Search

In this article, calcium carbonate filled low density polyethylene (LDPE) was prepared and the influence of filler content, particle size, and surface treatment with stearic acid on the strain hardening and viscoelastic properties of the composites were investigated. Both elongational and shear rheological measurements were conducted on the different formulations and completed by microscopical observations and by differential scanning thermal analysis. The obtained results indicate that the effect of filler content and particle size are negligible on strain hardening behavior. Also the filler surface treatment has a less important effect on the nonlinear elongational tests in comparison with low frequency range measurements. However in shear rheology, we noted the absence of yield stress and network structure at different filler contents, and the presence of shear thinning behavior. Scanning electron microscopy (SEM) observations showed the enhancement of dispersion for surface treated samples, while differential scanning calorimetry (DSC) experiments have shown that the content of crystallinity of LDPE matrix is slightly affected by the presence of filler. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

19NMR spectroscopy has been performed on PEEK samples in sulphuric acid, revealing that most chain ends are fluorine. Different chemical shifts have been observed on sulphonated samples due to already demonstrated long range shielding effects. The method appears suitable for Mn determination. Substitution of F chain ends, followed by 19NMR, appeared feasible leading to alkaline sulphonate end groups. Ionic chain ends associations act as seeds for nucleation. Fast crystallizing PEEK and PEK are thus obtained. This is a new demonstration of the concept of Chemical Nucleation.

Nanoporous templates have been developed and fabricated employing technology based on heavy ion bombardment and track etching of polymer films or polymer layers deposited on substrates; an alternative and unique tool based on the adaptation of an atomic force microscopy has been also developed to elaborate nanotemplates with pores of ultra-small dimensions down to a few nanometers. Different types of nano-objects elaborated using these templates have been further characterized regarding their specific properties: spin dependent phenomena in magnetic nano-objects (GMR, TMR, spin filtering, magneto-Coulomb effect. spin transfer torque phenomena), microwave properties of ferromagnetic nanowires arrays, optical properties of confined emitting polymer and biomedical applications of magnetic (Ni) and Ni/Au composite nanowires. Potential application of magnetic nanowire arrays has been also considered in sensor for automotive contact-less positioning system. (C) 2009 Elsevier B.V. All rights reserved.

When it is combined with other processing steps, radiation modification of polyethylene pellets prior to conversion into end products (formed parts) has brought about significant improvement of various properties of the polymers and products made from them despite the low cross-linking degree. The physical and chemical changes of the polymers after the radiation modification by electron beam (EB) and gamma ray at low dose levels are studied using various characterizations. Fourier Transform Infrared Spectroscopy (FTIR) showed the formation of carbonyl groups and changes of unsaturated bonds. Gel permeation chromatography (GPC) results indicated broadening of the molecular weight distribution. Rheological analysis in linear visco-elasticity regime showed increased dynamic viscosity and large amplitude oscillatory shear (LAOS) analysis showed increased hysteresis. It is proposed that the radiation at low dose levels and under ambient conditions induces various reactions on the polymer chains including long chain branching, oxidation and changes of unsaturated bonds. (c) 2005 Elsevier B.V. All rights reserved.

The conjugated effects of both reactive compatibilization and dynamic vulcanization on the phase inversion behavior of poly(butylene terephthalate) (PBT)/epoxide-containing rubber blends have been studied in detail. Pure ethylene-methyl acrylate random copolymer (E-MA) and ethylene-methyl acrylate-glycidyl methacrylate random terpolymer (E-MA-GMA) were used as non reactive or reactive rubber phase, respectively. Location of the phase inversion region was studied using several techniques, including transmission electron microscopy (TEM) and dynamical mechanical thermal analysis (DMTA). To evaluate the relative influence of the blend compatibilization and the dynamic vulcanization on the phase inversion behavior, the relative kinetics of the two reactions were modified using different PBT and E-MA-GMA grades. The obtained results show unambiguously that the position and the width of the phase inversion region is essentially governed by the kinetic of the dynamic vulcanization process. The effect of the blend compatibilization remains quite limited even in the case of fast interfacial reaction. The crosslinking of the rubber phase induces an important shift of the phase inversion composition to higher rubber content. For blends containing low molecular weight PBT, up to 60 wt% of rubber can be homogeneously dispersed in the PBT matrix at long mixing time. In this case, development of high performance PBT based thermoplastic vulcanisates can be envisioned. (C) 2004 Elsevier Ltd. All rights reserved.

The possibility to generate particle-in-particle morphology by controlling blending sequence has been investigated for reactive processing of poly(butylene terephthalate) (PBT) with ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) random terpolymer. Composite droplet morphology consisting of a PBT matrix, a E-MA-GMA dispersed phase and PBT sub-inclusions is spontaneously formed upon melt mixing due to the coalescence of poorly stabilized E-MA-GMA particles. The development and dimensions of this complex morphology is mainly controlled by the relative kinetics between the coalescence process and the chemical reactions occurring during the melt processing. This can be influenced by an adequate adjustment of various blending parameters such as blend composition, PBT viscosity and rubber phase reactivity. The generation of particle-in-particle morphology can also be forced by using a two-step blending sequence. In this latter case, blend morphology consisting in PBT matrix with PBT/E-MA-GMA core-shell particles can be generated. (C) 2004 Elsevier Ltd. All rights reserved.

