bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear and tensile creep of thermoplastics at finite strains
Authors: Ballard John W. , Darlington Michael W.
Published: April 2007

The shear and tensile creep behaviour of polypropylene and low‐density polyethylene has been determined for a range of stress levels and creep times from 5 to 105 seconds. The data at finite strains have been correlated using the concept of shear on octahedral planes. When the experimental 100 second shear strains were matched to those predicted from the tensile tests, the experimental and calculated shear creep curves remained coincident, even in tests where the shear strains reached 8% and the materials were highly non‐linear viscoelastic. Manipulation of data in the literature for two amorphous polymers suggests a different pattern of behaviour and this is related to differences in the affect of the hydrostatic component of stress in the tensile tests on the creep response of the four polymers.
The provision of useful mechanical properties in polymeric materials
Authors: Baer Eric
Published: April 2007

This paper describes four aspects of the work which has been performed by individuals within my research group during the past five years. The first subject discussed is the effect of pressure and environment on the yield and fracture behaviour of plastics. Secondly, a description is given of micro deformation processes in amorphous polymers, with emphasis on the control of the transition from the crazing to the shear banding modes of irreversible deformation. The third subject discussed emphasises the importance of the adhesive bond in composite materials. In addition to the usual concern with chemical interactions at the interface, some recent work is described showing the importance of moulded‐in thermal stresses which can be controlled by process history. Finally, a more sophisticated multi‐composite system is dealt with, which is found in nature; namely, the relationships between hierarchial organisation and mechanical function in tendon. Whether, as a result of understanding biological composites of this type, innovative synthetic materials will immerge makes for interesting speculation at the present time.

All of the subjects described contain many unsolved questions, and I am hopeful that these will provide us with useful and interesting territory for research in the future.
High temperature post manufacture heat treatment of thermoplastics
Authors: Lawrence Charles C.
Published: April 2007

This paper discusses the need for high temperature treatment of manufactured components and a new technique that enables this to be carried out with controlled loss of geometry on shaped components.
The detergent stress‐cracking of polythene
Authors: Owen D. Roger J. , Haward Robert N. , Burbery Anthony
Published: April 2007

Whenever the fracture of a polymer is preceded by crazing or other types of cavity formation, energy must be supplied both for local yielding and for the generation of a new surface. However previous calculations for rigid glassy polymers have shown that the surface energy contribution required for the formation of a craze, compared with that associated with plastic and elastic strains is small. In order to study this problem further, we have now made a finite element analysis of the cavitation of an elastic‐plastic solid introducing a surface energy term. This shows that the ratio of the plastic energy requirement to surface energy depends, not unexpectedly, on (I) the ratio of yield stress/ surface tension and (II) cavity size. Thus for polymers with a low yield stress such as polythene, the surface tension becomes significant if the hole diameter is below 100 nm. In these circumstances crazing and cracking is predictably accelerated by dilute aqueous detergents which do not need to penetrate the polymer, provided of course that the detergent has access to the cavities.

Hole growth also depends on the extent of orientation hardening during plastic strain and this contributes to the greater stress crack resistance of high molecular weight polythene. The occurrence of a larger amount of plastic deformation on the fracture surfaces of high molecular weight polymer has been demonstrated by Harman for high density polythene and is confirmed here in scanning electron micrographs of low density material.

Other electron micrographs show that very small cacities are indeed formed when high density polythene is broken in the coventional detergent stress cracking test, thus accounting for the accelerating effect of the detergent.
Polymeric Silver Ligands
Authors: De Winter Walter , Pollet Robert
Published: April 2007

Low molecular silver ligands are generally known and commonly used as ingredients in photographic baths and emulsions. Polymeric silver ligands on the contrary have been studied much less for these purposes although certain advantages connected to their application can be observed. The polymeric ingredients can indeed exert photographic effects which are not exhibited by the ligand group of the monomer (polydentation). The hydrophilic character can be accurately adapted by a judicious choice of the comonomer. Finally diffusion fastness, an important property for multilayer materials, can be imparted without losing the interesting photographic effects.
Light Scattering from Copolymer Solutions
Authors: Ali Sabz
Published: April 2007

A new type of copolymer from para‐aminobenzoic acid and 6‐aminohexanoic acid was obtained by reacting the monomers in four different mole ratios. The polycondensation was carried out at 80d̀C with triphenyl phosphite as the initiator in N‐methyl‐2 pyrrolidone/pyridine mixture. The molecular weights of unfractionated and fractionated samples were determined by light scattering techniques in solvents of varying refractive index. From the values of second virial coefficient it is concluded that the solvent power for copolymer increases with increasing aminohexanoic acid mole fraction in the case of dichloroacetic acid and trifluoroacetic acetic acid while in dimethyl acetamide it decreases.
Water Soluble Polymers for Medicine
Authors: Kálal Jaroslav , Drobnik Jaroslav , Kopeček Jindřich , Exner Josef
Published: April 2007

A number of general reviews have already been published on this topic and so the authors will present information on their approach and some results obtained.

