3HT layers. Moreover, the analysis predicts that aggregates in medium-MW P3HT undergo a "pre-melting" significantly below the actual melting temperature. The results suggest that macroscopic charge transport in samples of short-chain P3HT is strongly inhibited by the presence of disordered domains, while in high-MW P3HT the low-mobility disordered zones are bridged via inter-crystalline molecular connections. [source] Membranes of cellulose triacetate produced from sugarcane bagasse cellulose as alternative matrices for doxycycline incorporationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Guimes Rodrigues Filho Abstract Cellulose triacetate (CTA) membranes were prepared using polyethylene glycol, 600 g mol,1, (PEG) as additive and were utilized in essays of doxycycline (DOX) incorporation using two different procedures: (i) incorporation of the drug during the membrane preparation and (ii) incorporation of the drug to a previously prepared membrane. In the first, the produced membrane presented high compatibility between DOX and CTA, what was evidenced by analyzing the DSC curve for a CTA/PEG 50%/DOX system. Results showed that the drug is homogeneously distributed throughout the matrix, molecularly. In the second method, the drug was molecularly and superficially adsorbed, as seen through the DSC curve for the system CTA/PEG 10%/DOX, which nearly does not present alterations in relation to the original material, and through the isotherm of drug adsorption that follows the Langmuir model. Results showed that the membranes produced from sugarcane bagasse are adequate to produce matrices for drug-controlled release, both for enteric use (Method (i)) and topic use (Method (ii)). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Physicochemical characterization of carrageenans,A critical reinvestigationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Gisela Berth Abstract Kappa-, iota-, and lambda-carrageenan (food grade) were analyzed by static light scattering (MALS in batch mode) in 0.1M NaNO3 at 25 and 60°C, earlier heated up to 90°C or not. At 25°C, there was a strong tendency for a concentration-dependent aggregation in the order lambda < kappa < iota. At 60°C, all samples were molecularly dispersed. The strongly temperature-dependent refractive index increments (equilibrium dialysis) differ. Data interpretation in terms of the wormlike chain model using the Skolnik-Odijk-Fixman approach led to an intrinsic persistence length around 3 to 4 nm and expansion factors as high as 1.5 and above in a thermodynamically good solvent for all three types. Triple-detector HPSEC (DRI, MALS, viscometry) on the three commercial samples plus a degraded (by acidic hydrolysis) kappa-carrageenan in the same solvent/eluant at 60°C yielded a uniform and slightly curved [,]- M relationship for 5 × 103 , M/(g mol) , 3 × 106 and a nearly identical molar mass dependence of the radius of gyration. HPSEC at 25°C on kappa-carrageenan confirmed formation of soluble aggregates. Special emphasis was put on analytical and methodological aspects. The reliability of the experimental data was demonstrated by analogous measurements on dextran calibration standards. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Synthesis and characterization of novel poly(arylene ether)s based on 9,10-bis-(4-fluoro-3-trifluoromethylphenyl) anthracene and 2,7-bis-(4-fluoro-3-trifluoromethylphenyl) fluoreneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Arun K. Salunke Abstract Two new bisfluoro monomers 9,10-bis-(4-fluoro-3-trifluoromethylphenyl) anthracene and 2,7-bis-(4-fluoro-3-trifluoromethylphenyl) fluorene have been synthesized by the cross-coupling reaction of 2-fluoro-3-trifluoromethyl phenyl boronic acid with 9,10-dibromo anthracene and 2,7-dibromo fluorine, respectively. These two bisfluoro compounds were used to prepare several poly(arylene ether)s by aromatic nucleophilic displacement of fluorine with various bisphenols; such as bisphenol-A, bisphenol-6F, bishydroxy biphenyl, and 9,9-bis-(4-hydroxyphenyl)-fluorene. The products obtained by displacement of the fluorine atoms exhibits weight-average molar masses up to 1.5 ×105 g mol,1 and number average molecular weight up to 6.8 × 104 g mol,1 in GPC. These poly(arylene ether)s show very high thermal stability even up to 490°C for 5% weight loss occurring at this temperature in TGA in synthetic air and showed glass transition temperature observed up to 310°C. All the polymers are soluble in a wide range of organic solvents, e.g., CHCl3, THF, NMP, and DMF. Films cast from DMF solution are brittle in nature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Synthesis of 3H and fluorescence-labelled poly (DL -Lactic acid)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2001S. Ponsart Abstract The novel polymer modification method