We present the fabrication of vertically aligned cobalt nanowire arrays on planar surfaces as well as preliminary field-emission (FE) experiments using them as cold electron cathodes. These arrays are obtained by electrodeposition into nanoporous templates on Au/Ti/Si substrates at very low temperature (

Quantitative image analysis of transmission electron micrographs (TEM) of poly(ethylene terephthalate) (PET) thin sections was performed and compared to data obtained by small-angle X-ray scattering (SAXS) on the same samples. Different methods to analyze the TEM images are presented, and the results are compared with different ways to analyze the SAXS patterns. The results from TEM and SAXS correlate well and lift remaining ambiguities on the semicrystalline morphology formed on cooling from the melt, as a function of the isothermal crystallization temperature. A broad monomodal distribution of lamellar thickness was observed, while no large amorphous gaps were detected. The mean lamellar thickness was shown to be smaller than the mean thickness of amorphous regions, which was also characterized by a broad distribution.

Thin spin-casted films of poly(ethylene terephthalate), isothermally crystallized from the melt, were studied by transmission electron microscopy. An amorphous substrate was used to get rid of unwanted nucleating influences. The lamellar scale information gained by this technique agrees well with results obtained on bulk samples despite important differences in morphology at the spherulitic scale. Starting from thin films of constant thickness, crystallization involves the migration of the polymer to the growing spherulites, resulting in the formation of polymer-depleted interspherulitic gaps. Isolated and stacked lamellae growing on top of terrace-like flat-on crystals are also noticed, allowing the direct observation of the crystalline-amorphous interphase. (C) 2003 Elsevier Ltd. All rights reserved.

The influence of the functional groups concentrations on the reactive compatibilization of polybutylene terephthalate (PBT)/epoxide-containing rubber blends has been investigated by using various PBT and ethene-(methyl acrylate)-(glycidyl methacrylate) terpolymer (E-MA-GMA) grades. The reactivity of the rubber phase was modified using different strategies, including the use of commercial terpolymer grades, modification of E-MA-GMA or diluting E-MA-GMA terpolymers with non-reactive ethene-(methyl acrylate) (E-MA) copolymer. The reactive blends were analyzed amongst others by electron microscopy and fractionation experiments. It was shown that the final particle size is directly related to the amount of copolymer formed in situ at the blend interface, i.e. chain area density Sigma. A value of approximately 0.05 chains/nm(2) for Sigma is necessary to suppress dynamic coalescence and to obtain very fine dispersion (

This study was aimed at using micro-Raman spectroscopy for the local characterisation of phase separated blends based on epoxy polymer and copolyethersulphone thermoplastic. The morphologies developed in the blends containing 25% by weight of thermoplastic were studied. The calibrations of the Raman data for the determination of the copolyethersulphone content and the epoxide conversion are presented in this paper and their applicability for spatially resolved Raman characterisation discussed. From spectra collected in both phases after increasing cure times, the evolution of the copolyethersulphone content in each phase was quantitatively determined, whilst a qualitative evolution of the epoxide conversion was obtained. To our knowledge, this study provided for the first time direct measurements of phase characteristics in thermoset-thermoplastic blends. (C) 2003 Elsevier Science Ltd. All rights reserved.

Reactive blending is the preferred route for obtaining rubber-toughened engineering plastics. In this study the chemistry and morphology of in-situ compatibilised PA-6/EPM-g-MA blends and PBT/E-MA-GMA blends are compared. Despite the different chemical structures formed (PA-6: cyclic imide; PBT: ester), the different side-reactions that take place (PA-6: chain scission; PBT: rubber crosslinking) and the different reaction rates (PA-6: very fast; PBT: rather slow), a general description of reactive blending is proposed. First, a very fast physics-controlled dispersion of the rubber phase into the polycondensate matrix occurs (from milimeter to micrometer scale). Then the interface, thus generated, is covered via graft-copolymer formation. This results in a stabilisation against coalescence and in a reduction of the interfacial tension, enabling further dispersion of the rubber phase. In the case of PA-6/EPM-g-MA blends the graft formation occurs so quickly that when the physics-controlled dispersion is completed, the final dispersion is achieved. In the case of PBT/E-MA-GMA blends the graft formation is much slower and the chemistry-controlled dispersion can hence be considered as a secondary process, yielding the final morphology.

A series of aromatic liquid-crystalline polyesters with different composition have been synthesized to adjust transition temperatures and molecular weight. Miscibility of polyesters with bisphenol-A-diglycidyl ether (DEGBA), 4,4'-methylene-bis(3-chloro-2,6-dimethylaniline) (MCDEA) and the influence on transition temperatures has been studied. Miscibility of binary and ternary mixtures was found over the whole range of composition depending on the temperature. Thermoset formation by curing of LC-polyester / DEGBA / MCDEA mixtures containing different amounts of polyester resulted in reaction-induced phase separation with polyester content from 30 to 50 wt.%. Cloud point techniques, scanning electron microscopy (SEM) and dynamic mechanical thermal analysis (DMTA) have been applied.

This paper reports on the advances made in the laboratory in the development of porous media by track-etching process, and on their use by research partners as templates for the micro- or nanofabrication of polymeric and metallic wires or tubules with interesting properties. It mainly relates to the development of nanoporous polycarbonate-based templates, and more precisely to pore-shape control in polycarbonate films, to the development of supported track-etch templates and to the feasibility of template patterning; recent results on the development of templates from polyimide support are also reported. Finally, some nanontaterial synthesis processes and properties are listed, with references to published papers. (C) 2003 Elsevier B.V. All rights reserved.

