bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of polypyrrole having an alkyl side chain
Authors: Kaeriyama Kyoji , Masuda Hideyuki
Published: April 2007

Electrochemical polymerisation of 3‐octylpyrrole (OCPY) was studied. Its conductivity was 5 S/cm at an optimal current density of 0.5 mA/cm2. Cyclic voltammograms of poly(3‐octylpyrrole) (POCPY) films were measured in the presence of various electrolytes and their shapes were virtually independent of the electrolytes used. There was an anodic peak at 0.16 V (versus Ag) and a cathodic peak at 0.12 V. Optical absorption spectra were measured at various levels of doping. The neutral film showed one peak at 3.5 eV, corresponding to the π‐π* transition. The oxidised film showed two peaks in the lower energy regions, suggesting it was in the bipolaron state. Scanning electron microscope (SEM) observation revealed a process of unique morphology formation.
Step‐growth polymerization of aniline with unsaturated aldehydes
Authors: Šebenik A. , Osredkar U. , Zidar R.
Published: April 2007

Abstract: Reactions between aniline and acrolein, crotonaldehyde or cinnamaldehyde were studied by ID and 2D ' H and 13C NMR spectroscopy and by GPC. In the first step, two main reactions cursimultaneously: the addition of the amino groups of aniline to the double bond and to the aldehyde group of the unsaturated
aldehydes. In thc ncxt step of the reaction high molecular weight, red coloured resins soluble in organic solvents are formed. The molecular weights of the resins depend on reaction conditions and on the type of unsaturated aldehyde. From the concentration dependence of different molecular weight products on reaction time the rateconstants werecalculated. It was found that the values for the rate constants depend on the type and quantity of catalyst, on the reaction media and on the type of aldehyde.
Polyaniline/polyurethane. LiCIO4 conducting polymer composite
Authors: Yi‐Rui Chen , Dong‐Pu Fang , Xin‐Hua Xu
Published: April 2007

In the present paper, we describe a novel electrically conducting composite, PAn/Pu. LiClO4. The composite was obtained by in‐situ polymerization of aniline on to Pu. LiClO4 film. The composite film doped with HCl showed a conductivity of c. 1.65 S/cm, with good stability in air and good mechanical strength. The composite increased the interface area 2 to 8 times and depressed the contact resistance between the two polymer phases. A battery was constructed from this composite. The coulombic efficiency was c. 96%.
Influence of synthesis on the structure of electrochemically prepared electrically conducting polymers
Authors: Mitchell G. R. , Davis F. J. , Kiani M. S.
Published: April 2007

The inherent possibility of structural anisotropy in polypyrrole and other heterocyclic systems is introduced. By selecting the appropriate electrochemical variables including monomer and dopant type this intrinsic molecular anisotropy may be used to prepare films with well defined global anisotropy, in which the planes of the pyrrole rings prefer to lie parallel to the electrode surface. The conditions for obtaining such materials are discussed and some of the effects of these novel anisotropic structures on the resultant properties are highlighted. Attention is directed at charge transport and optical properties.
Doping studies of heterogeneous langmuir—blodgett thin films containing poly(3‐hexyl thiophene)
Authors: Watanabe Itsuo , Rubner Michael F.
Published: April 2007

Langmuir‐Blodgett multilayer thin films fabricated from mixed monolayers containing poly(3‐hexyl thiophene) and stearic acid were rendered electrically conductive with strong oxidizing agents such as SbCl5, I2 and NOPF6. In‐situ doping studies using dopants introduced in the gas phase revealed that the increase in conductivity was due to the formation of bipolaron‐type charged defect sites on the polymer backbone. The highest level of conductivity was achieved by doping with NOPF6 from solution (about 3 S/cm). Solution phase doping, however, was found to disrupt the molecular organization of the multilayer film completely. In contrast, doping could be accomplished with retention or modification of the original molecular organization if carried out in the gas phase using either SbCl5 or I2. The resultant in‐plane conductivities were a few orders of magnitude lower than films doped from solution due to the heterogeneous nature of the doped multilayer film. The conductivity of multilayer films doped with SbCl5 was found to be stable in vacuum whereas the conductivity of films doped with I2 decayed rapidly in either vacuum or air.
Doped glassy carbon materials (DGC): Their synthesis from polymeric precursors and investigation of their properties
Authors: Neenan Thomas X. , Callstrom Matthew R. , Bachman Bonnie J. , McCreery Richard L. , Alsmeyer Daniel C.
Published: April 2007

A low temperature route (200–600°C) to the preparation of glassy carbon containing high levels of heteroatoms has been developed. The synthesis involves the preparation of diacetylenic oligomeric precursors, molding of these materials, and thermal treatment under controlled conditions to form glassy carbon. Materials have been prepared which contain high levels (10–15%) of nitrogen, fluorine, and silicon by covalent attachment of these heteroatoms to the diacetylene oligomers. A Raman study confirmed the presence of diagnostic peaks for glassy carbon, including the E12 fundamental at 1582cm−1 and the A1g at 1360 cm−1. The physical properties of these materials, including thermal stability, microscopic structure, density, and elastic modulus are reported.
A study of the relationship between setting chemistry and properties of modified glass‐poly(alkenoate) cements
Authors: Wasson Eleanor A. , Nicholson John W.
Published: April 2007

