A Portuguese clay (BRN) from the North East city of Bragança was collected and characterized in terms of health treatment and applied towards the preparation of nanocomposites with Polylactide (PLA). The silt-clay fraction of BRN is mainly composed of smectite with less illite, kaolinite and other minerals. The physicochemical properties are applicable for the topical applications and are mainly influenced by smectite. With the hazardous elements present, further bioavailability tests should be conducted. PLA nanocomposites with BRN and Wyoming montmorillonite SWy-2 (MMT) were respectively prepared through the solution casting method with ultrasonic stirring and using cetyltrimethylammonium bromide (CTAB) as the surfactant. The X-ray diffraction patterns show the exfoliated structures in most samples. Thermal gravimetric analysis reveals the increased thermal stability of the nanocomposites. The complexes were also characterized by nitrogen adsorption, infrared analysis and nuclear magnetic resonance for comparing the differences between BRN and MMT.

Fibers are classified into two groups; natural fibers and man-made fibers (MMF). There are three kinds of MMF: those made by transformation of natural polymers, those made from synthetic polymers and those made from inorganic material. Chitosan is classified as a biobased polymer and can be spun into man-made fibers. Due to its various functions, including anti-microbial, biocompatibility, biodegradability, metal-chelating, metal ions-coupling properties and general high molecular affinity, much attention has been paid recently to include chitosan into various concepts. The overall aim of this master thesis was to investigate the possibilities to make an antibacterial paper. Because chitosan contain primary amino groups that are cationic under mildly acidic conditions, it has antibacterial properties. Lab scale spinning of chitosan filaments was attempted in order to produce chitosan staple fibers that could be mixed with pulp fibers to make paper with antibacterial properties. Spinning methods used for a particular polymer is determined by the characteristics of the polymer. In the development of chitosan spinning at laboratory scale three different spinning methods were tested. A successful filament was produced by dry wet spinning. The filament was superior to the others in terms of dope composition and weight ratio of chitosan/acetic acid for protonation of the amino groups. Furthermore, the addition of glycerol improved the swelling of the chitosan hydrogel (or dope). Moreover, the condition of the coagulation step resulted in a good solidified filament with satisfactory elasticity and strength to be able to be taken up by a drawing cylinder. However, too small amounts of chitosan were produced in the development of chitosan spinning at lab scale and for production of antibacterial paper of chitosan. A second option was melt spinning of polylactide (PLA) filaments containing various amounts of chitosan. In this case PLA act as a carrier of chitosan into the paper sheet. Continuous filaments were spun in a sufficient amount. The antibacterial activity of PLA/chitosan fibers on E. coli bacteria was tested both on PLA/chitosan fibers as well as on suspensions. Under nutrient free conditions weak antibacterial effects was observed both for fibers and suspensions. However, in a more nutrient rich environment no effect was observed. This suggests that the produced fibers only had a weak antibacterial activity. To my knowledge the use of PLA in fiber form to carry chitosan into paper has not been attempted previously although different approaches to use chitosan as e.g. wound dressing is well described. In conclusion, there is a possibility to produce man made biodegradable fibers using chitosan and PLA that potentially could be added to paper. This paper might exert antibacterial properties that could have an interest to the market, e.g. for cleaning, in hospitals, and in the food industry.

yes / 2D materials such as graphene, LAPONITE® clays or molybdenum disulfide nanosheets are of extremely high interest to the materials community as a result of their high surface area and controllable surface properties. While several methods to access 2D inorganic materials are known, the investigation of 2D organic nanomaterials is less well developed on account of the lack of ready synthetic accessibility. Crystallization-driven self-assembly (CDSA) has become a powerful method to access a wide range of complex but precisely-defined nanostructures. The preparation of 2D structures, however, particularly those aimed towards biomedical applications, is limited, with few offering biocompatible and biodegradable characteristics as well as control over self-assembly in two dimensions. Herein, in contrast to conventional self-assembly rules, we show that the solubility of polylactide (PLLA)-based amphiphiles in alcohols results in unprecedented shape selectivity based on unimer solubility. We use log Poct analysis to drive solvent selection for the formation of large uniform 2D diamond-shaped platelets, up to several microns in size, using long, soluble coronal blocks. By contrast, less soluble PLLA-containing block copolymers yield cylindrical micelles and mixed morphologies. The methods developed in this work provide a simple and consistently reproducible protocol for the preparation of well-defined 2D organic nanomaterials, whose size and morphology are expected to facilitate potential applications in drug delivery, tissue engineering and in nanocomposites. / University of Warwick, Materials GRP, EPSRC, The Royal Society, ERC

No description available.