Talc has been known to nucleate poly(ethylene terephthalate) (PET) for a long time, but the exact nucleation mechanism involved had remained unknown. This study presents evidence of an epitaxial relationship between the polymer and the inorganic substrate. Electron diffraction results suggest a contact between the (100) PET plane and (001) talc basal plane as well as an alignment of the [001] PET chain axis with the three quasi-hexagonal directions of talc. Transmission electron microscopy confirms these findings but highlights some matching imperfections, partly due to irregularities of the talc lattice. Besides, it suggests a tilt of the polymer chain axis with respect to the lamellar fold surface. The long period of PET lamellar stacks is also noticeably larger on the talc contact plane.

The staining of poly(ethylene terephthalate) (PET) by ruthenium tetroxide (RuO4) is used to obtain a contrast at the crystalline lamellar scale in transmission electron microscopy. This paper demonstrates the efficiency of this technique conducted in vapor phase on ultracut bulk samples. Advantages of this method against other contrast enhancing techniques and the parameters of staining are discussed. The depth of attack is measured and is shown to be limited by a crosslinking process. The chemical mechanisms are investigated by grazing infrared spectroscopy and involve the oxidation of the aliphatic moeities of PET. (C) 2003 Elsevier Science Ltd. All rights reserved.

Reactive processing of blends of poly(butylene terephthalate) (PBT) with the ethene-(methyl acrylate)-(glycidyl methacrylate) terpolymer (E-MA-GMA) is known to present a very complex reactivity since two competitive reactions take place spontaneously during melt blending, that is, blend compatibilization and rubber-phase crosslinking. In this article, the effects of several processing parameters, such as the shear rate, the processing temperature, and the matrix viscosity, on the reactive processing of those blends were investigated in terms of the blend morphology and of the amount of copolymer formed at the blend interface. It was shown that the morphology development could be divided in two successive regimes: In the early stages of the mixing process, the particle size is essentially deter-mined by the physical dispersion process, that is, breakup and coalescence, while, at longer mixing times, a further decrease in particle size is obtained as a result of the compatibilization reactions. The shift between the two regimes is progressive and intimately related to the processing conditions. Despite such a complexity, not only the blend morphology but also the elastic properties of the rubber particles can be controlled in a broad range by an adequate adjustment of the relative kinetics between both physical and chemical processes. (C) 2003 Wiley Periodicals, Inc.

Near-infrared spectroscopy was used to quantify the cure reaction of 4,4′-methylene- bis-(2,6-diethylaniline) (MDEA)–epoxy resins (E/A = 1.4) carried out at 72 and 160 °C. The absorption bands of the functional groups of interest in MDEA–epoxy resins are assigned according to the literature. A new assignment at 6580 cm−1 is also proposed for the secondary amine: it was supported by a synthesized model compound. Two different spectrum treatments were proposed. The first one is based only on a normalization at 4610–4620 cm−1, while the second one needs the subtraction of the normalized spectrum of a post-cure sample. To follow the curing process, amines and epoxy were studied at the same time in the combination and the overtone regions. The results are compared. In the combination region, quantitative results are obtained from absorbance measurements, while in the overtone region spectrum decompositions and area measurements are necessary. Complementary and reliable information are so obtained and allow us to calculate conversions of epoxide and amine I and concentrations in amine II, amine III, hydoxyl groups, and ether links. Kinetics are also established. The curing process mechanism is at last discussed for both curing temperatures.

This paper reports on the realisation of nanoporous supported templates by the track-etching method. Spin-coated polycarbonate films have been irradiated by energetic heavy ions (Ar9+, 220 MeV), UV irradiated and chemically etched in aqueous NaOH (2 N, 70 degreesC). The thickness of the supported templates has been varied between 200 nm and a few microns and the pore size between 15 and 100 nm. Dynamics of pore formation in these supported templates has been compared to dynamics of pore: formation in classical self-supported track-etched membranes. This new generation of templates has been successfully used to electrochemically synthesise polypyrrole nanotubes and copper (Cu) nanowires. The pore size and the nanostructure morphology, providing information on the pore shape, have been studied by high resolution electron microscopy. (C) 2002 Elsevier Science B.V. All rights reserved.

The possibility of using Raman spectroscopy to determine the local thermoplastic content within blends of epoxy resins and copolyethersulfone was studied. The required calibration of the Raman data is presented here. It was obtained by multivariate methods and was based on homogeneous samples of known content in amine-ended thermoplastic (expressed in weight %). Blends cured with two types of diamine curing agents were separately studied, the curing agents being the methylene bis(2,6-diethylaniline) (MDEA) and the 4,4′-diaminodiphenylsulfone (DDS). Partial least-squares (PLS) regressions with external validation were performed. With MDEA, root mean square error of prediction (RMSEP) values at validation were 3.2, 3.7, and 3.0% (depending on the spectral pre-treatment and on the wavenumber selection). RMSEP values were 2.4 or 3.0% with DDS (depending on the wavenumber selection). The applicability of the calibrations to blends containing chlorine-ended copolyethersulfone is discussed. Results obtained with small or large Raman confocal holes are also compared.