based on the activation of an aliphatic polyester chain by using lithium diisopropylamide at low temperature to form a polycarbanion bearing nucleophilic sites in a position , to the carbonyl groups was applied to rac -poly (lactic acid), PLA50, to label this polymer with radioactive tritium atoms or with a fluorescent dye. Despite simultaneous partial chain degradation, radioactive PLA50 and fluorescent PLA50 with Mn=14000 g mol,1, Mw/Mn=1.9 and Mn=32 000 g mol,1, Mw/Mn=2.4, respectively, were obtained. The specific activity of the final compound was 3.7 µCi g,1 that squared with 0.3, substitution reaction. The fluorescent polymer was substituted with 0.25% ratio. This work shows that the LDA activation method appears to have considerable potential. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis and characterization of a thiadiazole/benzoimidazole-based copolymer for solar cell applicationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010Guan-yu Chen Abstract In this study, we synthesized a new polymer, PCTDBI, containing alternating carbazole and thiadiazole-benzoimidazole (TDBI) units. This polymer (number-average molecular weight = 25,600 g mol,1), which features a planar imidazole structure into the polymeric main chain, possesses reasonably good thermal properties (Tg = 105 °C; Td = 396 °C) and an optical band gap of 1.75 eV that matches the maximum photon flux of sunlight. Electrochemical measurements revealed an appropriate energy band offset between the polymer's lowest unoccupied molecular orbital and that of PCBM, thereby allowing efficient electron transfer between the two species. A solar cell device incorporating PCTDBI and PCBM at a blend ratio of 1:2 (w/w) exhibited a power conversion efficiency of 1.20%; the corresponding device incorporating PCTDBI and PC71BM (1:2, w/w) exhibited a PCE of 1.84%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Synthesis of comb polymers via grafting-onto macromolecules bearing pendant diene groups via the hetero-Diels-Alder-RAFT click conceptJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2010Antoine Bousquet Abstract Comb polymers were synthesized by the "grafting-onto" method via a combination of Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and the hetero-Diels-Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans-hexa-2,4-dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration,whilst keeping monomer to polymer conversions low,resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n -butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridin-2-yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol,1 < Mn < 13,000 g mol,1) grafted chain and the reaction stoichiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol,1 to 58,000 g mol,1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1773,1781, 2010 [source] Determination of block size in poly(ethylene oxide)- b -polystyrene block copolymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2009Marion Girod Abstract Characterization of block size in poly(ethylene oxide)- b -poly(styrene) (PEO- b -PS) block copolymers could be achieved by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after scission of the macromolecules into their constituent blocks. The performed hydrolytic cleavage was demonstrated to specifically occur on the targeted ester function in the junction group, yielding two homopolymers consisting of the constitutive initial blocks. This approach allows the use of well-established MALDI protocols for a complete copolymer characterization while circumventing difficulties inherent to amphiphilic macromolecule ionization. Although the labile end-group in PS homopolymer was modified by the MALDI process, PS block size could be determined from MS data since polymer chains were shown to remain intact during ionization. This methodology has been validated for a PEO- b -PS sample series, with two PEO of number average molecular weight (Mn) of 2000 and 5000 g mol,1 and Mn(PS) ranging from 4000 to 21,000 g mol,1. Weight average molecular weight (Mw), and thus polydispersity index, could also be reached for each segment and were consistent with values obtained by size exclusion chromatography. This approach is particularly valuable in the case of amphiphilic copolymers for which Mn values as determined by liquid state nuclear magnetic resonance might be affected by micelle formation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3380,3390, 2009 [source] Functional syndiotactic poly(,-hydroxyalkanoate)s via stereoselective ring-opening copolymerization of rac -,-butyrolactone and rac -allyl-,-butyrolactoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2009Noureddine Ajellal Abstract The copolymerization of racemic ,-butyrolactone (rac -BLMe) with racemic "allyl-,-butyrolactone" (rac -BLallyl) in