Search

Tissue and biomaterial microenvironments provide architectural cues that direct important cell behaviors including cell shape, alignment, migration, and resulting tissue formation. These architectural features may be presented to cells across multiple length scales, from nanometers to millimeters in size. In this study, we examined how architectural cues at two distinctly different length scales, “micro-scale” cues on the order of ∼1–2 μm, and “meso-scale” cues several orders of magnitude larger (>100 μm), interact to direct aligned neo-tissue formation. Utilizing a micro-photopatterning (μPP) model system to precisely arrange cell-adhesive patterns, we examined the effects of substrate architecture at these length scales on human mesenchymal stem cell (hMSC) organization, gene expression, and fibrillar collagen deposition. Both micro- and meso-scale architectures directed cell alignment and resulting tissue organization, and when combined, meso cues could enhance or compete against micro-scale cues. As meso boundary aspect ratios were increased, meso-scale cues overrode micro-scale cues and controlled tissue alignment, with a characteristic critical width (∼500 μm) similar to boundary dimensions that exist in vivo in highly aligned tissues. Meso-scale cues acted via both lateral confinement (in a cell-density-dependent manner) and by permitting end-to-end cell arrangements that yielded greater fibrillar collagen deposition. Despite large differences in fibrillar collagen content and organization between μPP architectural conditions, these changes did not correspond with changes in gene expression of key matrix or tendon-related genes. These findings highlight the complex interplay between geometric cues at multiple length scales and may have implications for tissue engineering strategies, where scaffold designs that incorporate cues at multiple length scales could improve neo-tissue organization and resulting functional outcomes. [ABSTRACT FROM AUTHOR]

Conventional functionalization methods, such as oxidation, can be very damaging for the nanocarbons microstructure and therefore detrimental for their intrinsic thermal conductivity. In this study, nitrene chemistry was investigated as a non-disruptive approach for the covalent functionalization of graphene nanoplatelets (GNP). The nitrene precursor was synthesized and thermally decomposed in situ to functionalize GNP (cm-GNP). Temperature and solvents of reaction were found to have profound impact on the functionalization yield. Epoxy nanocomposites were then prepared with pristine, oxidized and cm-GNP. Influence of dispersion methodology was crucial for cm-GNP, as sonication was found to damage the functionalization. Oxidation caused a dramatic drop in thermal conductivity compared to pristine GNP. By contrast, nitrene chemistry produced the highest thermal conductivity enhancement. Finally, epoxy nanocomposites thermal conductivity results were correlated and discussed in light of SEM and micro-computed X-ray tomography (μCT) analyses. The μCT highlighted new features, such as micro-voids surrounding pristine GNP in epoxy nanocomposites, which are invisible with conventional methods. It was found that functionalization not only enhanced the dispersion but also improved GNP/polymer interactions. Moreover, μCT clearly demonstrated that nitrene functionalization eliminated the micro voids surrounding the fillers in the epoxy nanocomposites. Image 1 [ABSTRACT FROM AUTHOR]

Highlights: [•] In this paper, we study the adhesive, water resistance and thermo-mechanical properties of a bio-based DGEBA substitution candidate issued from Cardanol. [•] Bio-based networks outperformed the conventional epoxy in terms of adhesion and water uptake, representing interesting alternatives for applications close to ambient temperature. [•] An unconventional relationship between water uptake by the biobased adhesive and property loss due to plasticization was uncovered. [Copyright &y& Elsevier]

Abstract: Composite free standing membranes made by solvent casting of polyaniline (PANI) synthesized in the presence of water-soluble polyvinyl alcohol (PVA) as a steric stabilizer, were deposited on solid substrates to yield homogeneous and porous membranes. The acid used to dope PANI, either hydrochloric acid or formic acid, has a marked influence on the size distribution of PANI and the morphology as well as the conductivity of the composite PANI-PVA membranes. The absorption spectra of the membranes obtained using formic acid during the synthesis were sensitive to pH changes which allowed to design a dual wavelength (603nm and 845nm) optical pH sensor. The membranes displayed a marked hysteresis during the pH 12 to pH 2 titration with respect to the titration performed from acid to basic solutions. The effect of this hysteresis could be suppressed by prolonged incubation in a solution at pH 2. The second acid to basic titration curve was then identical to the first one. In addition to the optical response of the composite, the PANI-PVA membranes displayed excellent time stability, allowing to use such membranes as stable and reusable pH meters not only in solution but also in moist gas phases. [Copyright &y& Elsevier]

Abstract: Polymer materials degradation is a well-known limitation to their characterization in SEM. In this paper authors present an additional possibility for polymer imaging offered by the Environmental SEM applied to the PMMA with micrometric relief. As shown by the so-called double-scan procedure, increasing the pressure enables to delay the degradation of the polymer surface. To evaluate quantitatively this observation, the classical formula to calculate the electron dose is adapted to ESEM characteristic. It is shown first that pressure enables to decrease the electron dose and all that takes place as if the skirt electrons do not participate in the irradiation. Secondly this procedure allows to obtain the critical dose of topographic degradation, applied to the PMMA with micrometric relief D C was found to be 1.31±0.28Cm−2. Finally it becomes then possible, knowing the D C for a given sample, to evaluate the limit of investigation without topographic surface degradation: for example, the maximal field of view (linked to the magnification) depending on the other parameters. [Copyright &y& Elsevier]

