Tesi sul tema "Biopolymer"
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Mousia, Zoe. "Structural and mechanical properties of biopolymer and biopolymer-sugar blends". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341972.
Testo completoMoffat, Jonathan. "Assembly of biopolymer multilayers". Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435024.
Testo completoSimon, Mark David. "Fast flow biopolymer synthesis". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/117929.
Testo completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 125-129).
This thesis describes the development and application of fast flow solid phase synthesis for the preparation of peptides and phosphorodiamidate morpholino oligomers (PMOs), as well as the application of fast, reliable peptide synthesis to study non-natural protein folding and function. In the first chapter, solid supported peptide synthesis was accelerated using flow by continuously delivering preheated solvents and reagents to the solid support at high flow rate, thereby maintaining maximal concentrations, quickly exchanging reagents, and eliminating the need to heat reagents after they were added to the vessel. In the second chapter, these chemical principles were expanded upon and mechanical challenges particular to accelerated solid phase synthesis were overcome to build a fully automated fast flow peptide synthesizer than incorporates amino acids in as little as 40 seconds each. First, mechanical systems were developed to rapidly switch between the many reagents needed for peptide synthesis while maintaining the proper stoichiometry of all reaction components at all times. Second, conditions under which reagents did not appreciably degrade during storage or synthesis were found. Finally, synthetic outcomes were substantially improved by increasing temperature without degrading the protected, resin bound peptide. The third chapter describes the expansion of fast flow synthesis to PMOs. A 10-fold acceleration of PMO synthesis was realized using mechanical systems adapted from chapter 1, increasing the reaction temperature to 90°C, and introducing a Lewis acid catalyst. The acidity of the deprotection reagent was reduced to prevent cleavage of the backbone during 3' detritylation. In the final chapter, a "D-scan" of two small proteins, the disulfide-rich Ecballium elaterium trypsin inhibitor II (EETI-II) and a minimized Z domain of protein A (Z33), is reported. For each protein, the chirality of one amino acid at a time was inverted to generate a series of diastereomers, and study the critical stereocenters of EETI-I and Z33. Twelve out of 30 EETI-II analogs folded and were high-affinity trypsin inhibitors, but most active analogs were less stable to reduction than EETI-II. Similarly, twelve Z33 analogs retained high binding affinity to IgG, but most were substantially less stable than WT-Z33.
by Mark David Simon.
Ph. D.
Kvien, Ingvild. "Characterization of Biopolymer Based Nanocomposites". Doctoral thesis, Norwegian University of Science and Technology, Department of Engineering Design and Materials, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1479.
Testo completoThe field of nanocomposites is gaining considerable attention due to its potential for providing new materials with extraordinary physical properties compared to traditional composite materials. In this thesis cellulose nanowhiskers (CNW) were separated from microcrystalline cellulose (MCC) and dispersed in different biopolymer matrices to obtain polymer nanocomposites based on renewable resources. Moving from microstructure to nanostructure creates new challenges for structure characterization of materials. The overall aim of this work was to characterize the structure of CNW and their nanocomposites with different matrices. The sample preparation and microscopic examination of the bionanocomposites showed to be challenging because they are non-conductive, soft and water sensitive materials and consist of low atomic number elements. In the studies field emission scanning electron microscope was found to be a convenient and important first step in the analysis of the nanocomposite structure. More detailed information about the distribution of CNW was however obtained using transmission electron microscope (TEM) and atomic force microscope. X-ray diffraction analysis showed that the MCC consisted of both amorphous and crystalline regions. The sulfuric acid isolation treatment removed the amorphous regions and separated the cellulose nanowhiskers. From TEM analysis the size of the whiskers was measured to be 210 ± 75 nm in length and 5 ± 2 nm in width. It was also possible to separate the CNW from MCC using dimethyl acetamide containing a small amount of LiCl. It was however difficult to remove the organic solvent after treatment. CNW were well distributed in a hydrophobic matrix by the aid of a surfactant. Untreated CNW or untreated layered silicates in a thermoplastic starch matrix resulted in well dispersed nanocomposites. It was further found that it was possible to obtain oriented CNW in a matrix after exposure to a magnetic field. The dynamic mechanical thermal analysis of the different nanocomposites in this thesis showed that well dispersed cellulose whiskers have a large potential for improving the thermal mechanical properties of biopolymers.
Paper VII: The original publication is available at www.springerlink.com
Puaud, Max. "Mechanical properties of biopolymer films". Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/11624/.
Testo completoMuguda, Viswanath Sravan. "Biopolymer Stabilised Earthen Construction Materials". Thesis, Pau, 2019. http://www.theses.fr/2019PAUU3027.
