Cellulose consolidation under high-pressure and high-temperature uniaxial compression

Materials based on cellulose cannot be obtained from thermoplastic processes. Our aim is to prepare all-cellulose materials by uniaxial high pressure thermocompression of cellulose. The effect of moisture content (0–8 w/w%) and temperature (175–250 °C) was characterized through the mechanical properties (bending and tensile), morphology (scanning electron microscopy, X-ray tomography) and microstructure (viscometric degree of polymerization, Raman spectroscopy, X-ray diffraction, solid-state NMR) of the specimens. The specimens were mechanically stronger in bending than in tension. They exhibited a more porous heart, a dense but very thin skin on the faces (orthogonal to the compression axis) and thick and extremely dense sides. During thermocompression severe friction between fibers caused a decrease in molecular weight while heating above the glass transition temperature was responsible for water migration towards the specimen heart. Most of the cohesion came from the small sides of the test samples (parallel to the compression axis) and seemed mainly related to the entanglement of amorphized cellulose at the interface between particles. Around 200 °C water accumulated and provoked delamination upon pressure release, but at higher temperatures water, in a subcritical state, may have been consumed during the hydrolysis of amorphous cellulose regions. The all-cellulose material with the best mechanical properties was obtained at 2% moisture and 250 °C. This work shows that thermocompression at high temperature with limited moisture may be viable to produce renewable, sustainable all-cellulose materials for application in biobased plastic substitutes including binderless boards

Fonctionnalisation par voie physique de géotextiles destinés à la dépollution des sédiments de dragage

Le traitement des sédiments de dragage pollués aux métaux lourds est une alternative à leur stockage sur sites homologués et pourrait permettre la réutilisation des sédiments en technique routière ou en butte paysagère. Le procédé de dépollution envisagé dans ce projet consiste à déposer les sédiments contaminés sur des géotextiles, matériaux présentant une structure poreuse idéale pour la filtration. La lixiviation permet ensuite de rendre mobile une partie des polluants métalliques afin qu’ils puissent être adsorbés par les géotextiles. Cependant, ces matériaux, généralement synthétiques, n’ont pas de capacité intrinsèque à retenir les métaux et doivent donc être fonctionnalisés avec des molécules capables de fixer les métaux lourds. Cette thèse est orientée vers le développement de procédés de fonctionnalisation par plasma et laser, l’objectif final étant d’immobiliser des biomolécules chélatantes à la surface des géotextiles. Ces biomolécules sont fixées par couplage chimique sur des fonctions –COOH obtenues préalablement par greffage d’un agent intermédiaire, l’acide acrylique. La surface des fibres a été analysée à chaque étape de traitement par microscopie électronique à balayage, spectrométrie infrarouge, et par spectrométrie photoélectronique à rayons X, prouvant le greffage covalent de l’acide acrylique puis des biomolécules. Enfin, des tests avec des solutions métalliques ont été effectués afin de pouvoir sélectionner le textile fonctionnalisé le plus efficace pour réaliser des essais à l’échelle pilote. Parallèlement, une étude de modélisation a été amorcée afin d’étudier plus précisément la structure des complexes métal/biomolécule obtenus.The treatment of dredged sediments contaminated with trace metals is an alternative to the current storage in accredited sites and could allow the reusability of sediments in civil engineering. The remediation process considered in this project consists in the deposition of polluted sediments onto geotextiles, structures possessing filtration properties. The leaching then favors the release of metals that can be sequestered by the geotextiles. However, these textile structures are mainly composed of synthetic polymers and thus cannot retain heavy metals. Therefore, they have to be functionalized with molecules able to adsorb metal ions present in aqueous media. The main objective of this PhD thesis was to develop functionalization processes using plasma and laser techniques, in order to immobilize biomolecules with chelating properties at the surface of the fabrics. These biomolecules were immobilized by chemical coupling onto –COOH groups obtained at the fabric surface by the grafting of a spacer, namely acrylic acid. The surface of the fibers was characterized at the different grafting steps by scanning electron microscopy, infrared spectrometry and X-ray photoelectron spectrometry: evidence of the covalent grafting of acrylic acid and then of biomolecules was given. Some remediation tests were then carried out in order to select the most interesting functionalized materials for further studies at pilot scale. In parallel, a computational study was initiated in order to determine the structure of the metal/biomolecule complexes