A study aimed at increasing the understanding of the setting chemistry and final structure of glass‐poly(alkenoate) [‘Glass‐Ionomer’] cements has been carried out in which the decomposition of glasses in aqueous solutions of an organic acid has been examined. Two glasses, an aluminosilicate and a fluoroaluminosilicate respectively, were washed with solutions of acetic acid and the washings analysed by ICP‐OES. For both glasses calcium and aluminium were found to be released under all conditions of acid‐washing. In addition, significant quantities of silicon and sodium were also found to be released. These findings have led to a reappraisal of both the precise mode of setting and the final structure of these materials. The pattern of ion release was also capable of providing some information on the structure of the phases present in the original glass.
Bioconversions of cellulose—A major source of material for the biochemical industry
Authors: Kennedy John F. , Melo Eduardo H. M.
Published: April 2007

The abundance and renewability of lignocellulosic materials renders them to be a promising feedstock for production of energy, food and chemicals. Enzymatic hydrolysis of lignocellulose into fermentable sugars has been extensively studied in order to reach a more efficient utilization of renewable biomass energy. Enzymatic hydrolysis of lignocellulose means degradation of cellulose to D‐glucose, but the mechanism of cellulose hydrolysis by enzymes is still not well understood.

This paper deals with processes for obtaining lignocellulosic materials, for converting them into fermentables by use of acid and enzyme hydrolysis, and for fermentation of the sugars to useful products.
Photoresponsive polymers IV. Conformational changes of polypeptides upon irradiation
Authors: Hallensleben Manfred L. , Menzel Henning
Published: April 2007

Poly(5‐(4‐phenylazobenzyl)‐L‐glutamate) was synthesized to study the photoinduced helix coil transition of a unipolymer. The crucial point in the synthesis is the selective esterification of the L‐glutamic acid, which was carried out as an alcoholysis of the N‐protected cyclic anhydride. The 5‐ester was treated with phosgene to óbtain the N‐carboxyanhydride, which was polymerized by base catalysis. The polymer was investigated in dilute dioxane solutions. The photoinduced transition was followed by means of UV spectroscopy for the chromophore and viscosimetric experiments for the configuration of the polymer chain. The changes in viscosity are more complex than expected for a helix coil transition, so aggregates have to be taken into account.
Synthesis, characterization and degradation of aliphatic polyanhydrides
Authors: Albertsson A.‐C. , Lundmark Stefan
Published: April 2007

Poly(adipic anhydride) (PAA), poly(sebacic anhydride) (PSA) and poly(dodecanoic anhydride) (PDA) were prepared from the mixed anhydrides of diacids and ketene (in tetrahydrofuran (THF) solution), the mixed anhydrides being subjected to melt polycondensation. The polymerizations were carried out in the presence of diethyl zinc as a catalyst. The polymers were characterized by means of 1H NMR, IR spectroscopy, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The polymer yields and the molecular weights of the polymers increased in the presence of catalyst. From these results a mechanism for the reaction is proposed. The highest melting temperature of the resultant polymers was obtained from PDA (Tpeak = 90°C). The heat of fusion was approximately 100 J/g (PDA). The number‐average and weight‐average molecular weights of the polyanhydrides were 18000 and 33000 respectively (PDA). Poly(anhydride)‐b‐poly(ethylene glycol) and poly(anhydride)‐b‐poly(tetramethylene glycol) copolymers were prepared from the mixed anhydrides of dodecanoic acid, poly(ethylene glycol)‐succinic half‐ester and poly(tetramethylene glycol)‐succinic half‐ester respectively. The block copolymers were characterized by means of 1H NMR, IR and GPC. The hydrolytic degradation of PDA has been studied in a buffered salt solution (pH 7·2) at 37°C by examining the changes in molecular weight, heat of fusion, mass loss and surface structure of melt‐pressed PDA strips.
Poly(alkylene phosphates): Bioanalogous synthetic polymers
Authors: Penczek Stanislaw , Baran Jolanta , Biela Tadeusz , Lapienis Grzegorz , Nyk Andrzej , Klosinski Pawel , Pretula Barbara
Published: April 2007

Preparation, some properties and applications of the bioanalogous poly(alkylene phosphates), obtained according to the methods elaborated in these authors' laboratory, are reviewed. Ring‐opening polymerization, polyaddition, and two‐step polycondensation methods are effective in the synthesis of polymers with various moieties of nucleic and teichoic acids (NA and TA, respectively). The major aim of the work is to find relatively simple methods allowing high molecular weight polymers to be prepared. Thus, preparation of poly(glycerol phosphate) and poly(trimethylene phosphate) bearing NA bases and related polymers with M¯n ⩾ 104 are described.
Design of poly(α‐malic acid)‐5FU conjugate exhibiting antitumor activity
Authors: Ouchi Tatsuro , Kobayashi Hironao , Banba Toshio
Published: April 2007

Since poly(α‐malic acid) is a biodegradable and bioabsorbable lactic acid type polyester having pendent carboxylic acid groups, it is of interest for application as the polymer carrier to covalently attach both a parent drug and a targeting agent. In order to provide a macromolecular prodrug of 5‐fluorouracil (5FU) with reduced side‐effects and exhibiting high antitumor activity, the covalent attachment of 5FU to poly(α‐malic acid) through hydrophobic spacer groups, ester or amide and carbamoyl groups was carried out. In order to estimate the release behavior of 5FU from poly(α‐malic acid)‐5FU conjugates, the hydrolysis of the pendent ester or amide and carbamoyl groups in the conjugates obtained was investigated in vitro using various kinds of aqueous solution at 37°C. The effect on prolongation of life was tested in vivo against p‐388 lymphocytic leukemia in female CDF1 mice by intraperitoneal (i.p.) i.p. injection. These poly(α‐malic acid) 5FU conjugates gave a high survival rate and did not display acute toxicity in the high dose range of 200–800 mg/kg.
Enzyme immobilization in polymer coated liposomes
Authors: Őzden M. Yasar , Hasirci Vasif N.
Published: April 2007

