bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Adsorption of a Polystyrene‐b‐Polyisoprene Block Copolymer at the n‐Hexadecane/Air Interface
Authors: Price Colin , Chan Eddie K. M. , Hudd Alan L. , Stubbersfield Rita B. 
Published: April 2007

AbstractSurface‐tension measurements were used to investigate the surface adsorption and micellisation of a polystyrene‐b‐polyisoprene block copolymer in n‐hexadecane which is a selectively bad solvent for polystyrene. Measurements were made over a range of concentrations (1.29–2.88)x10−4 mol dm−3 and temperatures 25–40°C. The block copolymer was found to be positively adsorbed at the n‐hexadecane/air interface. The linearity of plots of γ against In c just below the critical micelle concentration (c.m.c.) indicated an approximately constant surface concentration. The area per block copolymer molecule at the surface had an average value of 4.1 nm2. A plot of In (c.m.c.) against T−1 gave a value for the standard enthalpy of micellisation of ‐41.9.3.0 kJ per mole of copolymer chains. The standard entropy contribution (‐TΔSΔ) to the standard free energy of micellisation was found to be 19.7.3.0 kJ mol−1. These thermodynamic values are in good agreement with results obtained earlier for this system by light scattering and calorimetry.
Ionic conductivity of polymer electrolytes and future applications
Authors: Watanabe Masayoshi , Ogata Naoya 
Published: April 2007

AbstractPolymer electrolytes are solvent‐free ion‐conducting polymers and provide new and attractive materials in both polymer chemistry and electrochemistry. A proper understanding of ion dissociation and ion transport in such polymers is necessary for their application as solid electrolytes in electrochemical devices. Ionic conduction behaviour in polymer electrolytes is described here in relation to the characteristic properties. Of special interest is the ability of polymer electrolytes to include various kinds of electroactive molecules within them. The combination of this ability with their high ionic conductivity has enabled polymer electrolytes to be used as media for electrochemical syntheses and redox reactions.
Preliminary results on a new polymer electrolyte, poly(ethyleneoxide)‐Hg(CIO4)2
Authors: Bruce Peter G. , Krok Franciszek , Evans James , Vincent Colin A. 
Published: April 2007

AbstractA new solid polymer electrolyte, poly(ethylene oxide)‐Hg(ClO4)2, has been prepared with the ratio of ethylene oxide units to mercury ions ranging from 4 to 20. The variation of conductivity with temperature does not follow a simple Arrhenius law. At high salt concentrations the films are entirely amorphous.
Radiotracer self‐diffusion measurements in poly(ethylene oxide) and poly(propylene oxide) electrolytes
Authors: Bridges Christopher , Chadwick Alan V. , Worboys Michael R. 
Published: April 2007

AbstractRadiotracer measurements of the 22Na+ and S14CN− diffusion coefficients in PEO‐NaSCN (x = 6, 8 and 12) and PPO‐NaSCN (x = 8) are reported, where PEO = poly(ethylene oxide), PPO = poly(propylene oxide), and x = [EO units]/[NaSCN] or [PO units]/[NaSCN]. The results are compared with ionic conductivity measurements on the same samples. Measurements for the PEO samples were taken above the melting point of pure PEO and the results interpreted, particularly for the sample most dilute in salt, in terms of ‘free ions’ as the dominant charge carriers. For PPO the results are less clear, although there is good evidence for the onset of ion aggregation prior to separation of salt at higher temperatures.
Self‐diffusion of ions in an ethylene oxide oligomer using the gelsectioning technique
Authors: Al‐Mudaris Arkan A. , Chadwick Alan V. 
Published: April 2007

AbstractThe gel‐sectioning technique has been used to measure the radiotracer diffusion coefficients of Na+ and SCN− ions in solutions of sodium thiocyanate in tetra(ethylene glycol) dimethyl ether (‘tetraglyme’), a liquid system which can be used as a model polymer electrolyte. Measurements were made at 298 K over the molar concentration range tetraglyme‐NaSCN between 2.5 and 50. At all concentrations the diffusion coefficients of both ions were virtually identical and decreased markedly at high salt concentrations. Comparison of the diffusion results with conductivity measurements on the same samples gives evidence for the aggregation of ions at low salt concentrations (tetraglyme‐NaSCN > 20). At higher salt concentrations aggregation does not need to be invoked to explain the results. The implications for other polyether electrolytes are discussed.
High frequency impedance of poly(ethylene oxide) and related polymers doped with lithium perchlorate
Authors: Linden E. , Owen J. R. 
Published: April 2007