Optimal templating synthesis of nanoscale materials by filling the porosity of track etched membranes requires membranes with controlled and predictable pore size and geometry. In this paper, we mainly show that improvement of existing track etching technology allows a reliable and reproducible lab-scale production of nanoporous membranes with cylindrical pores exhibiting smooth wall. (C) 2001 Elsevier Science Ltd. All rights reserved.

Methods have been developed to determine by Raman spectroscopy the epoxide conversion in a 4,4'-diaminodiphenylsulfone (DDS)-cured epoxy resin as well as in blends of this resin with copolyethersulfone thermoplastic. The proposed spectral treatments consisted of a peak ratio method and of multivariate analysis. The Raman data were first successfully calibrated on the basis of neat resin samples with the use of the values of epoxide conversions provided by differential scanning calorimetry (DSC) measurements. The use of DSC as a reference technique is discussed. In order to be applied to blends of the same epoxy resin and reactive copolyethersulfone, the calibrations were based on spectral data that would not be influenced by the presence of this thermoplastic. The blend samples were homogeneous at the scale of the Raman laser focusing. The epoxide conversions deduced from the Raman and the DSC results were compared for these blends. Limitations associated with both techniques are discussed.

The molecular mobility of polystyrene (PS) chains near the surface of carbon fibers was investigated. The glass transition temperature of very thin coatings deposited on carbon fibers was measured by supported DMTA in order to probe the properties of the thermoplastic interphase. Depending on the fiber impregnation method from the melt or from solution, T-g changed in an opposite way for the thinnest coatings, decreasing with coating thickness in the case of impregnation in the melt and increasing when a polymer solution was used. This observation is explained by degradation of PS in the melt and subsequent preferential segregation of low molar mass chains to the interface. This conclusion is supported by the study of the T-g of coatings made from a bimodal molar mass distribution.

This paper shows the possibility of preparing nanoporous particle track etched membranes (nanoPTM) with perfectly smooth and cylindrical pores from polycarbonate film. Interest in the template use of these nanoPTM for the production of polymeric or metallic nanoscale materials is also emphasized. (C) 2001 Elsevier Science B.V. All rights reserved.

Blends of polybutyleneterephthalate (PBT) with ethene-ethyl acrylate copolymer (E-EA) and ethene-methyl acrylate-glycidyl methacrylate terpolymer (E-MA-GMA) were investigated. E-MA-GMA terpolymers containing various concentrations of epoxide functions were synthesized in a preliminary step by melt modification of commercial E-MA-GMA with benzoic acid molecules. The blends were analyzed by several techniques including electron microscopy and separation experiments. PBT/E-EA (80/20 w/w) blends presented the general features of uncompatibilized polymer blends, such as a lack of interfacial adhesion and a relatively coarse unstabilized morphology. No evidence of transesterification reaction was found to occur according to the used blending conditions. In contrast, blends containing both virgin and modified E-MA-GMA terpolymers exhibited a very complex behavior. Fractionation experiments demonstrated that two competitive reactions take place during the melt blending viz. (1) compatibilization due to interfacial reactions between PET chains end and terpolymer epoxide groups, resulting in the formation of E-MA-GMA/PBT graft copolymer and (2) rapid crosslinking of the rubber phase due to the simultaneous presence of hydroxyl and epoxide groups on E-MA-CMA chains. This competition between compatibilization and crosslinking is clearly dependent on the type of the terpolymer, since the modified E-MA-GMA already contains hydroxyl groups before mixing but for the pure E-MA-GMA hydroxyl groups are formed as a result of the in situ compatibilization reaction with PET. Rubber phase crosslinking through double reaction with PET chain can not be excluded but is expected to occur only to a smaller extent. All these phenomena result in a very complex processing/morphology interrelationships and probably also affects the final blend properties. (C) 2000 Elsevier Science Ltd. All rights reserved.

Chlorinated polypropylene (CPO) is commonly used as an adhesion promoter for paint on polypropylene/ ethylene - propylene copolymer blends (PP/EP). An adhesion mechanism frequently proposed in the literature is the CPO diffusion into the substrate, leading to molecular entanglement. It is shown here that CPO and PP/EP are immiscible. On the other hand, the use of radiolabelled CPO allowed quantification of CPO diffusion into PP/EP substrates as a function of several parameters and under conditions which simulate industrial practice. Diffusion requires substrate swelling by the solvent. This explains that it increases with the EP content of the material, with the solvent ability to swell the substrate, and with the thickness of the paint. For baked samples, diffusion passes through a maximum when the delay between CPO application and baking is varied. This is due to a balance between two processes working in opposite directions, i.e. substrate swelling and solvent evaporation.

In this study we correlate parameters describing molecular structure (molar mass distribution, short chain branching content, intermolecular heterogeneity) of different ethylene-hexene Cr-catalyzed copolymers, with slow crack growth and rapid crack propagation resistances, respectively measured with Bent Strip and Charpy tests. The PTREF technique, coupled with classical techniques, was used. Two new indices were proposed to correlate mechanical properties and molecular structure. (C) 2001 John Wiley & Sons, Inc.