Introduction: Opioid sparing protocols should be formulated with appropriate demand. Specific fracture location has been hypothesized as an important predictor of post-operative pain. The purpose of this study is to evaluate the impact of fracture location on perioperative opioid demand after surgery with the hypothesis that this factor would be significantly associated with perioperative opioid demand in upper extremity fracture surgery.Methods: A national database was used to identify1-month pre-operative to 1-year postdischarge opioid demand in oxycodone 5-mg equivalents in 336,493 patients undergoing fracture fixation of the clavicle through distal radius between 2010 and 2020. Three timeframes were evaluated: 1-month pre-op to 90-days post-discharge, 3 months post-discharge to 1-year post-discharge, and 1-month pre-op to 1-year postdischarge. Multivariable main effects linear and logistic regression models were constructed to evaluate the changes in opioids filled, opioid prescriptions, and odds of two or more opioid prescriptions in these timeframes based on fracture location with adjustment for age, sex, obesity, pre-operative opioid usage, and polytrauma.Results: Compared to distal radius fracture fixation, fixation of elbow, distal humerus, humeral shaft, and proximal humerus fractures were associated with large, significant increases in 1-month pre-op to 1-year post-discharge opioid filling (33.5 - 63.4 additional oxycodone 5-mg equivalents, all p<0.05) and number of filled prescriptions (0.33 - 0.92 additional prescriptions, all p<0.05) compared to patients with other operatively treated upper extremity injuries.Discussion: Fracture location was a significant predictor of perioperative opioid demand. Elbow, distal humerus, humeral shaft, and proximal humerus fracture fixation was associated with the largest increases in opioid demand after upper extremity fracture fixation. Patients with these injuries may be at highest risk of extensive opioid consumption.Level Of Evidence: Level III, retrospective, observational cohort study. [ABSTRACT FROM AUTHOR]

• Thermal conductivity increases with GNP aspect ratio until a saturation value. • A reverse trend is observed between thermal conductivity and dispersion state. • Micro-tomography revealed micro-voids encapsulation caused by large aggregates. • Fillers aggregation, without voids, is best for thermal conductivity enhancement. An innovative combination of micro-computed X-ray tomography (μCT) and electron microscopy (SEM) coupled to an image-processing software was used to study the thermal conductivity of graphene nanoplatelets(GNP)/epoxy composites. This approach afforded a precise and systematic analysis of the dispersion state of the fillers in the epoxy matrix. Here, the influence of GNP aspect ratio on thermal conductivity enhancement (TCE) and the relationship between dispersion state of the fillers and TCE is revealed. The aggregation level of GNP was finely tuned by varying the sonication power. An unexpected trend towards enhanced thermal conductivity upon aggregation of the fillers is demonstrated. Moreover, μCT analysis revealed the encapsulation of micro-voids, undetectable with conventional methods, by large fillers aggregates. This study demonstrates that aggregation of the fillers increases the thermal conductivity of epoxy composites as long as it does not lead to voids encapsulation. [ABSTRACT FROM AUTHOR]

During the first stages of Atomic Layer Deposition (ALD) of Al 2 O 3 on silicon (Si), the substrate nature affects the surface chemistry, leading to an initial island growth mode. Furthermore, an interfacial zone develops between the Si surface and the dielectric, thus damaging the physical properties of the deposited structure. In this work, these two main shortcomings are investigated for the ALD of Al 2 O 3 films on Si from TMA and H 2 O. The film and the interfacial zone are characterized by a complete range of techniques, including XRR, TEM, XPS, EDX and ToF-SIMS. In parallel, a computational model is developed to study the initial nucleation and growth steps of the film. An induction period is experimentally evidenced and numerically reproduced, together with the island growth and coalescence phenomena. The chemical composition of the (Al, O, Si) interfacial layer is precisely analyzed to get insight in the mechanisms of its formation. We show that Si oxidation occurs during the island growth, catalyzed by the presence of Al, while it is also fed by species interdiffusion through the ALD film. Unlabelled Image • The initial steps of Al 2 O 3 ALD on Si are studied, experimentally and theoretically. • An induction period is evidenced leading to island growth. • An interface oxide layer is formed between the Al 2 O 3 film and the Si substrate. • The interface consists of SiO x , with possible presence of SiOAl. • The interface is formed during the island growth and through species interdiffusion. [ABSTRACT FROM AUTHOR]