toluene, catalyzed by the discrete amino-alkoxy-bis(phenolate) yttrium-amido complex 1, gave new poly(,-hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe - co -BLallyl) copolymers produced have a highly syndiotactic backbone structure (Pr = 0.80,0.84) with a random enchainment of monomer units, as evidenced by 13C NMR, and high molecular weight (Mn up to 58,000 g mol,1) with a narrow polydispersity (Mw/Mn = 1.07,1.37), as determined by GPC. The comonomer incorporation (5,50 mol % rac -BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side-chains in those poly(BLMe - co -BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration-oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (Tm, ,Hm, Tg) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177,3189, 2009 [source] Novel fluorescent (p -phenylene ethynylene)-calix[4]arene-based polymer: Design, synthesis, and propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008Alexandra I. Costa Abstract A novel fluorescent (p -phenylene ethynylene)-calix[4]arene-based polymer (CALIX-PPE) has been successfully synthesized by cross-coupling polymerization of bis-calix[4]arene 1 with 1,4-diethynylbenzene. The polycondensation was carried out in toluene/NEt3 at 35 °C for 24 h, using PdCl2(PPh3)2/CuI as the catalytic system, furnishing CALIX-PPE in excellent isolated yields (higher than 95%, several runs). The yellow polymer is freely soluble in several nonprotic organic solvents. The GPC trace of the isolated polymer showed a monomodal distribution and a number-average molecular weight of 23,300 g mol,1 (Mw/Mn = 2.05). No evidence was found in the structural analysis (FTIR and 1H/13C NMR) regarding the formation of alkyne homocoupled segments along the polymer chain. For comparative purposes, the synthesis of an analogous poly(p -phenylene ethynylene) containing p - t -butyl-phenoxymethyl side chains (TBP-PPE) was also undertaken. A great similarity was found between the photophysical properties of CALIX-PPE and TBP-PPE in solution (UV,vis and laser induced luminescence), clearly demonstrating their unique dependence on the structure and conformation of the conjugated PPE backbone. The fluorescence spectra of polymers are of nearly identical shape, displaying their maximum emission around 420 nm. The calculated solution photoluminescence quantum yields of CALIX-PPE and TBP-PPE are of similar magnitude (,F(CALIX-PPE) = 0.43; ,F(TBP-PPE) = 0.51). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6477,6488, 2008 [source] Controlled cationic polymerization of cyclopentadiene with B(C6F5)3 as a coinitiator in the presence of waterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2008Sergei V. Kostjuk Abstract The controlled cationic polymerization of cyclopentadiene (CPD) at 20 °C using 1-(4-methoxyphenyl)ethanol (1)/B(C6F5)3 initiating system in the presence of fairly large amount of water is reported. The number,average molecular weights of the obtained polymers increased in direct proportion to monomer conversion in agreement with calculated values and were inversely proportional to initiator concentration, while the molecular weight distribution slightly broadened during the polymerization (Mw/Mn , 1.15,1.60). 1H NMR analyses confirmed that the polymerization proceeds via reversible activation of the COH bond derived from the initiator to generate the growing cationic species, although some loss of hydroxyl functionality happened in the course of the polymerization. It was also shown that the enchainment in cationic polymerization of CPD was affected by the nature of the solvent(s): for instance, polymers with high regioselectivity ([1,4] up to 70%) were obtained in acetonitrile, whereas lower values (around 60%) were found in CH2Cl2/CH3CN mixtures. Aqueous suspension polymerization of CPD using the same initiating system was successfully performed and allowed to synthesize primarily hydroxyl-terminated oligomers (Fn = 0.8,0.9) with Mn , 1000 g mol,1 and broad MWD (Mw/Mn , 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734,4747, 2008 [source] Microwave-assisted ring-opening polymerization of p -dioxanoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2008Yu-Yan Chen Abstract The ring-opening polymerization (ROP) of p -dioxanone (PDO) under microwave irradiation with triethylaluminum (AlEt3) or tin powder as catalyst was investigated. When the ROP of PDO was catalyzed by AlEt3, the viscosity-average molecular weight (Mv) of poly(p -dioxanone) (PPDO) reached 317,000 g mol,1 only in 30 min, and the yield of PPDO achieved 96.0% at 80 °C. Tin powder was successfully used as catalyst for synthesizing PPDO by microwave heating, and PPDO with Mv of 106,000 g mol,1 was obtained at 100 °C in 210 min. Microwave heating accelerated the ROP of PDO catalyzed by AlEt3 or tin powder, compared with the conventional heating method. