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In this paper, the effect of the gaseous environment on recrystallization of amorphous paracetamol was investigated. The experiments were conducted with a headspace gas consisting of dry air, dry carbon dioxide, dry nitrogen and humid air in four temperatures ranging from 5 degrees C below onset of T-g to 5 degrees C above onset of T-g. The recrystallization was monitored using Raman spectroscopy and subsequent multivariate analysis. In temperatures below onset of T-g, the presence of oxygen delayed the onset of recrystallization, with an increasing delay with lower temperature. When comparing samples exposed to dry headspace gases, the crystallization was fastest below onset of Tg when exposed to nitrogen. Being an inert gas, nitrogen did not seem to interfere with the molecules allowing them to freely find their inherent arrangement, whereas the presence of oxygen delayed the formation of stabile nuclei. Above onset of T-g, no differences in onset of crystallization was detected between dry gas atmospheres. Amorphous paracetamol crystallized to form II in all measurements and the samples did not reach full crystallinity within the duration of the experiments. The results show that the headspace gas has an effect on nucleation in the amorphous sample.

Tuning the thermodynamic state of a material has a tremendous impact on its performance. In the case of polymers placed in proximity of a solid wall, this is possible by annealing above the glass transition temperature, Tg, which induces the formation of an adsorbed layer. Whether heating to higher temperatures would result in desorption, thereby reverting the thermodynamic state of the interface, has so far remained elusive, due to the interference of degradation. Here, we employ fast scanning calorimetry, allowing to investigate the thermodynamics of the interface while heating at 104 K s−1. We show that applying such rate to adsorbed polymer layers permits avoiding degradation and, therefore, we provide clear-cut evidence of desorption of a polymer melt. We found that the enthalpy and temperature of desorption are independent of the annealing temperature, which, in analogy to crystallization/melting, indicates that adsorption/desorption is a first order thermodynamic transition., SCOPUS: ar.j, info:eu-repo/semantics/published

Metallic glasses, with their short-range order structure, exhibit unique characteristics that do not exist in the corresponding crystalline alloys with the same compositions. These unusual properties are attributed to the absence of translational periodicity, grain boundaries, and compositional homogeneity. Cobalt (Co)-based metallic glassy alloys have been receiving great attention due to their superior mechanical and magnetic properties. Unluckily, Co-Ti alloys and its based alloys are difficult to be prepared in glassy form, due to their rather poor glass-forming ability. In the present work, the mechanical alloying approach was employed to investigate the possibility of preparing homogeneous (Co75Ti25)100&minus, xBx starting from elemental powders. The feedstock materials with the desired compositions were high-energy ball-milled under argon atmosphere for 50 h. The end products of the powders obtained after milling revealed a short-range order structure with a broad amorphization range (2 at% &le, B &le, 25 at%). The behaviors of these glassy systems, characterized by the supercooled liquid region, and reduced glass transition temperature, were improved upon increasing B molar fraction. The results had shown that when B content increased, the saturation magnetization was increased, where coercivity was decreased.

Poly(lactic acid) or PLA is currently considered as one of the most promising substitutes of conventional plastics, with low environmental impact, especially for food packaging applications. Nevertheless, some drawbacks, such as high permeability to oxygen, are still limiting its industrial applications. The objective of this study was to highly increase the oxygen barrier performance of PLA without compromising its sustainable nature and following the principles of circular economy perspective. Coproducts coming from mill industries, such as wheat gluten proteins (WG), were used to produce PLA-WG-PLA multilayer complexes with improved barrier performance. Different technologies of industrial interest were considered: high-pressure homogenization of WG film forming dispersions, corona treatment of industrial PLA films, wet casting and spin coating for tailoring the WG coating thickness, and hot-pressing for shaping the multilayers. The impact of all these strategies on the properties (surface and bulk) and performances (barrier and adhesion) were investigated on the single constituent layers as well as on the final laminate. The most efficient complex increased more than 20 times (or 2000%) the barrier properties to oxygen and ∼20% the barrier properties to water vapor, considering application conditions (50% relative humidity and 25 °C). The low thickness (∼60 μm) of this complex also matched the requirement for flexible packaging applications. High-pressure homogenization, WG coating thickness, and hot-pressing positively and highly impacted the final properties of the multilayer, while the contribution of corona treatment was limited. This study unambiguously evidenced the potential of PLA-WG-PLA complexes as a valid sustainable substitute for high performing conventional plastics, and it could open an unexplored PLA market opportunity. In addition, it could motivate further investigations on PLA-based laminates for industrial interest, using other biopolymers from agro-industrial waste or byproducts.

By using a novel protocol to spatially confine molecules in well-defined small 2D areas, the so-called nanocorrals, we show using scanning tunneling microscopy (STM) how this kind of confinement affects self-assembled molecular network (SAMN) formation at a liquid-solid interface. The 2D lateral confinement, imposed by the size of the nanocorrals, has a clear impact on the phase selectivity of a molecule that can form both low-density and high-density SAMNs, the high-density phase being promoted by the confinement. ispartof: CHEMICAL COMMUNICATIONS vol:55 issue:15 pages:2226-2229 ispartof: location:England status: published

Soft polymer colloidal water suspensions are extremely important formulations for industrial applications such as water-based environmental-friendly coatings, paints, and adhesives. Homogeneity of the final coating at the micrometer and nanoscale is a crucial factor for optimal coating performance, such as barrier properties against solvent permeation. Here, we investigated the remnant nanostructure in slot-die-coated micrometer-sized thick clear coating films (clearcoats) of three different waterborne polymer colloids (pure soft, pure hard, and soft/hard multiphase), commonly utilized as primers in paint formulations [Mader et al. Prog. Org. Coat. 2011, 71, 123-135], using variable-angle grazing incidence small-angle X-ray scattering (GISAXS) complemented with cross-sectional atomic force microscopy (cs-AFM). After complete macroscopic drying, the coating films exhibit the presence of residual nanostructure with characteristic distance (d*) smaller than the original particle size and even smaller (<< d*) heterogeneity dimensions. These nanostructural heterogeneities (i) develop due to partial particle coalescence, (ii) are preferentially located close to the air-film interface and (iii) demonstrate the tendency to align perpendicular to the air-film interface, implying vertical gradient in hydroplasticization effects having occurred earlier during film formation. The extent and size of the nanostructural heterogeneities, driven by the slot-die coating application, strongly depend on the polymer chemistry (glass transition temperature, T-g) and the colloidal architecture. Last, solvent exposure has a significant impact on the nanostructure, causing the removal of these heterogeneities and leading to a more strongly coalesced film.