In this study liposomes composed of only dicetylphosphate (DCP), or of a 7:2: 1 (mole ratio) mixture of phosphatidylcholine (PC), dicetylphosphate (DCP) and cholesterol (Chol.( were prepared. Resultant liposomes were coated with varying amounts of poly(1,4‐pyridinium diethylene salt(, P1,4 VN. The polymer was shown to be different from poly(4‐vinylpyridine(, P4VN, which is also obtained from the same monomer. The increase in the coating extent (or thickness( was shown by IR and UV through the increase in the peaks due to polymer. The strength of binding was indirectly shown by being able to obtain scanning electron micrographs for the coated liposomes while it was not possible for the uncoated ones. It was shown that the lipid membrane under the polymeric coat can be removed. The resultant structure is highly permeable in comparison to the impermeable, lipid‐containing form. The activity of the enzyme glucose oxidase was demonstrated using the enzyme encapsulated in the polymeric net.
Synthesis and properties of biodegradable aliphatic polyesters
Authors: Dahlmann Jürgen , Rafler Gerald , Fechner Klaus , Mehlis Burkhard
Published: April 2007

The ring‐opening polymerization of D, L‐dilactide and an equimolar dilactide‐diglycolide mixture has been investigated. Conversion and molecular weight in the lactide bulk polymerization are determined not only by the kinetics of the primary ring‐opening reaction, but also by the concentration and extent of consecutive reactions of reactive groups in the polyester formed. High conversions and high molecular weights are obtained only by high polymerization rates. For the characterization of the polymers, viscosity‐molecular weight relationships for monomer‐containing ‘equilibrium’ polymers and reprecipitated polymers were determined. The application of these polymers in parenteral drug delivery systems for a gonadotropin‐releasing hormone agonist has been investigated.
Controlled‐release model systems
Authors: Połowiński Stefan , Szosland Lidia , Szumilewicz Joanna , Połowińska Alina , Pierzchlewska Aurelia
Published: April 2007

The kinetics of the controlled release of biocides from simple model systems have been studied. Crosslinked dextran, modified crosslinked dextran and ion‐exchange resin (Wofatit) were used as carriers. Salicylic acid, 2,4,5‐trichlorophenol, 8‐hydroxyquinoline and codeine were used as biocides. Some systems were coated with poly(vinyl acetate), acetylchitin or a copolymer of methyl methacrylate with dimethylaminoethyl methacrylate. An exponential equation was proposed for the description of the release kinetics and checked experimentally. Good correlation with the equation was found.
Synthesis, structure and antiviral activity of sulfates of curdlan and its branched derivatives
Authors: Yamamoto Iwao , Takayama Kesayo , Gonda Takashi , Matsuzaki Kei , Hatanaka Ken‐Ichi , Yoshida Takashi , Uryu Toshiyuki , Yoshida Osamu , Nakashima Hideki , Yamamoto Naoki , Kaneko Yutaro , Mimura Tohru
Published: April 2007

Curdlan and its branched derivatives having oligo‐L‐ or oligo‐D‐arabinofuranose side chains, D‐glucopyranose side chains or D‐galactopyranose side chains were sulfated with piperidine N‐sulfonic acid or SO3‐dimethylform‐amide complex. The structures of the sulfated polysaccharides were analyzed by elemental analysis and 13C NMR spectroscopy. The 13C NMR spectra of curdlan sulfates were assigned and the degree of substitution (DS) value of each hydroxyl group was obtained. The reactivity was in the order C‐6  C‐4 = C‐2. However, a little different distribution of substituents was observed between curdlan sulfates synthesized with piperidine N‐sulfonic acid and SO3‐DMF complex. Sulfated polysaccharides with high d.s. values showed high anti‐HIV (AIDS virus) activity.
Soluble functional polymers for human haemoglobin modification for blood substitution
Authors: Prouchayret Florence , Bonneaux François , Léonard Michèle , Sacco Daniel , Dellacherie Edith
Published: April 2007

Aqueous solutions of certain polymers have been used as plasma expanders for a long time. However, these polymer solutions are only capable of correcting the volume of circulation in vivo and in particular they cannot replace the oxygen‐carrying function of blood. This property can be conferred to these polymer solutions by linking human haemoglobin, the natural oxygen carrier, to the polymers in such a way that the oxygen‐binding properties of the free protein are similar to those of blood. Such results can be achieved by designing and preparing special polyanionic derivatives of dextran and polyoxyethylene and linking them to free human haemoglobin under its deoxy form or its oxy form. The resulting covalent conjugates exhibit general properties quite fitted to a use in blood substitution.
Thermoplastic hydrogels
Authors: Brook M. Gordon
Published: April 2007

A range of thermoplastic hydrogels which combine the properties of conventional crosslinked hydrogels with the processing convenience of thermoplastics has been developed. The materials can be melt‐processed or cast from solution in organic solvents, making it practical to use them in a wide range of products and to easily combine other materials with them. These hydrogels are noncrosslinked copolymers of hydrophobic and hydrophilic monomers, the intramolecular interactions between the hydrophobic units performing the role of the crosslinks in conventional hydrogels.
Microcrystalline chitosan—Some areas of application
Authors: Struszczyk Henryk , Kivekäs Olli
Published: April 2007

Microcrystalline chitosan existing as a new microcrystalline form of standard poly(2‐deoxy‐2‐amino‐D‐glucose) is a special functional polymeric material suitable for several applications. New areas of microcrystalline chitosan use in the textile industry, waste water treatment and medicine are presented. Microcrystalline chitosan in the applications discussed has practical and economic advantages over standard chitosan.
Polyurethanes as biomedical materials
Authors: Kutay Sezer , Tincer Teoman , Hasirci Nesrin
Published: April 2007

Polyurethane films were prepared using diphenylmethanediisocyanate [MDI] or hexamethylenediisocyanate [HDI] and poly(propylene‐ethylene) glycol, in order to test them as biomedical materials specifically for use as skin grafts. Other ingredients such as catalysts, chain extenders, solvents, etc., where not used in order to obtain medical purity.