Polymers for medical uses are a traditional field at the Institute of Macromolecular Chemistry. However, crosslinked hydrophilic polymers ‐ so called hydrogels ‐ were the prevailing object in the past. Either as soft highly swollen materials for prothesis ‐ like soft contact lenses ‐ or heavily crosslinked macroporous beads designed as special sorbents or carriers of biologically active groups. Only a few years ago a research programme on soluble polymers was focussed mainly on general problems. The overall view about the main directions of the authors research is schematically presented on Fig. 1. It also shows the two types of polymers the authors are using in their experiments. The first one poly[N(2‐hydroxypropyl)methacrylamide]3a was chosen from the set of N‐substituted acryl‐and methacrylamides4 because of simple preparation and purification of the monomer. The other is a polyamide (polypeptide) described by Neri et al. in 1973.5 It is more hydrophilic and provides a good possibility to prepare a whole set of derivatives from a common polymeric intermediate ‐ polysuccinimide.
Polyester‐Polyether Block Copolymers II. Thermal and Mechanical Properties of Poly(hexamethylene terephthalate)/Poly(oxytetramethylene) Block Copolymers
Authors: Ghaffar Abdul , Goodman Isaac , Peters Raymond H.
Published: April 2007

The melting and crystallisation behaviour of crystalline phases in poly (hexamethylene terephthalate)/poly(oxytetramethylene) block copolymers have been investigated in relation to copolymer composition and polyether block molecular weight (m.w.). In contrast to that in corresponding homopolymer blends, the polyester crystallinity in the block polymers is greatly reduced by incorporation of polyether units, though some persists even at low polyester contents. Concomitant changes in the glass transition temperatures show part of the polyester component to form a homogeneous component of the amorphous phase.

The mechanical properties change with composition in parallel with the changes in copolymer crystallinity and Tg. Copolymers with 20‐60 w % of poly(oxytetramethylene) units of m.w. 2000 are highly extensible elastomers. Those with higher m. w. polyether blocks have higher modulus and strength but suffer a serious loss of properties at 60d̀C.

The observations are interpreted in terms of a model in which polyester crystallites (and polyether crystallites also, for the higher m. w. polyether blocks) are supported within an amorphous matrix by tie‐molecules whose nature changes with the copolymer compositions. The results are compared with those for analogous polyester‐polyethers having different structural components.
Polyester‐Polyether Block Copolymers III. Supramolecular Texture in Poly(hexamethylene terephthalate)/Poly(oxytetramethylene) Block Copolymers and Related Homopolymers and Blends
Authors: Ghaffar Abdul , Goodman Isaac , Peters Raymond H. , Segerman Ephraim
Published: April 2007

Optical and electron microscopy and small‐angle X‐ray scattering have been used to investigate the texture of poly(hexamethylene terephthalate)/poly(oxtetramethylene) multi‐block copolymers. The findings are consistent with a substantial separation of the combined sub‐species into separate phases, and with the aggregation of the alkylene terephthalate ‘hard’ segment blocks into crystalline forms analogous to those of the homopolymer alone and connected by microfibrillar units. The observations are correlated with the mechanical properties of the copolymers in terms of a ‘string of beads’ model, and compared with existing knowledge of phase‐separation morphology in other families of block copolymers. Some investigation has also been made into the morphology of poly(hexamethylene terephthalate) and poly(oxytetramethylene) homopolymers and their blends crystallised from the melt. The results are considered in relation to the properties of the corresponding copolymers.
The Reaction of Plumbonacrite (Basic Lead Carbonate) with Hot DOP, and the Stabilisation of Plasticised PVC
Authors: Michell E. W. John
Published: April 2007

The basic lead carbonate ‘plumbonacrite’, 6PbCO3.3Pb(OH)2.PbO, has been reacted with di‐2‐ethyl hexyl phthalate (dioctyl phthalate, DOP), C6H4(COOC8H17)2 at 180d̀C under nitrogen. Anhydrous monobasic lead orthophthalate, PbO.Pb6H4(COO)2, was the only product detected by X‐ray powder diffraction (X.R.P.D.). These studies are related to previous work on reactions taking place in hot polyvinyl chloride (PVC) blends containing DOP plasticiser and basic lead stabilisers. It is concluded that plasticiser stabiliser interaction can play a significant role in stabilising PVC against thermal decomposition, and that efficient stabilisation takes place largely by a free‐radical exchange mechanism. Characteristic X.R.P.D. data are tabulated for anhydrous monobasic lead orthophthalate, and for monobasic lead orthophthalate monohydrate, PbO. PbC6H4(COO)2‐ H2O, which can be made in aqueous suspension and which converts to the anhydrous salt at 180d̀C. X.R.P.D. data are also given for dibasic lead orthophthalate, 2PbO.PbC6H4(COO)2.1/2H2O, which is well known as a stabiliser for PVC, and which might have been expected to form in these experiments, (but did not in fact do so).
On the Applicability of Gardon's Equations for the Calculation of Particle Size in Emulsion Polymerisation
Authors: Dunn Alexander S. , Al‐Shahib Walid A. G. R.
Published: April 2007