Although nanostructured phase-change materials (PCMs) are considered as the building blocks of next-generation phase-change memory and other emerging optoelectronic applications, the kinetics of the crystallization, the central property in switching, remains ambiguous in the high-temperature regime. Therefore, we present here an innovative exploration, of the crystallization kinetics of Ge2Sb2Te5 (GST) nanoparticles (NPs) exploiting differential scanning calorimetry with ultrafast heating up to 40 000 K s(-1). Our results demonstrate that the non-Arrhenius thermal dependence of viscosity at high temperature becomes an Arrhenius-like behavior when the glass transition is approached, indicating a fragile-to-strong (FS) crossover in the as-deposited amorphous GST NPs. The overall crystal growth rate of the GST NPs is unraveled as well. This unique feature of the FS crossover is favorable for memory applications as it is correlated to improved data retention. Furthermore, we show that methane incorporation during NP production enhances the stability of the amorphous NP phase (and thereby data retention), while a comparable maximum crystal growth rate is still observed. These results offer deep 'insight into the crystallization kinetics of nanostructured GST, paving the way for designing nonvolatile memories with PCM dimensions smaller than 20 nm.

Here we present measurements of surface tension and viscosity of the bulk glass-forming alloy Pd43Cu27Ni10P20 performed during containerless processing under reduced gravity. We applied the oscillating drop method in an electromagnetic levitation facility on board of parabolic flights. The measured viscosity exhibits a pronounced temperature dependence following an Arrhenius law over a temperature range from 1100 K to 1450 K. Together with literature values of viscosity at lower temperatures, the viscosity of Pd43Cu27Ni10P20 can be well described by a free volume model. X-ray diffraction analysis on the material retrieved after the parabolic flights confirm the glassy nature after vitrification of the bulk samples and thus the absence of crystallization during processing over a wide temperature range.

The influence of nanohydroxyapatite on the glass transition region and its activation energy, as well as on the tribological and mechanical properties of polyoxymethylene nanocomposites, was investigated using DMA, TOPEM DSC, nanoindentation, and nondestructive ultrasonic methods. It was found that the glass transition for unmodified POM was in the lower temperature range than in POM/HAp nanocomposites. Moreover,ΔCpand activation energy were larger for POM/HAp nanocomposites. Friction coefficient was higher for POM/HAp nanocomposites in comparison to both POM homopolymer and POM copolymer. Simultaneously, the indentation test results show that microhardness is also higher for POM/HAp nanocomposites than for POM. From ultrasonic investigations it was found that the highest values of both longitudinal and transverse propagation waves and Young’s and shear modulus for POM homopolymer (DH) and POM copolymer T2H and their nanocomposites can be attributed to their higher degree of crystallinity in comparison to UH copolymer. Moreover, for POM/HAp nanocomposites with 5% of HAp, ultrasonic longitudinal wave velocity was almost constant even after 1000000 mechanical loading cycles, evidencing an enhancement of mechanical properties by HAp nanoparticles.

We use molecular dynamics simulations to investigate the tracer diffusion in a sea of polymers with specific binding zones for the tracer. These binding zones act as traps. Our simulations show that the tracer can undergo normal yet non-Gaussian diffusion under certain circumstances, e.g., when the polymers with traps are frozen in space and the volume fraction and the binding strength of the traps are moderate. In this case, as the tracer moves, it experiences a heterogeneous environment and exhibits confined continuous time random walk (CTRW) like motion resulting in a non-Gaussian behavior. Also the long time dynamics becomes subdiffusive as the number or the binding strength of the traps increases. However, if the polymers are mobile then the tracer dynamics is Gaussian but could be normal or subdiffusive depending on the number and the binding strength of the traps. In addition, with increasing binding strength and number of polymer traps, the probability of the tracer being trapped increases. On the other hand, removing the binding zones does not result in trapping, even at comparatively high crowding. Our simulations also show that the trapping probability increases with the increasing size of the tracer and for a bigger tracer with the frozen polymer background the dynamics is only weakly non-Gaussian but highly subdiffusive. Our observations are in the same spirit as found in many recent experiments on tracer diffusion in polymeric materials and question the validity of using Gaussian theory to describe diffusion in a crowded environment in general.

8 pags.; 4 figs.; 3 tabs.; 7th IDMRCS: Relaxation in Complex Systems, © 2014 Elsevier B.V. All rights reserved. The thermal conductivity of CBrnCl4 -n,(n = 0,1,2) and 2-adamantanone (C10H14O) crystals which exhibit substitutional disorder has been measured for temperatures between 2 K and 150 K. Such temperatures comprise signatures of dynamical processes involving the site occupancy of the chlorine and bromine atoms for CBrnCl4 -n,(n = 0,1,2) and the oxygen atom for (C10H14O), as it has been revealed by both, calorimetry and spectroscopic techniques. The data analysis is carried out in terms of several phonon scattering channels contributing to a resistive relaxation rate which can be represented by two contributions due to propagating phonons whose mean-free path exceeds half the phonon wavelength as well as a term attributed to localized short wavelength modes. The implications of the present findings for studies pertaining to glassy dynamics are briefly discussed., This work is supported by the Spanish Ministry of Science and Innovation (grant no. FIS2011-24439), the Catalonia Government (grant no. 2009SGR-1251). The authors acknowledge the support from the National Academy of Science of Ukraine in the frame of the joint Ukrainian– Russian Project (agreement no. 10-2012) on the subject “Metastable states of simple condensed systems”. One of us A.I. K. thanks the Spanish Ministry of Education (grant SAB2011-0070) for an invited position at the Universitat Politècnica de Catalunya.