Mechanical properties, oxygen permeation and blood compatibility of these films were examined. Tensile strength, ultimate elongation and elastic modulus values were calculated. An increase in ultimate elongation and a decrease in tensile strength were observed when the amount of isocyanate‐containing compound was decreased in the prepared polymers. Oxygen permeability values also increased with an increase in polyol content of the prepared films. Blood compatibility tests showed that the film surfaces do not have thrombogenicity and can be considered biocompatible.
Some fields of biomedical application of polyurethanes
Authors: Batyrbekov Erkesh O. , Moshkevich Sofia A. , Rukhina Larisa B. , Bogin Ruben A. , Zhubanov Bulat A.
Published: April 2007

Polyurethane foams have been studied as drug carrier matrixes for sustained delivery application. The drugs used in the investigation were the specific antituberculous drug isoniazid, the antibiotic rifampicin, and the local anaesthetic novocain. The release of the drugs into model biological media was studied by UV spectroscopy. It has been found that drug release occurs in accordance with first‐order kinetics. The possibility of application of drug delivery systems for treatment of tuberculosis and haemorrhoids has been shown by some medical‐biological tests.
Solubilities, viscosities and unperturbed dimensions of poly (2,6‐diisopropylphenyl methacrylate)
Authors: Gargallo Ligia , Hamidi Nasrolah , Radić Deodato
Published: April 2007

The dilute solution properties of poly(2,6‐diisopropylphenyl methacrylate) (PDPP) in various solvents were studied by viscosity, exclusion chromatography and osmotic pressure measurements. The Mark‐Houwink‐Kuhn‐Sakurada relationships were established. The unperturbed dimensions, the rigidity factor σ, the characteristic ratio C∞ and the thermodynamic parameters were determined using the Stockmayer‐Fixman equation and from data in theta solvent (binary mixture). The rigidity factor of PDPP is abnormally high. The conformational behaviour of this polymer is analysed in terms of the effect of the side chain structure. The results are compared with other polymers of the same series.
Photostability of polyetherurethaneureas
Authors: Thapliyal B. P. , Chandra R.
Published: April 2007

Polyetherurethaneureas (PEUUs) were synthesised from polyethylene‐glycols (PEGs) of molecular weight 400, 600 and 1000, 4,4′‐diphenylmethanediisocyanate (MDI) and aliphatic diamine chain extenders, 1,3‐propanediamine (PDA) and 1,6‐hexanediamine (HDA). Polymer films were irradiated with 365 nm light at 293 K and the effects of polyether soft segment length and urea hard segment on photo‐oxidative stability were studied by following the variation in weight‐average molecular weight (Mw), gel formation and stress‐strain properties. Changes in ultraviolet and infrared spectroscopy were monitored on photo‐oxidation and hydroperoxide content determined. The soft segment length was increased by increasing the molecular weight of PEG from 400 to 1000 and hard segment structure was changed by variation of diamine. It was noted that the structure of urea and polyether soft segment length plays an important role in photostability of PEUUs. PDA chain extended PEUUs were more stable than HDA chain extended PEUUs.
Comments on the accuracy of zero shear intrinsic viscosity of high molecular weight polyacrylamide
Authors: Tam K. C. , Tiu C. , Fang T. N.
Published: April 2007

The intrinsic viscosity of a polymer is traditionally measured with a capillary tube viscometer where the shear rate range is moderately high. Such method is valid when the polymers are non‐ionic and have low to moderate molecular weight. The viscosity‐shear rate curves obtained for dilute aqueous solutions of two high molecular weight polyacrylamides using two rotational viscometers indicate a strong shear‐dependent viscosity in the medium to high shear rate regions. The zero shear intrinsic viscosity of the polymers determined by extrapolation from the high shear rate region to the zero shear condition may result in large errors. Its implication in predicting the molecular weight of polymers using the Mark‐Houwink‐Sakurada equation is discussed. A rheological equation for intrinsic viscosity as a function of shear rate is proposed.
Thermotropic polyesters: Synthesis and properties of poly(p‐oxybenzoate‐co‐m‐phenylene terephthalate)s
Authors: Brown Philip J. , Karacan Ismail , Liu Jing , McIntyre J. Eric , Milburn Alexander H. , Tomka J. George
Published: April 2007

DSC, TMA, hot‐stage microscopy and WAXS have been used to examine the effect of concentration of angular units and molecular weight on the thermal transitions of poly(p‐oxybenzoate‐co‐m‐phenylene terephthalate)s. Copolymers containing molar fractions of m‐phenylenedioxy units between 0·20 and 0·30 are melt processable nematogenic materials. In contrast, poly(p‐oxybenzoate‐co‐p‐phenylene isophthalate)s remain nematogenic over a wider concentration range (0·20–0·40) of angular isophthaloyl units. Comparison of fibres produced from copolymers with the same fraction of angular units (0·25) indicates that those with isophthaloyl units have a higher modulus than those with m‐phenylenedioxy units. These differences are ascribed to differences in planarity of chains containing isophthaloyl and m‐phenylenedioxy units, respectively.
Dielectric and viscoelastic studies of poly(ethyl methacrylate) containing cholesteric compounds
Authors: Deshpande Dinkar D. , Basu Chandana , Pandya Madhav V.
Published: April 2007

