bluuebunny/crossref_metadata_2025_split huggingface dataset:
Control of polymerization processes of 10,12‐pentacosadiynoic acid LB films
Authors: Ogawa Kazufumi 
Published: April 2007

AbstractStudies have been carried out on KrF excimer laser light (EX), X‐ray or electron beam (EB) induced polymerization of 10,12‐pentacosadiynoic acid (PDA) Langmuir‐Blodgett (LB) films in relation to molecular density or molecular arrangement of the films using X‐ray diffraction analysis, infrared (IR) spectroscopy and Raman spectroscopy. The molecular arrangement or density of the PDA LB films was controlled by subphase conditions when the films were built up, such as pH, temperature of a subphase or salt concentration in the subphase. Polymerization sensitivity of the PDA LB film was affected by the arrangement or molecular density. On low density (A type) films the polymerization occurred by irradiation with EX, X‐ray or EB, but on high density (B type) films the polymerization occurred only when the irradiation was carried out by high energy beams such as X‐ray or EB. Decomposition of polymerized films was observed further by excessive irradiation of EX or X‐ray, but not on the B type films. It was revealed by X‐ray diffraction analysis that in the A type film, the PDA molecules bent to a larger extent than those in the B type film and the polymerization proceeded topochemically, that is, the thickness decreased little after EB irradiation in a helium atmosphere. On the other hand, in the B type film, the thickness decreased by about 10% as a result of EB irradiation. By IR reflection‐absorption (RA) and Raman measurements, it was confirmed that conjugated diacetylenic bonds disappeared and conjugated double and new conjugated triple bonds appeared after high energy beam irradiations. These results support the supposition that 1,4‐polymerization, i.e. polydiacetylene type polymerization, occurs easily in the A type film and 1,2‐ or 3,4‐polymerization, i.e. polyacetylene type polymerization, occurs in the B type film, and that the polymerized A type film was decomposed at the polydiacetylenic bond when the irradiation continued further. It was also shown that the polyacetylene type polymer was obtained only when the B type film was irradiated with the high energy beam.
Organic and polymer planar optical waveguides
Authors: Zheng Shu , Simon George P. , Binh Le N. 
Published: April 2007

AbstractSingle‐mode and multi‐mode planar optical waveguides with low loss were fabricated by spin‐coating thin films of poly(vinyl alcohol) (PVAl) and 4‐dihexylamino‐4′‐nitro‐stilbene (DHANS) doped poly(methylmethacrylate) (PMMA) onto glass substrates, and characterised by theoretical analysis and optical guided‐mode measurements. The optical constants of the waveguides were determined with good accuracy by measuring the coupling synchronised angles and fitting them, via a recursion method, into the waveguide dispersion equations. The number of the guided modes observed in these thin films can be controlled by tailoring the film thickness.
Syntheses and investigations of copolymers for improving the flow of middle distillate oils
Authors: Alan Holder G. , Macauley David 
Published: April 2007

AbstractThe results of a review of the patent literature on polymeric flow improvers for distillate fuels showed that a diverse range of polymeric compositions is effective. Ethylene‐containing compositions predominate and of these ethylene‐vinyl acetate (EVA) copolymers are the most common. Ethylene‐vinyl acetate copolymers were synthesised using a high pressure autoclave. The effectiveness of the copolymers varied greatly with the chemical composition of the copolymer. The techniques described in the literature for the determination of the composition of EVA copolymers are summarised and reviewed. A new technique using proton nuclear magnetic resonance was developed. A statistical analysis of the results is presented.
Mesomorphic polyblends of poly(p‐phenylene terephthalamide) and poly(4,4′‐terephthanilide adipamide)
Authors: Son Tae Won , Kim Byoung Chul 
Published: April 2007