Strength concept, which is based on the Williams-Landel-Ferry (WLF) model, was developed using mixed structured powders containing amorphous and crystalline components. At the present study, semi crystalline trehalose powders with various (100:0; 80:20; 60:40; 40:60; 20:80) amorphous to crystalline ratios were analyzed. Amorphous components were prepared from water solution by freeze-drying. Strength analysis, which included water sorption, differential scanning calorimetry, dynamic mechanical analysis and microscopy, was applied. The results indicated that water content significantly decreases glass transition (similar to 100 degrees C) and alpha-relaxation temperatures (similar to 90 degrees C) as well as structural strength parameter (similar to 10 degrees C), while, the effect of crystalline component is less pronounced. This study can be used in processing and characterization of various partially crystalline food products including nutritional formulations and infant formulas.

In this letter, we reported thorough the structural and molecular dynamics studies on 1,6-anhydro-β-D-glucose, the second compound reported so far that is capable to form rotator and supercooled liquid phases. In contrast to the data presented for ethanol, temperature dependences of structural dynamics in both phases are very comparable. On the other hand, X ray measurements revealed unusually long range ordering/correlations between molecules in the ODIC (d ≈ 95 Å) and supercooled phases (d ≈ 30–40 Å) of this carbohydrate. Our consideration clearly demonstrated that the interplay between length scales of static range ordering and dynamical heterogeneities as well as internal molecular arrangement seem to be the key to understanding the molecular dynamics of different materials characterized by varying degree of disorder in the vicinity of the glass transition temperature.

International audience; The rheological response of a colloidal system concentrated to near the glass concentration has been investigated using a cone and plate geometry. The prime purpose of the work was to interrogate the nonlinear response using the so-called "tickle" experiment in which small deformations are superimposed on a single large deformation to probe "rejuvenation" and "reinitiated aging" behaviors as has been done in polymer glasses and solutions. Counterintuitively, we find that the superposition of a small positive probe onto the large deformation gives different results from the superposition of a small negative probe. Such a result is contrary to simple fading memory ideas of viscoelastic materials. We also find that the rejuvenation and reinitiated aging behavior in the positive probe case is dependent on whether one considers the probes at "first" probe or at "second" probe, in spite of following the protocol first suggested by Struik [Physical Aging in Amorphous Polymers and Other Materials (Elsevier, Amsterdam, 1978)], which avoids sequence effects in viscoelastic materials. It is suggested that colloidal systems, while exhibiting some features of fading memory behavior that is expected in molecular (polymer) glasses, in fact also undergo a mechanically induced structural change, perhaps similar to that found in highly filled materials such as rocket propellants and carbon black filled rubber

Retrogradation of amorphous thermoplastic starch (TPS) films obtained by compression moulding of spray dried amorphous powder was investigated. The aim of the work was to study the influence of malto-oligosaccharide molecular weight, i.e. dextrose equivalents (DEs), on the performance of the powders and the films. Amorphous TPS films were obtained, irrespective of the additive used. At a relative humidity (RH) of 0% and 50% all samples maintained their amorphous nature while at RH100% retrogradation was suppressed for all formulated starch films. It is shown that the rate of moisture uptake, and as a consequence, the rate of retrogradation, depends on the molecular weight of the additive. FT-IR and TGA measurements proved a more effective interaction of starch with low molecular weight additives such as maltose and glucose syrup (DE 38.2) than for the higher molecular weight maltodextrine (DE 19.1). (c) 2013 Elsevier Ltd. All rights reserved.

The aim of this paper is to investigate the physicochemical properties of binary amorphous dispersions of poorly soluble sulfonamide/polymeric excipient prepared by ball milling. The sulfonamides selected were sulfathiazole (STZ), sulfadimidine (SDM), sulfamerazine (SMZ) and sulfadiazine (SDZ). The excipients were polyvinylpyrrolidone (PVP) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft co-polymer, commercially known as Soluplus (R). Co-milled systems were characterised by powder X-ray diffraction and differential scanning calorimetry. PVP was shown to form amorphous dispersions over a wider composition range than Soluplus (R) for the four sulfonamides tested. Moreover, amorphous dispersions made with PVP were homogeneous [single glass transition (Tg)], while amorphous dispersions made from Soluplus (R) were heterogeneous (two Tgs). This behaviour is consistent with the fact that all the sulfonamides tested presented a lower solubility in Soluplus (R) than in PVP, as evidenced by Flory-Huggins parameters determined. Amorphous dispersions of SDM with Soluplus (R) could be produced even though SDM does not amorphise alone upon milling and Soluplus (R) presents Tg at a lower temperature than SDM. Amorphous dispersions of SMZ could be prepared with a lower excipient concentration compared to STZ, SDM and SDZ, which may reflect the one-dimensional H-bonding network in SMZ compared to the 2D or 3D H-bonding network found in the other sulfonamides. Stability tests (60% RH/25 degrees C) revealed that dispersions made with Soluplus (R) remained dry and powdery compared to those made with PVP that formed a sticky paste in less than 2 weeks, indicating a possible advantage of using Soluplus (R) in terms of increased physical stability under high humidity storage conditions.

This study investigated the influence of pre-crystallisation and water plasticization on flow properties of lactose/whey protein isolate (WPI) solids systems. Powder characteristics of lactose/WPI mixtures with different amounts of α-lactose monohydrate (1.01%, 11.18%, 29.20%, and 46.84%, w/w) were studied. Dairy powders with higher amounts of crystalline lactose showed larger tapped bulk density and particle density. Morphological characteristic study indicated that dairy solids with higher crystallinity had less rounded shape and rougher surface. Increasing protein content or crystalline lactose content could decrease the molecular mobility of dairy solids. Flow function tests indicated that dairy solid with 11.18% crystallinity was more easy-flowing than lactose/WPI mixtures with 1.01%, 29.20% and 46.84% crystallinity at 0% and 44% relative humidity (RH) storage conditions. Furthermore, dairy solids with higher amount of crystalline lactose showed better resistance to develop cohesive at high RH storage conditions. The friction angle of dairy solid with 1.01% crystallinity increased with increasing water content, while friction angles of lactose/WPI mixtures with higher crystallinity decreased with increasing water content.