Composition and Stability of Plasma Polymer Films Exhibiting Vertical Chemical Gradients

Controlling the balance between stability and functional group density in grown plasma polymer films is the key to diverse applications such as drug release, tissue-engineered implants, filtration, contact lenses, microfluidics, electrodes, sensors, etc. Highly functional plasma polymer films typically show a limited stability in air or aqueous environments due to mechanisms like molecular reorganization, oxidation, and hydrolysis. Stabilization is achieved by enhancing cross-linking at the cost of the terminal functional groups such as −OH and −COOH, but also −NH₂, etc. To overcome such limitations, a structural and chemical gradient was introduced perpendicular to the surface plane; this vertical gradient structure is composed of a highly cross-linked base layer, gradually changing into a more functional nanoscaled surface termination layer. This was achieved using CO₂/C₂H₄ discharges with decreasing power input and increasing gas ratio during plasma polymer deposition. The aging behavior and stability of such oxygen-functional vertical gradient nanostructures were studied in air and in different aqueous environments (acidic pH 4, neutral pH ≈ 6.2, and basic pH 10). Complementary characterization methods were used, including angle-resolved X-ray photoelectron spectroscopy (ARXPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) as well as water contact angle (WCA) measurements. It was found that in air, the vertical gradient films are stabilized over a period of months. The same gradients also appear to be stable in neutral water over a period of at least 1 week. Changes in the oxygen depth profiles have been observed at pH 4 and pH 10 showing structural and chemical aging effects on different time scales. The use of vertical gradient plasma polymer nanofilms thus represents a novel approach providing enhanced stability, thus opening the possibility for new applications

Suppression of Hydrophobic Recovery by Plasma Polymer Films with Vertical Chemical Gradients

Vertical chemical gradients extending over a few nanometers were explored. The gradients are based on plasma-polymerized oxygen-containing ethylene (ppOEt) films. Using plasma conditions with low CO2/C2H4 ratio and high energy input, cross-linked films were deposited as base layer, while increasing CO2 and lowering energy input resulted in less cross-linked yet highly functional films as applied as top layer. Aging studies indicate that, in particular, for very thin gradient structures, the cross-linked subsurface zone effectively hinders reorientation of the surface functional groups, thus restricting hydrophobic recovery and oxidation effects

Cellulose consolidation under high-pressure and high-temperature uniaxial compression

Abstract: Materials based on cellulose cannot be obtained from thermoplastic processes. Our aim is to prepare all-cellulose materials by uniaxial high pressure thermocompression of cellulose. The effect of moisture content (0–8 w/w%) and temperature (175–250 °C) was characterized through the mechanical properties (bending and tensile), morphology (scanning electron microscopy, X-ray tomography) and microstructure (viscometric degree of polymerization, Raman spectroscopy, X-ray diffraction, solid-state NMR) of the specimens. The specimens were mechanically stronger in bending than in tension. They exhibited a more porous heart, a dense but very thin skin on the faces (orthogonal to the compression axis) and thick and extremely dense sides. During thermocompression severe friction between fibers caused a decrease in molecular weight while heating above the glass transition temperature was responsible for water migration towards the specimen heart. Most of the cohesion came from the small sides of the test samples (parallel to the compression axis) and seemed mainly related to the entanglement of amorphized cellulose at the interface between particles. Around 200 °C water accumulated and provoked delamination upon pressure release, but at higher temperatures water, in a subcritical state, may have been consumed during the hydrolysis of amorphous cellulose regions. The all-cellulose material with the best mechanical properties was obtained at 2% moisture and 250 °C. This work shows that thermocompression at high temperature with limited moisture may be viable to produce renewable, sustainable all-cellulose materials for application in biobased plastic substitutes including binderless boards

Vulnerabilities in Older Patients when Cancer Treatment is Initiated: Does a Cognitive Impairment Impact the Two-Year Survival?