Gardon's revision of the Smith‐Ewart theory of emulsion polymerisation makes it possible to calculate the average particle size of the latex produced from the conditions used for the polymerisation at least for monomers with a low monomer transfer constant. Good agreement has been found between the calculated particle sizes and the turbidity averages measured by light scattering for polystyrene latices prepared with various emulsifiers. However the theory neglects the effect of the ionic strength of the aqueous phase although Gardon's own results show this to be a significant parameter: increase of ionic strength increases the average size of the latex particles by reducing electrostatic stabilisation. The difference between the total and the micellar surfactant concentration is significant for surfactants with relatively high critical micelle concentrations and a considerable improvement in agreement between measured and calculated particle sizes is found when the concentration of micellar surfactant is used in the calculation. The theory requires the reaction rate to depend on the 3/5ths power of the concentration of micellar surfactant and although this would appear to have been satisfactorily verified experimentally, replotting of the extensive series of precise results published by Bartholome, Gerrens, Herbeck and Weitz shows that the double logarithmic plot is not actually linear. This is probably the result of a slow change of micelle size as the surfactant concentration is increased.
The Effect of Acid Acceptors on the Temperture Activated Creep of a Vinylidene Fluoride/Hexafluropropene/Tetrafluoroethylene Terpolymer (Viton B)
Authors: Barton John M.
Published: April 2007

Creep under compressive stress, modulus, and solvent swelling characteristics were determined with a thermomechanical analyser for a vinylidene fluoride/hexafluropropene/ tetrafluoroethylene elastomer at various temperatures. Significant creep occurs above 200d̀C where the elastomer undergoes oxidative degradation. The rubber was compounded with various metal oxides and hydroxides as acid acceptors, and the effect of these on creep at elevated temperatures was studied. At 250d̀C MgO, CaO and Ca(OH)2 were all found to produce a relatively low creep rate compared to that of a control sample.
The Efficiency of Polymer Fractionation at Lower Critical Solution Temperatures
Authors: Wolf B. A. , Bieringer H. F. , Breitenbach J. W.
Published: April 2007

The efficiency of a single fractionation step (i.e. of the partition of a given polymer sample between the coexisting phases which form when its solution demixes) is governed by the variation of the mass ratio of the individual P‐mers with chain length. These dependences have been measured for the system dimethoxymethane/diethylether/ polystyrene which exhibits lower critical solution temperatures by means of the Baker‐Williams method and by means of g.p.c. Their comparison with the results of previous investigation on systems showing upper critical solution temperatures reveals no thermodynamic differences in the aptitude of upper and lower critical solution temperatures for fractionation from dilute solutions.

The extension of the molecular weight distribution into the low molecular weight region by the addition of oligomer, answered the question whether the monomer concentration in the coexisting phases is practically identical, as predicted by classical theories, or larger by a factor of nearly ten in the polymer‐rich phase, as extrapolated from the information concerning the polymer. The direct observation yields intermediate values which demonstrate that the variation of the logarithm of the partition coefficient with the degree of polymerisation P cannot be represented by a linear function with sufficient accuracy when a broader range of molecular weights is considered; in this case it is necessary to replace P by P2/3.
Intermolecular interactions in blends of functionalised propylene polymers with poly(vinylchloride) or polystyrene
Authors: Benedetti Enzo , Posar Francesco , D'Alessio Aldo , Vergamini Piergiorgio , Aglietto Mauro , Ruggeri Giacomo , Ciardelli Francesco
Published: April 2007

Atactic and isotactic polypropylene (APP and IPP), and ethylene‐propylene copolymers (EP). functionalised by reacting the molten polymer with diethylmaleate (DEM) in the presence of dicumylperoxide (DCP). have been blended with poly(vinylchloride) (PVC) and polystyrene (PS). These mixtures have been investigated by means of infrared spectroscopy at different compositions in the region of carbonyl absorption. The features of this last band in the mixture suggest the occurrence of intermolecular interactions involving mainly the carbonyl groups of the functionalised polymer and the methine hydrogens of PVC.
Ring‐opening polymerisation of bicyclo[2.2.2]oct‐2‐ene
Authors: Hamilton James G. , Ivin Kenneth J. , Rooney John J.
Published: April 2007

Bicyclo[2.2.2]oct‐2‐ene has been polymerised by ring opening using a catalyst consisting of (mesitylene)W(CO)3/EtAlCl2/2,3‐epoxynorbornane/Me4Sn and a trace of norbornene. The polymer was characterised by 13C n.m.r. and contained 32% cis double bonds, with a somewhat blocky cis/trans double bond distribution.
Studies on the structural features of sodium alginate entrapped Kluyveromyces marxianus NCYC179 cells used for alcohol production from whey permeate
Authors: Marwaha Satwinder S. , Kennedy John F.
Published: April 2007