AbstractA simultaneous dissolution of two lyotropic polyamides, poly(p‐phenylene terephthalamide) (PPTA) and poly(4,4′‐terephthanilidc adipamide) (PTAd), in a concentrated H2SO4 (1 to 1.5% wt) produced an isotropic single phase solution. The crystallinity of PPTA/PTAd blends confirmed formation of a mesomorphic polyblend to the molecular level. With increasing concentration, solutions of these PPTA/PTAd blends in 100% H2SO4 showed a sequential phase change typical of a single lyotropic polymer. Further, the ternary solution exhibited a wider biphase range than both binary solutions of PPTA/100% H2SO4 and PTAd/100% H2SO4. Dry‐jet wet spinning of anisetropic solution of this ternary composition with a PTAd weight fraction less than 0.5 enabled us to obtain PPTA/PTAd blend fibers. Including a PTAd weight fraction of 0.1‐0.15 reduced both the orientation angle and fibrillation. The particular blend fiber with a PTAd weight fraction of 0.15 exhibited a synergistic effect on the mechanical properties.
Viscoelastic behaviour in the molten state of low density polyethylene‐polybutene 1 blends
Authors: Deri F. , Behar O. 
Published: April 2007

AbstractThe viscoelastic behaviour in the molten state of low density polyethylene‐polybutene 1 blends has been studied according to temperature, shearing stress and shearing rate. Measurements were made with a capillary viscometer for the static properties and a balance‐rheometer system of Kepes for the dynamic properties. Correction of experimental data has been performed and flow activation energies at a constant shear stress determined, whilst elasticity was investigated by means of the Barus factor. Furthermore, an investigation has been performed on variations of the real η′ and imaginary η″ parts of the complex viscosity with regard to the pulsation frequency ω. The Cole‐Cole and the Smyth representations were utilised to determine the Newtonian viscosity ηo, the parameter of distribution of relaxation time h and the average relaxation time ηo.
Solid state NMR detection of molecular mixing in bieutectic blends, d‐metal complexes, and phase‐separated copolymers
Authors: Belfiore Laurence A. , Graham Hugh , Veda Eiji , Wang Yinghua 
Published: April 2007

AbstractThis research contribution addresses micromixing in polymer blends that exhibit strong intermolecular association. Specific interactions between dissimilar blend components are detected via high‐resolution solid state proton and carbon‐13 NMR spectroscopy. The isotropic chemical shifts of the critical component provide strong evidence that molecular complexes form. NMR spectral differences between the blends versus the undiluted components arise from crystal structure modifications (if appropriate), conformational changes, hydrogen bonding, d‐metal coordination, or altered packing geometries that occur concomitantly with the mixing process. More convincing evidence that two components of a strongly interacting blend reside in a near‐neighbor environment is obtained from the measurement of proton spin diffusion between dissimilar species. Proton spin diffusion is measured directly via the high‐resolution CRAMPS experiment (Combined Rotation And Multiple Pulse Spectroscopy) in a homogeneous solid solution of poly(ethylene oxide) and resorcinol, and indirectly via the carbon‐13 spin system in a modified version of the Goldman‐Shen experiment for microphase‐separated ionic and tri‐block copolymers. One of the primary objectives of this research endeavor is to bridge the gap between macroscopic and site‐specific probes of phase behavior and strong interaction in mixtures that form homogeneous solid solutions or coordination complexes. In this respect, results from a macroscopic phase of the polymer‐blend research are included in this contribution. Thermal and mechanical properties are measured for strongly interacting systems, whose interaction sites are characterized via solid state NMR. Metal‐ligand coordination in blends of nickel acetate with poly(4‐vinylpyridine) produces an extraordinary synergistic effect on the glass transition response. The maximum increase in blend Tg relative to the undiluted polymer is in the order of 100°C. Coordination between the nitrogen lone pair in poly(4‐vinylpyridine) and the zinc cation in DuPont's SURLYNTM ionomers produces a 15% enhancement in mechanical fracture stress relative to the undiluted ionomer. The success of our structure‐property relationship scheme described herein, which bridges microscopic detection of site‐specific interactions (via NMR) with practical macroscopic (DSC and stress‐strain) measurements, depends upon our ability to understand material properties at a level where continuum hypotheses are no longer valid.
Temperature transitions and compatibility in gradient interpenetrating polymer networks
Authors: Lipatov Yu. S. , Karabanova L. V. , Gorbach L. A. , Lutsyk E. D. , Sergeeva L. M. 
Published: April 2007