Testo completoEarthen structures (i.e. structural units manufactured from soil) are often regarded as sustainable forms of construction due to their characteristically low carbon footprint. Unstabilised earthen construction materials have low embodied energy, excellent hygroscopic properties and recycling potential. However, in this form, the material is susceptible to deterioration against water ingress and most modern earthen construction materials rely on cement to improve their durability properties. Using cement leads to compromises in hygroscopicproperties and recyclability potential. In this situation, it is imperative to look for alternatives to cement, which can address these issues without compromising on the desired engineering properties of these materials. This thesis explores the use of biopolymers, namely guar and xanthan gum, as stabilisers for earthen construction materials. As an initial step, an experimental campaign was undertaken to understand biopolymer stabilisation and optimise their use to stabilise earthen construction materials. The results from this campaign reveal that biopolymer stabilised soils derive their strength through a combination of soil suction and hydrogel formation. The intrinsic chemical properties of the biopolymer affect the nature of hydrogel formation and in turn strength. In a subsequent campaign of experimental work, hydraulic and mechanical properties of these biopolymer stabilised soils were determined. The hydraulic properties of the biopolymer stabilised soils indicate that for the range of water contents, the suction values of biopolymer stabilised soils are higher than unamended soils. The soil water retention curves suggest that both biopolymers have increased the air entry value of the soil while affecting the void size distribution. Shear strength parameters of biopolymer stabilised soils were obtained through constant water triaxial tests, and it was noted that both biopolymers have a significant and yet different effect on soil cohesion and internal friction angle. With time, guar gum stabilised soils derive strength through the frictional component of the soil strength, while xanthan gum stabilised soil strength has a noticeable contribution from soil cohesion. Macrostructural analysis in the form of X-RCT scans indicate that both biopolymers form soil agglomerations and increase overall porosity. The void size distribution curves obtained from XRCT scanning complement the findings of the suction tests. As a final study, the performance of biopolymer stabilised earthen construction materials was assessed as a building material. Durability performance of these materials against water ingress was evaluated, and it was noted both biopolymers provide satisfactory stabilisation to improve the erosional resistance of the material. In conclusion, unlike cement, biopolymer stabilised earthen materials do not compromise on hygroscopic properties and have better mechanical performance than unamended earthen construction materials. Finally, recyclability tests suggest that apart from improving the strength, durability and hygroscopic properties of the material, biopolymer stabilised earthen construction materials have a better potential for recycling without any environmental concerns
Kubalová, Barbora. "Fázově separované systémy biopolymer-lipid". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240581.
Testo completoEdmonds, Christopher Michael. "Computational investigations of biopolymer translocation through nanopore devices". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50260.
Testo completoBondeson, Daniel. "Biopolymer-based Nanocomposites : Processing and Properties". Doctoral thesis, Norwegian University of Science and Technology, Department of Engineering Design and Materials, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1923.
Testo completoThe aim of this study was to produce biopolymer-based nanocomposites using extrusion as an industrially adaptable manufacturing process, and to study how this production process influenced the structure and properties of the nanocomposites produced. Cellulose nanowhiskers (CNWs) were prepared and used as nanoreinforcement in two different biopolymers, polylactic acid (PLA) and cellulose acetate butyrate (CAB). The CNWs were added to PLA and CAB in order to improve the thermal and mechanical properties of these polymers. Two different preparation methods of CNWs were used; isolation by sulfuric acid hydrolysis and isolation by hydrochloric acid hydrolysis. Different feeding procedures were used and evaluated during compounding. The CNW suspension was either freeze-dried and dry-mixed with the polymer prior the extrusion, or fed as a suspension directly into the extruder during compounding. However, the CNW suspension required modification in order to prevent re-aggregation of the whiskers as the dispersing medium was removed and to uniformly disperse the whiskers in the polymer matrix. In order to improve the dispersion of the CNWs in the matrix, a surfactant and a water soluble polymer were used for PLA, and a plasticizer was used for CAB. No major improvements in mechanical or thermal properties were seen for the PLA/CNW nanocomposites, either because of degradation of the matrix or poor dispersion of the whiskers. The material system of CAB/CNW was more successful and showed great improvements in mechanical and thermal properties. This study demonstrated that it is possible to produce nanocomposites by pumping a suspension of CNWs into the extruder during compounding, but compatibility between the CNWs and the matrix is required.
Morris, Eliza. "Mechanics and Dynamics of Biopolymer Networks". Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11647.
Testo completoEngineering and Applied Sciences
Danks, Ashleigh Edwards. "Biopolymer synthesis of pourous carbon nanocomposites". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7730/.
Testo completoHumphries, Daniel. "Structural aspects of modelling biopolymer networks". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:f8a5fe54-c2e6-463a-9c2f-9b234ce6947a.
Testo completoJones, Erica Nicole. "Development of Biopolymer Based Resonant Sensors". University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1272992841.
Testo completoLiu, Weipeng. "Biopolymer-based ocular drug delivery systems". Diss., Connect to online resource - MSU authorized users, 2008.
Cerca il testo completoEsmaeili, Morteza. "Thermoset biopolymer reinforced with carbon-nanotubes". Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-21320.
Testo completoPlotěná, Michaela. "Fázová separace v systému aminojíl-biopolymer". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2017. http://www.nusl.cz/ntk/nusl-316185.
Testo completoBellomo, Francesca. "Biopolymer based scaffolds for tissue engineering". Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/4474.