The industrial production of wheat gluten (WG)-based biomaterials implies to improve their actual mechanical properties as well as to reduce their water sensitivity. In this study, the effect of Kraft lignin (KL) content on the processability and on the physical properties of WG materials was investigated. WG plasticized with glycerol was blended with KL, and processed into materials by mixing and thermomolding. Materials were characterized by dynamic mechanical thermal analysis, tensile test, and water absorption measurements. The introduction of KL in plasticized WG resulted in an increase of the material glass transition temperature (Tg) and in a strong decrease of the rubbery storage modulus, which will favor industrial processing. The increase in Tg did not follow a simple mixing rule, demonstrating specific interaction between KL and WG. The resulting materials effectively showed improved properties when compared with pure WG-based materials: they exhibited higher tensile strength and lower water sensitivity in ambient conditions. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This paper reports a methodology of half-embedding nanoparticles into metallic materials. Transparent and opaque nanoparticles are chosen to demonstrate the process of laser assisted nanoparticle embedding. Dip coating method is used to coat transparent or opaque nanoparticle on the surface of metallic material. Nanoparticles are embedded into substrate by laser irradiation. In this study, the mechanism and process of nanoparticle embedding are investigated. It is found both transparent and opaque nanoparticles embedding are with high densities and good uniformities. (C) 2011 Elsevier B. V. All rights reserved.

The dynamical susceptibility has been introduced to characterize the dynamical heterogeneities in glass forming liquids. We have used it as a tool to investigate the slow dynamics of other disordered systems such as gels, granular media and spin glasses. We review here the results obtained via numerical simulations of different model systems. The comparative study of the behaviour of the dynamical susceptibility sheds some light on the significant differences in the complex slow dynamics of glasses, spin glasses, granular media, irreversible gels, and colloidal gels.

International audience; A series of cholinium cation-based bioionic liquids (BioILs) were synthetized with the aim of screening their performance as potential plasticizers of thermoplastic starch. To synthesize these BioILs, two easy and fast synthetic routes were selected: an ion exchange reaction, direct and economical, and a two-step acid-base reaction. Most of these BioILs allowed efficient plasticization of starch by film casting. The structure of the anion used significantly influences the thermo(hygro) mechanical and recrystallization behavior, making it possible to modulate the properties of the final material.

The potential energy landscape (PEL) formalism is a valuable approach within statistical mechanics for describing supercooled liquids and glasses. Here we use the PEL formalism and computer simulations to study the pressure-induced transformations between low-density amorphous ice (LDA) and high-density amorphous ice (HDA) at different temperatures. We employ the ST2 water model for which the LDA-HDA transformations are remarkably sharp, similar to what is observed in experiments, and reminiscent of a first-order phase transition. Our results are consistent with the view that LDA and HDA configurations are associated with two distinct regions (megabasins) of the PEL that are separated by a potential energy barrier. At higher temperature, we find that low-density liquid (LDL) configurations are located in the same megabasin as LDA, and that high-density liquid (HDL) configurations are located in the same megabasin as HDA. We show that the pressure-induced LDL-HDL and LDA-HDA transformations occur along paths that interconnect these two megabasins, but that the path followed by the liquid is different than the path followed by the amorphous solid. At higher pressure, we also study the liquid-to-ice-VII first-order phase transition, and find that the behavior of the PEL properties across this transition are qualitatively similar to the changes found during the LDA-HDA transformation. This similarity supports the interpretation that the LDA-HDA transformation is a first-order-like phase transition between out-of-equilibrium states., Comment: 29 pages, 8 figures

It is well accepted that adding nanoparticles (NPs) to polymer melts can result in significant property improvements. Here we focus on the causes of mechanical reinforcement and present rheological measurements on favourably interacting mixtures of spherical silica NPs and poly(2-vinylpyridine), complemented by several dynamic and structural probes. While the system dynamics are polymer-like with increased friction for low silica loadings, they turn network-like when the mean face-to-face separation between NPs becomes smaller than the entanglement tube diameter. Gel-like dynamics with a Williams–Landel–Ferry temperature dependence then result. This dependence turns particle dominated, that is, Arrhenius-like, when the silica loading increases to ∼31 vol%, namely, when the average nearest distance between NP faces becomes comparable to the polymer’s Kuhn length. Our results demonstrate that the flow properties of nanocomposites are complex and can be tuned via changes in filler loading, that is, the character of polymer bridges which ‘tie’ NPs together into a network., Partial support has been provided by the EU FP7 (ETN Supolen GA-607937, Infrastructure ESMI GA-262348) and the Greek General Secretariat for Research and Technology (Thalis-380238 COVISCO). M.R. acknowledges financial support from the National Science Foundation under grants DMR-1309892, DMR-1436201 and DMR-1121107, the National Institutes of Health under grants P01-HL108808 and 1UH2HL123645 and the Cystic Fibrosis Foundation. D.Z., S.G., R.H.C. and S.K.K. gratefully acknowledge the National Science Foundation grant DMR-1408323 for financial support.

The crystallization kinetics of phase-change materials (PCMs) entails a crucial aspect of phase-change memory technology, and their study is also of interest to advance the understanding of crystallization in general. Research on crystallization of PCMs remains challenging because of the short (nanosecond) time and small (nanometer) length scales involved. Ultrafast differential scanning calorimetry (DSC) offers a powerful tool to study crystallization via ultrahigh heating rates. Here, we used this tool to study the crystallization kinetics of growth-dominant Ge7Sb93. Two models describing the viscosity of the undercooled liquid were used to interpret the data and were subsequently crosschecked by independent growth-rate data. With both models the data in Kissinger plots could be fitted well, but one of the models resulted in a large discrepancy with the independent data. These results demonstrate that great care is needed when deriving crystal-growth rates from ultrafast DSC measurements because orders of magnitude errors can be made. The present analysis showed a slightly non-Arrhenius crystallization behavior for the Ge7Sb93 alloy, corresponding to a fragility of 65 and a glass transition temperature of 379 K. The overall viscosity and growth rate of this alloy between the glass and melting temperatures have been revealed, as well as a maximum growth rate of 21 m s(-1) at similar to 800 K. Models based on ultrafast DSC data offer interpretation of crystallization kinetics of PCMs and thereby strongly support the design of PCMs for memory applications.