Alginate‐entrapped living Kluyveromyces marxianus NCYC179 cells were successfully used in alcohol production from whey permeate. Using 10% whey lactose as substrate, an alcohol production efficiency of 81.5–84.9% and 84.0–88.2% with cell viability maintenance between 82.8–84.3% and 81.0–84.3% of the immobilised cells during the monitoring periods, in batch (six repeat runs) and continuous (23 days of experimenting time) systems, respectively. The immobilised samples remained stable during the course of fermentation with no leakage of K. marxianus cells into the surrounding medium in the case of the batch system. However, slight leakage after 10 days of continuous run in the continuous process was recorded. The scanning electron microscopic studies of the beads containing entrapped yeast cells and sections or crushed samples of the beads carried out at the start and termination of fermentation in both the processes (batch and continuous) revealed that the immobilisation procedure does not influence any morphological change in the entrapped cells during the prolonged periods of fermentation. Moreover, the gel matrix structure was also found to be unaffected by the fermentation conditions employed during the course of present studies.
Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)
Authors: Varma D. S. , Agarwal Radha , Varma Indra K.
Published: April 2007

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (Tg). melting points (Tm) and crystallisation temperatures (Tc) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in Tg, Tm and Tc. The as‐prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.
Deuterium magnetic resonance studies on strained selectively deuterated elastomers
Authors: Gronski Wolfram , Emeis Detlef , Brüderlin Alfred , Jacobi Marly Maldaner , Stadler Raimund , Eisenbach Claus D.
Published: April 2007

The lineshape analysis of the 2H nuclear magnetic resonance of uniaxially strained poly(1,4‐butadiene) networks deuterated homogeneously and selectively at network junctions shows that the orientation of chain segments attached to crosslinks is larger than the average segmental orientation. In addition, it is shown that the molecular effective extension ratio of all elastically effective chains is smaller than the macroscopic extension ratio, and short chains are stretched to a higher extent than long chains. The deviation from the affine deformation behaviour and the onset of inhomogeneous deformation of individual chains takes place at the transition from the Gaussian to the non‐Gaussian network. In the Gaussian regime the segmental orientation varies with the inverse of the molecular weight of elastically effective chains in agreement with molecular theories of rubber elasticity. 2H n. m. r. spectra of a thermoplastic poly(styrene‐b‐butadiene‐b‐styrene) block copolymer carrying selectively deuterated butadiene segments at the block boundaries reveal an enhanced mobility of these segments under deformation. 2H n. m. r. experiments on amorphous segmented polyurethanes selectively deuteratured in hard and soft segments, respectively, show that the elasticity in these samples is achieved by physical crosslinks formed by very small highly mobile aggregates of hard segments dispersed in the soft phase. Within the hard domains two processes for motion due to phenyl groups in 4. 4'‐methylenebis(phenylisocyanate) units and CH2 groups in 1. 4‐butanediol units can be discriminated.
Bimodal networks and networks reinforced by the in situ precipitation of silica
Authors: Mark James E.
Published: April 2007

The goal of primary interest in these investigations was the development of novel methods for preparing elastomeric networks having unusually good ultimate properties. The first technique employed involves endlinking mixtures of very short and relatively long functionally‐terminated chains to give bimodal networks. Such (unfilled) elastomers show very large increases in reduced stress or modulus at high elongations because of the very limited extensibility of the short chains present in the networks. The second technique employs the in situ precipitation of reinforcing silica either after, during, or before network formation. The reaction involves hydrolysis of tetraethylorthosilicate, using a variety of catalysts and precipitation conditions, and the effectiveness of the technique is gauged by stress‐strain measurements carried out to yield values of the maximum extensibility, ultimate strength, and energy of rupture of the filled networks. Information on the filler particles thus introduced is obtained from density determinations, light scattering measurements, and electron microscopy.
Interpenetrating polymer networks
Authors: Frisch Harry L.
Published: April 2007

Interpenetrating polymer networks (IPNs) composed of two or more chemically distinct networks are not only intrinsically interesting as examples of macromolecular chemical topological isomerism but are in practice useful means of controlling mutual miscibility and phase morphology in crosslinked polymers. We will first review briefly the synthesis and properties of such IPN systems. This will be followed by an outline of a phenomenological theory of the phase stability and linearised theory of spinodal decomposition of binary, chemically quenched, low crosslink density IPNs recently developed by K. Binder and the author. Finally, we will discuss some aspects of the synthesis of ternary IPNs and the thermochromic properties of IPNs containing a crosslinked polydiacetylene.
Networks in nature
Authors: Burchard Walther
Published: April 2007

Synthetic networks, their structure and mechanical properties have been studied since the beginning of polymer science, while the considerable variety of networks in nature has been largely neglected, though use has been made of them as long as human culture has existed. In principle synthetic and natural networks are equivalent, but there are significant differences.

(1) The main difference consists in the high polarity of the polymeric components and the related capability of binding large quantities of water. (2) The biosynthesis of covalently linked, macroscopic networks is rare and often too slow a process. In many cases the networks are formed via physical forces between various polymeric components. (3) Often the network formation can be reversed by changing the temperature, or pH, or by adding urea or detergents. (4) The viscoelastic behaviour is often governed by the rigidity of the macromolecular substructures.