Abstract The deposition of thin coatings by plasma processes operated at atmospheric pressure is a versatile process for the deposition of functional coatings. However, there is a need to understand their mechanical properties as a function of plasma deposition process parameters since the durability of the coatings is strongly dependent on these properties. In this work, a new approach to obtaining plasma coatings with a controlled level of cross-linking was developed. The precursor molecule to plasma polymer coatings is hexanediol dimethacrylate (HdiMA), a di-functional methacrylate; the plasma deposition conditions were chosen to strongly decrease the precursor fragmentation, so that the plasma polymerization of this precursor leads to a cross-linked structure through the reaction of methacrylate bonds. Plasma coatings from HdiMA are deposited in different plasma conditions. The chemical structure of plasma polymers is investigated by means of infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The mechanical properties of the coatings are determined by nanoscratch and atomic force microscopy (AFM) force curves tests. Better mechanical properties are obtained for coatings deposited with a low concentration of aerosol in the plasma and a higher plasma power. This corresponds to coatings exhibiting the higher conversion rate. Graphical abstract Unlabelled Image Highlights • Thin plasma polymer coatings are deposited from hexanediol dimethacrylate • Deposition is performed in a DBD plasma at atmospheric pressure • Plasma deposition conditions are changed to modify the coating structure • The low precursor fragmentation and the plasma polymer cross-linking are evaluated • Better mechanical properties are obtained when the aerosol concentration is lows [ABSTRACT FROM AUTHOR]

The mechanics of structure genome has been extended to heat conduction problem of composite materials with a general linear thermal imperfect interface model. This full field micromechanics approach is applied to predict the effective thermal conductivity of composite materials containing thermal imperfect contact between the matrix and the reinforcements. Examples of spheroidal particles reinforced composites are used to demonstrate the robustness and accuracy of this micromechanics theory. The size-dependency of the overall thermal conductivity shows the importance of imperfect interfaces in modeling the thermal behavior of composite materials. The proposed micromechanics method is versatile and can be applied for estimating the effective thermal conductivity of nanocomposite materials. [ABSTRACT FROM AUTHOR]

Protective coatings from diethylphosphatoethyltriethoxysilane (DEPETS) have been deposited on different polymer substrates in a plasma discharge operated at atmospheric pressure. Plasma polymer chemistry and structure were characterized by means of Fourier transform infrared spectroscopy (FTIR), laser desorption ionization-mass spectrometry (LDI-MS), nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). A chemical structure of the plasma polymer has been proposed based on the coating molecular characterization. Coatings were deposited on polycarbonate (PC) and polyamide 6 (PA6) substrates. The flame retardant properties of coated substrate samples were assessed using cone calorimetry and compared to those of bare substrates. A significant increase in the time to ignition (TTI), up to +143%, was recorded after coating deposition due to the formation of a high-performance barrier layer at the surface of both polymer substrates. [ABSTRACT FROM AUTHOR]

New intumescent flame retardant coating made from poly(allylamine) (PAH), sodium polyphosphates (PSP) and TiO 2 nanoparticles was designed using layer-by-layer assembly. The (PAH-PSP-PAH-TiO 2 ) n (where “ n ” denotes the number of quadralayers) assembly has been deposited on silicon wafers in order to evaluate its thickness as well as its topography by ellipsometry and by atomic force microscopy (AFM), respectively. According to AFM measurements, the coating appears smooth and continuous. The film exhibits a linear growth regime with a thickness of approximately 500 nm for 15 quadralayers (QL). However, when deposited on polyamide or polyester fabrics, this coating displays different morphologies as it was shown by scanning electron microscopy (SEM) analysis. The thermo-oxidative degradation and flammability properties of the coatings and their effect on polyamide and polyester fabrics have been evaluated by thermogravimetric analyses (TGA) and pyrolysis combustion flow calorimeter (PCFC) respectively. We have found that the coating acts efficiently in reducing the peak of the heat release rate (pHRR) value for polyamide fabric while very limited effect was observed on polyester fabric. [ABSTRACT FROM AUTHOR]

Novel ultra-high molecular weight polyethylene (UHMWPE) composites were processed by micro-extrusion with polyaniline (PANI) as potential reinforcing and radical scavenging agent and with lauryl gallate (LG) as coupling agent. By means of UV–vis spectroscopy, it was found that the presence of PANI reduced at maximum by 27.3% the concentration in free radicals of a 2,2-dimethyl-1-picrylhydrazyl (DPPH) solution in which was immersed the composite. This result was obtained with the UHMWPE/LG/PANI weight composition 89/1/10, which also demonstrated to retain the viscoelastic and tensile properties of neat UHMWPE. The dispersion of PANI micro-particles within the UHMWPE matrix may be an alternative to the stabilization step of crosslinked UHMWPE used in joint prosthesis. [ABSTRACT FROM AUTHOR]