Testo completoTissue engineering in the orthopedic field is mainly focused on the development and design of material to serve as a temporary extracellular matrix or scaffold to overcame the limitation of actual treatments. In fact, current treatments are based on autologous or autogenous bone grafts and as an alternative to these, metals and ceramics. The limitation of this kind of implants is related to shortage of autograft that can be obtained and to donor site morbidity; the possibility of immune rejection and of pathogen transmission from donor to host in the case of allograft; the poor overall integration with the tissue at the implantation site for the metal and ceramic. The aim of study is the development of bio-composite scaffolds for orthopedic applications, based on the combination of polysaccharides (mainly alginate, Alg) engineered with bioactive molecules and nano-hydroxyapatite (nHap). The first step was the synthesis and characterization of the different components of the scaffold. The nHap was synthesized with sol-gel method and the obtained crystals have been chemically and morphologically characterized by mean of Raman spectroscopy, X-Ray Diffraction and Transmission Electron Microscopy. All the collected results confirm the chemical composition of nHap and information about the average dimension of crystals (120nm). The synthesized nHap was used to produce composite hydrogels of Alg and nHap. The porous structure was achieved through freeze-casting. The obtained scaffold was characterized with µCT (µComputed tomography) and confocal microscopy; the histomorphometric data were compared with the parameters of native tissue with an high level of similarity between trabecular bone and scaffolds structure. Subsequently, the scaffolds have been investigated for their cytocompatibility and the results shows high rate of proliferation of cells seeded into the scaffold. The modification with specific proteins or peptides of the backbone of a polymer can be an effective strategy to tailor and control cell attachment, migration, proliferation and differentiation. Incorporation of peptide motifs containing sequences that are recognized by integrin receptors, such as arginine-glycine-aspartic acid (RGD)-based sequences, are now a common strategy to enhance the biological properties as well as differentiation and proliferation of a variety of cells, including osteoblasts. Along the same line, reducing bacterial adhesion is important since microorganism surface attachment is the first critical step in the development of implant-associated infections. To introduce bioactive molecules and antimicrobial agents, enhancing in this way the biological property of the scaffolds, Chitlac was exploited as vector. Chitlac is a lactitolated-derivative of chitosan that can be modified by chemical grafting of bioactive peptides like RGD and that can be use to produce and stabilize silver nanoparticles (nAg) with antimicrobial activity. By adsorbing the Chitlac on the scaffold’s surface we spread the bio-signal inside the structure to induce a specific cell reaction. Alg/nHap scaffolds were coated with Chitlac-RGD and Chitlac-nAg, respectively, and on those, biological and antimicrobial in vivo tests were performed. For both scaffolds we observed good cytocompatibility and, in the case of scaffold with RGD, an improved cell proliferation; moreover, the scaffold with nAg showed a high level of antimicrobial activity. According the results obtained from the previous cytocompatibility tests, preliminary cytocompatibility in vivo tests were performed. The animal model was New Zealand rabbit and the produced scaffolds were inserted into bone defects on femur. Post-operatively, three fluorochromes were administered sequentially every week. After 5 weeks the rabbits were sacrificed and all the implanted bones were analyzed using µ-CT and light and confocal microscopy. We observed a high level of osteointegration of the scaffolds and ingrowth of newly deposited structured lamellar bone inside them, indicating good osteoconductive properties. In conclusion, the developed scaffolds have suitable biological properties both bioactive and antimicrobial. The in vitro results shows a high level of cytocompatibility for all the scaffolds studied and that the presence of Chitlac-nAg does not compromise the compatibility of scaffolds. In the case of scaffolds modified with RGD the results confirm that the presence of bioactive molecule is able to enhance the healing process also with respect to the BAG (BioActive Glass) control. The findings of the present study revealed that the structures here developed could serve as promising filler for orthopedic application.
XXIII Ciclo
1983
Wolff, Lars. "Inelastic mechanics of biopolymer networks and cells". Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-78203.
Testo completoCurtis, Daniel Jonathan. "Rheological and microstructural studies of biopolymer systems". Thesis, Swansea University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678405.
Testo completoPaes, Sabrina Silva. "Understanding the mechanical properties of biopolymer films". Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.490994.
Testo completoAnderson, V. J. "Phase separation and gelation in biopolymer mixtures". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595515.
Testo completoSuwannasom, Nittiya [Verfasser]. "Biocompatibility of Biopolymer Submicron Particles / Nittiya Suwannasom". Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1202044433/34.
Testo completoBradley, T. "A rheological investigation of biopolymer thermal transitions". Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234681.
Testo completoTwaites, Beverley Ruth. "Polymer-biopolymer interactions : applications in gene delivery". Thesis, University of Portsmouth, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402281.
Testo completoBalinskiy, M., Тетяна Миколаївна Плохута, Татьяна Николаевна Плохута e Tetiana Mykolaivna Plokhuta. "Apatite-biopolymer materials and coatings for biomedicine". Thesis, Sumy State University, 2020. https://essuir.sumdu.edu.ua/handle/123456789/77838.
Testo completoWelsh, Calum D. M. "Infrared and multivariate studies of a biopolymer". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41503/.
Testo completoPatil, P. A. "Study of biopolymer gels based on polyhydroxyalkonates". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4356.
Testo completoOhlhoff, Colin Walter. "Biopolymer gene discovery and characterization using metagenomic libraries". Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1801.
Testo completoXu, Zuxiang. "Underwater Adhesion between Biopolymer Model Surfaces and Hydrogels". Electronic Thesis or Diss., Université Paris sciences et lettres, 2022. http://www.theses.fr/2022UPSLS020.