PLA nanofibers were successively produced by thermo-responsive transformation of PLA particles in water. The morphological structure of the nanofibers could be optimized by the heat treatment as well as the incorporation of GO to the fiber surface. PLA/GO fiber demonstrated a more stable morphology and GO provided good compatibility between PLA and starch. Both PLA and PLA/GO fibers incorporated in starch films resulted in increased thermal stability and mechanical properties. However, the most favorable properties were assigned starch films containing high concentration of PLA/GO fibers. These films with completely green components could possibly be utilized in biodegradable packaging applications.

Current degradable orthopedic fixation devices do not typically facilitate tissue integration during healing. Proposed here is a novel combination of processing methods to enhance the tissue integration capability of degradable thermoplastics used in temporary orthopedic fixation devices. The provision of open pores in devices used to affix reconstructed hard tissues would allow for local cells to infiltrate during the healing process. Any openly porous structure is inherently weakened in comparison to its monolithic peers (i.e. decreased relative bulk modulus), such that the matrix materials must be made more resilient in keep the device from becoming friable. These processing methods aim to improve degradable surgical fixation devices at multiple levels of design: both through the inclusion of porous morphology, processing changes, and additives to regain mechanical integrity. Biomimetic pores are added for cellular infiltration by dissolving a porogen’s interpenetrating polymer network. The addition of open pores significantly reduces the bulk stiffness. More uniform phase separation has led to better pores, but the objects still need more resilience. Carbon nanomaterials are used to improve on the mechanics and surface chemistry of the polymer matrix material, composites of polylactide/nanodiamond are produced through cryogenic milling and solid state polycondensation. The addition of minute amounts of functionalized nanodiamond has remedied the brittle failure of the material, by cryogenic milling and solid state polycondensation of poly((D,L)lactide-co-glycolide) and hydroxyl functionalized detonation nanodiamonds. This composite has also demonstrated increased cytocompatability with 7F2 osteoblasts, as analyzed by cellular adhesion through fluorescence microscopy and alamar blue assay. / Bioengineering

Des polyacides lactiques hydroxy téléchélique de masses molaires variées ont été synthétisés par polymérisation par ouverture de cycle du LLA en présence de 1,4 -butane diol. Des polyhydroxybutyrate hydroxy téléchéliques ont été préparés transesterification du PHB et du 1,4-butanediol catalysée par l'acide p-toluène sulfonique .Ces oligomères ont été utilisés pour préparer des polyesters amides fonctionnalisés acrylates ou mercaptans. Dans une approche parallèle, du PCL multi acrylate a été préparé avec succès par copolymérisation par ouverture de cycle de méthacrylate de glycidyle avec du caprolactone. Des copolymères (GMA -co- CL) ayant des masses molaire et de la fonctionnalité variables, ont été préparés en modifiant les paramètres de la réaction tels que le catalyseur, la nature du co-amorceur et le rapport des stœchiométriques des différents réactifs. Les polymères multi acrylates ont été copolymérisés principalement avec l'HEMA sous irradiation UV pour obtenir des réseaux PLA, PHB et PCL segmentés. Les mécanismes de dégradation de ces réseaux ont été étudiés en examinant particulièrement les décompositions des liaisons uréthanes et esters. Des dépolymérisations du PHEMA ont été détectées avec TGA -FTIR à plus haute température (450°C). Pour les réseaux à base de PCL, les propriétés thermo -mécaniques ont été étudiées. Le résultat montre que les phases riches en PCL ont une bonne compatibilité avec le poly HEMA. Les modules caoutchoutiques et l’étendue des températures des zones d’amortissement peuvent être contrôlées en fonction des paramètres réactionnels. Les Polymères multifonctionnels Thiols du PCL, PHA et PLA ont été utilisés pour faire croître des chaines méthacrylates et construire des polymères de type étoile / Hydroxyl telechelic polylactic acids of various molecular weights were synthesized by ring opening polymerization in the presence of LLA and 1,4-butanediol. Telechelic hydroxy polyhydroxybutyrate were prepared transesterification of PHB and 1,4- butanediol catalyzed by p- toluene sulfonic acid. These oligomers were used to prepare polyesteramides functionalised acrylates or mercaptans. In a parallel approach, the PCL multi acrylate was successfully prepared by ring-opening copolymerization of glycidyl methacrylate with caprolactone. Copolymers (GMA-co-CL) with variable molar masses and functionality were prepared by changing the reaction parameters such as catalyst, the nature of the co-initiator and the ratio of different stoichiometric reagents. Multi-acrylated polymers were copolymerized with HEMA under UV irradiation to obtain PLA, PHB and PCL segmented networks. Degradation mechanisms of these networks have been studied by examining particular decomposition of urethane bonds and esters. Depolymerization of the PHEMA was detected with TGA -FTIR at higher temperature (450°C). For PCL based networks, the thermo- mechanical properties were studied. The result shows that the PCL-rich phases have good compatibility with poly HEMA. The rubber and the working temperature range of the damping zones modules can be controlled as a function of reaction parameters. Multi mercapto functionalized polymers with PCL, PLA and PHA segments were used to grow methacrylate polymer chains and build star type