Modifications induced by different energetic heavy ions (Ar-40(9+), Kr-80(15+), Xe-129(24+), Pb-208(53+) and Pb-20(56+)) on poly(epsilon -caprolactone) (PCL) and poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) have been investigated by electron spin resonance (ESR). Indeed, film irradiation by heavy ions leads to, among other phenomena, the formation of radicals in the ion tracks. Thanks to ESR, it is possible to detect these radicals and to identify them or at least to characterize them by following the evolution of the radical signal as a function of parameters, like temperature, or the kinetic of disappearance of the radical species at ambient temperature in vacuum or ambient atmosphere. This study confirmed the generation of radicals by the irradiation of PHB/HV samples with energetic heavy ions reported in the literature. The study on PCL was not pursued after a few preliminary studies, revealing the presence of an ESR signal in the nonirradiated sample. Electronic stopping power has a major influence on radical decrease at ambient temperature. The ion used for the irradiation did not modify very much the radical signal and the evolution of the radicalar signal intensity with temperature. Different reasoning and experiments revealed that the glass transition temperature is a key temperature above which irreversible recombinations of the most stable radicals take place. A simulation study indicated that the most stable radical produced was probably a tertiary radical formed by the stabilization of the secondary radical resulting from the abstraction of a highly mobile hydrogen adjacent to the carbonyl. (C) 2000 Elsevier Science B.V. All rights reserved.

Modifications induced by different energetic heavy ions in poly(epsilon -caprolactone) (PCL) and poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) have been investigated by the differential scanning calorimetry (DSC) and steric exclusion chromatography (SEC). A certain dose of damages, depending mainly on the charge and mass of the ion and on the intensity of irradiation, has to be overcome in order to detect any effect on PHB/HV. Actually, at a given intensity of irradiation, superior to 10(10) ions/cm(2), the level of damage intensity increased with the increase in charge and mass of the ion. Moreover, according to the SEC results, there seems to be a critical mass and/or charge threshold above which the dominant type of damages changes. As a matter of fact, high-density irradiation with Ar9+ and Kr15+ resulted mainly in chain scission whereas cross-linking was dominant when irradiating the polymer with Xe24+ and Pb56+. Th, irradiation of PCL in the conditions studied did not modify significantly the values of the melting point, the crystallisation temperature and the molecular masses of the system studied. The main effect of the irradiation detected by the DSC is the cross-linking of the polymer chains. (C) 2000 Elsevier Science B.V. All rights reserved.

Reactive thermoplastics are increasingly used as toughening modifiers for epoxy resins. A way to understand the influence of the reactive end-groups on the toughening and curing mechanisms is to observe in situ the reaction between the thermoplastic and the growing epoxy network. For this purpose, Raman spectroscopy has been used to follow the reaction of aromatic amines with epoxide monomers through the evolution of an amine-substituted aromatic vibration. A double shift of this peak was correlated with the formation of secondary and tertiary amines. Band assignment was confirmed by the study of model compounds. Through this method, qualitative observation of the reaction between an amine-ended copolyethersulphone thermoplastic and epoxide was performed. Unfortunately, in the studied blend containing the curing agent, a band appearing upon curing overlapped with the band characterising the end-group reaction. (C) 2000 Elsevier Science Ltd. All rights reserved.

Two electrochemical methods designed for the synthesis of polypyrrole (PPy) wires and nanotubules are the topic of this paper. The concept that allows the morphology of PPy to be controlled is discussed for each method, and the performances of the two complementary techniques are compared in terms of dimension, shape and conductivity of PPy.

Polypropylene (PP) and polypropylene/(ethylene-propylene) copolymer (EP) blend (PP/EP) injection-moulded plates were painted with a chlorinated polypropylene (CPO) based adhesion promoter. Three-point bending and crosscut adhesion tests performed on these plates show that adherence is better on PP/EP than on PP. X-ray photoelectron spectroscopy (XPS) and force modulation microscopy (FMM) analyses were performed on the failure surface obtained after the three-point bending test. XPS shows that the Cl atomic fraction is less than 0.5% on the polymer side and close to 4% on the paint side indicating that the fracture is located at the CPO-polymer interface. The analysis of the PPEP surface by FMM reveals that paint debonding occurs with plastic deformations located into the EP elastomer phase. The magnitude of the plastic deformation is dependent on the depth location of the nodules. The adherence improvement induced by the presence of EP nodules can thus be explained by energy dissipation occurring during EP deformation. (C) 2000 Elsevier Science Ltd. All rights reserved.

Micro- and nano-structures composed of polyaniline (PANi) have been prepared by chemical and electrochemical oxidative polymerization of aniline within the pores of particle track-etched membranes (PTM). Their morphology has been studied by field-emission scanning electron microscopy. Hollow tubules are formed because PANi initially deposits on the surface of the pore walls. Raman spectroscopy was used to probe the oxidative state of PANi in order to optimize the chemical polymerization conditions with respect to the electrical conductivity. The nanoscopic materials show an enhancement of the electronic conductivity compared to analogous polymer bulk conductivity. (C) 2000 Elsevier Science S.A. All rights reserved.