Testo completoWhile the adhesion between synthetic materials has been rather well-studied experimentally and theoretically, there is still a lack of knowledge on bioadhesion, which could be tackled with biopolymer systems which could mimic biosurfaces, biotissues and bioadhesives. However, this idea is limited by the difficulty in designing a model structure and controlling the physical chemistry properties of biopolymer-made materials. Bioadhesion mechanisms can be tackled by studying the underwater adhesion between hydrogel adhesives and solid substrates modified by hydrogel thin films. This allows to separate interfacial contribution with molecular specific interactions and bulk contribution with viscoelastic properties to adhesion. First, a model system based on gelatins has been designed and underwater adhesion promoted by electrostatic interactions was investigated. On one side, stable surface-attached gelatin films with finely adjustable thickness and swelling were achieved using Cross-Linking and Grafting (CLAG) strategy. On the other side, dual-crosslinked gelatin hydrogel adhesives were synthesized by adding chemical crosslinks to physical gelatin networks. The microscopic structure of both physical and chemical crosslinks was well-controlled, with the determination of the chain length between crosslinks from shear modulus and phantom network model. Underwater adhesion measured by probe tack tests showed that dual-crosslinked gelatin hydrogels have the same adhesive properties at all temperatures even if their strength decreases with heating. We were also able to separate the effects of physical and chemical networks on adhesion. Second, the underwater adhesion between double-networks containing carrageenan and solid substrates modified by micro-patterned hydrogels was investigated. It was shown that the smaller the micro-patterns the higher the adhesion energy. This work has provided an insight of the physico-chemical and physical parameters that control underwater adhesion of biopolymers systems such as the bulk viscoelastic properties, the charge and the topography of the surface. It would help for better understanding bioadhesion and designing underwater adhesives
Pettignano, Asja. "Alginate : a versatile biopolymer for functional advanced materials". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2016. http://www.theses.fr/2016ENCM0004.
Testo completoAlginates, polysaccharides produced by brown algae, are linear block-copolymers formed by mannuronate (M) and guluronate (G) units. Because of their huge natural abundance, cheapness and physicochemical properties, alginates represent a highly attractive and still relatively unexplored class of biopolymers for applications in the field of advanced materials. In this context, the present work aimed to enrich the range of possible applications of alginate-derived materials, making the most of the peculiar features of this class of natural polysaccharides. In particular, the preparation of alginate-based active materials to be employed in the catalysis, adsorption and biomedical field was studied, achieving encouraging results in all the tested applications. The beneficial use of alginic acid in heterogeneous catalysis, both as reaction promoter and as support for the heterogeneization of an organocatalyst, was demonstrated. The activity of the material was found highly dependent on the accessibility of the active functions, highlighting the advantage of employing more accessible alginate formulations. The texturation of alginates was further advantageous for the preparation of materials with improved flowability. Alginic acid foams, bearing a hierarchical macro-mesoporous structure were developed by means of a simple procedure. Accurate characterization was performed to optimize the preparation procedure and to correlate the textural properties of the obtained materials with the parameters used. The interest of the prepared alginic acid foams was demonstrated in a model application, the adsorption of methylene blue from aqueous solutions, both in batch and in flow conditions. The possibility to easily modify alginate functional groups, coupled with the biocompatible and biodegradable nature of alginates, was finally employed for the development of self-healing gels, thanks to the formation of two types of dynamic covalent interactions: Schiff base and boronate ester bonds. Both the examined systems presented a marked ability to recover after damage, even if the extent of the recovery and the stability of the gels was highly dependent on the preparation parameters and environmental conditions used. The results obtained in the course of this study clearly demonstrate how a full comprehension and conscious employment of alginate physicochemical properties can maximize the potential of this sustainable resource in the field of material chemistry
Ward-Passey, Claire Elizabeth. "Interfacial Studies of Ternary Phase Separated Biopolymer Solutions". Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485080.
Testo completoBoyd, Matthew. "The phase behaviour of xanthan based biopolymer mixtures". Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/11588/.
Testo completoWang, Yan. "Exploring Biopolymer-Clay Nanocomposite Materials by Molecular Modelling". Doctoral thesis, KTH, Teoretisk kemi och biologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166299.