Des copolymères à blocs polylactide-poly(éthylène glycol) (PLA-PEG) ont été synthétisés par polymérisation par ouverture de cycle du L- ou D-lactide en présence de PEG mono- ou dihydroxylé. La masse molaire, la composition, la cristallisation et les propriétés thermiques des copolymères ont été caractérisées à l'aide de la DSC, NMR, GPC, etc. Des micelles biorésorbables ont été obtenues par la méthode dissolution directe sans utiliser de solvants organiques. Des mesures de tension de surface ont permis de déterminer la concentration micellaire critique des copolymères. Les résultats montrent que les micelles mélange L/D sont plus stables que les micelles seules en raison de l'effet stéréocomplexation entre les blocs L-PLA et D-PLA. Les comportements d'agrégation des micelles en milieu aqueux ont été étudiés en détail. Il apparaît que les micelles mélange présentent un nombre d'agrégation inférieur à celui des micelles seules. La dégradation hydrolytique des micelles a été étudiée dans les conditions in vitro. Le paclitaxel a été utilisé comme modèle de principes actifs pour évaluer les comportements in vitro et in vivo des micelles. Les méthodes dissolutio n directe et dialyse conduisent à des résultats comparables en ce qui concerne l'efficacité d'encapsulation et la teneur en principe actif. Les micelles mélange L/D présentent une meilleure capacité d'encapsulation que les micelles seules. Les expériences in vivo montrent que le paclitaxel est distribué dans tous les organes avec concentrations élevées après injection des micelles chargées. En comparaison avec la formulation clinique et les micelles par dialyse, les micelles chargées en paclitaxel par dissolution directe présentent un effet antitumeur plus important. / A series of polylactide-poly(ethylene glycol) (PLA-PEG) block copolymers were synthesized by ring-opening polymerization of L- or D-lactide in the presence of mono- or dihydroxyl PEG. The molar mass, composition, crystallization and thermal properties were characterized by using DSC, NMR, GPC, etc. Bioresorbable micelles were obtained by direct dissolution method without using any organic solvents. Surface tension measurements were used to determine the critical micellar concentration of the copolymers. The results show that L/D mixed micelles are more stable than single ones due to strong stereocomplexation effect between L-PLA and D-PLA blocks. The aggregation behavior of micelles in aqueous medium was investigated in detail. It appears that mixed micelles present lower aggregation number than single ones. The hydrolytic degradation of the micelles was investigated under in vitro conditions. Paclitaxel was used as a model drug to investigate the in vitro and in vivo behavior of micelles as drug delivery system. The direct dissolution method yields comparable drug encapsulation efficiency and loading content as the traditional dialysis method. The drug encapsulation ability is higher for L/D mixed copolymer micelles than single micelles due to stereocomplexation. In vivo experiments show that paclitaxel is widely distributed and kept at high concentration levels in various tissues after administration of drug-loaded micelles. Compared with the current clinical formulation and micelles by dialysis, paclitaxel-loaded micelles by direct dissolution exhibit the highest antitumor ability.