Thin films (300 Angstrom) of homodisperse polystyrene (PS) chains tagged at one end by a short chlorinated polybutadiene (CPB) segment have been spin-coated on Si wafers covered or not by a thin (300 Angstrom) layer of amorphous carbon. These strongly asymmetric P(CB-b-S) diblock copolymers do not microphase-separate in the bulk. Depth profiles from X-ray reflectivity (XRR) and DSIMS have been obtained on thin films of this diblock before and after annealing. Whatever the surface studied, the electron density profiles derived from XRR measurements did not show any significant difference with the ones obtained with homodisperse PS. By contrast, DSIMS and XPS experiments showed a clear depletion of the CPB short block starting from the air interface when the copolymers are deposited onto the silicon substrates. Such a depletion cannot be detected when the copolymers are deposited onto the almost apolar carbon surface. This suggests a preferential accumulation of the chlorinated block toward the silicon oxide polar surface, in agreement with an estimation of the interfacial energy reduction implied by the process, indicating that segregation effects in these systems are dominated by energetic balances.

We have studied by means of X-ray scattering, DMA and densitometry the evolution of the semi-crystalline structure of poly(aryl-ether-ether-ketone) (PEEK) upon reheating specimens initially crystallized isothermally near T-g. Two regimes of reorganization behavior were evidenced. In the low-temperature interval (temperatures below T-g + similar to 50 degrees C), the slow dynamics of amorphous segments prevents large-scale rearrangements, strongly limiting the process of reorganization. Only lamellar-scale reorganization occurs, resulting in a slight increase of the crystal thickness and perfection, and in an increase of the constraints in amorphous regions, reflected by an increase of T-g. At higher temperatures, however, a larger-scale melting/recrystallization mechanism sets in. It consists in the recrystallization of whole lamellar stacks to give a state of overall lower free energy, with much thicker and dense crystals separated by larger and less constrained amorphous regions of lower T-g. (C) 2000 Elsevier Science Ltd. All rights reserved.

The article presents the state-of-the-art of alternating physisorption of oppositely charged polyelectrolytes, the so-called "layer-by-layer" method or "electrostatic self-assembly" (ESA), for the preparation of thin polymer coatings. In comparison to other, more established self-organization techniques, this recent method is distinguished by its simplicity, versatility, and speed. In particular, the tendency for self-healing is unique. Emphasis is given to the role of the molecular structure of the polyelectrolytes, and to the nature of the support. Also, various parameters for the preparation of multilayer films are highlighted, which are very important due to the kinetic control of the build-up process. The structure of the resulting coatings, their quality and stability, chemical reactions in the films, and potential applications are discussed.

A detailed study of the interface formation between polystyrene (PS) and chlorinated polybutadiene (CPB) at 150 degrees C is carried out on bilayer samples by X-ray reflectometry(XRR) and X-ray diffuse scattering (XDS). An equilibrium melt interfacial width sigma(m)(150 degrees C) = 18.8 +/- 0.3 Angstrom is determined by XRR. Lateral fluctuations being averaged over the coherence area in this method, a, must be considered as originating from both homopolymer interdiffusion (sigma(CPB/PS)) and interfacial roughness (sigma(r)): sigma(m)(2) = sigma(CPB/PS)(2) + sigma(r)(2). Interfacial roughness is generally described in the literature to be due to either a residual roughness from sample preparation (hypothesis 1) or capillary fluctuations building up at the interface (hypothesis 2). The nature and importance of the interfacial roughness are assessed by XDS scans, which include the detection of the diffuse (off-specular) scattering arising from lateral correlations in the roughness profile. While hypothesis 1 can be unambiguously rejected from the analysis of our XDS data, at least two equally valuable fits of theory to data are found under the hypothesis that the interfacial roughness changes during annealing. In the first one, interdiffusion is restricted, and the interfacial width is dominated by roughness (sigma(r) > sigma(CPB/PS)). In the second one, the reverse is true: sigma(CPB/PS) much greater than sigma(r). The former picture is closer to predictions from existing molecular theories of capillarity and gives for the Flory-Huggins interaction parameter computed through mean-field arguments a better agreement with the interaction parameter obtained from solubility parameters of CPB and PS.

An acid-base titration method for an accurate and reproducible quantification of maleic anhydride grafted onto polyolefins is proposed. The use of an organic base (tetra-butylammonium hydroxide) enhances the base solubility in organic solvents and prevents phenomena like coarcervation. The titration goes on until the visual endpoint of a coloured indicator, corresponding to the neutralisation of the grafted functions. Bromothymol blue is chosen as the coloured indicator to determine this equivalence point. It is critically correlated with a Fourier transform-infrared spectroscopy quantification developed previously by De Roovers et al. [J Polym Sci, Part A: Polym Chem 1995;33:829] and with a viscosimetric titration method here-proposed Finally, the titration mechanism is confirmed by the titration of some well-defined amount of anhydride model compounds and by FTIR analyses of their products after titration. (C) 1999 Elsevier Science Ltd. All rights reserved.

A low percentage of cyclic oligomers can be found in poly(ethylene terephthalate) (PET) from its synthesis onward. In this article, a cyclic-oligomer-fr ee PET (COFP) obtained by solvent extraction was used to study the thermodynamics of the re-formation of cyclics from the melt. The cyclic-oligomer content re-increased into molten COFP, finally reaching an equilibrium. An analysis of the fraction of the re-formed cyclic oligomers showed that a majority of cyclic trimer (60-70%) was found at the equilibrium Before the establishment of the equilibrium, an unusual behavior was observed in the relative proportion of cyclic trimer and tetramer during the first steps of their formation that was probably due to a competition between kinetic and thermodynamic products. (C) 2000 John Wiley & Sons, Inc.