AbstractTraditional and gradient IPNs of various composition have been prepared from cross‐linked polyurethane and poly(butyl methacrylate). For various layers of gradient IPN cut from the surface to the centre the glass transition temperatures and composition have been determined. The sorption of benzene vapour by various layers was measured, and from these data the free energy of mixing IPN components has been calculated.For all the layer compositions free energies of mixing are positive and dependent on the distance from the sample centre. This effect is thought to be connected not only with composition but with various conditions for phase separation in various layers.Each layer consists of two phases with their own glass transition temperatures. From these data, using the Fox equation, the composition of each phase for various layers have been calculated and the volume ratio of phase evolved was estimated.
Synthesis and characterization of polyimides and polyamide‐imides containing azomethine linkages
Authors: Idage Susheela B. , Idage Bhaskar B. , Vernekar Subhash P. 
Published: April 2007

AbstractPolyimides and polyamide‐imides containing azomethine linkages in the polymer backbone have been synthesized from 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenylether (ODAI), 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenyl‐methane (MADI), 4,4′‐bis(4‐isocyanatobenzylidene)‐diaminodiphenylsulphone (SDAI), pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and trimellitic anhydride (TMA), by a one‐step process. The diisocyanates ODAI, MDAI and SDAI were prepared from the corresponding diacids, namely, 4,4′‐bis(4‐carboxybenzylidene)‐diaminodiphenylether (ODAA), 4,4′‐bis(4‐carboxybenzylidene)‐diaminodiphenylmethane (MDAA) and 4,4′‐bis‐(4‐carboxybenzylidene)‐diaminodiphenylsulphone (SDAA) by a Weinstock‐modified Curtius rearrangement method. All the polycondensation reactions were conducted in N‐methyl‐2‐pyrrolidone (NMP) under identical conditions and the polymers obtained were characterized by IR spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry and X‐ray diffraction.
Non‐steady‐state model for kinetics of free radical polymerization, 3. Direct photo‐initiation
Authors: Lin Jianming , Yan Deyue , Yuan Cuiming 
Published: April 2007

AbstractThe non‐steady‐state kinetics of directly photo‐initiated polymerization were studied theoretically. Taking account of the facts that the amount of monomer consumed in propagation is much more than that in initiation for a process producing high polymer and that the rate constant of chain termination is much larger than that of chain propagation or transfer, a few very close approximations were adopted to solve the set of kinetic differential equations of the polymerization under consideration. The inexplicit function method developed in a previous paper of this series for the derivation of the molecular weight distribution function is still valid in this work. Some numerical computation was implemented to show the tendency of free radical concentration decay and the plots of molecular size distribution.
The effect of the vinyl acetate content and distribution in poly(vinyl alcohol/vinyl acetate) copolymers upon their electronic absorption spectra in aqueous and electrolyte solutions
Authors: Eagland Donald , Crowther Nicholas J. , Donners Wim A. B. , Vercauteren Frank F. 
Published: April 2007

AbstractAbsorbance measurements over a temperature range of 1‐35°C, at wavelengths of 205 and 262 nm, are presented for a series of aqueous and electrolyte solutions of poly(vinyl alcohol/vinyl acetate) copolymers, of varying acetate group content and distribution. The results reflect the effect of both the nature of the solvent and the microarchitecture of the macromolecule in dictating the conformation of the polymer and hence the degree of exposure of the carbonyl moiety of the acetate group to the solvent.
Aqueous polyurethane dispersions: Effects of dmpa and bisphenol a polyol on dispersion and physical properties of emulsion cast films
Authors: Lee Young Min , Kim Tae Kyoon , Kim Byung Kyu 
Published: April 2007

AbstractAqueous dispersions of polyurethane (PU) ionomers were prepared from hydrogenated diphenylmethane diisocyanate (H12MDI), poly(tetramethylene adipate) glycol (PTAd), bisphenol A propylene oxide ether glycol (LER), and dimethylol propionic acid (DMPA) as potential ionic centres. The urethaneforming reaction was carried out in N‐methyl‐2‐pyrrolidone (NMP) with dibutyltin dilaurate (DBT) as catalyst. The effects of DMPA and bisphenol A polyol on the particle size of the dispersions, and the physical properties of the emulsion cast films were determined. It was found that the particle size decreased with DMPA, and increased with bisphenol A polyol contents. Initial modulus and tensile strength of the emulsion cast films increased, and the elongation at break decreased with DMPA and bisphenol A polyol contents. The results were interpreted in terms of increased interchain Coulombic forces and urethane linkages with DMPA, and increased chain rigidity of PU with bisphenol A polyol incorporation.
Synthesis and biological activity of polyketones
Authors: Patel N. Z. , Patel J. N. , Patel R. M. , Ray R. M. 
Published: April 2007