Examples are given for reversible gels with some charged polysaccharides and with fibrin. Special interactions are demonstrated with the network of connective tissue. The important role of comb‐like macromolecules with protein backbone and polysaccharide side chains is outlined. Special interactions are crucial also for immunologic response, i.e. for cell recognition and antibody‐antigen complex formation. The latter is one of the best examples of a successful application of the Flory‐Stockmayer theory of branching and gelation. Most of the reversible gels are not yet fully understood in their properties, and theory is lacking. This is particularly true for products like gelatin and starch.
Gelation of pectinic acids in the presence of calcium counterions
Authors: Thibault Jean‐Francois , Rinaudo Marguerite
Published: April 2007

Pectins are polysaccharides which are able to gel in the presence of calcium ions if their degree of esterification is lower than 40%. From a purified pectin, a de‐esterification was carried out by alkali and by enzymes in order to obtain samples with a different charge density and esterification pattern (random or blockwise distribution of carboxylic acid sites). The pectin‐calcium interactions were studied in a dilute solution of calcium pectinates by conductimetry. If the concentration of highly charged polymer is increased, a multichain association can occur: the same process is observed with dilute solutions (cp≤10‐3 eq. 1−1) but in the presence of an excess of calcium ions. This first step of the gelation was followed by light scattering and by viscometry. The gelling system can be described by a power law including a critical ratio (equivalent concentration of calcium ions/pectin carboxylic sites) and quasi‐critical exponents. The values of these critical parameters have been discussed as a function of charge density of the pectins, their esterification pattern, their concentration, and the nature of the divalent counterion.
Cure and properties of thermosetting systems
Authors: Gillham John K.
Published: April 2007

A generalised time‐temperature‐transformation cure diagram for thermosetting systems is discussed from the point of view of understanding relationships between cure, properties, and thermal degradation.
Rheological changes during crosslinking
Authors: Macosko Christopher W.
Published: April 2007

Huge rheological changes occur during thermoset polymerisation. Methods for measuring these changes and relating them to molecular structure through branching theory and reaction kinetic data are reviewed. Applications to thermoset processing are discussed.
Electro‐copolymerisation of indene and styrene
Authors: Toppare Levent , Eren Sami , Akbulut Ural
Published: April 2007

Electroinitiated cationic copolymerisation of indene and styrene was investigated by constant potential electrolysis. Effects of copolymerisation potential and temperature on the copolymer composition and the reactivity ratios are discussed. The reactivity ratios of the monomers were calculated according to the integrated Lewis‐Mayo equation.
The thermo‐softening process of SBS thermoplastic rubber
Authors: Birley Arthur W. , Canevarolo Sebastiäo V. , Hemsley Derek A.
Published: April 2007

This paper discusses the thermo‐softening process of a triblock copolymer of styrene‐butadiene‐styrene. The specific volume vs temperature curve shows an anomalous expansion above ∼ 165°C, compared with a theoretical curve obtained from applying the simple law of mixtures to the pure components. The amount of crosslinking developed in the copolymer in terms of its gel content is found to increase suddenly, starting from 200°C and being fully developed at 230°C. Form birefringence vs temperature curves obtained during temperature cycling tests, show that a rearrangement takes place in the imperfect original domain structure above 145°C. This significantly increases the birefringence at room temperature. There is a maximum value of birefringence which is not destroyed even when the sample is heated up as high as 290°C. Dynamic mechanical thermo‐analysis shows a large broad peak for the tan δ in the studied region due to this rearrangement. The processes involved are, in general, irreversible although the specific volume vs temperature curve below 150°C is reproducible.
QM polymers and other products derived from parabola vermiculite
Authors: Currell Brian R. , Hayes Peter R. , Midgley Henry G. , Parsonage John R.
Published: April 2007

The trimethylsilylation of parabola vermiculite gives polyorganosiloxanes of the structure QxMy. (Q = SiO42: M = ((CH3)SiO12) which will form gels in a wide range of organic solvents and resins. No other mineral has so far been reported to yield trimethylsilylated products capable of forming gels. The effect on the nature and yields of these QM polyorganosiloxanes' of variation in reaction time, particle size and vermiculite/hexamethyldisiloxane ratio have been investigated. The QM polyorganosiloxanes produced are hydrophobic insoluble powders which gel in a wide range of organic solvents. Reaction with NaOH/EtOH mixtures gives ‘silicone‐silicate’ hybrids by replacement of trimethylsilyl groups with sodium ions. i.e. ‘QMNa’ products. The ability of these products to form films is compared to that of parabola vermiculite itself and also acid‐leached vermiculite. QM polyorganosiloxanes give films which can either be peeled off as an integral film or, after heating on a glass slide at 50°C. will give a hard hydrophobic surface. Preliminary investigation has also shown that QM polymers can be used as fillers in epoxy resins.
Further studies of polycarbonate‐poly(butylene terephthalate) blends
Authors: Birley Arthur W. , Chen Xin Yue
Published: April 2007