Cardanol and cardanol derivatives are among the most important biobased materials currently investigated in green chemistry, as renewable and promising building blocks in lieu of traditional raw materials from non renewable resources, in particular owing to the olefinic linkages on the C15 alkyl side-chain. Despite the increasing interest they arouse, analytical chemistry dedicated to cardanol and associated resins has been rarely reported in the literature, found even poorer when dealing with chromatography and mass spectrometry. In this work, a thorough molecular characterization was conducted using matrix assisted laser desorption ionization (MALDI) mass spectrometry, size exclusion chromatography (SEC), and SEC–MALDI coupling to gain insights into the composition of phenolated, epoxidized, and epoxidized phenolated cardanol. A nomenclature was proposed to properly describe the numerous species found in these materials, while simulations of the unsaturation patterns and their comparison with the detected patterns in MALDI-MS gave useful details about the phenolation treatment expected to occur on the polyunsaturated C15 side chain. Finally, the SEC–MALDI off-line coupling allowed SEC peaks to be deconvoluted by mass spectrometry and MALDI artefacts related to matrix adduction to be pointed out. [ABSTRACT FROM AUTHOR]

It is well established that the chemical structure of surfactants used to promote the dispersion of clay minerals in polymers plays a major role in clay polymer nanocomposites preparation. However, much less explored is the incorporation of reactive surfactants capable of covalently grafting to monomers and polymer chains. In this work, the effect of the reactivity degree of bio-based surfactants onto the exfoliation of montmorillonite in epoxy is evidenced. For this purpose, 3 surfactants were prepared from a derivative of Cardanol, incorporating reactive groups: N(CH 3 ) 2 , NH 2 or two NH 2 functions. In each case, the organomodification of the clay mineral results in a similar interlayer space increase. Combined chemical derivatization and MALDI-TOF/MS was used to evidence the differences of the residual reactivity of the intercalated surfactants. Finally each organomodified clay mineral was used for the preparation of epoxy nanocomposites. Interestingly, for the most reactive surfactant, X-ray diffraction analysis evidenced a fully exfoliated structure while semi-exfoliation or intercalated structure was found for the less reactive surfactants. [ABSTRACT FROM AUTHOR]

Abstract: A polymeric bilayer composed of two poly(styrene) layers differing by their molecular weights (MW) was elaborated to mimic a MW gradient and analyzed by a combination of TOF-SIMS, MALDI-MS and Nanoscratch (NS). A direct TOF-SIMS profiling conducted using a Cs+ ion beam lead to the detection of fragments from carbonated layers without any data about their MW, making the fine bilayer architecture indistinguishable. Spots of various depths were hence created using the same Cs+ ion bombardment for different sputtering times, and further mass-analyzed by the recently developed Surface-Layer MALDI-MS technique, to evaluate the MW of the very top polymeric layer of each crater. The off-line combination of ion etching and LASER analysis allowed a molecular weight depth profile to be plotted, as a function of the physical depth measured by NS in each crater (instead of the usual sputter time). This original coupling is expected to provide useful molecular and/or molecular weight data about complex organic and/or polymeric multi-layers or gradients. [Copyright &y& Elsevier]

Abstract: In this work, an intumescent coating of (polyallylamine-polyphosphate)n (“n“ denotes the number of bilayers (BL) deposited) was elaborated through Layer-by-Layer assembly in order to improve the fire performance of polyamide 6.6 fabrics (PA). The thickness of this intumescent assembly increases linearly as a function of the number of bilayers deposited. Thermogravimetric analysis results indicate that the presence of such assembly catalyzes and changes the degradation pathway of virgin polyamide fabrics. The fire performance was evaluated by Pyrolysis Combustion Flow Calorimeter. The fire results show on the one hand a significant decrease of peak of heat release rate (pHRR) and on the other hand a shift to lower temperatures (assigned to a catalytic effect) as a function of the number of bilayers deposited. A maximum decrease of pHRR (−36%) is obtained for the 40 BL coated fabric in comparison with uncoated polyamide fabric. [Copyright &y& Elsevier]

Abstract: A new ammonium-based surfactant (PkH+), synthesized from a 3-alkyl phenol glycidyl ether issued from renewable cashew nutshell liquid (CNSL), has been used to modify the surface of sepiolite clay. This surfactant is especially designed to enhance the compatibility of the needle-like clays with epoxy networks (e.g. DGEBA): ionic PkH+–sepiolite interactions are provided by the ammonium groups, and covalent grafting of DGEBA onto the surfactant is enabled by NH and OH reactive groups. MALDI-ToF-MS was used with success to evidence the grafting of DGEBA units onto the modified clay. Morphological analyses by SEM highlighted the promoted compatibilization and dispersion of sepiolite in DGEBA networks. The properties of the filled networks were characterized by DSC, DMA and evidenced a strong shift of 20°C of the Tg of the network to higher temperatures and an enhancement of the storage modulus below the Tg. Interestingly, the thermal stability of the network was not affected by the modification of sepiolite by the ammonium. In conclusion, the intercalation of PkH+ onto sepiolite subserves its compatibilization into epoxy networks with a remarkable thermal and thermomechanical properties improvement. [Copyright &y& Elsevier]