Poly(ethyl methacrylate) (PEMA) containing small amounts of cholesteryl additives was studied by dielectric and dynamic mechanical spectroscopy. Dielectric data from pure PEMA and PEMA + additive systems were fitted to the WLF equation. Using the WLF constants obtained from the data for pure PEMA, the To values for PEMA + additive systems were determined in order to get the best fit of the experimental points to the WLF curve. Values of tan δmax (dielectric and mechanical) for all the PEMA + additive systems shift to higher temperatures compared with that for pure PEMA. In the glassy region, the moduli of PEMA + additive systems are higher than that of pure PEMA. Viscometric studies of PEMA + additive systems indicate the presence of some interaction. FTIR spectra of the polymer + additive systems show no shift in carbonyl bond frequency. The shift of Tg to higher temperatures indicates that chain motion in this region is hindered greatly by these additives and the reason for this may be the fitting or aligning of the additive molecules in the polymer matrix.
Chain transfer in vinyl chloride polymerization in the presence of polybutadiene
Authors: Beati E. , Pegoraro M. , Gianotti G. , Cassani F.
Published: April 2007

Vinyl chloride (M) was polymerized in the presence of a low molecular weight polybutadiene (S) at 60°C in the presence of x,x′‐azobisdiisobutyronitrile as initiator, which does not affect the transfer reaction.

The raw material was fractionated for the purpose of separating the pure PVC homopolymer.

The number‐average molecular weight of PVC homopolymer, determined by size exclusion chromatography (SEC), was used in Mayo's equation to obtain the value of the transfer constant Cs, which was found to be 11. A simplified reaction scheme is given according to which it is possible to explain why the reaction yield decreases and the crosslinking density increases by increasing the [S]/[M] ratio.
pH‐stat methodology in continuous monitoring of the kinetics of hydrolysis of phosphate esters catalysed by alkaline phosphatase from human placenta: Limitations, advantages and theoretical aspects
Authors: Roig M. G. , Serrano M. A. , Bello J. F. , Cachaza J. M. , Kennedy J. F.
Published: April 2007

The appropriateness of pH‐stat methodology in the dynamic monitoring of the kinetics of hydrolysis of phosphate esters catalysed by alkaline phosphatase (from human placenta) has been studied. This methodology involves autotitration of the H+ released or consumed during a given reaction time. The lack of specificity of the method, titrating the total H+, together with the known effect of the dissolution of environmental CO2 on the reacting system, giving rise to carbonic acid, implies an overtitration of the H+ released in the hydrolysis reaction. Because of this, parallel to each series of reaction kinetics, the dissolution kinetics of environmental CO2 under working conditions are quantified with suitable blanks, thus enabling one to subtract them from the global kinetics of the release of H+. Although no background buffers are added to the reacting system in order to maintain a constant pH, the buffering capacity of the system itself obliges one to quantify it by calibrations in order to calculate the true release rate of H+ in the reaction. These two principal limitations of the pH‐stat methodology, the dissolution of environmental CO2 and the inherent buffering capacity of the system, can be partially mitigated by working within an inert atmosphere of N2 and having a good knowledge of the acid/base characteristics of the reagents and reaction products, which together will permit the choice of a working pH range in which the second limitation will be negligible. Having studied theoretically the acid/base balances of the system in reaction, it is concluded that optimum working conditions for the pH‐stat methodology are between pH 8·5 and 11·0, since over this pH range the buffering capacity is null (thus eliminating the need for calibrations) and the stoichiometry of H+ (nH+) is close to unity. These theoretical predictions have been confirmed experimentally with calibrations and measurements of nH+ at different pH values.
Copolymerization propagation kinetics of styrene with alkyl acrylates
Authors: Davis Thomas P. , O'Driscoll Kenneth F. , Piton Mark C. , Winnik Mitchell A.
Published: April 2007

Propagation rate constants have been determined at two temperatures (298 K and 323 K) for the copolymerizations of styrene (STY) with methyl acrylate (MA) and STY with n‐butyl acrylate (BA) over a range of monomer feed compositions. A pulsed UV laser was used as an initiation source and gel permeation chromatography (GPC) was utilized to analyse the products. None of the copolymerizations conformed to the Mayo‐Lewis model, with respect to their propagation rate constants. The results were interpreted on the basis of a penultimate effect on the propagation reaction. In addition, Mark‐Houwink constants were determined for poly(MA) and poly(BA) in tetrahydrofuran (THF) at 298 K. These constants are given as [K(dm3 kg−1),α]: 7·88 × 10−3, 0·885 and 8·57 × 103, 0·865 for poly(MA) and poly(BA) respectively.
Raman spectroscopy of Kevlar fibres during deformation—Caveat emptor
Authors: Young R. J. , Lu D. , Day R. J.
Published: April 2007

It has been demonstrated that when aromatic polyamide fibres such as Kevlar 49 are subjected to mechanical deformation, significant frequency shifts are obtained for the peak position of the 1610 cm−1 Raman band using both 632·8 nm and 488 nm laser radiation. Two earlier reports of the deformation of fibres in a 488 nm argon ion laser beam reported no such frequency shifts. It has been shown that this wavelength of laser light can degrade Kevlar fibres. This causes premature failure of the fibres through chain scission and the fibres break at low strains before significant levels of stress or strain can be achieved. Hence, the previous conflicts can be resolved and it has been demonstrated that simultaneous Raman spectroscopy and mechanical deformation is a powerful method of following the micromechanics of fibre deformation.
Synthesis and characterization of polyurethanes containing arylene sulfone ether linkages
Authors: Idage Susheela B. , Idage Bhaskar B. , Vernekar Subhash P.
Published: April 2007