The purpose of this study is to propose a correlation between IR spectra and molecular structure of ethylene-propylene (EP) copolymers possibly blended with isotactic polypropylene (iPP). The method is based on the deconvolution of the spectrum in the CH2-rocking range, i.e., 800-680 cm(-1), where the bands of interest overlap. The six bands present in this region were signal averaged in position and width. The spectra were then deconvoluted (curve fitted) assuming a Lorentzian shape for the bands. The band at 1167 cm(-1) (with a shoulder at 1156 cm(-1)) corresponding to a CH3 vibration is considered as an internal standard. The method was checked by varying some fitting parameters. In order to realize some quantitative measurements, calibration curves were established with some EP samples, characterized by C-13 NMR, which were used as standards. The amounts of total -(CH2-CH2)- units (ethylene units), isolated ethylene and structural defaults in PP were determined for different iPP/EP blends. Ethylene crystallinity has also been determined. A good correlation was evidenced between infrared and C-13 NMR measurements. (C) 2000 John Wiley & Sons, Inc.

Crystals of monodisperse linear poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) (PEEK) oligomers have been reinvestigated by wide-angle and small-angle X-ray scattering and atomic force microscopy (AFM). For the shorter oligomer investigated (containing six phenyl groups), a correlated packing of the chains is observed in the direction of the chain axis, with the formation of crystals being much thicker than the oligomer extended chain length. This results from the alignment of chain ends in planes, as revealed by AFM. A crystal structure is proposed for this oligomer, consistent with both AFM and X-ray diffractometry results. By contrast, the longer oligomer (containing 12 phenyl groups) presents a crystalline morphology consisting of stacks of atomically uncorrelated thin lamellar crystals, whose thicknesses are about the extended chain length computed for the oligomer. This is due to random staggering of the chains along their axes in the crystals, as suggested previously. CP/MAS C-13 solid-state NMR proton spin-lattice relaxation experiments reveal that these morphological differences induce variations in the chain dynamics of the oligomers and confirm that only the longer oligomer can be taken as a good model for a isolated crystal phase. From this study, reference values at room temperature are proposed for the specific mass of a perfect PEEK crystal [1.412(1) g.cm(-3)] and for the proton spin-lattice relaxation time of such a crystal [3.6(2) s].

High-resolution solid-state C-13-NMR, differential scanning calorimetry, and Fourier transform infrared spectroscopy were used to compare the very low crystalline degree and crystallite dimensions of ethylene runs in a series of isotactic polypropylene/ethylene-propylene copolymer blends exhibiting a range of properties. Results obtained from the three techniques on samples with the same thermal history are in a satisfying qualitative agreement. They show that the morphology of the polyethylene domains is only very slightly dependent on the viscosity ratio of the two blend components. On the opposite, it is largely governed by the ethylene content of the ethylene-propylene copolymer. (C) 1999 John Wiley & Sons, Inc.

The fractionation of a statistical copolyester made of poly(ethylene terephthalate- isophthalate) has been performed using Temperature Rising Elution Fractionation (TREF). TREF fractions were analyzed by size exclusion chromatography, thermal analysis, H-1-nuclear magnetic resonance and small angle X-Ray diffractometry. Results show that the fractions exhibit both interchain and intrachain defect distribution. As the intrachain defect distribution can not be determined by experimental techniques, a computer simulation based on the determination of terephthalic sequences length in a virtual polymeric distribution was performed. The simulated chains were constructed using a stochastic process. The analysis of the results obtained on the distribution of the simulated sequences in the polymer correlates quantitatively well between the new fractionation mechanism proposed for copolyesters and the experimental results.

The morphology of free surfaces of polyetherimide (PEI) samples has been characterized using atomic force microscopy in noncontact mode (NC-AFM), x-ray reflectivity (XRR), and x-ray diffuse scattering (XDS). PEI slabs have been prepared by molding pellets onto float glass. In order to characterize the roughness and morphology mathematically, we considered the surfaces as being self-affine with a rms roughness sigma and Hurst coefficient H up to a finite correlation length xi. NC-AFM topographs with sigma = 61 +/- 6.3 Angstrom showed the presence of blobs on the surface having a slight tendency to form clusters. These features are reflected in the height-height correlation function which shows the presence of "strong'' short-range (xi(1) = 1064 Angstrom, H-1 = 0.46) and "weak" long-range (xi(2) = 14537 Angstrom, H-2 = 0.99) correlations. The detection of the specularly reflected contribution in XRR scans only gives access to sigma, the lateral fluctuations being averaged out over the coherence area. Scans in XDS include the detection of the diffuse (off-specular) scattering arising from lateral correlations in the surface fluctuations profile and are hence sensitive to sigma, xi and H. The XDS data have been analyzed by simultaneous fits using the distorted-wave Born approximation up to the first order. Calculations were performed using previously published approximations. Best fits to the experimental data provided strongly different correlations length values (7570 Angstrom less than or equal to xi less than or equal to 1245 Angstrom) indicating that the estimation of the latter by XDS is somewhat ambiguous. This is in agreement with the strong discrepancy between the correlation lengths determined with x rays and NC-AFM, which can be accounted for by the limits of the perturbation theory for interfaces with high rms roughnesses. [S0163-1829(99)04032-1].

