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<p>A series of bismaleimide and bisfuran monomers were synthesized and then combined to produce thermally reversible polymers. Reversibility was demonstrated through multiple heating and cooling cycles, and verified using ¹H NMR spectroscopy. Variation of the spacer chemistry in the monomers was found to profoundly influence the physical properties of the resulting polymers. A tripodal maleimide and furan system was then synthesized, but it was found that the incorporation of cross-linking into the polymer network did not significantly alter the mechanical properties of the resulting polymers.</p> <p>Dilute solutions of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends containing PS- or PMMA-functionalized single-walled carbon nanotubes (SWNT) were spin cast and annealed at 180°C for 12 h. Characterization of the annealed films by scanning Raman spectroscopy confirmed that the migration of the nanotubes in the films could be controlled using the appropriate functionality on the nanotubes, thus the PS-functionalized nanotubes were found to migrate to the PS domains, while the PMMA-functionalized nanotubes migrated to the PMMA domains.</p> <p>SWNTs were then functionalized using linear reversible polymers, resulting in significant solubilization of the nanotubes. Heating of this solution resulted in the collapse of the DA polymer, and precipitation of the dissolved nanotubes, illustrating the reversible nature of the polymers, and their influence on carbon nanotube solubilization.</p> / Doctor of Philosophy (PhD)

Yes / Shape memory polymer (SMP) products have been developed for application as crack closure de-vices in concrete. They have been made from PET in the form of both fibres and hollow tubes. Here, manufacturing methods using die-drawing and mandrel-drawing to induce shape memory are reported. The fibre-based devices are incorporated into concrete and, upon triggering, exert shrinkage restraint forces that close cracks in the concrete. The evolution of shrinkage restraint force in the fibres as manufactured was measured as a function of temperature, showing stresses in excess of 35 MPa. Tendons consisting of fibre bundles are incorporated into concreate beams subjected to controlled cracking. When activated, the tendons reduce the crack widths by 80%. The same fibres are used to produce another class of device known as knotted fibres, which have knotted ends that act as anchor points when they incorporated directly into concrete. Upon acti-vation within the cracked concrete, these devices are shown to completely close cracks. The tubes are used to enclose and restrain prestressed Kevlar fibres. When the tubes are triggered, they shrink and release the prestress force in the Kevlar, which is transferred to the surrounding con-crete in the form of a compressive force, thereby closing cracks. The Kevlar fibres also provide substantial reinforcement after activation. The devices are shown to be able to partially and fully close cracks that have been opened to 0.3 mm and achieve post-activation flexural strengths com-parable to those of conventional reinforced and prestressed structural elements. Finally, a pre-liminary life cycle assessment study was used to assess the carbon footprint a nominal unit of concrete made with SMPs fibres compared to conventional concrete. / This research was funded by the UKRI-EPSRC Resilient Materials 4 Life (RM4L), grant number EP/P02081X/1 and the support of ARUP via the UKIMEA research funding.