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3207,3213, 2008 [source] Simultaneous reversible addition fragmentation chain transfer and ring-opening polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Maude Le Hellaye Abstract The simultaneous ring-opening polymerization (ROP) of ,-caprolactone (,-CL) and 2-hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ,-CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2-ethylhexanoate (Sn(Oct)2) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA- g -PCL. Graft copolymer formation is evidenced by a combination of size-exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000,10,000 g mol,1) the copolymer grafting density is higher than 90%. The ratio of free HEMA-PCL homopolymer produced during the "one-step" process was found to depend on the HEMA concentration, as well as the half-life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058,3067, 2008 [source] Vinyl polymerization of norbornene by mono- and trinuclear nickel complexes with indanimine ligandsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Guangrong Tang Abstract A series of new indanimine ligands [ArNCC2H3(CH3)C6H2(R)OH] (Ar = Ph, R = Me (1), R = H (2), and R = Cl (3); Ar = 2,6- i -Pr2C6H3, R = Me (4), R = H (5), and R = Cl (6)) were synthesized and characterized. Reaction of indanimines with Ni(OAc)2·4H2O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni3[ArN = CC2H3(CH3)C6H2(R)O]6 (Ar = Ph, R = Me (7), R = H (8), and R = Cl (9)) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArNCC2H3(CH3)C6H2(R)O]2 (Ar = 2,6- i -Pr2C6H3, R = Me (10), R = H (11), and R = Cl (12)). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X-ray structure analyses were performed for complexes 7, 10, 11, and 12. After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition-type polynorbornene (PNB) with high molecular weight Mv (106 g mol,1), highly catalytic activities up to 2.18 × 107 gPNB mol,1 Ni h,1. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489,500, 2008 [source] An efficient synthesis of telechelic poly (N -isopropylacrylamides) and its application to the preparation of ,,,-dicholesteryl and ,,,-dipyrenyl polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Florence Segui Abstract Poly(N -isopropylacrylamide)s (PNIPAMs) with cholesteryl or pyrenyl moieties at each chain end (CH-PNIPAMs or Py-PNIPAMs) were prepared via end-group modification of ,,,-dimercapto poly(N -isopropylacrylamides), ranging in molecular weight from , 7000 to 45,000 g mol,1 with a polydispersity index of 1.10 or lower. The telechelic thiol functionalized PNIPAMs were obtained by aminolysis of ,,,-di(isobutylthiocarbonylthio)-poly(N -isopropylacrylamide)s (iBu-PNIPAMs) obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of N -isopropylacrylamide in the presence of the difunctional chain transfer agent, diethylene glycol di(2-(1-isobutyl)sulfanylthiocarbonylsulfanyl-2-methyl propionate) (DEGDIM). The self-assembly of the polymers in water was assessed by fluorescence spectroscopy, using the intrinsic emission of Py-PNIPAM or the emission of pyrene added as a probe in aqueous solutions of CH-PNIPAM. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 314,326, 2008 [source] Synthesis of crosslinkable fluorinated polyesters for optical waveguide devicesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Xu Fei Abstract A series of novel crosslinkable, highly fluorinated polyesters were synthesized by copolycondensation reactions of terephthaloyl chloride with 4, 4,-(hexafluoroisopropy-lidene)-diphenol and 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-octane-1,8-diol, followed by reaction with 2-hydroxyethyl methacrylate. The resulting polyesters with the molecular weights (Mn: 12,100,20,000 g mol,1) and polydispersities (1.49,2.25) were useful for the fabrication of polymer optical devices because of their good solubility in common organic solvent and the processable flexibility. The ratios of the components of the polyesters were characterized by FTIR and NMR. The polyesters had high glass transition temperature (Tg,: up to 170 °C) and good thermal stabilities (Td: up to 470 °C). The refractive index of the polyester film was tuned and controlled in the range of 1.447,1.576 at 1550 nm by monitoring the component fractions during the preparation procedures. Low-loss optical waveguides were fabricated from the resulting polyesters and the propagation loss of the channel waveguides was measured to be around 0.56 dB/cm at 1550 nm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5923,5931, 2007 [source] Homogeneous phase polymerization of vinylidene fluoride in supercritical carbon dioxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007Sabine Beuermann Abstract For the first time, stabilizer-free vinylidene fluoride (VDF) homopolymerizations were carried out in homogenous phase with supercritical CO2 using the conventional initiator di- tert butyl peroxide (DTBP). In-line FT-NIR spectroscopy showed that complete monomer conversion may be obtained. Molecular weights were determined via size-exclusion chromatography and polymer endgroup analysis by 1H-NMR spectroscopy. The number average molecular weights were below 104 g mol,1 and polydispersities ranged from 3.1 to 5.7 depending on DTBP and VDF concentration. For allowing isothermal reaction, high CO2 contents ranging from 61 to 83 wt % were used. The high-temperature and high-pressure conditions required for homogeneous polymerization did not alter the amount of defects in VDF chaining. Scanning electron microscopy indicated that regular stack-type particles are obtained upon expansion of the homogeneous polymerization mixture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5626,5635, 2007 [source] Synthesis and characterization of poly(ethylene oxide- co -ethylene carbonate) macromonomers and their use in the preparation of crosslinked polymer electrolytesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2006Anette Munch Elmér Abstract Methacrylate-functionalized poly(ethylene oxide- co -ethylene carbonate) macromonomers were prepared in two steps by the anionic ring-opening polymerization of ethylene carbonate at 180 °C, with potassium methoxide as the initiator, followed by the reaction of the terminal hydroxyl groups of the polymers with methacryloyl chloride. The molecular weight of the polymer went through a maximum after approximately 45 min of polymerization, and the content of ethylene carbonate units in the polymer decreased with the reaction time. A polymer having a number-average molecular weight of 2650 g mol,1 and an ethylene carbonate content of 28 mol % was selected and used to prepare a macromonomer, which was subsequently polymerized by UV irradiation in the presence of different concentrations of lithium bis(trifluoromethanesulfonyl)imide salt. The resulting self-supportive crosslinked polymer electrolyte membranes reached ionic conductivities of 6.3 × 10,6 S cm,1 at 20 °C. The coordination of the lithium ions by both the ether and carbonate oxygens in the polymer structure was indicated by Fourier transform infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2195,2205, 2006 [source] Dendrimers as scaffolds for multifunctional reversible addition,fragmentation chain transfer agents: Syntheses and polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2004Xiaojuan Hao Abstract The synthesis and characterization of novel first- and second-generation true dendritic reversible addition,fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3-benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z-group architecture based on 1,1,1-hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free-radical polymerization at 60 °C. The novel dendrimer-based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number-average molecular weight (Mn) with the monomer,polymer conversion, yielding star polymers with molecular weights of up to Mn = 160,000 g mol,1 for PBA (based on a linear PBA calibration) and up to Mn = 70,000 g mol,1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1-hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star-shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star-shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877,5890, 2004 [source] Novel, biodegradable, functional poly(ester-carbonate)s by copolymerization of trans -4-hydroxy- L -proline with cyclic carbonate bearing a pendent carboxylic groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004Ren-Shen Lee Abstract Water-soluble poly(ester-carbonate) having pendent amino and carboxylic groups on the main-chain carbon is reported for the first time. This article describes the melt ring-opening/condensation reaction of trans -4-hydroxy- N -benzyloxycarbonyl- L -proline (N -CBz-Hpr) with 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) at a wide range of molar fractions. The influence of reaction conditions such as catalyst concentration, polymerization time, and temperature on the number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the copolymers was investigated. The polymerizations were carried out in bulk at 110 °C with 3 wt % stannous octoate as a catalyst for 16 h. The poly(ester-carbonate)s obtained were characterized by Fourier transform infrared spectroscopy, 1H NMR, differential scanning calorimetry, and gel permeation chromatography. The copolymers synthesized exhibited moderate molecular weights (Mn = 6000,14,700 g mol,1) with reasonable molecular weight distributions (Mw/Mn = 1.11,2.23). The values of the glass-transition temperature (Tg) of the copolymers depended on the molar fractions of cyclic