AbstractHigh frequency complex impedance measurements at room temperature have been used to obtain dielectric constants, sample dimension ratios and conductivities for poly(ethylene oxide), PEO, and poly(propylene oxide), PPO, doped with LiClO4. The corrections required to compensate for artefacts due to instrumentation (leads, cables, etc.) at high frequencies are presented. It is concluded that an area/length ratio (A/l) of about 300 cm is preferable for high frequency work. Dielectric constants varied by less than an order of magnitude over a variety of samples, so that the conductivity of an irregularly shaped sample can be estimated from the dielectric relaxation frequency. It was also concluded that the depression of the impedance semicircle for semi‐crystalline PEO was due mainly to the microstructure.
Poly(ethylene oxide)‐sodium perchlorate electrolytes in solid‐state sodium cells
Authors: West Keld , Zachau‐Christiansen Birgit , Jacobsen Torben , Hiort‐Lorenzen Emil , Skaarup Steen 
Published: April 2007

AbstractThe behaviour of poly(ethylene oxide)‐sodium perchlorate as electrolyte in solid‐state batteries was characterized by impedance spectroscopy with respect to the conductivity and chemical reactivity of the sodium/polymer interface. Formation of a corrosion layer on the sodium electrode was found, and the growth of this layer was followed during open circuit and cycling conditions. It is concluded that the surface resistance is a major contribution to the cell impedance.
Ionic conductivity in mixtures of salts with comb‐shaped polymers based on ethylene oxide macromers
Authors: Cowie John M. G. , Martin Agnes C. S. , Firth Anne‐Marie 
Published: April 2007

AbstractA comb‐shaped polymer was prepared from a vinyl ether monomer comprising three oxyethylene units with a terminal methoxy group. The polymer could dissolve LiClO4, NaClO4, and LiSO3CF3 salts to form homogeneous amorphous mixtures, and the glass transition temperatures in each system were observed to increase with added salt. A.c. conductivity studies on the mixtures of polymer‐LiClO4 showed a dependence on both salt concentration and temperature. Room temperature conductivities were around 10−5Scm−1 rising to about 10−3Scm−1 at ∼ 380K. A maximum in the conductivity was detected which altered with temperature. Conductivities which displayed non‐Arrhenius behaviour were analysed using the Vogel‐Tammann‐Fulcher equation and interpreted on the basis of the configurational entropy model derived by Gibbs and coworkers.
Crosslinked polyethers as media for ionic conduction
Authors: Nest Jean‐Francois Le , Gandini Alessandro , Cheradame Hervé 
Published: April 2007

AbstractA broad outline is given of a comprehensive investigation dealing with solid polymeric electrolytes containing ionic species. These materials are based on various types of polyethers (homopolymers, block and graft copolymers) crosslinked via urethane chemistry and either filled with a salt or transformed into ionomers with the anions attached to the chains. The properties studied were specific volume, swelling, glass transition temperature, viscoelasticity, ionic conductivity, transport numbers, magnetic relaxation of nuclei from both the polymer chains and the ions, and redox stability. Mechanisms and models are proposed to explain chain partitioning by cations and the mode of ionic transport. An all‐solid‐state battery was prepared with one of these materials to prove its good performance.
Solid polymer electrolytes with stable electrochemical properties
Authors: Carré Claudine , Hamaide Thierry , Guyot Alain , Mai Christian 
Published: April 2007

AbstractIn order to build solid‐state ambient‐temperature batteries with stable electrochemical performances over a period of months, the crystallization process in polymer electrolytes can be suppressed by the addition of an elastomer and a styrenic macromonomer of PEO to a PEO‐lithium salt electrolyte. Complex impedance measurements and X‐ray diffraction studies were carried out in an attempt to understand the effect of the macromonomer on the electrochemical behaviour. The conductivity was found to increase with macromonomer content and values as high as 10−5S cm−1 at room temperature can be obtained. X‐ray, diffraction patterns have shown that addition of the elastomer and the macromonomer does not alter the monoclinic unit cell of the crystallized PEO. During ageing, the diffraction lines were found not to vary appreciably over a period of 15 months. Similarly, no appreciable change in the conductivity level was noticed within the same period. The observed behaviour was explained as a suppression of the crystallization process.
The conductivity behaviour of gamma‐irradiated PEO‐LiX electrolytes. I
Authors: Kronfli Esam , Lovell Keith V. , Hooper Alan , Neat Robin J. 
Published: April 2007