Testo completoI denna avhandling har molekylär modellering och molekyldynamisk (MD) simulering använts för att studera modellsystem för bio-nanokompositer bestående av montmorillonit-lera samt två olika sorters biopolymerer – xyloglukan (XG) och kitosan (CHS). Båda dessa polymerer är naturligt förekommande och mycket vanliga. De är dessutom förnyelsebara och kostnadseffektiva. Då polymererna förstärkts med nanopartiklar av montmorillonit får det resulterande kompositmaterialet en unik kombination av egenskaper såsom mekaniska, elektriska, termiska och barriär egenskaper etc. Genom att använda molekyldynamiska (MD) simuleringar, studeras här växelverkan mellan dessa biopolymerer och lernanopartiklar (Mnt) på grundläggande atomistisk detaljnivå. Mellan XG och Mnt i ett fullt hydrerat system kunde stark bindningsaffinitet påvisas. Den dominerande drivkraften för affiniteten var entalpi, d.v.s. potentiell växelverkansenergi. Den adsorberade XG-kedjan antar en platt konformation på ytan. Ett förslag utifrån simuleringsresultaten var att galaktosresidyn i xyloglukanets sidokedja underlättar adsorptionen till lerytan. Simuleringarna kunde också visa att adsorption av XG till Mnt beror starkt på motjonernas hydreringsförmåga. Bindningsaffiniteten mellan XG och Mnt var som starkast i K-Mnt/XG- systemet. Därefter följde, i minskande ordning, Na-Mnt/XG, Li-Mnt/XG och Ca-Mnt/XG. Det kunde visas att strukturen vid gränsytan styrs av konkurrerande mekanismer mellan joner, vatten och XG. Dimensionsstabilitet vid fuktexponering, d.v.s. förmågan hos ett material att motverka svällning, är en viktig egenskap för biopolymer-lernanokompositer. Ren lera sväller signifikant även vid låga fukthalter. Dock kunde MD simuleringar visa att ett modellsystem av XG-Mnt behåller sitt ursprungliga interlamellära avstånd vid hydreringsnivåer under 50%, vilket indikerar ett stabilare material. Vid högre hydrering uppmättes dock svällningen vara densamma som för ren lera. I CHS-Mnt-systemet visade det sig att direkt elektrostatisk växelverkan med signifikant styrka mellan laddningar på polymer och Mnt-yta spelar störst roll för kompositformeringen. Olika effekt på polymer-lerväxelverkan uppnåddes genom att variera acetyleringsgraden (DA) respektive protoneringsgraden (DPr). För den tungt acetylerade CHS-polymeren (DA > 50%, även kallad kitin) visade sig den starka vidhäftningen bero på korrelation mellan acetylgrupperna och motjonerna som i sin tur verkade som ett elektrostatiskt “lim”. På liknande sätt kunde den svaga vidhäftningen mellan fullt deprotonerad (DPr = 0%) neutral CHS och lera förklaras med en betydligt svagare korrelation mellan aminogrupperna och motjonerna. Spänning-töjningsbeteendet hos CHS-Mnt modellen visar att dess mekaniska egenskaper beror kraftigt på volymsandelen Mnt och graden av exfoliering i kompositen. Materialets struktur är nära relaterat till materialegenskaperna. Framtiden för nanokompositer av biopolymerer och lera är ljus då de kan komma att ersätta oljebaserade plaster och användas frekvent i våra dagliga liv. Materialen kommer successivt förbättras genom utveckling av experimentella metoder i kombination med molekylmodellering för ökad förståelse för växelverkan mellan polymer, lera, vatten, joner och lösningsmedel.
本论文利用分子动力学模拟技术研究了两种备选生物大分子与蒙脱土(Montmorillonite, Mnt)(一种粘土)组成的生物纳米复合材料,分别是木葡聚糖(Xyloglucan, XG)/蒙脱土和壳聚糖(Chitosan, CHS)/蒙脱土。木葡聚糖与壳聚糖都是自然界广泛存在的生物大分子,资源丰富且取材面宽,提取及加工成本低廉,加之可以生物降解并可再生,是优秀的生物复合材料备选原料。经过蒙脱土纳米颗粒加固后,这些基于生物大分子的复合材料将获得多功能且有多种独特特性相结合的优点,比如,更好的力学性能,生物可降解,良好的导电性能,传热性能和屏蔽气体与液体侵扰的能力等等。论文中,我们采用分子动力学模拟的方法着重对生物大分子与蒙脱土在界面上的粘附相互作用机理进行了深入探讨。 首先,对于木葡聚糖/蒙脱土纳米复合材料,我们发现糖分子与土分子间有着很强的天然亲和力。研究证明它们之间的这种相互作用,热焓是主要的推动力,也就是糖和土分子间的相互作用势能。含有半乳糖残基的木葡聚糖分子(本文中亦称天然木葡聚糖分子)吸附到粘土表面后,分子构型呈现扁平状,半乳糖残基似有辅助木葡聚糖大分子吸附到粘土颗粒上的作用。 进一步研究发现,木葡聚糖分子在粘土表面上的吸附与溶液中抗衡离子的水和作用密切相关。在钾离子平衡的糖/粘土系统中,糖分子与土分子的相互作用最强,钠离子平衡的糖/粘土系统次之,紧接着是锂离子平衡的糖/粘土系统,最弱的是钙离子平衡的糖/粘土系统。研究发现,离子,水分子,以及糖分子在粘土层间的竞争机制在糖分子的粘附过程中起着重要的作用。 材料暴露于潮湿环境中的尺寸稳定性,也就是材料抗肿胀的能力是生物大分子/蒙脱土所构成的复合材料的重要参数。蒙脱土自身即使在很低的潮湿环境下就会有明显地膨胀现象,然而,对木葡聚糖/蒙脱土复合材料来说,尺寸稳定性可以在水和值低于50%以下有效保存。其夹层尺寸的稳定保持暗示了材料在这个程度的潮湿环境下的稳定性。然而,当水和值高于50%时,木葡聚糖/蒙脱土复合材料将出现明显的肿胀现象,表现在夹层尺寸的明显增大,且其膨胀速率与粘土自身的膨胀速率逐渐趋于相当水平。 其次,对于壳聚糖/蒙脱土复合材料,我们发现由电荷-电荷间直接产生地强烈的静电吸引作用是壳聚糖分子与蒙脱土分子相互粘附并构成复合材料的关键因素。通过改变壳聚糖分子的乙酰化程度(Degree of acetylation, DA)和质子化程度(Degree of protonation, DPr),糖分子与土分子的相互作用有着显著地不同。对于乙酰化程度(DA)高于50%的壳聚糖分子(亦成为甲壳素分子chitin, CHT),电中性的甲壳素分子与土分子间的强吸附作用源于乙酰基功能团与抗衡离子的强相关性。抗衡离子此时扮演着类似于“电子胶”的作用,可以有效地将电中性的甲壳素分子与土分子粘结在一起。类似地,当质子化程度最低时,亦即壳聚糖分子完全非质子化,即呈现电中性时,较差的糖/土吸附作用源于氨基功能团与抗衡离子的较弱的相关性。 进一步对壳聚糖/蒙脱土复合材料的分子系统进行应力应变计算发现,复合材料的力学性能直接受蒙脱土体积分数和其剥离程度的影响,通常,粘土的体积分数越大体系的力学性能越高,且剥离程度对材料的整体性能也有直接影响。因此,材料的结构与其性能的表征有着密切联系。 我们相信生物大分子与蒙脱土构成的生物复合材料有着光明的前景,可以取代石油提取物制成的塑料材料,并将能够广泛应用在日常生活中。通过实验技术的改善和应用分子模拟技术对复合材料体系中生物大分子,蒙脱土分子,水分子,离子,溶液环境等混合物质相互作用的理解增加,这种可再生的新材料将会得到重要改进,这也是整本论文的主旋律。
QC 20150520
Bio-nanocomposites
Suntivich, Rattanon. "Inkjet-assisted printing of encapsulated polymer/biopolymer arrays". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52300.
