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  • 1
    Electronic Resource
    Electronic Resource
    An examination of the use of principal component analysis and target factor analysis for the determination of Auger depth profiles in two magnetic multilayer metal systems - Cu/Co and Co/PtEnlarged version of papers presented at QSA8 and ECASIA '95. (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 858-872 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Target factor analysis and principal component analysis have been applied to Auger spectra acquired from two metallic multilayer systems (Cu/Co and Co/Pt) depth profiled using ion beam bevelling. Both multilayers contained alternating 10 nm films, the Co/Pt being capped with 25 nm of Co. The results reveal the expected improvement in the precision of the depth profiles because of the amount of information included in the factor analysis. However, the data sets always contain more factors than expected from the number of different elements present. These extra factors are revealed by examination of the principal components as being due to the depth dependence of the inelastic scattering at energies lower than the Auger features. This yields more information about the samples than can be obtained from inspection of the raw spectra but compromises the accuracy of quantification of the depth profiles.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740231303
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanism of emulsion polymerization of styrene in soap-free systems (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2193-2218 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation and growth of monodisperse polystyrene latex particles in the absence of added surfactant has been studied by sampling polymerization reactions at different times and determining the surface and bulk properties of the latex. A large number of nuclei in excess of 5 × 1012/ml were generated during the first minute of reaction, but this fell due to coagulation until a constant number (1011-1012/ml) was reached. The rate of polymerization per particle was then found to be proportional to the particle radius. Gel-permeation chromatography has shown that the initial particles consist mainly of material of MW 1000 with a small amount of polymer up to MW 106, and the presence of this low molecular weight polymer, which in many cases can still be detected after 100% conversion, is taken as being indicative of particle formation via a micellization-type mechanism involving short-chain (MW 500) free-radical oligomers. M̄n values determined for the latex particles throughout the course of reactions show that the molecular weight increases to a maximum of about 105 as the particles grow. The presence of anomalous regions within the particles has been confirmed by transmission electron microscopy, scanning electron microscopy, and gas adsorption studies. It has also been found possible to re-expose these regions within apparently homogeneous particles by stirring with styrene monomer; this is indicative of a molecular weight heterogeneity within the latex particles. The presence of sulfate, carboxyl, and hydroxyl groups upon the latex particle surfaces has been determined by conductometric titration.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150912
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  • 3
    Electronic Resource
    Electronic Resource
    Study of the anomalous particles formed during the surfactant-free emulsion polymerization of styrene (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2311-2319 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The presence of anomalous regions within polystyrene latex particles prepared in the absence of added emulsifier has been investigated. It appears that they arise through loss of monomer from particles consisting of a discrete monomer-rich region surrounded by a polymer shell. It is likely that in most cases, monomer is lost from the region on evacuation prior to electron microscope examination, although there is some evidence from γ-irradiated samples (prior to electron microscopy) that loss of monomer can also occur during storage and/or dilution of the sample. Scanning electron microscopy and carbon replication techniques have been used to determine the shapes of the voids. Gas adsorption studies and carbon replication have also served to illustrate that the presence of the regions was not due to electron-beam damage. The presence of extrusions on some samples has been attributed to incomplete loss of monomer on evacuation due to the thickness of the surrounding polymer shell.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170151003
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  • 4
    Electronic Resource
    Electronic Resource
    Permeation through homopolymer latex films (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 2947-2972 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helium permeabilities of homopolymer films cast from polymer solutions and latex dispersions have been measured as a function of time. The permeability coefficients of most polymer latex films started off at a value which was considerably higher than that of the corresponding solvent-cast film, but then dropped at a rate dependent on the polymer concerned. The permeability coefficients levelled off at a value which was closer to, but still higher than that of the equivalent solvent-cast film. Solvent-cast film permeabilities remained constant for the period of several months over which time they were examined. The reduction in the permeability of latex films is attributed to ageing processes occurring within the film after casting. The fact that latex film permeability coefficients are always higher than those of solvent-cast films suggests that latex films never become completely homogeneous. The effect on permeability of the latex type and characteristics, and preparation and storage conditions has been examined. The polymer molecular weight, particle size, and surface-change density did not appear to exert any influence, within experimental error. However, the time-dependent permeability behavior was affected by the film preparation and storage temperatures.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.170231205
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  • 5
    Electronic Resource
    Electronic Resource
    Problems associated with the surface characterization of polystyrene latices (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1019-1037 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been shown that polystyrene latices prepared by the surfactant free emulsion polymerization process often contain sufficient residual monomer and possibly low-molecular-weight material and reaction by-products, such as benzaldehyde, which are not efficiently removed by dialysis, to affect their bulk and surface characteristics. These materials have been identified by gel permeation chromatography (GPC) and infrared (IR) spectroscopy studies and their effective removal by steam stripping has been investigated. Steam stripping has proved to be efficient in this process but it led to rapid hydrolysis of the surface sulfate groups and a consequent change in the surface characteristics. The problem of hydrolysis of sulfate groups under various environments has been studied. The problems associated with the identification of weak acid end groups are discussed and several alternative explanations for their occurrence are advanced.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170408