AbstractIn an attempt to enhance the room temperature ionic conductivity of PEO‐LiX films, samples have been exposed to gamma‐irradiation at 78°C. The success with which cross‐links have been introduced into the amorphous form has been evaluated from d.s.c. analysis and temperature‐dependent conductivity data. Retardation of the recrystallisation event, associated with uncomplexed poly(ethylene oxide), does not occur over a range of total doses. Changes in overall conductivity levels for the PEO‐LiCF3SO3 ([EO units]/[Li] = 9) system, indicate light cross‐linking at 2.25 Mrad of exposure. However, higher doses result in a substantial amount of chain scission, leading eventually to poor mechanical properties. A similar study on PEO‐LiClO4 ([EO units]/[Li] = 20) confirms that the above route is an ineffective method to improve room temperature conductivity.
Polymer electrolyte complexes of LiCIO4 and comb polymers of siloxane with oligo‐oxyethylene side chains
Authors: Fish Daryle , Khan Ishrat M. , Wu E. , Smid Johannes 
Published: April 2007

AbstractPolysiloxanes with oligo‐oxyethylene side chains of the type —O(CH2CH2O)7CH3 and —(CH2)3O(CH2CH2O)nCH3 (average n ≈ 7 and 11) were synthesized from poly(hydrogenmethylsiloxane) and characterized by 1H n.m.r., 29Si n.m.r., i.r. and g.p.c. Cyclic analogues were used as model compounds and synthesized from tetramethylcyclotetrasiloxane. Polymer electrolyte complexes were made from the comb polymers and LiClO4 by solvent‐casting from THF, and their conductivities measured as a function of temperature and studied by differential scanning calorimetry and correlated with their conductivity behaviour. Maximum conductivities close to 10−4S cm−1 were achieved at room temperature and at ethylene oxide units to Li+ ratios of about 25. Cross‐linking or blending with high molecular weight poly(oxyethylene) lowers the conductance somewhat but vastly improves the mechanical properties of the complexes, and the blends with PEO can be cast into thin, flexible and tough films with good conducting properties.
Improved synthesis of oxymethylene‐linked poly(oxyethylene)
Authors: Nicholas Christian V. , Wilson David J. , Booth Colin , Giles Jeremy R. M. 
Published: April 2007

AbstractPolyethylene glycol 400 was reacted with CH2Cl2 in the presence of KOH to form oxymethylene‐linked chains. The method gave a high yield of colourless high‐molecular‐weight elastomer. The ionic conductivity of a mixture of the polymer with LiCF3SO3 ([O]/[Li] = 25) was about 5 × 10−5S cm−1 at 25°C.
Monomer sequence determinations of aryl ether sulphone copolymers as determined by 13C n.m.r.
Authors: Bunn Alan 
Published: April 2007

AbstractThe monomer sequence distributions of three types of aryl ether sulphone copolymers have been determined by 13C n.m.r. spectroscopy. Two amorphous aryl ether sulphone copolymers were shown to have transetherified (or ether interchanged) during polymerisation to become random copolymers. The residues in these copolymers were (i)—OøOøSO2øS—and (ii)—OøSO2øøSO2ø—‐where ø denotes 1,4‐phenylene. Copolymers of 50:50 aryl ether sulphone and aryl ether ketone made from different combinations of monomers were found to have different solubilities in dimethyl sulphoxide, and from 13C n.m.r. data this was shown to correlate with the amount of transetherification which had taken place during the polymerisations. The 13C n.m.r. chemical shifts for some of the carbon nuclei in these polymers were sensititive to functional groups situated even as far away as three or four aromatic nuclei along the polymer chain.
Phase separation in non‐solvent/dimethylformamide/polyethersulphone and non‐solvent/dimethylformamide/polysulphone systems
Authors: Swinyard Brian T. , Barrie James A. 
Published: April 2007

AbstractThe cloud point curves for the ternary solutions non‐solvent/dimethyl‐formamide/polyethersulphone and non‐solvent/dimethylformamide/polysul‐phone were determined by a titration technique, at 303 K. In both systems the following order of increasing non‐solvent content at the cloud point was obtained: water < methanol < ethanol < 1‐propanol < acetone < carbon tetrachloride. For each non‐solvent the cloud point curve for the PES system occurred at higher non‐solvent concentrations than for the corresponding PSN system.
New production technologies and applications of poly(vinyl alcohol) film
Authors: Moroi Hiroyuki 
Published: April 2007