Testo completoKeenan, Robert Daniel. "CE and NMR studies of some biopolymer mixtures". Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387621.
Testo completoBamford, Rebecca. "Biopolymer supports for metal nanoparticles in catalytic applications". Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675702.
Testo completoHasnain, Imran Ali. "Measurement of anisotropy in biopolymer gels via microrheology". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612871.
Testo completoTraitler, Nikolaus. "Physical and mechanical properties of biopolymer cellular solids". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612327.
Testo completoBarnes, Samesha Rosánne. "Injectable biopolymer gel compositions for neural tissue repair". [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024088.
Testo completoTasker, Alison Louise. "Water resistance properties of water-based biopolymer films". Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/5847/.
Testo completoRapp, Telana. "Isolation and characterisation of genes encoding biopolymer manufacturing enzymes". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/19968.
Testo completoENGLISH ABSTRACT: Biopolymers exhibit the required material properties to replace conventional, non-biodegradable, petroleum-based polymer products. They have a closed carbon cycle, making them carbon neutral and environmentally friendly. Biopolymers are produced from non-toxic substrates during in vivo enzymatic reactions. Biosynthesis of the most commercially important biopolymers is too complex to be reproduced in in vitro reactions. Identification of the genes responsible for their biosynthesis has been under investigation, with some pathways already elucidated. The genes involved in the biosynthesis of these polymers have been targeted for genetic manipulation to increase productivity, as well as create tailor-made polymers. Novel biopolymers and the genes responsible for their synthesis are of interest for their potential commercial applications. Bacteria produce a wide range of biopolymers and are being implemented as the bio-factories for biopolymer production. They are capable of utilising easily accessible and renewable carbon sources such as sucrose for polymer biosynthesis. Bacteria thus allow for economical production of these environmentally beneficial polymers. In this study, the gene responsible for the production of an unknown biopolymer from an unknown bacterium was identified. The biopolymer producing bacteria were grown on media enriched with sucrose as carbon source, during an expression library screening in a previous study. Expression library technology was used to search for the gene and it was identified as a 424 amino acid levansucrase which had a 100% homology to Leuconostoc mesenteroides M1FT levansucrase (AAT81165.1). Biopolymer analysis revealed that the biopolymer was a levan, a polysaccharide consisting of only fructose molecules with a molecular weight of ± 5 kDa. Analysis of a 516 bp fragment of the 16S rRNA determined that the unknown bacteria were a Pseudomonas species.
AFRIKAANSE OPSOMMING: Bio-polimere besit noodsaaklike materiële eienskappe wat toelaat dat dit konvensionele, nie bio-afbreekbare, petroleum-gebasseerde polimeer produkte kan vervang. Hulle het n geslote koolstof kringloop en is dus koolstof neutraal en omgewingsvriendelik. Bio-polimere word vervaardig van nie-toksiese substrate, gedurende ensiematiese reaksies in vivo. Die belangrikste kommersiële bio-polimere se ensiematiese produksie is te kompleks om in ʼn in vitro reaksie te herproduseer. Ondersoeke tot die identifikasie van die gene wat verantwoordelik is vir die produksie van die polimere is onderweg, en sommige produksie paaie is reeds bekend. Die bekende gene word geteiken vir genetiese manipulasie om hulle produktiwiteit te vermeerder en om unieke polimere te produseer. Unieke bio-polimere en die gene wat vir hul produksie verantwoordelik is, is van belang vir hulle potentiële implimentering in komersiële toepassings. Bakteria produseer ʼn verskeidenheid bio-polimere en word as die bio-fabrieke vir polimeerproduksie geimplimenteer. Hulle kan maklik bekombare koolstofbronne, soos sukrose, gebruik om bio-polimere te produseer. Bakteria laat dus die ekonomiese produksie van hierdie omgewingsvriendelike polimere toe. In hierdie studie word die geen wat verantwoordelik is vir die produksie van ʼn onbekende bio-polimeer van ʼn onbekende bakteria, geidentifiseer. Die bakteria was gevind op media, wat verryk was met sukrose as koolstofbron, tydens ʼn vorige studie, waartydens ʼn uitdrukkingsbiblioteek gesif was op hierdie media. Uitdrukkingsbiblioteek tegnologie was gebruik om die geen te vind. Die geen was geidentifiseer as ʼn 424 aminosuur, homo-fruktose-polimeer produseerende geen, ʼn “levansucrase”. Die geen het ʼn 100% homologie met die M1FT “levansucrase” geen (AAT81165.1) van Leuconostoc mesenteroides gehad. Analise van die bio-polimeer het bepaal dat die polimeer ʼn polisakkaried was, wat slegs uit fruktose molekules bestaan het. Die molekulêre gewig van die polimeer was ± 5 kDa. Analise van ʼn 516 bp fragment van die 16S rRNS het bepaal dat die bakteria van die Pseudomonas spesie afkomstig was.