Polypropylene/ethylene - propylene copolymer blends (PP/EP) were characterized by time-of-flight (ToF), SIMS, by dynamic wetting and by atomic force microscopy and force modulation spectroscopy (AFM-FMM), In a first step, model systems of compression-moulded PP/EP physical blends were prepared. With these materials, ToF-SIMS provides linear relationships between the selected peak and the EP content in the material. This indicates that both phases are present at the surface in the same concentrations as in the bulk. However, the EP signal is weak. In dynamic wetting measurements with water, for each tested blend composition the advancing contact angle corresponds to that of PP and the receding contact angle corresponds to that of EP, This method is thus suitable for detecting the presence of the two phases at the surface even for low concentrations of one consituent, The force modulation image gives elastic contrasts between EP and PP and is thus able to reveal the surface morphology, In a second step, these methods were used to characterize injection-moulded PP/EP reactor blends. Both AFM-FMM and ToF-SIMS suggest that a PP skin covers EP nodules at the surface. This is confirmed by electron microscopy examinations of cross-sections. This surface phase segregation leads to the presence of PP in the first 100 mm of the surface and could be explained by preferential wetting of the mould by the phase with the lower viscosity, PP in this case. However, dynamic wetting reveals that the PP skin is not complete. Thus, a low EP concentration may be found at the surface, in the form either of EP nodules or of EP molecules having migrated through the PP skin, Copyright (C) 1999 John Wiley & Sons, Ltd.

Chemical and electrochemical techniques were used for generating ensembles of randomly distributed organic and metal nanocylinders into the pores of nuclear track-etched polycarbonate membranes. This so-called “template method” makes it possible to synthesize a variety of materials including metals, ferromagnets, superconductors, semimetals, and conducting polymer and structures such as solid wires, tubules, composite nanostructures, and multilayers. Numerous interesting properties have been identified in relation to the nanoscopic dimensions of the materials.

In a previous paper [Dupont, Jonas & Legras (1997).J. Appl. Cryst.30, 921–931], a variant of the Rietveld method was applied to the characterization by X-ray scattering (powder diffractometry) of disordered and small crystals as found in semicrystalline polymers. In the present study, a new version of the model is described, which is designed to take into account the possible existence of a non-zero tilt angle (ψ) of the chain axesversusthe large faces of the lamellar crystals. Fits of this model to the diffractograms of various samples of cold-crystallized PEEK [poly(ether-ether-ketone)] and of a monodisperse PEEK oligomer are presented. For the oligomer, the fits converged only towards ψ = 0°. For the polymers, two equivalent solutions were found, one with thick lamellae and ψ = 0°, another with thinner lamellae and ψ = 20°. Models with and without chain tilt give similar goodness-of-fit parameters, indicating that results coming from other techniques than X-ray diffractometry are required in order fully to characterize the dimensions and shape of crystals in isotropic polymer samples. Comparing the present values with results obtained by such other techniques suggests the existence of a tilt angle for cold-crystallized PEEK samples.

This paper aims at the end-capping of poly(ethylene terephthalate) (PET) chain-ends in order to introduce anhydride moieties on this polymer. An acid chloride reactive carrier of anhydride was chosen because it selectively reacts by alkoxy-dehalogenation with the hydroxyl chain ends of PET. This type of functionalization has already been described and claimed (1-3) on various polymers. However, in the present paper, a solid-liquid synthesis is reported for the first time: The reaction was performed on solid PET powder swollen in a solvent of the trimellitic anhydride chloride. This new reaction method prevents the polymer from degrading. This point is supported by parallel studies of similar reactions performed in the melt and in solution.

The influence of the viscosity ratio between (ethylene-propylene) copolymer (EP) and polypropylene (PP) on the EP surface distribution in injection moulded disks of PP/EP resins has been investigated by transmission electron microscopy (TEM) and by atomic force and force modulation microscopies (AFM and FMM). TEM images taken on transverse sections parallel to the injection direction reveal that, for high EP/PP viscosity ratios, large (>1 mu m) undeformed EP nodules are observed up to the surface. The AFM and FMM observations performed on the surface reveal soft regions of the same size embedded in a more rigid matrix (undeformed EP nodules present at or just below the surface). For low viscosity ratios, EP rubber nodules, strongly elongated parallel to the surface, are observed by TEM. From FMM measurements, the elastic modulus is found to be homogeneous across the surface and is comparable to that measured above EP nodules on the high viscosity ratio resin. (C) 1999 Society of Chemical Industry.

We have studied the isothermal cold crystallization of poly(ether-ether-ketone) (PEEK) by atomic force microscopy, densitometry, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and small- and wide-angle X-ray scattering (SAXS and WAXS), A two-stage process was clearly evidenced. The first stage results in the progressive consumption of free amorphous regions by growing spherulites. Lamellae grow in tightly packed bundles, with no evidence for a random insertion mechanism. DSC and DMA consistently show the progressive disappearance of the alpha(1) relaxation typical of the initially amorphous PEEK. Simultaneously, a new relaxation appears a few degrees higher (alpha(2) relaxation) and develops at the expense of alpha(1) relaxation. It corresponds to the formation of amorphous regions constrained by neighboring crystals. On the basis of a simple simulation, we show that the experimental data in this second stage of crystallization can be accounted for by a simple stack thickening process in which new lamellae are progressively added in parallel to previously formed lamellar stacks.