AbstractThe following aspects of the manufacture, properties and applications of biaxially oriented poly(vinyl alcohol) (PV‐OH) films are discussed: selection of starting PV‐OH; method of production by successive biaxial orientation: technical aspects of production; characteristics and applications of the film. Biaxially oriented PV‐OH films have good antistatic properties, good thermal resistance, oil and solvent resistance, and excellent gas barrier properties, and are used in food packaging applications.The following aspects of the manufacture, properties and applications of poly(vinyl alcohol) film produced by a blown film technique are discussed: selection of starting PV‐OH; process for the production of hot‐water‐soluble (HWS) film; technical aspects of film production; characteristics and applications of the film. Blown films, which are hot‐water‐soluble, are produced in tubular form, for conversion into disposable laundry bags.
The influence of poly(vinyl alcohol) suspending agents on suspension poly(vinyl chloride) morphology
Authors: Ormondroyd Stephen 
Published: April 2007

AbstractThe requirements for PVC suspension resin have changed considerably in the last few years, so much so that few companies have products on their ranges that are more than 4 or 5 years old. The suspending agent has a crucial influence on the morphology of the resin, so the changes in resin characteristics have largely been achieved by changes in the suspending agent systems.After a brief review of the mechanism of PVC suspension polymerisation, the properties of polymers made using PVOH suspending agents are related to changes in the latter. The effect of variations in PVAc degree of hydrolysis and viscosity are related to changes in surface tension. Methods of achieving higher porosity by using low hydrolysis co‐suspending agents are described. It is shown that higher bulk densities can be achieved by delayed addition of the PVOH. Levels of conjugated unsaturation and copolymer distributions are also shown to have important influences.
Inhibition period of vinyl acetate monomer in suspension, emulsion and bulk polymerization at 730mm Hg and 760 mm Hg
Authors: Rao Vyakaranam K. , Singh Rajendra P. , Bisarya Satish C. 
Published: April 2007

AbstractA trend in the inhibition period of vinyl acetate monomer (VAM), using benzoyl peroxide (Bz2O2), azobisisobutyronitrile (AIBN) and potassium peroxy disulphate (K2S2O8), during suspension, emulsion and bulk polymerizations, with change in pressure from 730 mm Hg to 760 mm Hg, is reported.
PMR‐15 processing, properties and problems—a review
Authors: Wilson Douglas 
Published: April 2007

AbstractThe frontrunner in the race to develop a high temperature resin for use in advanced composites intended for high temperature applications is the NASA developed polyimide PMR‐15. One of the key factors in the success of the material is the relatively easy processing which is due mainly to the use of the PMR approach (Polymerisation of Monomeric Reactants). Prepreg and high quality composite laminates (glass or carbon) can be prepared with ease. Laminate properties compare well with conventional epoxy based systems but thermal stability is much greater. Continuous use temperatures are in the range 280‐300°C, some 150‐170°C higher than epoxy systems. Applications of PMR‐15 composites include aero‐engines, missiles, spacecraft and military aircraft. Despite being the leading system available today PMR‐15, like all materials, has a number of limitations affecting its widespread use. Included in these are reliable methods of quality control, prepreg batch to batch variability, microcracking from thermal cycling, health and safety hazards and high temperature processing. This paper reviews the present status of PMR‐15 development and outlines work designed to identify and where possible overcome these limitations.
Reaction mechanism, kinetics and network structure of the DGEBA‐DDS system
Authors: Grenier‐Loustalot Marie‐Florence , Grenier Philippe , Horny Patrick , Chenard Jean‐Yves 
Published: April 2007

AbstractDifferent techniques were used to analyse the reaction mechanisms and kinetics of the system 2,2‐[4‐(2,3‐epoxypropyl)phenyl]propane polycondensed with 4,4′‐sulphonyl‐dianiline in the temperature range 100−185°C. The results show the role of catalysts, of stoichiometry and of curing cycles in the reaction mechanisms and paths.Based on chemical balances of residual epoxy groups, and of hydroxy and ether groups formed, we have shown the effect of these functions on the thermal properties of the material.
Entrapping of acid phosphatase in poly(2‐hydroxyethyl methacrylate) matrices: Preparation and kinetic properties
Authors: Cantarella M. , Cantarella L. , Alfani F. 
Published: April 2007