Une série de copolymères à blocs amphiphiles polylactide/poly(éthylène glycol) (PLA/PEG) a été synthétisée par polymérisation par ouverture de cycles, chimie clic, ou couplage des homopolymères PLA et PEG avec des extrémités de chaînes fonctionnels (OH, COOH ou NH2). Différentes configurations de PLA (PLLA et PDLA) ont été considérées pour élucider l'effet de stéréocomplexation sur les propriétés physico-chimiques des copolymères. Les copolymères présentent différentes structures de chaînes, y compris dibloc PEG-PLA, tribloc PLA-PEG-PLA du type ABA ou PEG-PLA-PEG asymétrique du type BAB-type. La masse molaire des copolymères varies de 2 000 à 20 000, et le rapport EO/LA de 1.0 to 7.0 environ. Différents agrégats formés par auto-assemblage tels que des nanotubes, polymersomes, filomicelles, micelles anisotropiques et micelles sphériques ont été obtenus par dissolution directe de copolymères, mélange de différents copolymères, ou mélange de copolymères avec surfactant dans une solution aqueuse. Des modèles théoriques ont été proposés pour simuler la formation des agrégats et expliquer l'évolution de leur taille et morphologie en fonction du rapport EO/LA, longueur de bloc, etc. / A series of amphiphilic polylactide/poly(ethylene glycol) (PLA/PEG) block copolymers was synthesized by ring-opening polymerization, click chemistry, or coupling PLA and PEG homopolymers with functional end groups (OH, COOH or NH2). Different configurations of PLA (PLLA and PDLA) were considered to elucidate the effect of stereocomplexation on the physico-chemical properties of copolymers. The obtained copolymers exhibit diverse chain structures, including PEG-PLA diblock, PLA-PEG-PLA ABA-type or asymmetric PEG-PLA-PEG BAB-type triblock structures. The molar mass of copolymers ranges from c.a. 2,000 to 20,000, and the EO/LA ratio from c.a. 1.0 to 7.0. Diverse self-assembled aggregates, including nanotubes, polymersomes, filomicelles, anisotropic micelles and spherical micelles, were obtained by dissolving the resulting copolymers, mixing different copolymers, or mixing copolymers with surfactant in aqueous solution. Theoretical models are proposed to simulate the formation of aggregates and to explain the evolution of their size and morphology as a function of EO/LA ratio, block length, etc.

L'emballage alimentaire est l'un des principaux acteurs de la préservation de la sécurité alimentaire et de la qualité au cours du stockage. Toutefois, de transferts de masse se produisent entre le l'emballage polymère et les denrées alimentaires. Polylactide (PLA) est un nouveau polymère biosourcé utilisé dans les applications d'emballage. Pour cela son interaction avec des denrées alimentaires a été étudiée dans des conditions réelles d'utilisation. Une méthodologie originale basée sur l'extraction multiple de l'espace de tête (MHE) et l'extraction multiple de l'espace de tête couplée à la microextraction sur phase solide (MHS-SPME) pour la mesure de sorption de composés organiques volatils (COVs) dans le PLA a été développé à des activités faibles et dans le domaine vitreux du polymère. Les COVs ayant une structure chimique modérément hydrophobe et des similarités de structure avec le PLA montrent une forte affinité pour le polymère. Plus surprenant, la forte sorption de composés aromatiques, notamment du benzaldéhyde, a été montrée. En mélange avec d'autres COVs le benzaldéhyde favorise leur sorption par un effet synergique. De plus, même à des activités faibles (0,01) et en présence de benzaldéhyde, la sorption de COVs induit une cristallisation du PLA. En contact avec un aliment aqueux, le PLA se montre résistant à l'hydrolyse et la sorption des matières grasses est faible, même en utilisant des conditions de stockage proches de sa transition vitreuse. L'apparition de COVs pendant le procédé de transformation a été étudiée par MHS-SPME. Des lactides, l'acétaldéhyde et le 2,3-pentanedione étaient détectés après extrusion et thermoformage. Les quantités des deux derniers composés diminuaient cependant pendant le procédé de thermoformage. / Packaging plays a major role in the preservation of food but mass transfer between the packaging material and foodstuff occurs during shelf life leading to the quality deterioration. Polylactide (PLA) is a novel packaging material; therefore its interaction with food was investigated at service conditions. The sorption of ethyl esters, benzaldehyde and 2-nonanone at low concentrations and in mixture and the effects on the thermal properties of PLA were studied. Multiple Headspace Extraction (MHE) and Multiple Headspace coupled to Solid Phase MicroExtraction (MHS-SPME) developed here allow to show a high affinity for moderately hydrophilic molecules sharing structure similarities with PLA such as ethyl acetate. However, a very high affinity for the aromatic structure of benzaldehyde was revealed which seems to favor interaction and sorption of the aroma compounds present in the mixture. At 0.01 activities, a plasticization by aroma compounds was observed and a solvent induced crystallization seemed to be correlated to the sorption of benzaldehyde. The contact between a flavored food emulsion and PLA, using conditions near the PLA glass transition showed that PLA hydrolysis was moderate and oil and aroma compound sorption was low. The formation of VOC during the PLA manufacturing process was assessed by MHS-SPME. Lactides, acetaldehyde and 2,3-pentanedione are VOCs present in PLA after extrusion and thermoforming. The two latter compounds increased after extrusion and then decreased or disappeared after thermoforming.