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics of the surfactant-free emulsion polymerization of styrene:-The post nucleation stage (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 1869-1883 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the surfactant-free emulsion polymerisation of styrene have been studied. Reactions were sampled at several stages throughout their course, and the samples characterized by electron microscopy, gravimetric weights analysis and gel permeation chromatography, After an initial period of particle nucleation and coagulation, the reaction proceeds at a constant number density. The theories developed for emulsion polymerisation in the presence of surfactant above its critical micelle concentration might be expected, in Interval II, to apply to the surfactant-free system if due regard is taken of the lower number densities and larger particle sizes developed. The results are in best accord with theories invoking a surface phase polymerisation mechanism. None of these theories predict a bimodel molecular weight distribution as found here and which is ascribed to polymerisation in two loci. The activation energy was found to be the same as for surfactant containing emulsion polymerisations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.170230703
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  • 7
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, I. Films containing no or only low levels of additivesBased on a paper presented at the second meeting of the UK Polymer Colloids Forum 22-23 September 1994, Keele University, UK. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 1-12 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; permeability ; Eudragit® ; poly(methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A range of permeation techniques were employed to investigate the transport mechanisms across polymer films cast from lattices containing either no or only low levels of water soluble leachates such as residual surfactant from polymerisation or added plasticiser essential to film formation. Hydrophilic pathways can provide a mechanism of transport, in addition to partition into and solution-diffusion in the polymer phase. Loss of porosity by low Tg polymers on drying highlights the value of solute probes in studying film morphology.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380101
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  • 8
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, III. Modification using soluble polymeric additives (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 23-32 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; film permeability ; Eudragit® ; soluble polymeric film additives ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of two distinct types of water leachable polymeric additives upon the transport properties across polymer latex films is considered. Hydroxypropyl methylcellulose, added as an aqueous solution, and a methyl methacrylate-methacrylic acid copolymer, added as latex particles, are both shown to be more effective than lower molecular weight rapidly water soluble additives, typified by sucrose, in enhancing solute transport and creating pathways for convective diffusion.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380103
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  • 9
    Electronic Resource
    Electronic Resource
    Studies on permeation through polymer latex films, II. Permeation modification by sucrose addition (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 13-22 
    Details
    ISSN: 0959-8103
    Keywords: polymer latex films ; permeability ; convective transport ; Eudragit® ; poly(methacrylate) ; sucrose ; film porosity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation of the effect of leachable sucrose on the permeability of polymer latex films showed that the additive can be used to vary the solute permeability in a systematic manner, as a result of increased free volume resulting from additive leaching. However, the extent of the permeability enhancement is dependent on both the glass transition temperature of the polymer and its ability to sustain porosity and prevent pore reduction by wet sintering and/or film drying, and also the compatibility of the sucrose additive with the polymer. The loading of additive dictates how readily it is leached and, hence, the presence, or not, of continuous porosity through the full thickness of film. Although continuous porosity can be conferred on the film by the sucrose leaching, the resulting porosity still greatly inhibits the permeation of electrolyte, and the film fails well before the level of porosity approaches that required for unimpeded transport.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380102
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of soft-segment prepolymer functionality on the thermal and mechanical properties of RIM copolymers (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 41 (1996), S. 283-292 
    Details
    ISSN: 0959-8103
    Keywords: reaction injection moulding ; polyurea ; polyurethane-urea ; thermomechanical properties ; fracture behaviour ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Segmented copolyureas (PUr) and copoly(urethane-urea)s (PUU) comprising 50% by weight of polyurea hard segments (HS) and polyether soft segment (SS) with different functionalities, have been formed by reaction injection moulding (RIM). The HS were formed from 4,4′-diphenylmethane diisocyanate reacted with mixed isomers of 3,5-diethyltoluene diamine. The nominal functionality of the SS prepolymers used (either amino- or hydroxyl-functionalised polyoxypropylenes with a constant molar mass per functional group of ∼ 2000 g mol-1) was systematically increased from 2 to 4. RIM materials were characterised using dynamic mechanical thermal analysis, differential scanning calorimetry, tensile stress-strain and fracture mechanics studies. Generally, the PUr exhibited far superior thermal-mechanical properties than equivalent PUU materials but inferior fracture resistance, owing to morphological variations resulting from differences in copolymerisation behaviour. For both systems, tensile behaviour was shown to be dominated by the degree of phase separation, whereas fracture properties showed a degree of dependence on SS functionality.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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