Polyurethanes containing arylene sulfone ether linkages were synthesized by solution polymerization of 4,4′‐bis(4‐isocyanatophenoxy)diphenylsulfone (SPI) and 4,4′‐bis(3‐isocyanatophenoxy)diphenylsulfone (SMI) with various aliphatic glycols such as ethylene glycol (EG), 1,2‐propylene glycol (PG), 1,4‐butylene glycol (BG), polyethylene glycol (PEG 300 and 1000), polypropylene glycol (PPG 300 and 1000) and polytetramethylene glycol (PTMG 1000. TERACOL) in dimethylacetamide (DMAC) at 120°C. The diisocyanates SPI and SMI were prepared from the corresponding diacid chlorides via Curtius rearrangement. The polyurethanes were obtained in high yields. The effect of structures of diisocyanate and aliphatic diols on the molecular weight and thermal properties of polyurethanes was also investigated. The polyurethanes prepared were characterized by infrared spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis and X‐ray diffraction. Physical and thermal properties of polyurethanes prepared from SPI and various aliphatic glycols were compared with the polyurethanes from SMI and various aliphatic glycols.
Studies on polymer latex films: I. A study of latex film morphology
Authors: Roulstone B. J. , Wilkinson M. C. , Hearn J. , Wilson A. J.
Published: April 2007

Polymer films have been formed from poly (butyl methacrylate) latices prepared by surfactant‐free emulsion polymerisation. The latices having also been cleaned by microfiltration constitute model colloid particles and hence form ‘model’ films.

A novel freeze fracture replication and transmission electron microscopy technique was employed to study film morphology. It demonstrated the presence of interparticle boundaries between latex particles deformed into dodecahedra and the particle packing order without the need for a staining technique. The time and temperature of film formation and storage was shown to affect the degree of particle coalescence. Solvent cast films were also studied for comparison purposes.
trans‐polyoctenylene as a processing aid for rubber: Influence on energy consumption and properties of rubber compounds
Authors: Lau Wayne W. Y. , Swee‐Hin Teoh , Suat‐Hong Goh
Published: April 2007

trans‐Polyoctenylene rubber, TOR, was melt blended with different types of rubber in various proportions in a Brabender Plasti‐corder. Energy consumption in mixing the blends indicated that TOR is an effective processing aid for a variety of rubber and inclusion of TOR in a blend can result in significant saving of energy. TOR of lower molecular weight (e.g. Vestenamer 8012) performs significantly better than TOR of higher molecular weight (e.g. Vestenamer 6213), both as a processing aid and as a dimension stabilizer.
Grafting of low density poly(ethylene) with butyl acrylate: Synthesis and characterisation
Authors: Raval Heta , Singh Y. P. , Mehta M. H. , Devi Surekha
Published: April 2007

Low density poly(ethylene) was grafted with butyl acrylate using benzoyl peroxide as free radical initiator in an inert atmosphere and toluene as solvent. Various parameters such as reaction time, temperature, initiator concentration and ratio of monomer to polymer were varied to study their effects on percentage of grafting and grafting efficiency of butyl acrylate on to low density poly(ethylene). The graft copolymers were characterised by IR spectroscopy. The change in the solubility behaviour of low density poly(ethylene) due to grafting was studied by turbidometric titration. Thermal stability of graft copolymers was found to be higher than that of LDPE. Intrinsic viscosity data showed an increase in viscosity with increasing grafting percentage.
Polymerization of some oxiranes using the diphenylzinc‐butanone system in benzene at 60°C
Authors: López Francisco , Calcagno María P. , Contreras Jesús M. , Torrellas Zulay , Felisola Katania , Rabagliati Franco M. , Katime Issa A.
Published: April 2007

The diphenylzinc‐butanone system was used as polymerization catalyst for some oxiranes in benzene solution at 60°C. This system is greatly influenced by the molar ratio of butanone to diphenylzinc, and the maximum catalytic activity for propylene oxide and ethylene oxide was found for a ratio of unity. GPC results strongly suggest the presence of more than one active species for the system. 13C NMR analysis indicates that the resulting poly(propylene oxide) has a head‐to‐tail arrangement. For the polymerization of propylene oxide with butanone/diphenylzinc = 1, after an initial induction period, the reaction was first‐order with respect to monomer with k = 2·51 × 10−5 s−1. Ethylene oxide polymerizations using butanone/diphenylzinc = 1 and 5 were also first‐order with respect to monomer after an initial induction period with k = 7·80 × 10−6 s−1 and k = 5·71 × 10−6 s−1, respectively. The diphenylzinc‐butanone system was not an effective catalyst for styrene oxide polymerization.
Wood fibre‐polyester dough moulding compounds
Authors: Freischmidt G. , Michell A. J. , Lewis M. J. , Vanderhoek N.
Published: April 2007

The mixing of wood fibres into dough moulding compounds (DMC) has been enhanced through thickening the mix by using zinc oxide or by adding an increased amount of scrap polystyrene. In both cases, the requirement for expensive styrene monomer has been reduced. The time needed for mixing has been shortened from up to 10 h to only 0·5 h as a result of the more efficient mixing. The electrical insulation properties of the compounds easily meet industry standards. Attempts to reduce the brittleness and increase the mechanical properties of the compounds by pretreating the fibres have not been successful.
Behaviour of poly(β‐hydroxybutyric acid) in dilute solution
Authors: Huglin Malcolm B. , Radwan Mostafa A.
Published: April 2007