The mechanical properties (tensile strength, low temperature falling weight impact strength) of XENOY CL‐100 (a blend of polycarbonate and polybutylene terephthalate) have been studied. This blend is comprised of tough components and the property combinations that result may be useful for certain applications. The hydrolysis resistance of the blend in deionised water at 40°C has been studied. After 30 weeks it did not lose its tensile strength, but subsequently it did lose 50% of the low temperature (−70°C) falling weight impact strength. If the −70°C low temperature toughness is an important quality, this should be taken into account. However, the low temperature (−70°C) falling weight impact strength of pure polycarbonate and of pure poly(butylene terephthalate) is very low, whilst XENOY CL‐100 is still tough material, even after 30 weeks immersion at 40°C. Further study of the composition of XENOY CL‐100 showed that this blend is composed of polycarbonate. poly(butylene terephthalate) and crosslinked acrylic rubber; traces of titanium‐catalyst residue for the poly(butylene terephthalate) polymeristaion and black dye have also been found.
Molecular weights of poly(butyl 2‐cyanoacrylate) produced during nanoparticle formation
Authors: Douglas S. J. , Davis S. S. , Holding S. R.
Published: April 2007

The molecular weights and distributions of poly(buty1 2‐cyanoacrylate) produced during the formation of nanoparticles under a range of polymerisation conditions have been determined by gel permeation chromatography. The data indicate that the type of steric stabiliser and concentration of the monomer added to the polymerisation medium influences the resulting molecular weight of the polymer. In all systems the bulk of the polymer had a low molecular weight (<10000) but nanoparticles stabilised with dextrans or poloxamer 188 also yielded a high molecular weight component (>20000). The results are interpreted with regard to the possible effects on the degradation of nanoparticles and their drug release characteristics. Tentative proposals are made concerning the mechanisms of nanoparticle formation.
Thermal degradation of cinnamoylated poly(vinyl alcohol)
Authors: Caşcaval C. N. , Buruianǎ E. C. , Roşu D. , Rusu E. , Grigoriu G. E. , Bârboiu V.
Published: April 2007

Thermogravimetry and pyrolysis in combination with gas chromatography and infrared spectroscopy were the experimental techniques applied to the thermal degradation of cinnamoylated poly(vinyl alcohol) samples, constituted from vinyl alcohol‐vinyl cinnamate photocrosslinkable copolymers. The thermal decomposition products include gases, liquids and solids. The gases are formed from saturated and unsaturated volatile hydrocarbons C1C4, carbon monoxide and carbon dioxide. The liquid fraction includes aromatic hydrocarbons and some oxygenated organic compounds. The solid product identified in the greatest amount was cinnamic acid. The content in the thermal decomposition products varies considerably both with copolymer composition and temperature.
Resonance raman spectroscopy of polydiacetylene langmuir‐blodgett films
Authors: Lyall Iain R. J. , Batchelder David N.
Published: April 2007

Resonance Raman excitation profiles of two vibrational modes have been measured for Langmuir‐Blodgett films of a polydiacetylene. The polymer films were formed by exposing multilayer samples of the Cd salt of 10,12‐pentacosadiynoic acid to ultraviolet radiation. Raman spectra were measured for incident laser photon energies between 1.85 and 2.20 eV (670‐564 nm), the region over which the films exhibited optical absorption associated with an electronic transition of the π‐electrons on the conjugated backbone. The excitation profiles have been used to determine both the strength of the vibronic coupling and the differences in vibrational frequency between the ground and excited states. The results are in reasonable agreement with those obtained previously for polydiacetylene single crystals.
Polyvinylpyrrolidone – Some Problems and Pitfalls
Authors: Molyneux Philip
Published: April 2007

The characteristics of the commercially available grades of polyvinylpyrrolidone are discussed, specifically in relation to the provenance of these materials, and the validity of the molecular weights quoted for them in the manufacturers and suppliers literature.
The Use of Dynamic Mechanical Methods to Study the Effect of Absorbed Water on Temperature‐dependent Properties of an Epoxy Resin‐Carbon Fibre Composite
Authors: Barton J. M. , Greenfield D. C. L.
Published: April 2007

Dynamic mechanical methods were used to study the effect of absorbed moisture on the properties of an epoxy resin matrix CFRP. The glass transition temperature (Tg)of the matrix resin, determined as the onset of the characteristic fall in dynamic modulus with increasing temperature, was found to decrease with increasing moisture content. Maximum shifts in Tg of 80 to 90°C, relative to the dry material, were observed for a resin moisture content of 5.2% by weight. The effects of sample geometry, fibre orientation, and frequency of oscillation, on the dynamic mechanical properties are discussed. Results are given of an analysis of the observed dependence of Tg on water content using two theoretical models.
Group A streptococcus cell‐associated pathogenic proteins as revealed by growth in hyaluronic acid‐enriched media
Authors: Zhang Meng , McDonald Fiona M. , Sturrock Shane S. , Charnock Simon J. , Humphery‐Smith Ian , Black Gary W.
Published: April 2007