AbstractPolyketones have been prepared by reacting benzene, chloroacetyl chloride, 1,2‐dichloroethane and dichloromethane using anhydrous aluminium chloride as catalyst and nitrobenzene as solvent. Polyketones were characterized by IR which showed the presence of carbonyl and chlorine groups in the resins. Thermal analysis showed the remarkable thermal stability of the resins. All the polyketones were tested for their biological activity against P.fluorescens, B. subtilis, A. niger and T. viride. The results show that most of the polyketones can be used as antibacterial and antifungal agents.
Polymerization of monomer films of triazine dithiols on a copper surface
Authors: Mori Kunio , Oishi Yoshiyuki , Miyashita Tokuji , Matsuda Minoru 
Published: April 2007

AbstractOn heating films of long‐chain alkylamino‐1,3,5‐triazine‐2,4‐dithiols, substituted with unsaturated groups in the 6‐position, on copper plates in air, the films become partially insoluble in benzene. The polymerization rate and monomer conversion increased with temperature above 80°C and with time. At low temperatures, an induction period was observed. The detailed behavior was dependent upon the number and length of the alkyl chains. Films with high packing density polymerized more slowly. In the presence of azobis(isobutyro)nitrile (AIBN) and benzoyl peroxide (BPO), the rate and conversion increased and the induction period disappeared. The optimum concentration of initiators was approximately 0.0025 mol% of monomer. The polymerization of the films was initiated by oxygen activated with copper, or by radicals derived from AIBN and BPO. It is proposed that the growth of polymer proceeded mainly by the addition of thiyl radicals to unsaturated groups, the insoluble polymers being formed by the coupling of thiyl radicals.
N,N′‐methylene‐bis‐acrylamide‐crosslinked polyacrylamides as supports for dithiocarbamate ligands for metal ion complexation
Authors: Mathew Beena , Rajasekharan Pillai V. N. 
Published: April 2007

AbstractThe complexation behaviour of dithiocarbamate functions supported on polyacrylamides with varying extents (2‐20 mol%) of N,N′‐methylene‐bis‐acrylamide (NNMBA) crosslinks was investigated. The crosslinked polyacrylamides were prepared by the free radical solution polymerization of the monomers in water at 80°C using potassium persulphate as initiator. The dithiocarbamate ligands were introduced by polymer‐analogous reaction involving transamidation with ethylenediamine and dithiocarbamylation with carbon disulphide and alkali. The complexation behaviour of these dithiocarbamate resins with the ligand functions in different macromolecular environments were investigated towards Co(II), Ni(II), Cu(II), Zn(II) and Hg(II) ions by a batch equilibration technique. The metal ion intake varied with the extent of the NNMBA‐crosslinking. Thus the 8% crosslinked system has the highest complexation capacity. The values for metal ion intake followed the order Hg(II)> Cu(II)> Zn(II)> Ni(II)> Co(II). The time‐course of complexation, the possibility of recycling and the swelling characteristics of the uncomplexed and complexed resins were considered, and IR characterization and thermal studies were undertaken. The swelling values of the complexed resins are lower than those of the uncomplexed resins. The thermal stability of dithiocarbamates varied with the extent of NNMBA‐crosslinks and with the metal ion.
Ageing effects on mechanical properties of gutta‐percha (trans‐polyisoprene)
Authors: Arvanitoyannis Ioannis , Blanshard John M. V. , Kolokuris Ioanniis 
Published: April 2007

AbstractThis study examined both the effect of chemical composition and of storage (ageing), for periods up to 28 weeks, and at temperatures from ‐ 15 to 50°C on the mechanical properties.The presence of high contents of barium sulphate, zinc oxide and colouring agent in commercial dental gutta‐percha has the same effect on the mechanical properties of gutta‐percha as prolonged storage time, i.e. increase in brittleness. On the contrary, the presence of Thermoplast or Wax (75%) has an accentuated plasticising effect on gutta‐percha improving thus, to a certain extent, its clinical characteristics.
Dielectric relaxations in poly [2,2‐propane‐bis‐(4‐phenyl thiocarbonate)]
Authors: Sanchez Martínez E. , Díaz‐Calleja R. , Montserrat Ribas S. , Gargallo L. , Radić D. 
Published: April 2007