The refractive indices of poly(β‐hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (Mw = 20·9 × 103−929 × 103 g mol−1) in 2,2,2‐trifluoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.
Tetramethylammonium 3‐aminopropyl dimethylsilanolate—aminopropyl dimethylsilanolate—a new catalyst for the synthesis of high purity, high molecular weight α,ω‐bis(aminopropyl) polydimethylsiloxanes
Authors: Hoffman Jerome J. , Leir Charles M.
Published: April 2007

Tetramethylammonium 3‐aminopropyl dimethylsilanolate, readily prepared from bis(3‐aminopropyl) tetramethyldisiloxane and tetramethyl‐ammonium hydroxide pentahydrate, has been found to serve as a highly effective catalyst for the ring opening polymerization of cyclic siloxanes with an end blocker such as bis(3‐aminopropyl) tetramethyldisiloxane to give aminopropyl terminated linear polydimethylsiloxanes. By following a novel two stage procedure, even high molecular weight (5,000–55,000 g/mol) silicone diamines were able to be prepared in a high state of purity; chain extension reactions of these diamines with diisocyanates gave a series of high molecular weight silicone polyureas with good elastomeric properties.
Magnetic resonance imaging studies of the polymerisation of methylmethacrylate
Authors: Jackson Peter , Clayden Nigel J. , Walton Nicholas J. , Carpenter T. Adrian , Hall Laurance D. , Jezzard Peter
Published: April 2007

Magnetic resonance imaging has been used to spatially map the time course of the bulk polymerisation of methylmethacrylate. Both two‐dimensional projection and slice‐selective techniques have been employed. Image intensities give qualitative information about viscosity, reaction rates and the localised extent of polymerisation. The importance of proton relaxation measurements in drawing quantitative conclusions is stressed.
Photoresponsive peptide and polypeptide systems: Part 9. Synthesis and reversible photochromism of azo aromatic poly(L‐α,ω‐diaminobutyric acid)
Authors: Yamamoto Hiroyuki , Nishida Ayako
Published: April 2007

Poly(L‐α,ω‐diaminobutyric acid) having azo aromatic side chains was synthesized by the water‐soluble carbodiimide procedure. The photoresponsive properties of the polypeptide poly[N7‐p‐(phenylazo)benzoyl‐L‐α,ω‐diaminobutyric acid] (PPABLDBA) due to the trans (about 71%, under visible light) cis (under ultraviolet light) photoisomerization of the azo aromatic moieties in the side chains were investigated by absorption and circular dichroism spectroscopy in hexafluoro‐2‐propanol (HFIP). The starting slightly turbid solution of trans‐PPABLDBA becomes clear on irradiation at 360 nm, accompanied by photoconversion of the conformer of the azo moieties to cis. The backbone conformation of PPABLDBA in HFIP is right‐handed helical (helical content, about 60%) when the azo moieties are trans (71%), while the conformation is random coil when cis. The backbone conformational transition of PPABLDBA from helical to coil is mostly reversible under the influence of light.
Physico‐chemical studies of polyetherurethaneurea in phosphate buffer solution
Authors: Ray Alok R. , Neelamegham Sriram , Bhowmick Ashis
Published: April 2007

Polyetherurethaneureas are increasingly used as implants in the human body, where they come in contact with body fluid. Most of the reported properties of polyetherurethaneureas have been determined in the dry state. The present work deals with the properties of these materials in aqueous systems. A number of linear polyetherurethaneureas based on polyethoxyglycol and polypropoxyglycol of different molecular weights, 4,4′‐diphenylmethane diisocynate, 1,3‐propanediamine and 1,6‐hexanediamine have been prepared. Their swelling characteristics and phase composition in phosphate buffer solution are evaluated. The role of water in changing various properties of polyetherurethaneureas is discussed.
Ultrasonic degradation of polymer solutions. 1. Polystyrene revisited
Authors: Price Gareth J. , Smith Paul F.
Published: April 2007

The results of ultrasonic irradiation of polystyrene solutions in toluene, benzene and carbon tetrachloride are described. The effect of a range of conditions such as ultrasonic intensity, solution concentration and varying solvents were investigated. The non‐random nature of the degradation process was clearly demonstrated and the effect of different solvents was interpreted in terms of their thermodynamic properties.
Effects of plasticizer on shear modification of polystyrene
Authors: Qian J. W. , Rudin A. , Teh J. W.
Published: April 2007

The elastic and viscous properties of polymer melts may be affected by the shear history of the polymer. The extrudate swell of a polymer melt is primarily a manifestation of the elasticity of the polymer melt. In this study, a single screw extruder was used to impose different shear histories on a polystyrene polymer which was processed with and without added plasticizer. The extrudate swell and apparent viscosity of these melts were measured with a capillary rheometer. These characteristics of unplasticized polystyrene are almost not affected by the various preshearing processes. However, the extrudate swell and viscosity of polystyrene containing plasticizer are affected by plasticizer level, shear history and thermal history. After most of the plasticizer in the presheared plasticized polystyrene was extracted, the extrudate swell was still lower than that of the parent sheared polystyrene with the same shear history and the same plasticizer content. These results were obtained without significant changes in molecular weight.