Abstract: In this paper, a polyamide-6 (PA6) substrate has been coated with a flame retardant film, made from polyallylamine (PAH) (polycation) and montmorillonite (MMT) (polyanion), elaborated by Layer-by-Layer (LbL) technique. The (PAH–MMT) n assembly (with n the number of bilayers deposited) exhibits an exponential growth regime. At n = 20 bilayers deposition of PAH and MMT, the film reaches a considerable thickness of ∼5 μm with the alignment of MMT in the direction parallel to the substrate. Scanning Electron Microscopy (SEM) analysis of the cross-section and Atomic Force Microscopy (AFM) analysis display a regular and continuous morphology of the obtained films. Thermogravimetric analysis shows that the presence of (PAH–MMT) n films at 10 and 20 bilayers enhances the thermal stability of the polyamide substrate. Cone calorimetry evidences excellent reaction to fire of the material since peak of heat release rate (HRR) is decreased by more than 60% in the presence of 20 bilayers of PAH–MMT film in comparison with uncoated PA6. Continuous charred layer was observed during the combustion and the thickness of the coating at the end of the combustion test is twice higher than that of the initial thickness. The presence of this expanded charred layer at the surface acts as protective limiting heat and mass transfer. [Copyright &y& Elsevier]

Abstract: We developed experimental as well as theoretically based hierarchical multiscale procedures for the evaluation of effective elastic modulus and thermal conductivity of poly-lactide (PLA)/expanded graphite (EG) nanocomposites. The incorporation of EG fillers into PLA was carried out by a twin-screw micro-extruder. The dispersion/delamination of EG in PLA was studied using Raman spectroscopy, SEM and TEM. In the multiscale modeling, the thermal conductivity constants and stiffness tensor of EG were first acquired by the means of molecular dynamics (MD) simulations. Using the fillers’ properties obtained by the MD, we developed finite elements (FE) models to evaluate the effective thermal conductivity and elastic modulus of PLA/EG nanocomposites. Our results, for a wide range of temperatures revealed the efficiency in thermal and mechanical reinforcement of PLA by incorporation of EG nanoparticles. [Copyright &y& Elsevier]

Abstract: The present article focuses on the influence of the salt concentration as well as on the influence of the nature of the salt on the deposition of (PAH-PSP) n films in the case where PSP is made from only 24 monomer units on average. The two main messages of this article are that: (i) for salt concentrations lower than about 0.2M, the film thickness increases linearly with the number of adsorption cycles after the deposition of a coating with a critical thickness necessary to prime the deposition of the film. In addition, for salt concentrations lower than 0.2M, there is no effect of the influence of the supporting electrolyte on the film thickness but a marked influence on the film composition as revealed from XPS measurements. (ii) For salt concentrations higher than about 0.2M, the films are extremely rough, and we demonstrate that the use of a homogeneous and isotropic model is not suited anymore to calculate the film thickness and its refractive index from the measured ellipsometric angles. Finally we try to rationalize all the data obtained so far on the (PAH-PSP) n films on the basis of counterion condensation of Na+ cations on the PSP chains. [Copyright &y& Elsevier]

Abstract: The deposition of polyelectrolyte multilayer films consists of the sequential adsorption of polycationic and polyanionic species at solid–liquid interfaces. The adsorption process can be performed either by alternated dipping of the substrate to be coated in the polyelectrolyte containing solutions, by alternated spin coating of these solutions or by alternated spraying of them. Different coating technologies can lead to different properties of the obtained coatings even for the same combination of polycations and polyanions. The aim of this article is to show that by playing on the concentration of the supporting electrolyte, NaCl, the films obtained by alternated spraying and alternated dipping grow differently and display different properties, in terms of refractive index, surface morphology, wettability for water and surface composition. [Copyright &y& Elsevier]

Abstract: Photo-oxidation at λ > 290 nm was performed on vulcanised styrene butadiene rubber (SBR) designed for flooring applications. The effect of the presence of coated titanium dioxide (TiO2), used as a pigment, was evaluated. The chemical and nano-mechanical changes occurring at the surface during irradiation were studied by micro-FTIR spectroscopy and atomic force microscopy (AFM). Both techniques were used to obtain the oxidation profiles in the depth of the composites (in the absence and presence of TiO2) to characterise the oxidative layer formation. The nano-mechanical and chemical profiles were superimposed for both composites (SBR and SBR/TiO2) suggesting a correlation between both properties. Indeed, the increase of the DMT modulus determined by AFM reflects the crosslinking reactions which occur simultaneously with the formation of oxidised photo-products. Moreover, during irradiation, the mechanical properties were followed at low and high degree of deformation by means of dynamic mechanical analysis (DMA) and tensile test until break, respectively. We demonstrate that the physico-chemical properties of the oxidised layer which represents 20 μm of the 600 μm of the material can explain the loss of mechanical properties for both composites based on vulcanised SBR and SBR/TiO2 during irradiation at λ > 290 nm. We also demonstrate a different mechanical behaviour in presence of TiO2 compared to neat SBR that could be due to a competition between formation of photo-products and the filler-rubber debonding during photo-oxidation. [Copyright &y& Elsevier]