International audience; During cryopreservation ice nucleation and crystal growth may occur within cells or the intracellular compartment may vitrify. Whilst previous literature describes intracellular vitrification in a qualitative manner, here we measure the intracellular vitrification temperature of bacteria and yeasts under conditions relevant to cryopreservation, including the addition of high levels of permeating and nonpermeating additives and the application of rapid rates of cooling. The effects of growth conditions that are known to modify cellular freezing resistance on the intracellular vitrification temperature are also examined. For bacteria a plot of the activity on thawing against intracellular glass transition of the maximally freeze-concentrated matrix (Tg’) shows that cells with the lowest value of intracellular Tg’ survive the freezing process better than cells with a higher intracellular Tg’. This paper demonstrates the role of the physical state of the intracellular environment in determining the response of microbial cells to preservation and could be a powerful tool to be manipulated to allow the optimization of methods for the preservation of microorganisms.

The production of bioplastics directly from wheat flour has been demonstrated to be reliable, but scarce knowledge is available on how flour characteristics may affect the performance of thermoplastic films. In this work, we first established the most suitable recipe and process for the production of extruded films and then we used eight single-cultivar wheat flours with different baking technological properties to assess how they affect the mechanical properties of thermoplastic films. The results have shown that flours from soft grain cultivars offered more rigid and deformable films than flours from hard grain cultivars. For similar hardness, the alveographic P/L ratio of the dough was inversely related to rigidity and directly related to deformability of plastic films, while the deformation energy of the dough (W) played a role only for great differences of it. The subsequent fabrication of blends between each of the flours that yielded the best film properties and polycaprolactone (PCL) at different proportions indicated that a wheat flour/PCL ratio (TWF/PCL) of 75/25 offered the most suitable films for further application. Our results are likely to be useful for improving the plasticization of flour, in that selection of wheat flours could be tailored on the properties desired for the bioplastic films.

International audience; Poly (butyl methacrylate-co-methacrylic acid) copolymers/calcium carbonate (CaCO3) composites were synthesized by radical polymerization. Ca2+ cationic sites, present at the CaCO3 surface, in interaction with carboxylate groups from polymer chains structured the material, particularly above the glass transition temperature. The composites were studied by transmission electron microscopy, X-ray diffraction, and dynamic mechanical analysis. Multiplets and clusters were detected. The material's behavior is principally controlled by the methacrylic acid (MA) content in the copolymer chain and CaCO3/MA ratio. Under well-defined conditions, ionic cross-linked materials were obtained.

The objective of the present work is to get insights into the mechanistic origin of the reinforcement effects of nanoclay on a segmented polybutadiene polyurethane-urea system. To this end, a convergent analysis of the hard domain morphology and conformational state of soft segment in the nanocomposites was carried out by using a combination of complementary characterization techniques, namely, Fourier transform infrared spectroscopy, small angle neutron scattering, transmission electron microscopy, modulated differential scanning calorimetry and dynamic mechanical analysis. Analysis of small angle neutron scattering data by a combination of Percus-Yevick hard sphere and Zernike-Ornstein model coupled with direct visualization of the dispersed hard domain morphology from transmission electron microscopy provided insight on clay induced changes in the hard domain morphology. A monotonic decrease in the domain size as well as the average interdomain distance was observed with increasing nanoclay content in the polymer matrix. Analysis of the carbonyl stretching region from FTIR showed increased degree of hydrogen bonding for the urethane carbonyl groups of the nanocomposites compared to the neat matrix. A combination of calorimetric and dynamic mechanical analysis revealed the existence of a constrained amorphous region; quantified to be approximate to 16% at the highest clay content experimented. The manifestation of these morphological and conformational changes on the nano-, micro- and macro scale reinforcements in the nanocomposites was investigated by mechanical properties at these length scales using nanoindentation, DMA and tensile testing, respectively. (C) 2014 Elsevier Ltd. All rights reserved.

To develop n-type processable polymeric materials for photovoltaic applications, a series of polymers was synthe- sized by grafting fullerene C60 onto polystyrene (PS). Grafted polymers were studied and compared with PS:fullerene blends. Electronical and electrical properties were first measured to define the minimal amount of C60 required for solar cells applica- tion. Then, thermal properties and rheological behavior of grafted polymers were analyzed to determine whether they could be processed from the melt. A throughout experimental study revealed that C60-grafted polymers exhibit two thresholds. The first threshold at 3-4 vol % (detected by electrical conductiv- ity, electron mobility, and melt viscosity measurements) is asso- ciated to the percolation of C60 molecules. The second threshold (evidenced by glass transition and melt viscosity measurements and confirmed by optical and atomic force micrograph observa- tions) at about 12-13 vol % is assumed to be related to the for- mation of C60 aggregates. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 000: 000-000, 2012

Although many polymer nanocomposites have been described, the impact of colloidal nanoparticles (NPs) used as fillers on the thermal behavior of the matrix has been described only in a few cases. Here we apply thermal methods to inquire the effect of organically capped Ag and Au particles on poly(tert-butyl acrylate) (PtBA) based composites. The nanocomposites have been prepared by ex situ and in situ methods; in the former method the metal NPs were isolated from the respective colloids and then blended into cast films obtained from tetrahydrofuran solutions of the polymer; while in the latter the in situ polymerization of tert-butyl acrylate using miniemulsions was carried out in the presence of homogeneously dispersed colloidal NPs. The nanocomposite materials were then characterized by differential scanning calorimetry (DSC) to assess the effect of colloidal metal NPs on the glass transition temperature of the polymer (T-g) namely by considering their chemical nature, average particle size, and metal load. Although similar effects have been observed when Au or Ag NPs were employed as nanofillers, it was also found that the T-g depends on the NPs morphological characteristics and on the preparative method employed to obtain the nanocomposite. This research also highlights the relevance of the surface chemistry of colloidal nanofillers on the thermal behavior of the respective composites. (C) 2013 Elsevier B.V. All rights reserved.