Group A streptococcus (GAS), also know as Streptococcus pyogenes, is a human pathogen and can cause several fatal invasive diseases such as necrotising fasciitis, the so‐called flesh‐eating disease, and toxic shock syndrome. The destruction of connective tissue and the hyaluronic acid (HA) therein, is a key element of GAS pathogenesis. We therefore propagated GAS in HA‐enriched growth media in an attempt to create a simple biological system that could reflect some elements of GAS pathogenesis. Our results show that several recognised virulence factors were up‐regulated in HA‐enriched media, including the M1 protein, a collagen‐like surface protein and the glycolytic enzyme glyceraldehyde‐3‐phosphate dehydrogenase, which has been shown to play important roles in streptococcal pathogenesis. Interestingly, two hypothetical proteins of unknown function were also up‐regulated and detailed bioinformatics analysis showed that at least one of these hypothetical proteins is likely to be involved in pathogenesis. It was therefore concluded that this simple biological system provided a valuable tool for the identification of potential GAS virulence factors.
Proteome and phosphoproteome dynamic change during cell dedifferentiation in Arabidopsis
Authors: Chitteti Brahmananda Reddy , Peng Zhaohua
Published: April 2007

Cell dedifferentiation is a cell fate switching process in which a differentiated cell reverts to a status with competence for cell division and organ regeneration like an embryonic stem cell. Although the phenomenon of cell dedifferentiation has been known for over two and a half centuries in plants, little is known of the underlying mechanisms. Here, we have established the proteome map of Arabidopsis cotyledons and investigated the dynamic change of the cotyledon proteome in the time course of cell dedifferentiation. Among the 353 distinct genes, corresponding to 500 2‐DE gel protein spots identified with high confidence, 12% have over twofold differential regulations within the first 48 h of induction of cell dedifferentiation. The distributions of these genes among different Gene Ontology categories and gene differential regulations within each of the categories have been examined. In addition, we have investigated the cotyledon phosphoproteome using Pro‐Q Diamond Phosphoprotein in Gel Stain followed by mass spectrometry analyses. Among the 53 identified putative phosphoproteins, nine are differentially regulated during cell dedifferentiation. These studies have provided significant new insight into protein and phosphoprotein differential expression during cell dedifferentiation in plants.
Proteomic analysis of roots growth and metabolic changes under phosphorus deficit in maize (Zea mays L.) plants
Authors: Li Kunpeng , Xu Changzheng , Zhang Kewei , Yang Aifang , Zhang Juren
Published: April 2007

Phosphorus (P) deficiency is a major limitation for plant growth and development. Plants can respond defensively to this stress, modifying their metabolic pathways and root morphology, and this involves changes in their gene expression. To better understand the low P adaptive mechanism of crops, we conducted the comparative proteome analysis for proteins isolated from maize roots treated with 1000 μM (control) or 5 μM KH2PO4 for 17 days. The results showed that approximately 20% of detected proteins on 2‐DE gels were increased or decreased by two‐fold or more under phosphate (Pi) stress. We identified 106 differentially expressed proteins by MALDI‐TOF MS. Analysis of these P starvation responsive proteins suggested that they were involved in phytohormone biosynthesis, carbon and energy metabolisms, protein synthesis and fate, signal transduction, cell cycle, cellular organization, defense, secondary metabolism, etc. It could be concluded that they may play important roles in sensing the change of external Pi concentration and regulating complex adaptation activities for Pi deprivation to facilitate P homeostasis. Simultaneously, as a basic platform, the results would also be useful for the further characterization of gene function in plant P nutrition.
Transcriptome and proteome analyses in response to 2‐methylhydroquinone and 6‐brom‐2‐vinyl‐chroman‐4‐on reveal different degradation systems involved in the catabolism of aromatic compounds in Bacillus subtilis
Authors: Van Duy Nguyen , Wolf Carmen , Mäder Ulrike , Lalk Michael , Langer Peter , Lindequist Ulrike , Hecker Michael , Antelmann Haike
Published: April 2007

Bacillus subtilis is exposed to a variety of antimicrobial compounds in the soil. In this paper, we report on the response of B. subtilis to the fungal‐related antimicrobials 6‐brom‐2‐vinyl‐chroman‐4‐on (chromanon) and 2‐methylhydroquinone (2‐MHQ) using proteome and transcriptome analyses. Chromanon, a derivative of aposphaerins from Aposphaeria species caused predominant protein damage in B. subtilis as indicated by the induction of the HrcA, CtsR, and Spx regulons. The expression profile of the ganomycin‐related substance 2‐MHQ was similar to that of catechol as reflected by the common induction of the thiol‐specific oxidative stress response. Several putative ring‐cleavage dioxygenases and oxidoreductases were differentially up‐regulated by 2‐MHQ, catechol, and chromanon including yfiDE, ydfNOP, yodED, ycnDE, yodC, and ykcA. The nitroreductase encoding yodC gene is induced in response to catechol, 2‐MHQ, and chromanon, which depend on the MarR‐type repressor YodB. The yfiDE (catDE) operon encodes a catechol‐2,3‐dioxygenase which is most strongly induced by catechol. The yodED (mhqED), ydfNOP (mhqNOP) operons, and ykcA (mhqA) respond most strongly to 2‐MHQ and encode putative hydroquinone‐specific extradiol dioxygenases. The ycnDE operon was most strongly induced by chromanon. Mutational analyses revealed that the putative hydroquinone‐specific dioxygenases MhqO and MhqA confer resistance to 2‐MHQ in B. subtilis.
Electronic and structural properties of biazulene, terazulene, and polyazulene isomers
Authors: Dias Jerry Ray
Published: April 2007