Abstract: The thermal and fire-resistance properties of the ternary system ammonium polyphosphate/melamine polyphosphate/titanium dioxide (APP/MPP/TiO2) was studied in poly(methyl methacrylate) (PMMA). PMMA-7.5%APP/7.5%TiO2 showed an interesting thermal stability and synergy effects on the peak of heat released rate (pHRR). Mechanisms were investigated following the analysis of residues and gas phase. Residues were analyzed by Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM). Gases emitted during degradation were analyzed by Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). Comparison between cone calorimetry and pyrolysis–combustion flow calorimetry (PCFC) tests was a helpful tool for determining whether fire-retardancy mainly occurred by a physical or chemical pathway and for explaining the obtained results. [Copyright &y& Elsevier]

Abstract: Among various atmospheric pressure plasma deposition techniques, the so-called “Atmospheric Pressure Plasma Dielectric Barrier Discharges” (APDBD) has recently received a lot of attention due to the easy ignition of a stable discharge and its scalability. In the present work we aim at designing plasma polymer based films for biomedical applications, in which the drug to be released will be directly incorporated in the film during its deposition. Plasma polymer films made of methacrylic acid (MAA) and of ethylene glycol dimethacrylate (EGDMA) were prepared, allowing to obtain smart coatings able to release the molecule of interest, acetaminophen. A combination of different analytic tools shows that the functional groups of the film are well preserved with respect to the monomer structure and that the drug initially put in the gas phase is embedded in the plasma film with its structure being preserved. The physical and chemical characteristics of the elaborated film allowed for the progressive release of acetaminophen by simply dipping the film into a deionized water solution. However only 8% of the acetaminophen present in the monomer mixture could be released slowly in the presence of water. The significance of this result will be discussed. [Copyright &y& Elsevier]

Abstract: Polydopamine coatings are promising new versatile coatings able to be deposited on almost all kinds of materials. Such films synthesized either by oxygenation or by electrochemistry on indium tin oxide (ITO) and glassy carbon substrates, were degraded by an oxidizing sodium hypochlorite solution. Films were successively immersed in a sodium hypochlorite solution (1 g/L) during different times. The characterizations of film degradation were made by XPS spectroscopy and AFM. They confirmed a homogeneous degradation of polydopamine, due to an oxidation reaction. The influence of the synthesis method and the nature of the substrate on the polydopamine degradation were also studied in this paper: coatings deposited on ITO by oxygenation degrade much faster than those deposited on glassy carbon or by electrochemistry. This suggests that the adhesion of the polydopamine films and their stability is markedly dependant on the used substrate (ITO vs. glassy carbon) as well as on the deposition method (oxygenation vs. electrochemistry), whereas the film thickness reached during deposition is almost substrate independent. [Copyright &y& Elsevier]

Abstract: Compact and linearly growing polyelectrolyte multilayer films have been used to suppress desorption of drugs, nanoparticles or proteins from underlying polyelectrolyte multilayer films as well as to significantly change their mechanical properties. The polyelectrolyte based capping layers are however cumbersome to deposit and alternative barrier layers offering enzymatic retention in the films as well as permeability to small molecules, for example the substrates of the embedded enzymes, are highly desired. In this article we show that barrier layers made through atmospheric pressure dielectric barrier discharge polymerization of ethylene glycol dimethacrylate offer the opportunity to simultaneously suppress enzyme desorption from the underlying polyelectrolyte multilayer film and to ensure accessibility of the enzymatic substrate. This holds true when the barrier film totally covers the underlying film and as long is not too thick. When the plasma deposited barrier becomes 300nm thick, the hydrolysis curve of the enzyme presents a lag phase typical of a diffusion-limited process. [Copyright &y& Elsevier]

Abstract: Plasma polymerization is a powerful coating technology for many technological areas, notably in the coating of biomaterials, particularly when it is applied under atmospheric pressure conditions which allow to avoid expensive pumping systems. In the present investigation, the properties of coatings based on acrylic acid and on methacrylic acid prepared using atmospheric pressure plasma in dielectric barrier discharge conditions and at atmospheric pressure under various operating parameters were compared. The obtained films were characterized using different analytical and spectroscopic techniques with the aim to understand the influence of small changes in the monomer structure as well as in the operational plasma parameters on the film structure. Differences in chemical structure, deposition rate and functional group preservation were determined using FTIR, X-ray photoelectron spectroscopy combined with chemical labeling, and mass spectrometry (MALDI-TOF). As a main result, we show the possibility to quickly design architectures with tunable carboxylic functions by modifying the structure of the used monomer as well as the plasma processing parameters. Our investigation is one of the first in which the molar mass distribution of the plasma polymers, made either from acrylic acid or methacrylic acid, is directly measured from the solid state film without selective solvent extraction. [Copyright &y& Elsevier]