Polysaccharides are known as among the most abundant natural polymers on the Earth. As this class of material is usually renewable, biodegradable, biocompatible in many contexts and environmentally friendly, it is of great interest to use these benign polymers to design and prepare materials, especially for applications with green and biomedical purposes. In this dissertation we will discuss novel pathways to two different types of polysaccharide-based materials: block copolymers and hydrogels. Block copolymers are composed of two or even more covalent bonded polymer blocks that have quite distinct properties. Synthesis of polysaccharide-based block copolymers is an attractive and challenging research topic, opening up promising application potential and requiring advances in polysaccharide regio- and chemoselectivity. Herein, we report two independent approaches to prepare these interesting and potential useful materials. In one approach, trimethyl cellulose was modified regiospecifically at the reducing end anomeric carbon to create an ω-unsaturated alkyl acetal by solvolysis with an ω-unsaturated alcohol. Then, olefin cross-metathesis, a known versatile and mild tool for polysaccharide chemical modification, was used to couple the trimethyl cellulose block with various polymer blocks containing acrylates. To demonstrate the method, trimethyl cellulose-b-poly(tetrahydrofuran), cellulose-b-poly(ethylene glycol), and cellulose-b-poly(lactic acid) were synthesized by this coupling strategy. In another approach, we introduced a simple and novel method to prepare dextran-based block copolymers. In this strategy, N-bromosuccinimide (NBS)/triphenyl phosphine (PPh3) was chosen to regioselectively brominate the only primary alcohol of linear unbranched dextran. The resulting dextran, bearing a terminal C-6 bromide, was coupled with several amine terminated polymers via SN2 substitution to obtain block copolymers, including dextran-b-polystyrene, dextran-b-poly(N-isopropylacrylamide) and dextran-b-poly(ethylene glycol). Dextran-b-poly(N-isopropylacrylamide) exhibits thermally-induced micellization as revealed by dynamic light scattering, forming micelles with 155 nm diameter at 40 °C. Dextran-b-polystyrene film was analyzed by small angle X-ray scattering, suggesting the existence of microphase separation. This dissertation also introduces a novel, simple and effective strategy to prepare polysaccharide-based hydrogels. Hydrogels are typically crosslinked hydrophilic polymers that have high water affinity and no longer dissolve in water. Polysaccharide-based hydrogels are of great interest to for biomedical applications due to their benefits including biocompatibility, polyfunctionality, and biodegradability. Recently the Edgar group has discovered that chemoselective oxidation of oligo(hydroxypropyl)-substituted polysaccharides impairs ketone groups at the termini of the oligo(hydroxypropyl) side chains. These ketones can condense with amines to form imines, leading hydrogel formation., Based on this concept, we prepared oxidized hydroxypropyl polysaccharide/chitosan hydrogels. This class of all-polysaccharide hydrogels exhibits a series of interesting properties such as tunable moduli (300 Pa to 13 kPa), self-healing, injectability, and high swelling ratios. To further explore imine-crosslinked hydrogels, we designed thermally responsive hydrogels by using a Jeffamine, a polyethylene oxide-b-polypropylene oxide-b-polyethylene oxide triblock copolymer with two terminal amines. As the Jeffamine has a lower critical solution temperature, oxidized hydroxypropyl cellulose/Jeffamine hydrogels display moduli that are tunable by controlling the temperature. / Doctor of Philosophy / Polysaccharide are natural polymers that are among the most abundant polymers on Earth. It is greatly in society's interest to extend the scope of their applications, due to the benign nature of polysaccharides. This dissertation mainly focuses on two polysaccharides: cellulose and dextran. Cellulose is a long linear polymer of linked glucose molecules. As cellulose is sustainable, biodegradable, non-toxic, affordable and accessable for chemical modification, it is a suitable polymer for biomedical and environmentally friendly application. Dextran is also a polymer chain made up only of glucose but connected with each other differently from cellulose by, bacterial fermentation, and it may be lightly branched. It is biocompatible in many situations and is biodegradable both in vivo and in the environment, thus it has been investigated for drug delivery and many other medical applications. Using these two polysaccharides, we designed and prepared two quite different classes of materials: block copolymers and hydrogels. Block copolymers consist of two or more different types of polymer blocks connected by strong covalent bonds. As block copolymerization enables construction of a single polymer comprising segments with distinct properties, it is appealing to