AbstractThe dielectric relaxation properties of poly[2,2‐propane‐bis‐(4‐phenyl thiocarbonate)] (PTC) have been studied. The existence of crystallinity, which can be eliminated by quenching, is detected. The degree of crystallinity of polymer samples was determined by differential scanning calorimetry in order to investigate the effect of this factor on the dielectric behaviour of this polymer. The thermal degradation of the samples was studied by thermogravimetry. The degradation of the polymer begins before the glass transition temperature Tg. The dielectric spectrum is complex showing several relaxation phenomena. With increasing temperature a γ relaxation can be observed at ‐ 100°C (5 kHz). The activation energy obtained from an Arrhenius plot (lnfvs T−1) is 6 kcal mol−1. At 160°C the α relaxation which is associated with the glass transition temperature Tg is detected. The dielectric behaviour of this poly(thiocarbonate) is compared with the corresponding poly(carbonate).
Radiation degradation of statistical terpolymers of two aromatic diols with diphenyl sulphone
Authors: Hill David J. T. , Lewis David A. , O'donnell James H. , Pomery Peter J. , Hedrick James L. , McGrath James E. 
Published: April 2007

AbstractThe variation in radiation resistance with composition of statistical terpolymers of (1) bisphenol‐A and biphenol, and (2) hydroquinone and biphenol, with diphenyl sulphone was studied by electron spin resonance spectroscopy after γ irradiation at 77 K and by analysing volatile products after irradiation at 423 K. Approximately linear relationships were obtained between the radiation chemical yields for both radicals, G(R), and sulphur dioxide, G(SO2), and the mole fraction of biphenol units in the terpolymers. Substantially higher radiation resistance was shown by biphenol units compared with either bisphenol‐A or hydroquinone.
A study of polycarbonate‐liquid crystal polymer blends
Authors: Magagnini P. L. , Paci M. , La Mantia F. P. , Valenza A. 
Published: April 2007

AbstractThe morphology and the thermal and mechanical properties of blends of bisphenol‐A polycarbonate (PC) with a wholly aromatic liquid crystal copolyester‐amide (Vectra‐B of Hoechst‐Celanese) are discussed with reference to the conditions used for their preparation. The blends made by extrusion behave as mixtures of incompatible polymers: the dispersed liquid crystalline phase is more or less oriented in the extrusion direction and acts as a reinforcing filler for the PC matrix. The behaviour of the blends prepared in a batch mixer depends strongly on mixing time. A slight decrease in the mechanical properties (especially tensile strength and elongation) accompanies the morphological changes associated with a progressive improvement in the compatibility of the two polymers, which finally leads to an apparently homogeneous material after 45 min mixing at 290°C and 150 rpm. These effects are interpreted in terms of chemical interactions taking place between the two components of the blends.
Surface properties of carbons from poly(vinyl chloride)
Authors: Youssef A. M. , Abdel‐Bary E. M. , Dowidar A. M. 
Published: April 2007

AbstractNon‐activated carbons were prepared by the thermal degradation of poly(vinyl chloride) (PVC) in air or nitrogen atmosphere in the temperature range 600‐1000°C. Carbon dioxide‐activated carbons from PVC were also obtained by gasification of non‐activated carbon from PVC at 900°C burn‐off (4‐50%).Thermal degradation in air atmosphere gave high carbon yield because the oxygen of air increased crosslinking at lower temperature and chemisorbed on the carbon surface at high temperatures. Thermal degradation in air and gasification with carbon dioxide created carbon‐oxygen surface groups which increased the hydrophilicity of the carbon surface and consequently increased water adsorption capacity. Gasification with carbon dioxide to high burn‐off created new pores and widened already existing pores.
Flow stress of high density polyethylene and nylon 66 at high rates of strain
Authors: Ahmad S. H. 
Published: April 2007

AbstractMeasurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 103 s−1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 103s−1.