Piluso, Susanna. "Design of biopolymer-based networks with defined molecular architecture". Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/5986/.
Testo completoIn dieser Arbeit wird die Synthese Biopolymer-basierter Hydrogelnetzwerke mit definierter Architektur beschrieben. Um Materialien mit definierten und einstellbaren Eigenschaften zu erhalten, wurde die chemoselektive Kupferkatalysierte Azid-Alkin-Cycloadditionsreaktion (auch als Click-Chemie bezeichnet) für die Synthese Gelatine-basierter Netzwerke eingesetzt. Alkin-funktionalisierte Gelatine wurde mit vier verschiedenen Diazid-Quervernetzern oberhalb der Gel-Sol-Übergangstemperatur umgesetzt, um die Formierung tripelhelikaler Bereiche durch Gelatineketten zu unterdrücken. Durch Variation der Menge an Quervernetzer (und damit der Netzdichte) sowie der Länge und Flexibilität der Quervernetzer konnten u.a. die Quellung (Q: 150-470 vol.-%) sowie der Young’s - und Schermodul im kPa Bereich eingestellt werden (E: 50 kPa - 635 kPa, G’: 0.1 kPa - 16 kPa). Um die Netzwerkarchitektur zu verstehen, wurde eine Methode basierend auf dem Labeln unreagierter Azid- und Alkingruppen im Hydrogel entwickelt. Die Gelatine-basierten Hydrogele wurden mit Alkin-funktionalisiertem Fluorescein umgesetzt, um freie Azidgruppen zu detektieren, die bei einem Grafting entstehen. Darüber hinaus wurden die Hydrogele mit Azid-funktionalisiertem Fluorescein reagiert, um die Menge an freien Alkingruppen zu bestimmen, die zudem potentiell für die Anbindung bioaktiver Moleküle geeignet sind. Quervernetzung, Grafting, und die Anzahl freier Alkingruppen konnten dann mit Hilfe der konfokalen Laser Scanning Mikroskopie und der Fluoreszenzmikroskopie qualitativ und quantitativ nachgewiesen werden. Gegraftete Ketten wurden in Systemen nachgewiesen, die mit einem Überschuss an Quervernetzer hergestellt wurden, entstanden aber auch beim Einsatz äquimolarer Mengen Alkin- und Azidgruppen. Im letzteren Fall wurde in Abhängigkeit von der Struktur des Diazids unterschiedliche Anteile gegrafteter Ketten festgestellt. 0.1 mol-% von gegrafteten Ketten wurden für 4,4’-Diazido-2,2’-stilbendisulfonsäure gefunden, 0.06 mol-% für 1,8-Diazidooktan, 0.05 mol% für 1,12-diazidododecan und 0.022 mol-% für PEG-Diazid. Diese Beobachtung kann durch die unterschiedliche Flexibilität der Vernetzer erklärt werden. Während der Netzwerkbildung werden die Bewegungen der Gelatineketten eingeschränkt, so dass kovalente Netzpunkte nur erhalten werden können, wenn der Vernetzer lang und flexibel genug ist, um eine andere Alkingruppe zu erreichen. Die Strategie zur Synthese von Biopolymer-basierten Hydrogelen mit einstellbaren Eigenschaften wurde von Gelatine- auf Hyaluronsäure-basierte Gele übertragen. Alkin-funktionalisierte Hyaluronäure wurde mit drei verschiedenen Diaziden quervernetzt, wobei Menge, Länge, und Flexibilität des Quervernetzers variiert wurden. In dieser Weise wurden sehr weiche Hydrogele mit E-Moduli im Bereich von 0.5-3 kPa hergestellt. Die Variation der Vernetzungsdichte und des Vernetzertyps beeinflusste weiterhin den hydrolytischen und enzymatischen Abbau der Hydrogele. Hydrogele mit einem geringerem Anteil an Quervernetzer wurden schneller abgebaut als solche mit einem höheren Quervernetzeranteil. Darüber hinaus konnte gezeigt werden, dass Hydrogele mit Quervernetzern mit einer rigiden Struktur deutlich langsamer degradierten als Hydrogele mit flexibleren Quervernetzern. Während des hydrolytischen Abbau wurden die Materialien weicher, behielten aber ihre Form bei, was mit einem Bulk-Abbau-Modell übereinstimmt. Während des enzymatischen Abbaus hingegen änderten sich die Materialeigenschaften kaum, jedoch wurden die Proben kleiner. Diese Beobachtung stimmt mit einem Oberflächenabbaumechanismus überein. Da in allen vorgestellten Systemen nur eine kleine Menge synthetischer Vernetzer eingesetzt wurde (0.002 – 0.02 mol%), können die Materialien noch als Biopolymer-basierte Materialien klassifiziert werden. Jedoch enthalten die Materialien synthetische Abschnitte. In Zukunft könnte es interessant sein, einen Zugang zu Materialien zu haben, die ausschließlich aus Biopolymeren aufgebaut sind. Daher wurde der Zugang zu Biopolymer basierten Telechelen untersucht, die potentiell als Vernetzer dienen können. Dazu wurden durch die kontrollierte Spaltung von Gelatine mit Hydroxylamin Gelatinefragmente mit definiertem Molekulargewicht hergestellt. Hydroxalamin reagiert unter Spaltung mit der Amidbindung zwischen Asparagin und Glycin, wobei Aspartylhydroxamate und Aminoendgruppen entstehen. Die Reaktion von Gelatine mit Hydroxylamin ergab Fragmente mit Molekulargewichten von 15, 25, 37, und 50 kDa (bestimmt mit SDS-PAGE), und die Formierung dieser Fragmente war unabhängig von den weiteren Reaktionsbedingungen und der Reaktionszeit. Jedes dieser Fragmente kann potentiell für die Synthese von Hydrogelen eingesetzt werden, die ausschließlich aus Biopolymeren bestehen.