AbstractThe present work was undertaken to determine the influence of immobilization of acid phosphatase by entrapment in poly(2‐hydroxyethyl methacrylate) (poly‐HEMA) gels on the rate and duration of p‐nitrophenyl phosphate hydrolysis. This enzyme was selected as model system for the sake of comparison with other immobilization techniques studied previously making use of natural polymers. Under certain conditions, catalyst inactivation induced by chemical agents employed during polymerization was very low. Activity recovery in the enzymatically filled hydrogels depends on acid phosphatase loading and attains a maximum at 2 mg per gram of support. The use of low molecular weight linear polymers as matrix fillers is advisable. The best results were achieved with poly(ethylene oxide) PEG 1500, but PEG 6000 and poly(N‐vinylpyrrolidone) PVP 10 000 are also effective. Bovine serum albumin (BSA) is useless. The highest value of activity recovery obtained was 24% that of free enzyme. Roughly 30% of enzyme is retained in active form in the hydrogel and works with an efficiency ranging from 97% to 90% depending on average particle size. The kinetic parameters Km and Ea suggest the presence of a combined diffusive and enzymatic reaction‐controlling mechanism. Only a minor shift of optimum pH was observed. Both operational and storage stability are largely improved upon entrapping in hydrogels.
Studies on the polymerization of propylene using high activity ziegler‐natta catalysts. 1: Kinetic models for rate decay in ziegler‐natta polymerization
Authors: Tait Peter J. T. , Wang Shemin 
Published: April 2007

AbstractKinetic models for describing the time dependence of the polymerization rate and active centre concentration for high activity Ziegler‐Natta catalyst systems are discussed. It is demonstrated that the decay in the rate of polymerization and in the concentration of active centres with time for the polymerization of propylene with the heterogeneous catalyst system MgCl2/EB/TiCl4Al(i‐Bu)3/EB can be represented better by a modified multi‐centre first order decay model than by the other models which are considered.
Morphology and mechanical properties of styrene‐butadiene‐styrene/polystyrene semi‐interpenetrating polymer networks and their blends
Authors: Shyu Shin‐Shing , Chao An‐Chong 
Published: April 2007

AbstractSBS/PS semi‐interpenetrating polymer networks (semi‐IPNS) were synthesized by swelling a linear styrene‐butadiene‐styrene (SBS) triblock copolymer (SBS, Kraton 1102) with styrene monomer plus benzoin as photoinitiator and divinylbenzene as cross‐linking agent. Polyblends were prepared by solution casting of SBS and polystyrene (PS) in their ideal solvents. Measurements were made for viscoelastic properties and mechanical properties of phase‐separated polymer alloy (including SBS copolymers Kraton 4122), semi‐IPNs and polyblends of several SBS and PS, with the same total PS content (48% PS). The dynamic mechanical behaviour shows distinct transitions for each polymer, in agreement with electron microscopy results that SBS/PS polymer alloy forms two phases; however, the phase domains were finer in the semi‐IPNs than in SBS triblock copolymer and in polyblends of the corresponding polymers. Stress‐strain data show that semi‐IPNs exhibit higher tensile strength and modulus than the other two corresponding polymer alloys. A master curve was plotted to illustrate the stress relaxation behaviour of samples at higher temperatures. Our results also reveal that semi‐IPNs have much better high‐temperature mechanical strength.
Emulsion polymerisation of highly water‐insoluble monomers
Authors: Satpathy Uma S. , Dunn Alexander S. 
Published: April 2007

AbstractContrary to an earlier report, monomers (e.g. p‐tert‐butylstyrene and octadecyl methacrylate) which are less soluble in water than styrene have been found to polymerise in emulsion using persulphate initiation. At 60°C, the order of the Interval II polymerisation rate of octadecyl methacrylate is 0.48 in persulphate concentration and 0.68 in sodium dodecyl sulphate concentration. The rate is increased by addition of methanol to the aqueous phase. Unlike styrene, p‐tert‐butylstyrene could not be polymerised in aqueous suspension by persulphate in the absence of emulsifier. High emulsifier‐monomer ratios were used in these experiments so that it is possible that mini‐emulsion droplets were a significant reaction locus.
Interpenetrating polymer networks from castor oil based polyurethanes and poly(ethyl acrylate)
Authors: Patel Prashant , Patel Mayur , Suthar Bhikhu 
Published: April 2007

AbstractPolyurethanes were obtained by the reaction of hydroxyl groups of castor oil with hexamethylene diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate using an NCO/OH ratio of 1.6. These polyurethanes were swollen in ethyl acrylate monomer and subsequently polymerized by radical polymerization initiated with benzoyl peroxide in the presence of the crosslinking agent ethylene glycol dimethacrylate. A series of interpenetrating polymer networks (PU/PEA IPNs) were obtained as tough films by casting in glass moulds. The characteristics of these films were determined: resistance to chemical reagents, thermal behaviour (DSC, TGA), tensile strength, Young's modulus, elongation at break (%) and Shore A hardness. The morphology was determined by scanning electron microscopy, and the dielectric properties such as electrical conductivity, dielectric constant (ε′), dielectric loss (ε″) and loss tangent (tan δ) were studied.