Experimental results by Fisher et al. [Faraday Discuss. Chem. Soc. 1979, 68, 26] showed the existence of local orientational correlations of segments of the n-alkane molecules in the liquid state. Since the estimated correlation volume is below 10(3) angstrom(3), molecular dynamics simulations appear to be a suitable method for their identification and characterization. We used molecular dynamics to fully characterize short-range order in polyethylene melts. The characterization started by identifying sequences of aligned segments in chains, each one having at least one Kuhn monomer in length. Afterward, a search was made for interactions of a tagged aligned chain segment with others fulfilling the same condition, laying within a limiting separation distance (18 angstrom) and making a limiting orientation angle (40 degrees). When, at least, four interactions are counted, a short-range ordered region is defined. Chain placement in these regions has similarities to that of the unit cell at the solid phase, although with different separation distances and angle. Overall, short-range order resembles a dynamic uniaxial nematic phase, the local order parameter increasing with the chain length in agreement with experimental results. Segments at the ordered regions persist over time, for times longer than the Rouse relaxation time of the chain. Those in random conformational sequences between the ordered regions have a mass distribution in agreement with the Flory distribution, with a number-average value comparable to experimental results for the molecular mass between entanglements.

Nanocomposite films were prepared by a thermo-mechanical process from wheat gluten (WG) and unmodified montmorillonite (MMT). The present work aims at predicting the relationships between the decrease in relative diffusivity of liquid water and the structure of the nanocomposite films, from in situ evaluation of the MMT size aspect ratio and volume fraction, and by using a simple tortuous path mathematical model. The modelling approach first allowed predicting and validating the tortuosity effect of MMT particles on liquid water transport properties of WG-based films. In spite of a well-exfoliated nanocomposite structure, the liquid water diffusivity in WG-based films can at best be decreased by a factor of 2 with this type of clay nanoparticle, which was in agreement with the Bharadwaj model predictions. This study underlines the necessity to achieve a totally exfoliated nanocomposite structure, and above all, to select layered silicates displaying higher size aspect ratio values in order to efficiently improve water barrier properties of WG-based nanocomposite films. Furthermore, the extremely complex structure of nanocomposite materials makes detailed morphological studies often difficult, time and cost consuming. (c) 2012 Elsevier Ltd. All rights reserved.

International audience; In this work, we aimed at studying formulation and design of powders by modified wet compression method. In order to focus only on the role of the liquid binder in the mechanical cohesion of compacts, glass beads were used as model particles because they do not deform or fragment at the compression pressure used (35kN). The three different binders studied were sugars: fructose, glucose and saccharose, used as solutions. Therefore, compacts were stored at controlled conditions until reaching water activity equilibrium at a fixed temperature of 25 degrees C. Then, the tensile strength of the compacts was determined using a Brazilian test. It was found to be dependent on the water activity. Critical values of Aw were measured (A(w) = 0.23 for the fructose, A(w) = 0.33 for the glucose, and A(w) = 0.44 for the saccharose), beyond which the glass transition phenomenon of the sugars appeared, and resulted in a sharp drop in the mechanical strength of the compacts. The classification of the sugars according to their respective glass transition temperature (Tg(fructose) < Tg(glucose), < Tg(saccharose)) permitted to confirm the role of the glass transition of the sugars as binders in the mechanical resistance of the compacts. Finally, sorption isotherms of the sugars coupled to the tensile strength results showed that the main parameter for predicting mechanical strength of the compact was the amount of sorbed water by the sugar, regardless to his nature.

[EN] The aim of this study is to analyze the mobility of polymer chains in semicrystalline poly(vinylidene fluoride) (PVDF). PVDF crystallizes from the melt in the crystalline phase. The transformation from the phase to the electroactive phase can be induced by stretching at temperatures in the range between 80 and 140 ◦C. The spherulitic structure of the crystalline phase is deformed during stretching to form fibrils oriented in the direction of the strain. The amorphous phase confined among the crystalline lamellae is distorted as well and some degree of orientation of the polymer chains is expected. Dynamicmechanical and dielectric spectroscopy measurements were performed in PVDF films stretched to strain ratios up to 5 at temperatures between 80 and 140 ◦C. Dynamic-mechanical measurements were conducted between −60 ◦C and melting and in this temperature range the relaxation spectra show the main relaxation of the amorphous phase (called -relaxation) and at higher temperatures a relaxation related to crystallites motions (c-relaxation). Although the mean relaxation times of the -relaxation are nearly equal in PVDF before and after crystal phase transformation, a significant change of shape of the relaxation spectrum proves the effect of chain distortion due to crystal reorganization. In stretched PVDF the elastic modulus of the polymer in the direction of deformation is significantly higher than in the transversal one, as expected by chain and crystals fibril orientation. The recovery of the deformation when the sample is heated is related with the appearance of the c-relaxation. Dielectric spectroscopy spectrum shows the main relaxation of the amorphous phase and a secondary process (-relaxation) at lower temperatures. Stretching produces significant changes in the relaxation processes, mainly in the strength and shape of the main relaxation. The Havriliak-Negami function has been applied to analyze the dielectric response., This work is funded by FEDER funds through the "Programa Operacional Factores de Competitividade-COMPETE" and by national funds by FCT-Fundacao para a Ciencia e Tecnologia, project references NANO/NMed-SD/0156/2007, PTDC/CTM/69316/2006 and PTDC/CTM-NAN/112574/2009. V. S. thanks the FCT for the SFRH/BPD/63148/2009 grant. JLGR acknowledges the support of the Spanish Ministry of Science and Innovation through MAT2010-21611-C03-01 (including the FEDER financial support), and EUI2008-00126 projects and funding in the Centro de Investigacion Principe Felipe in the field of Regenerative Medicine through the collaboration agreement from the Conselleria de Sanidad (Generalitat Valenciana), and the Instituto de Salud Carlos III (Ministry of Science and Innovation). The authors also acknowledge support from the COST Action MP1003, 2010 "European Scientific Network for Artificial Muscles".