Abstract: Electrospray tandem mass spectrometry was used here to study the soluble part of a thin film prepared by plasma polymerization of octamethylcyclotetrasiloxane (D4). Accurate mass measurements and 29Si nuclear magnetic resonance (NMR) spectroscopy, as well as synthesis of authentic compounds used as models to understand the MS/MS behavior of plasma polymers, were combined to structurally investigate oligomers present in this extract. All precursor ions were protonated or ammoniated molecules, known to provide more useful information for dimethylsiloxane (DMS)-based polymers as compared to alkali adducts. Apart from a major compound consisting of two D4 units connected via an oxygen bridge, it was found that the soluble part of this plasma polymer was mainly composed of cyclolinear polysiloxanes, in which cyclic units composed of four DMS were covalently connected by linear DMS segments. As the size of precursor ions increases, discrepancies observed between MS/MS data of synthesized molecules and of plasma oligomers would reveal the presence of branched isomers in the soluble part of the film, consistently with the expected propensity of the plasma polymerization process to favor random branching. [Copyright &y& Elsevier]

Abstract: New plasticization ways based on low molecular plasticizers from citrates family were investigated to improve the ductility of poly(lactide) (PLA). Grafting reactions between anhydride-grafted PLA (MAG-PLA) copolymer with hydroxyl-functionalized citrate plasticizer, i.e. tributyl citrate (TbC), were so-carried out through reactive extrusion. TributylO-acetylcitrate (ATbC) was used as a non-functionalized reference. Both plasticizers drastically decreased the T g of PLA. However, the grafting reaction of TbC into MAG-PLA revealed a shift of PLA T g toward higher values. After 6months of aging, no phase separation was observed. However, plasticizer leaching was noticed in the case of PLA/ATbC materials, leading to the shift of T g toward lower temperatures. In contrast, no major leaching phenomenon was noticed in PLA/TbC and PLA/MAG-PLA/TbC blends, indicating that the mobility restriction derived from the hydrogen bonding that can occur between PLA and TbC as well as the grafting reaction of TbC into MAG-PLA enabled to reduce leaching phenomena. [Copyright &y& Elsevier]

Abstract: A new approach has been developed to study the dispersion/delamination of expanded graphite (EG) in poly(lactide) (PLA) by using Raman spectroscopy. This technique is more sensitive and therefore fully complementary to more standard dispersion characterization techniques like SEM, TEM and X-ray diffraction. The incorporation of EG into PLA was carried out by a twin-screw micro-extruder. The effects of the dispersion and delamination of EG on the thermal and thermo-mechanical properties of polylactide-EG nanocomposites were investigated. In contrast to the standard techniques, Raman spectroscopy was able to show a partial exfoliation, which could therefore explain the slight improvement of the PLA–EG thermal and thermo-mechanical properties. [Copyright &y& Elsevier]

Abstract: Gas impact on the EDS profile resolution at the interface of composite interface resin/Al was investigated with two gaseous environments: helium and water vapor. Two main components of the global profile at the interface were investigated: the contrast of the profile and the spatial resolution. A complementary approach was developed by comparing gas nature impact versus the pressure and versus the scattering regime. The results show that the unscattered electron beam mainly governs EDS profile spatial resolution as long as the scattering regime is single or oligo scattering. Then for plural scattering, spatial resolution is dramatically degraded. In addition, the contrast is degraded since a gas is introduced, whatever the gas, the pressure and so the scattering regime. This approach would enable to better understand the respective contributions of the unscattered beam and the skirt and the influence of the gases nature on them. [Copyright &y& Elsevier]

Abstract: In this work, new ways of plasticizing polylactide (PLA) with low molecular poly(ethylene glycol) (PEG) were developed to improve the ductility of PLA while maintaining the plasticizer content at maximum 20wt.% PLA. To this end, a reactive blending of anhydride-grafted PLA (MAG-PLA) copolymer with PEG, with chains terminated with hydroxyl groups, was performed. During the melt-processing, a fraction of PEG was grafted into the anhydride-functionalized PLA chains. The role of the grafted fraction was to improve the compatibility between PLA and PEG. Reactive extrusion and melt-blending of neat and modified PLA with PEG did not induce any dramatic drop of PLA molecular weight. The in situ reactive grafting of PEG into the modified PLA in PLA/PEG blends showed a clear effect on the thermal properties of PLA. It was demonstrated by DSC that the mobility gained by PLA chains in the plasticized blends yielded crystallization. The grafting of a fraction of PEG into PLA did not affect this process. However, DSC results obtained after the second heating showed an interesting effect on the T g when 20wt.% PEG were melt blended with neat PLA or 10wt.% MAG-PLA. In the latter case, the T g displayed by the reactive blend was shifted to even lower temperatures at around 14°C, while the T g of neat PLA and PLA blended with 20wt.% PEG was around 60 and 23°C, respectively. Regarding viscoelastic and viscoplastic properties, the presence of MAG-PLA does not significantly influence the behavior of plasticized PLA. Indeed, with or without MAG-PLA, elastic modulus and yield stress decrease, while ultimate strain increases with the addition of PEG into PLA. [Copyright &y& Elsevier]