carbonate. When the MBC content decreased from 76 to 12 mol %, the Tg increased from 16 to 48 °C. The relationship between the poly(N -CBz-Hpr- co -MBC) Tg and the compositions was in approximation with the Fox equation. In vitro degradation of these poly(N -CBz-Hpr- co -MBC)s was evaluated from weight-loss measurements and the change of Mn and Mw/Mn. Debenzylation of 3 by catalytic hydrogenation led to the corresponding linear poly(ester-carbonate), 4, with pendent amino and carboxylic groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2303,2312, 2004 [source] Low-temperature route to thermoplastic polyamide elastomers,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2004Gouher Rabani Abstract Thermoplastic polyamide elastomers were obtained by polymerization of aminobenzoyl-substituted telechelics derived from poly(tetrahydrofuran)-diols (number-average molecular weight: 1400 or 2000 g mol,1) with several diacid dichlorides (terephthaloyl dichloride, 4,4,-biphenyldicarbonyl dichloride, or 2,6-naphthalenedicarbonyl dichloride) and chlorotrimethylsilane in N,N -dimethylacetamide at 0,20 °C. The as-prepared polymers had melting temperatures above 190 °C and exhibited elastic properties at room temperature, as evidenced by dynamic mechanical analysis and stress,strain measurements. The polymer with 2,6-naphthalenedicarboxamide hard segments had the widest rubbery plateau within the series, the highest extension at break, and good recovery properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1449,1460, 2004 [source] Fluoropolyethers end-capped by polar functional groups.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Abstract The kinetics of the dibutyltin dilaurate (DBTDL)-catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z-DOL H-1000 of various molecular weights (100,1084 g mol,1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30,60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl-containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero-order, first-order, second-order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771,3795, 2002 [source] Domain structure and miscibility studies of blends of styrene,butadiene,styrene block copolymers (SBS) and styrene,glycidyl methacrylate statistical copolymers (PS-GMA) using SAXS and DMTAPOLYMER INTERNATIONAL, Issue 3 2007LB Canto Abstract The domain structure and miscibility in the solid state of a series of blends of styrene-butadiene-styrene (SBS) block copolymers and styrene-glycidyl methacrylate (PS-GMA) statistical copolymers with varying molecular weights and compositions were studied using small angle X-ray scattering and dynamic mechanical thermal analysis. Depending on the molecular characteristics of each component, different types and degrees of solubilization of PS-GMA in SBS were found which, in addition to the initially SBS phase morphology, lead to materials with multiphase domain morphologies with differences in size and structure. The degree of solubilization of PS-GMA into the PS domains of SBS was found to be higher for blends containing PS-GMA with lower molecular weight (Mw = 18 100 g mol,1) and lower GMA content (1 wt%) and/or for SBS with higher PS content (39 wt%) and longer PS blocks (Mw = 19 600 g mol,1). Localized solubilization of PS-GMA in the middle of PS domains of SBS was found to be the most probable to occur for the systems under study, causing swelling of PS domains. However, uniform solubilization was also observed for SBS/PS-GMA blends containing SBS with composition in the range of a morphological transition (PS block Mw = 19 600 g mol,1 and 39 wt% of PS) causing a morphological transition in the SBS copolymer (cylinder to lamella). Copyright © 2006 Crown in the right of Canada. Published by John Wiley & Sons, Ltd [source] Effect of poly(ethylene glycol) on the solid-state polymerization of poly(ethylene terephthalate)POLYMER INTERNATIONAL, Issue 3 2006E Bhoje Gowd Abstract Poly(ethylene glycol) (PEG) and end-capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol,1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in Tg and similar crystallization behavior. Solid-state polymerization (SSP) was performed on these blend samples using Sb2O3 as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry [source] Synthesis of a novel luminescent copolymer based on bisphenol APOLYMER INTERNATIONAL, Issue 9 2005Hager Trad Abstract A new luminescent copolymer (BPAEt2 -BP; Scheme 1), with short alternating divinylbiphenyl units and O -diethylated bisphenol A (BPAEt2), was synthesized via the Wittig reaction. The polymer is fully soluble in common organic solvents and has a number-average molecular weight of 4600 g mol,1 with a polydispersity index of 1.79. The structure of the polymer was confirmed by 1H NMR, 13C NMR, FTIR and Raman analysis. Thermal