International audience; The influence of kaolinite content within a plasticized starch matrix on the glass transition and decomposition temperatures, water uptake, transparency and UV-vis blocking is reported. Exfoliation of the kaolinite clay within the composite is enhanced when previously intercalated with DMSO. The DMSO-intercalated kaolinite brings in advantages for the clay dispersion within the polymer matrix, the transparency and the water uptake. The transparency of the films is better preserved when DMSO intercalated kaolinite is used and a clay load between 2% and 6%, leads to a significant reduction of the UV light transmission.

BACKGROUND: Beverage powders can exhibit caking during storage due to high temperature and moisture conditions, leading to consumer dissatisfaction. Caking problems can be aggravated by the presence of sensitive ingredients. The caking behaviour of cocoa beverage powders, with varying amounts of a carbohydrate sensitive ingredient, as affected by climate conditions was studied in this work. Sorption isotherms of beverage powders were determined at water activities (aw) ranging from 0.1 to 0.6 in a moisture sorption analyser by gravimetry and fitted to the Brunauer–Emmett–Teller (BET) or the Guggenheim–Anderson–de Boer (GAB) equation. Glass transition temperatures (Tg) at several aw were analysed by differential scanning calorimetry and fitted to the Gordon–Taylor equation. Deduced Tg = f(aw) functions helped to identify stability or caking zones. Specific experimental methods, based on the analysis of mechanical properties of powder cakes formed under compression, were used to quantify the degree of caking. Pantry tests complemented this study to put in evidence the visual perception of powder caking with increasing aw. RESULTS: The glass transition approach was useful to predict the risks of caking but was limited to products where Tg can be measured. On the other hand, quantification of the caking degree by analysis of mechanical properties allowed estimation of the extent of degradation for each product. CONCLUSION: This work demonstrated that increasing amounts of a carbohydrate sensitive ingredient in cocoa beverages negatively affected their storage stability. Copyright © 2011 Society of Chemical Industry

A waterborne latex-based technique has been used to prepare acrylic films with laponite contents up to about 25 vol%. The laponite was attached to the surfaces of the latex particles, giving a cellular arrangement of laponite-rich regions at high laponite contents. Two regimes of reinforcement were observed, depending on whether T was above or below T-g, reinforcement at T > T-g being significantly greater than predicted by micromechanical models. Modulated differential scanning calorimetry and dynamic mechanical analysis showed part of the organic content of the films not to contribute to the glass transition. This "rigid amorphous fraction" (RAF) was argued to correspond to intercalated regions of the matrix. However, the RAF alone was insufficient to account for the observed increases in stiffness at T > T-g. The mechanical response is therefore discussed in terms of a four-phase model, in which intercalated laponite stacks are embedded in a matrix with reduced mobility, forming a foam-like structure, in turn embedded in a matrix with the properties of the bulk polymer. (C) 2011 Elsevier Ltd. All rights reserved.

Several evidences have helped to establish the two-state nature of liquid water. Thus, within the normal liquid and supercooled regimes water has been shown to consist of a mixture of well-structured, low-density molecules and unstructured, high-density ones. However, quantitative analyses have faced the burden of unambiguously determining both the presence and the fraction of each kind of water "species". A recent approach by combining a local structure index with potential-energy minimisations allows us to overcome this difficulty. Thus, in this work we extend such study and employ it to quantitatively determine the fraction of structured molecules as a function of temperature for different densities. This enables us to validate predictions of two-state models.

High-performance printed circuit board or electronic packaging substrate with low warping particularly at high frequency is the key demand of manufacturers. In the present work, poly(etheretherketone) (PEEK) matrix composites reinforced with untreated micron size aluminum nitride (AlN) and alumina (Al(2)O(3)) particles have been studied for dynamic modulus in the temperature range varying from 30 to 250 degrees C. At 48 vol % particles, the room temperature modulus of the PEEK/AlN composites increased by approximately fivefold (similar to 23 GPa), whereas it increased by twofold for PEEK/Al(2)O(3) composite. The reinforcing efficiency is more pronounced at higher temperatures. The significant improvement in modulus was attributed to the better adhesion between the matrix and the AlN particles. Scanning electron microscope (SEM) and Kubat parameter showed that the poor adhesion between the matrix and the Al(2)O(3) particles resulted in comparatively smaller increase in modulus of PEEK/Al(2)O(3), despite higher intrinsic modulus of Al(2)O(3) than that of AlN. SEM showed almost uniform distribution of particles in the matrix. The experimental data were correlated with several theoretical models. The Halpin-Tsai model with xi (xi) is equal to four correlates well up to 48 vol % AlN composites while xi is equal to two correlates only up to 18 vol % Al(2)O(3) composites. Guth-Smallwood model also correlates well up to 28 vol % AlN and 18 vol % Al(2)O(3)-filled composites. Thereafter, data deviated from it due to the particles tendency to aggregate formation. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 436-444, 2011

Water sorption of gluten and wheat starch films as a function of water activity was studied using gravimetric step-change sorption experiments. Films of different thicknesses were used with the aim to vary the characteristic diffusion time and to get insights in the contribution of the polymer-chain rearrangement in the sorption behaviour. It is shown that both starch and gluten are in the glassy state for a water activity aw below 0.9. From comparison of the dynamical sorption curves with a Fickian diffusion model, it is shown that water diffusion in gluten films seems Fickian for aw 0.7, while for starch films, non-Fickian sorption behaviour is observed for aw > 0.1. The results show that polymer-chain rearrangement and the stress built up in the matrix play an important role in the sorption dynamics of these films. Even when the material is in the glassy state matrix relaxation phenomena play a role in the sorption behaviour of starch and gluten.

International audience; Processed cereal solid foods can often be considered as solid foams, i.e. cellular solids, and their constitutive walls, mostly a blend of starch and proteins, may be envisioned like a composite material. The change between cellular intermediate scale and composite micro-scale may be achieved by mechanical modelling using numerical methods. For both scales, imaging methods (microscopy and tomography) provide relevant description of product structure, which can be meshed and used in computer software for mechanical simulation. This paper reviews the latest applications of mechanical modelling by finite element method to the field of cereal foods, outlines their actual limits and prospects for texture prediction.