Abstract: Possible relationships between fire-retardant properties and thermal diffusivity for poly(methyl methacrylate) (PMMA) filled by melt blending with titanium dioxide (TiO2), alumina (Al2O3) and boehmite (AlOOH) were investigated for a better understanding of the mode of action of metal oxides as fire-retardants (FR) in PMMA. Fire-retardancy was measured with a cone calorimeter and thermal diffusivity (α) by Laser Flash Analysis (LFA). LFA measurements have shown that heat dispersion is higher with titanium dioxide and boehmite than with alumina despite a larger surface area. For thermal diffusivity, discrepancies between the different nanofillers were only visible from 10 wt% onwards. Thermal degradation of PMMA-oxide nanocomposites and their thermal diffusivity could be linked. Moreover, a bi-linear relationship between the peak of heat release rate (pHRR) and the average of heat release rate (AHRR) showed the occurrence of a barrier effect. [Copyright &y& Elsevier]

Abstract: The yield behaviour of dimer acid-based polyamides (DAPA) and DAPA reinforced with cellulose fibres (CF) was examined in this study. Both dynamic mechanical analysis (DMA) and tensile tests were used to follow the effect of strain rate or frequency, temperature and filler content on the transitions temperatures, the storage modulus and the yield stresses. The DMA results show that the storage modulus increases with increasing CF concentration. The tensile tests reveal that the yield stress is strain rate, temperature and CF concentration sensitive. Both activation enthalpy and activation volume calculated by the Eyring’s model reveal a slight increase of activation energy with increasing filler content and a decrease of the activation volume. A micromechanically-model was used to predict the yield stress of both DAPA and DAPA/cellulose composites. The model predictions of the yield stress are in good agreement with the experimental data. [Copyright &y& Elsevier]

Abstract: The aim of this work is to introduce the use of low vacuum scanning electron microscopy (LVSEM) coupled with an X-ray energy dispersive spectrometer (EDS) in the field of structural adhesives, more precisely aluminium/epoxy resin assembly. Such assembly is characterized by the creation of an interphase resulting from the metal diffusion inside the resin during cross-linking. As the performance of the final bond is strongly links by the interphase properties, fine characterization of this interphase, in particularity the evaluation of its thickness is essential to understand the macroscopic properties of the adhesive assembly. First, the EDS acquisition parameters were investigated in order to limit the sample/resin damage/degradation due to the incident electrons beam irradiation. Then a specific methodology of stacked profiles was defined to improve the precision of the measures. To evaluate the true Al diffusion profile, the impact of the interaction volume of incident electron in the material on the Al signal variation during the interface crossing was calculated and the effect of the gas pressure on the electron beam characteristic and so on the measured profiles was examinated. According to our developed methodology and data treatments, Al diffusion profile was interpreted and interphase thickness was qualitatively determined by comparison with an experimental baseline. This innovative methodology promotes the use of LVSEM–EDS in the field of adhesive structural assemblies, but also, deals with a comparative study on the effect of the gas pressure on the EDS profile analysis. [Copyright &y& Elsevier]

Abstract: Thermophysical properties of yttria partially stabilized zirconia (8Y2O3–ZrO2) thermal barrier coatings manufactured implementing in situ laser remelting process (a hybrid process which combines laser remelting and thermal spraying) were characterized from ambient temperature to 1100 °C. Their properties were compared to conventional as-sprayed coatings. The evolution of the thermal properties as a function of the undergone laser treatments permits to select the suitable treatments improving the insulation function of thermal barrier coatings. The stability of the coating thermal properties during thermal cycles was also evaluated to guarantee the performances under service conditions. [Copyright &y& Elsevier]

Summary: The stabilising effects of various structures of the distal radioulnar joint (DRUJ) have been heavily debated. This biomechanical cadaveric study examined the effects of the volar and dorsal lips of the sigmoid notch and the volar and dorsal aspects of the triangular fibrocartilage complex (TFCC) on DRUJ stability. Sequential fractures of the distal radius and sectioning of the TFCC were performed followed by measurements of ulnar translation with the forearm in pronation, neutral and supination. A dorsal lunate facet fracture created instability in pronation. Lunate facet fractures alone did not create instability in other forearm positions. Sectioning of the volar TFCC after loss of the dorsal TFCC by a dorsal lunate facet fracture caused DRUJ instability with the forearm in neutral position. Sectioning of the dorsal TFCC after loss of the volar TFCC due to a volar lunate facet fracture created instability in neutral and pronated positions. [Copyright &y& Elsevier]