Facile graph theoretical MO solutions are demonstrated. The dihedral angles between the azulene units at the bridging bond in biazulenes were determined by MM2 calculations. Polyazulenes are predicted to be conductive only via the polaron mechanism. Polaron conduction in 1,3‐ and 2,6‐polyazulene is qualitatively predicted to be more facile than in 4,8‐ and 5,7‐polyazulene. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of poly(L‐lactide)s and poly(D‐lactide)s of controlled molecular weight
Authors: Jalabert Matthieu , Fraschini Carole , Prud'homme Robert E.
Published: April 2007

High molecular weight poly(L‐lactide)s (PLLAs) and poly(D‐lactide)s (PDLAs) were synthesized in toluene at 70 °C by ring‐opening polymerization of optically pure L‐lactide and D‐lactide, using tin(II) 2‐ethylhexanoate (SnOct2) and 2‐(2‐methoxyethoxy)ethanol as initiator and coinitiator, respectively. Under these conditions, polarimetry as well as 13C NMR spectroscopy indicated that the synthesized poly(lactide)s (PLAs) are more than 99% isotactic. The molecular weight was successfully controlled by adjusting the monomer‐to‐initiator molar ratio. Gel permeation chromatography and MALDI‐TOF mass spectrometry analyses showed that the polydispersity index of the PLAs is below 1.1. Moreover, MALDI‐TOF spectra showed two different chain distributions, one characterized by an even number of lactic acid repeat units and the other by an odd number of lactic acid repeat units. The second distribution, indicative of the presence of intermolecular transesterification reactions, appears at the very beginning of the polymerization and its intensity increases with the polymerization time. Finally, a reversible reaction kinetic model was used to determine the monomer equilibrium concentration ([M]eq = 1.4 ± 0.5%) and the propagation rate constant (kp = 14.4 ± 0.5 L mol−1 h−1) of the polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1944–1955, 2007
Effect of monomer structures and preparation methods on the morphology and properties of UV cured organic–inorganic hybrid films
Authors: Chang Chi‐Jung , Wu Maw‐Song , Kao Pei‐Chun
Published: April 2007

The effects of preparation methods and monomer chemical structures on the microstructure, morphology, and properties of the hybrid films were studied. 7DBPA‐3S was synthesized by the sol–gel reaction of precondensed silica particles with alkoxysilane‐modified polymers DBPA. DBP‐POBG3T3 was prepared by the radiation curing of comb‐like UV curable alkoxysilanes POBG3T3 with UV curable polymer DBP, followed by the sol–gel reaction of alkoxysilanes. The DBP‐POBG3T3 film consisted of polymer matrix and large tethered aggregates with tiny silica connected by organic chains. On the contrary, silica nanoparticles were well‐dispersed in the 7DBPA‐3S hybrid film. The TEM, energy dispersive X‐ray Si‐mapping and P‐mapping images are good experimental approaches to characterize the texture of the tethered aggregates. The 7DBPA‐3S hybrid composite with well‐dispersed silica nanoparticles exhibited smoother surface, higher transparency, and better thermal stability than the DBP‐POBG3T3 composite did. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1152–1165, 2007
Adaptive style and differences in parent and child report of health‐related quality of life in children with cancer
Authors: Jurbergs Nichole , Russell Kathryn M. W. , Long Alanna , Phipps Sean
Published: April 2007

The objective of this study was to examine the self‐reported health‐related quality of life (HRQL) of children with cancer, and the consistency between child and parent reports of child HRQL, as a function of the child's adaptive style. Participants included 199 children with cancer, 108 healthy children, and their parents. Children completed self‐report measures of HRQL and adaptive style. Measures of adaptive style were used to categorize children as high anxious, low anxious, defensive high anxious or repressor. Parents completed measures reporting their children's HRQL. Adaptive style was a significant predictor of child‐reported HRQL, particularly on the psychosocial scales, with children identified as repressors reporting the best HRQL. Adaptive style was also predictive of discrepancies between parent and child report of child HRQL. Repressor and low anxious children reported better HRQL than did their parents, while high anxious children reported poorer HRQL, regardless of health status. Adaptive style is a significant determinant of self‐reported HRQL in children, particularly in psychosocial domains, while health status (i.e. cancer patient vs healthy control) is predictive only of physical health domains. Researchers and clinicians should be aware of the impact of child adaptive style when assessing HRQL outcomes using self‐ or parent report. Copyright © 2007 John Wiley & Sons, Ltd.