No comment; International audience; Polyurethane (PU) catheters made of Pellethane 2363-80AE® were treated in two different ways: a new treatment with low temperature plasma that could be used to decontaminate reusable polymer devices in hospitals, and an e-beam (EB) irradiation. Polymer structure and bulk properties were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR) and size exclusion chromatography (SEC). Although PU was strongly modified by the e-beam irradiation leading to branching of polymer chains, it had no or little impact on the thermo-mechanical properties of the catheters and on the hard/soft segment organization of PU. For plasma-treated samples, no modification in the polymer bulk was observed, confirming that plasma treatment might be considered as an alternative to e-beam irradiation. The analysis of surface modifications showed an evolution of superficial topology and chemical composition (grafting of oxygen and nitrogen species) of the catheters after treatment, with a more polar and hydrophilic surface. © 2009 Elsevier Ltd. All rights reserved.

Nanocomposites based on attapulgite clay and shape-memory polyurethane were fabricated by mechanical mixing. The mechanical properties of samples were evaluated using a micro-indentation tester. The untreated commercial attapulgite clay resulted in a significant decrease in glass transition temperature and hardness of the nanocomposite due to the presence of moisture as well as the clay's amorphous structure and surface hydroxyl groups. The attapulgite nanoparticles were heat-treated at 850 degrees C, which resulted in crystallization of the particles and formation of layered attapulgite structure. The hardness of the nanocomposites composed of the heat treated clay powder dramatically increased as a function of clay content, which is attributed to the homogeneous dispersion of the nanofillers in the polymer matrix and strong filler-polymer interactions. Shape recovery of indentations has been demonstrated upon heating. (C) 2009 Elsevier Ltd. All rights reserved.

The long-standing observations that different amorphous materials exhibit a pronounced enhancement of viscosity and eventually vitrify on compression or cooling continue to fascinate and challenge scientists(1), on the ground of their physical origin and practical implications. Glass formation is a generic phenomenon, observed in physically quite distinct systems that encompass hard and soft particles. It is believed that a common underlying scenario(2,3), namely cage formation, drives dynamical arrest, especially at high concentrations. Here, we identify a novel, asymmetric glassy state in soft colloidal mixtures, which is characterized by strongly anisotropically distorted cages, bearing similarities to those of hard-sphere glasses under shear. The anisotropy is induced by the presence of soft additives. This phenomenon seems to be generic to soft colloids and its origins lie in the penetrability of the constituent particles. The resulting phase diagram for mixtures of soft particles is clearly distinct from that of hard-sphere mixtures and brings forward a rich variety of vitrified states that delineate an ergodic lake in the parameter space spanned by the size ratio between the two components and by the concentration of the additives. Thus, a new route opens for the rational design of soft particles with desired tunable rheological properties.

The incoherent approximation for the determination of the vibrational density of states of glasses from inelastic neutron or x-ray scattering data is extended to treat the coherent scattering. The method is applied to new room temperature measurements of vitreous silica and germania on the thermal time-of-flight spectrometer IN4 at the High Flux Reactor in Grenoble. The inelastic dynamic structure factor at the boson peak turns out to be reasonably well described in terms of a mixture of rotation and translation of practically undistorted SiO4 or GeO4 tetrahedra. The translational component exceeds the expectation of the Debye model by a factor of two. A possible relation of this excess to the phonon shift and broadening observed in x-ray Brillouin scattering experiments is discussed., Comment: 13 pages, 13 figures, 39 references

International audience; We present spectacular evidence of metallization of amorphous Ge films under high pressure using optical micrographs and Raman-scattering and x-ray-absorption spectroscopies. This transformation is identified as a low-density amorphous LDA to high-density amorphous HDA transition, relevant to a large class of systems including amorphous ice, semiconductors, and oxides. We have discovered that this transition initiates at the surface of the LDA sample, characterized intrinsically by a thickness dependent density of voids. Contrary to the case of transitions involving stable crystalline solid phases, our observations show that pressure-induced phase transitions in inhomogeneous amorphous samples are morphology driven and are favored for lower defect void densities. The metal disordered phase is observed first at 8 GPa for a lower density of voids, transforming to a metastable ordered phase upon depressurization. The local HDA structure is characterized by an increase in the first-neighbor coordination number, average distance, and variance.

The poly(methyl methacrylate) (PMMA) segmental dynamics in miscible blends of PMMA with poly(ethylene oxide) (PEO) were studied as a function of pressure by means of dielectric spectroscopy (DS). This facilitates a test of the predictions of the self-concentration model proposed by Lodge and McLeish, at elevated pressures. We find that pressure increases the glass temperature and slows down the segmental dynamics but does not affect the length scale or the self-concentration associated with the dynamic glass transition. This is in agreement with the expectations borne out from the model. Macromolecules

Dielectric spectroscopy has been used to monitor the cold crystallization kinetics of poly(3-hydroxy butyrate), PHB, just above the glass transition temperature of the amorphous chains. Although the polymer shows a relatively complex dielectric scenario, an easy and fast analysis of the crystallization kinetics was performed by choosing an appropriate temperature range in which the structural relaxation is the only process present in the spectra of the amorphous samples. It was possible to monitor in real time the crystallization kinetics by analysing the changes in the intensity of the a-relaxation process. A recently proposed methodology to overcome some systematic deviation of the Avrami approach, was applied to treat the experimental data. (c) 2007 Elsevier B.V. All rights reserved. ispartof: Journal of non-crystalline solids vol:353 issue:47 pages:4357-4361 ispartof: location:POLAND, Poznan status: published

The molecular dynamics of three dipole functionalized hexa-peri-hexabenzocoronenes have been studied using site-specific NMR techniques and dielectric spectroscopy as a function of temperature and pressure. These probes (i) suggest that the thermodynamic state completely controls the dynamic response, (ii) clarify the origin of two dynamic processes associated with the presence of two glass temperatures, and (iii) provide the first phase diagram for substances of this kind. Phys Rev Lett