Cornwell, Kevin G. "Collagen and fibrin biopolymer microthreads For bioengineered ligament regeneration". Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050407-104302/.
Testo completoKeywords: Ligament; ACL; Collagen; Fibrin; Microthread; Fiber; Thread; FGF-2; Fibroblast; Tissue regeneration; Tissue engineering. Includes bibliographical references.
Huang, Yaduo. "The flow behaviour of xanthan biopolymer in porous media". Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1456.
Testo completoFarhat, Imad Akil. "Molecular mobility and interactions in biopolymer-sugar-water systems". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339660.
Testo completoTobitani, Atsumi. "Rheological and structural studies of biopolymer gels and gelation". Thesis, King's College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338701.
Testo completoFarnell, S. J. "An investigation into the structure of some biopolymer systems". Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370701.
Testo completoKasapis, Stefan. "Conformations and interactions of single and mixed biopolymer systems". Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358940.
Testo completoWERNER, PATRICIA BORBA. "ANALYSIS OF A BIOPOLYMER FOR DEVELOPMENT OF A TOOTHBRUSH". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=15334@1.
Testo completoO uso indiscriminado de polímeros derivados do petróleo como matériaprima tem resultado no acúmulo de resíduos de lenta biodegradabilidade nos aterros sanitários, pois os plásticos convencionais levam cerca de meio século para serem degradados. Diante desse cenário, o estudo de polímeros derivados de fontes renováveis, os biopolímeros, é totalmente relevante e, em muitos casos, os polímeros derivados do petróleo podem ser substituídos por biopolímeros. Pesquisas apontam a escova dental como um produto ideal para sofrer esta mudança, por ser um produto de uso pessoal rapidamente descartado e por ser, geralmente, produzido a partir do polipropileno (PP), polímero que apresenta lenta biodegradabilidade. Dessa forma, este trabalho multidisciplinar tem como objetivo o desenvolvimento de um protótipo de escova dental fabricado em poliuretano derivado do óleo de mamona, bem como a caracterização desse material a partir de ensaios de absorção de água e de saliva artificial, análise térmica dinâmico-mecânica (DMTA) e ensaios mecânicos de tração, estabelecendo uma comparação com o PP. A partir dos ensaios pode-se concluir que o PU derivado de mamona apresentou absorção de saliva superior à de água e esta, por sua vez, superior ao PP. Com relação a tração, o PP superou o PU em todos os aspectos, mostrando-se um material mais resistente e de maior rigidez. Contudo, concluiu-se que com algumas alterações no design, uma escova fabricada em PU derivado do óleo de mamona pode alcançar a mesma carga de ruptura e rigidez estrutural de uma escova convencional.
Indiscriminate use of raw materials by various industries such as polymers from petroleum has been causing an ever-increasing accumulation of slow biodegrading residue materials in sanitary pits. Many modern life utensils are made out of conventional plastic that are estimated to take up to half a century to decompose. In view of this situation, the study of polymers from renewable sources, the biopolymers, is key in the search for alternatives that may decrease the damaging effects on the environment. Petroleum based polymers can in many instances be replaced by biopolymers. Amongst such products, research has been indicating that toothbrush manufacturing can make use of alternative materials. A toothbrush is a personal hygiene device that should be used for relatively short periods. It is commonly made out of polypropylene (PP), a polymer with slow biodegrading characteristics. This study uses a multidisciplinary approach and its objective is the development of a toothbrush handle made out of polyurethane derived from castor oil. Water and artificial saliva absorption, DMTA and traction experiments were carried out to compare chemical and mechanical properties of traditional polypropylene and castor oil polyurethane toothbrushes. From the tests we can conclude that the derivative of castor oil PU showed absorption of saliva superior to water and also superior to PP. With respect to traction, the PP over the PU in all aspects and is a material more resistant and more rigid. However, it was concluded that with some changes in design, a brush made of PU derivative of castor oil might reach the same tensile strength and structural rigidity of a conventional toothbrush.
Sun, Xiaohua. "Biopolymer mediated drug delivery using a grafted cleavable linker". Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708018.
Testo completo