Dementia is a known predictor of shorter survival times in older cancer patients. However, no empirical evidence is available to determine how much a cognitive impairment shortens survival in older patients when cancer treatment is initiated.To longitudinally investigate how much a cognitive impairment detected at the initiation of cancer treatment influences survival of older patients during a two-year follow-up duration and to compare the predictive value of a cognitive impairment on patients survival with the predictive value of other vulnerabilities associated with older age.Three hundred and fifty-seven consecutive patients (≥65 years old) admitted for breast, prostate, or colorectal cancer surgeries were prospectively recruited. A cognitive impairment was assessed with the Montreal Cognitive Assessment (MoCA<26). Socio-demographic, disease-related, and geriatric vulnerabilities were assessed using validated tools. Univariate and subsequent multivariate Cox proportional hazards models stratified for diagnosis (breast/prostate cancer versus colorectal cancer) and disease status (metastatic versus non-metastatic) were used.A cognitive impairment was detected in 46% (n = 163) of patients. Survival was significantly influenced by a cognitive impairment (HR = 6.13; 95% confidence interval [CI] = 2.07-18.09; p = 0.001), a loss in instrumental autonomy (IADL ≤7) (HR = 3.06; 95% CI = 1.31-7.11; p = 0.009) and fatigue (Mob-T<5) (HR = 5.98; 95% CI = 2.47-14.44; p <0.001).During the two years following cancer treatment initiation, older patients with a cognitive impairment were up to six times more likely to die than patients without. Older patients should be screened for cognitive impairments at cancer treatment initiation to enable interventions to reduce morbidity and mortality. Further studies should address processes underlying the relationship between cognitive impairments and an increased risk of dying in older cancer patients

Cardiac assessment of early breast cancer patients 18 years after treatment with cyclophosphamide-, methotrexate-, fluorouracil- or epirubicin-based chemotherapy

Background Epirubicin-based chemotherapy improves the outcome of early breast cancer (BC) patients. However, cardiotoxicity remains an important side effect. Methods We re-consented node-positive BC patients enrolled in a phase III trial between 1988 and 1996 which compared six cycles of oral cyclophosphamide, methotrexate, fluorouracil (CMF) versus two epirubicin-cyclophosphamide regimens differing by the anthracycline cumulative dose [standard-dose epirubicin and cyclophosphamide (SDE) (8 × 60 mg/m2) and higher-dose epirubicin and cyclophosphamide (HDE) (8 × 100 mg/m2)]. Eligible patients were those who were alive and free of disease and had no contra-indications to the proposed tests (cardiac evaluation). Cardiotoxicity was defined as asymptomatic systolic dysfunction (left ventricular ejection fraction (LVEF) < 50%, New York Heart Association (NYHA) Class I) or symptomatic heart failure (NYHA Class II-IV). Differences in cardiotoxicity between CMF and SDE/HDE were assessed using chi-square and Fisher Exact tests for binary variables and t-test and Wilcoxon test for continuous variables. Results Among the 777 patients, 20 cases of CHF were reported (CMF = 1, SDE = 5, HDE = 14; p < 0.001). Between September 2010 and June 2013, 82 patients (30%) out of 269 eligible patients accepted to participate in this substudy. Median follow-up was 18 years (range 15-24). Epirubicin-treated patients had significantly higher heart rate, more abnormal echocardiograms and LVEF by magnetic resonance imaging (MRI) compared to CMF-treated ones. A trend towards higher BNP was also observed in the SDE/HDE group (P = 0.08). No differences were observed in LVEF assessed by echocardiogram or troponin T levels. Conclusions Participation rate in this substudy was lower than expected highlighting the complexity of re-calling patients several years after the initial BC diagnosis. After 18 years, epirubicin-treated patients had a lower LVEF by MRI, more abnormal echocardiograms, higher heart rates compared to patients treated with CMF. However, no major delayed cardiotoxicity was observed.SCOPUS: ar.jinfo:eu-repo/semantics/publishe