Shear modification by conventional process equipment may become impractical if the shear field intensity or dwell time of the material in the apparatus is limited. In such cases, shear refinability by standard process equipment may be observed if the coupling density in the polymer is reduced by some additional means, such as blending with a plasticizer.
Melting and curie transition behavior of blends of vinylidenefluoride‐tetrafluoroethylene copolymer and polymethylmethacrylate
Authors: Cho Jae Whan
Published: April 2007

Thermal properties were investigated using differential scanning calorimetry of blends of vinylidenefluoride‐tetrafluoroethylene (VDF‐TFE) copolymer and polymethylmethacrylate. Curie transition behavior was strongly dependent on the crystallization temperature. A Curie temperature was shown in pure VDF‐TFE copolymer and in the blend with 91 wt % VDF‐TFE copolymer, which were crystallized above the Curie temperature. The samples crystallized above the Curie temperature showed higher melting temperatures than those crystallized below the Curie temperature, resulting in an upturn of slope at high temperatures in the Hoffman‐Weeks plot. The polymer‐polymer interaction parameter was calculated to be −0·165 at 130°C from the equilibrium melting temperatures, indicating miscibility of the two components.
Sulphur‐containing polyacrylates. III: UV‐induced copolymerization of methyl methacrylate with some dimethacrylates containing ether or thioether linkage
Authors: Andrzejewska Ewa
Published: April 2007

The UV‐induced copolymerization of methyl methacrylate (MM) with 2,2′‐thiobisethanol dimethacrylate (TEDM) and MM with 2,2′‐oxybisethanol dimethacrylate (OEDM) was investigated for a wide range of the diester content (6‐80 mol%) in the initial mixture. The influence of the feed composition on the course of copolymerization was determined. It was found that there exists a minimum on the plot of maximum yield of soluble copolymer versus diester content at a diester content of 30 mol%. The total copolymer yields were lower in the case of mixtures containing TEDM comonomer. Determination of the reactivity ratios gave the following values: for MM + TEDM ra = 0·21, rb = 4·59 and for MM + OEDM ra = 0·55. rb = 4·42. A possible explanation of the results obtained is discussed.
Surface inhibition of double base rocket propellants with photocurable unsaturated esters
Authors: Mirza Meher S. , Navale N. G. , Sadafule D. S. , Kumbhar C. G. , Panda S. P.
Published: April 2007

Inhibition of a double base propellant surface with a good percentage of nitro bodies in the propellant composition is a rather difficult process. One of the methods of inhibiting the surface is to use unsaturated polyesters with free radical cure having high exotherm as a barrier coating. This system has been improved by using a 1:1 mix of photocurable vinyl ester with pendant —OH groups and unsaturated polyester that underwent room temperature free radical cure. Adhesion of the barrier coat to the propellant surface through its —OH groups was stronger than the propellant strength itself. Additional layers of commercially available unsaturated polyester could be easily grafted on to the barrier coat through chemical cure.
Dilithium initiators based on 1,3‐bis(1‐ phenylethenyl)benzene. Tetrahydrofuran and lithium sec‐butoxide effects
Authors: Quirk Roderic P. , Ma Jing‐Jing
Published: April 2007

The adduct (3) from 2 moles of sec‐butyllithium with 1,3‐bis(1‐phenyl‐ethenyl)benzene has been prepared and evaluated as a hydrocarbon‐soluble, dilithium initiator for butadiene and styrene polymerization in cyclohexane or benzene solution. Under high vacuum conditions with purified reagents, bimodal molecular weight distributions are observed for polybutadienes with Mn < 150 × 103 g/mol and for polystyrenes with Mn < 50 × 103 g/mol; monomodal distributions are observed only for higher molecular weights. Addition of tetrahydrofuran ([THF]/[Li] = 14 to 32) or preformed lithium sec‐butoxide ([LiOBu]/[3] = 1·1) produces narrow, monomodal molecular weight distributions even at Mn = 26·2 × 103 g/mol polybutadiene and at Mn = 10 × 103 g/mol for polystyrene. Added lithium sec‐butoxide is the preferred additive since high 1,4‐polybutadienes are obtained. These results provide an explanation for the contradictory results reported previously; under less rigorous experimental conditions, oxygen and hydroxylic impurities can form lithium alkoxides in situ.
Kinetic behaviour of muscle LDH immobilized in nylon tubing
Authors: Roig M. G. , Bello J. F. , Cachaza J. M. , Kennedy J. F.
Published: April 2007

Immobilization was carried out of the lactate dehydrogenase (LDH) from rabbit muscle (EC 1.1.1.27), cross‐linked through the bifunctional reactive glutar‐aldehyde on to nylon tubing (1 m long, 53cm2 internal surface area). Immobilized LDH inactivation kinetics are of first order (t1/2 = 3·6 years, k = 5·4,e−4 day−1 to 5°C). The smaller effect of pH on activity than in the case of LDH in solution can be explained on the basis of limitation to proton diffusion towards the support. A limiting effect to free external diffusion of the substrate towards and products from the support was also observed, an effect which seems to determine the effective kinetic behaviour of immobilized LDH. The apparent optimum temperature is centred around 40°C, observing a clear inactivation (thermal denaturation) above this temperature. In the temperature range studied (10–40°C), the co‐existence was seen of a kinetic control accompanied by another control, involving diffusional transport of substrates and products, on the global activity of the immobilized enzyme. This makes the Arrhenius profiles curvilinear. Both graphic and statistical non‐linear regression analysis of the kinetic data—rate, v, versus substrate concentration [S]—carried out under conditions in which the diffusional limitations can be considered negligible (high recirculation flow rate), permitted investigation of the intrinsic kinetic behaviour of immobilized LDH. In this sense, it can be deduced that the rate equation to which these data seem to be fitted is of the polynomial quotient type in [S] of minimum degree 2:2. Although the diffusional limitations have a marked effect on the type of global kinetics shown by immobilized LDH, temperature was not found to affect its v[S] behaviour. The experimental evidence obtained thus indicates that the rate equation in the 10‐40°C temperature range continues to be a rational equation of at least degree 2:2 in [S].