analysis of the polymer showed good stability up to 280 °C. Furthermore, polymer film absorbs at 360 nm and emits in the blue at 426 and 451 nm. The band-gap calculated from the UV-vis spectrum was about 2.80 eV. A single-layer device of the configuration indium tin oxide (ITO)/BPAEt2 -BP/Al has a relatively low turn-on voltage of 3 V. Copyright © 2005 Society of Chemical Industry [source] Ring-opening polymerization of D,L -lactide by rare earth 2,6-dimethylaryloxidePOLYMER INTERNATIONAL, Issue 8 2004Lifang Zhang Abstract Ring-opening polymerization of D,L -lactide (LA) has been successfully carried out by using rare earth 2,6-dimethylaryloxide (Ln(ODMP)3) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)3 exhibits higher activity to prepare poly(D,L -lactide) (PLA) with a viscosity molecular weight of 4.5 × 104 g mol,1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)3 has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)3 is 69.6 kJ mol,1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ,coordination,insertion' mechanism with selective cleavage of the acyl,oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry [source] Nickel(II) complexes bearing pyrazolylimine ligand: synthesis, structure, and catalytic properties for vinyl-type polymerization of norborneneAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2010Yuan-yuan Wang Abstract Two nickel(II) complexes of {2-[C3HN2(R1)2 -3,5]}[C(R2)N(C6H3iPr2 -2,6)]NiBr2 (complex 1: R1 = CH3, R2 = 2,4,6-trimethylphenyl; complex 2: R1 = R2 = Ph) were synthesized and characterized. The solid-state structure of complex 1 has been confirmed by X-ray single-crystal analysis. Activated by methylaluminoxane (MAO), complexes 1 and 2 are capable of catalyzing the polymerization of norbornene with moderate activities [up to 10.56 × 105 gPNBE (mol Ni h),1] with high molecular weights (Mw,13.56 × 105 g mol,1) and molecular weight distributions were around 2. The influences of polymerization parameters such as reaction temperature and Al,Ni molar ratio on catalytic activity and molecular weight of the polynorbornene were investigated in detail. The obtained polynorbornenes were characterized by means of 1H-NMR and FTIR techniques. The analytical results of polymer structures indicated that the norbornene polymerization is vinyl-type polymerization rather than ROMP. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of excluded volume and polydispersity on solution properties of lentinan in 0.1 M NaOH solution,BIOPOLYMERS, Issue 4 2005Xufeng Zhang Abstract Seven lentinan fractions of various weight-average molecular weights (Mw), ranging from 1.45 × 105 to 1.13 × 106 g mol,1 were investigated by static light scattering and viscometry in 0.1M NaOH solution at 25°C. The intrinsic viscosity [,] , Mw and radius of gyration ,s2, , Mw relationships for lentinan in 0.1M NaOH solution were found to be represented by [,] = 5.1 × 10,3M cm3 g,1 and ,s2, = 2.3 × 10,1M nm, respectively. Focusing on the effects of the Mw polydispersity with the Schulz,Zimm distribution function, the data of Mw, ,s2,, and [,] was analyzed on the basis of the Yoshizaki,Nitta,Yamakawa theory for the unperturbed helical wormlike chain combined with the quasi-two-parameter (QTP) theory for excluded-volume effects. The persistence length, molecular weight per unit contour length, and the excluded-volume strength were determined roughly to be 6.2 nm, 980 nm,1, and 0.1, respectively. Compared with the theoretical value calculated by the Monte Carlo model, the persistence length is longer than that of the single (1 , 3)-,- D -glucan chain. The results revealed that lentinan exists as single-stranded flexible chains in 0.1M NaOH solution with a certain degree of expansion due to the electrostatic repulsion from the interaction between the OH, anions and lentinan molecules. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 187,196, 2005 [source] Modeling Thermal and Mechanical Effects on Retention of Thiamin in Extruded FoodsJOURNAL OF FOOD SCIENCE, Issue 8 2003J.Y. Cha ABSTRACT: A model was proposed to predict separate thermal and mechanical effects of extrusion cooking on thiamin retention. Thermal effects were determined by heating small samples of wheat flour mixed with 0.30% (wt/ wt) thiamin hydrochloride isothermally at 140 °C, 151 °C, and 161 °C for different times. The calculated activation energy and rate constants at each temperature were 67.28 kJ/g mol and 0.00869/min, 0.0145/min, and 0.0224/min, respectively. The "extruder constant" was estimated as 27.7/rev, based on a matching-viscosity method. Wheat flour with 0.30% (wt/wt) thiamin was extruded at different screw speeds. Mechanical effects caused 89.7% to 94.4% of total thiamin loss. This research provides a generalized method to "fingerprint" the extrusion process. [source] | |||||||||||||