synthesize a block copolymer which preserves the properties of natural polymers coupled to very different polymers, such as polyolefins (e.g. the polyethylene that is used for milk bottles). In order to prepare polysaccharide-based block copolymers, we developed two different synthetic routes to end-functionalize methyl cellulose and dextran , and these resulting products were used to prepare two independent series of polysaccharide-based block copolymers via combination (in other words, sticking the polysaccharide and, e.g., the polyethylene together end to end). This study confirms the feasibility of this method to make methyl cellulose-based and dextran-based block copolymers. We expect these classes of materials will have significant potential in applications including drug delivery, as compatibilizers for polymer blends of materials that otherwise cannot be mixed (polyolefin/polysaccharide), membrane and adhesive. Hydrogels are crosslinked polymer networks with high water affinity, and they have been heavily investigated in the field of tissue engineering, drug delivery, agriculture and 3D printing. Polysaccharide-based hydrogels are attractive materials for these applications because they are biocompatible, biodegradable and have polyfunctionality. However, any use of toxic small molecules to crosslink the hydrogels diminishes their usefulness in biomedical applications. In this work, we demonstrate a simple, green and efficient method for preparation of all-polysaccharide-based hydrogels. The starting materials, oxidized hydroxypropylpolysaccharide, were simply prepared by using household bleach (NaOCl) as the oxidation reagent. We discovered that oxidized hydroxypropyl polysaccharides readily form hydrogels with hydrophilic amine-containing polymers like chitosan (a natural polysaccharide that comes from shells of crustaceans like crabs or shrimp) and Jeffamines, affording interesting properties including tunable stiffness, self-healing, injectability, and responsiveness to acidity and temperature. We expect that this new class of hydrogel will be very promising for biomedical-related applications.

Los materiales autosanables son materiales con la capacidad de reparar sus daños de forma autónoma o con ayuda mínima de estímulos externos. En el campo de la construcción, el desarrollo de elementos autosanables aumentará la durabilidad de las estructuras y reducirá las acciones de mantenimiento y reparación. Los elementos de hormigón armado presentan frecuentemente pequeñas fisuras (< 0.3 mm), no relevantes mecánicamente, pero que pueden suponer un punto de entrada para agentes agresivos. El hormigón tiene una cierta capacidad de autosanación, capaz de cerrar pequeñas fisuras, producida principalmente por la hidratación continuada y la carbonatación. Estudios recientes han intentado mejorar dicha capacidad y diseñar productos específicos para conseguirla. Estos productos incluyen, entre otros, aditivos cristalinos, agentes micro o macroencapsulados, e incluso el uso de bacterias. Los aditivos cristalinos (CA) son un tipo de aditivo para hormigón que se considera que aporta propiedades de autosanación. No obstante, la falta de conocimiento sobre su comportamiento limita su uso. Además, los métodos para evaluar la autosanación en hormigones no están estandarizados todavía. Esto complica la realización de un análisis crítico de los diferentes productos y métodos de evaluación propuestos en la literatura. Para responder a esta falta de conocimiento, los objetivos de esta tesis son: 1) estudiar y proponer procedimientos experimentales para evaluar los fenómenos de autosanación en hormigón y, 2) evaluar experimentalmente las mejoras producidas al introducir aditivos cristalinos. Esta tesis incluye como ensayos para la determinación de la autosanación: la evaluación del cierre de fisuras, la permeabilidad al agua, flexión a tres puntos y absorción capilar. Además, se han realizado varias campañas experimentales para validar los ensayos propuestos. Posteriormente, estos ensayos se han utilizado para analizar la influencia de varios parámetros, incluyendo entre otros: presencia de aditivos cristalinos, nivel de daño, tiempo necesario para el sanado, composición del hormigón y condiciones de sanado. Finalmente, se analizan los efectos producidos al añadir aditivos cristalinos en hormigón en la fluidez, resistencia e hidratación. Los resultados muestran que el cierre de fisuras es un ensayo eficaz y sencillo para evaluar la autosanación. Sin embargo, la orientación de la fisura durante el sanado ha resultado ser de gran importancia, y no considerar este aspecto puede llevar a conclusiones engañosas. El ensayo de permeabilidad al agua propuesto en este trabajo presenta una buena estabilidad y es fácil de implementar en laboratorios. Además, las relaciones obtenidas entre los parámetros de fisura y la permeabilidad del agua han confirmado la relación cúbica indicada en la literatura. Este trabajo muestra que analizar la eficiencia de autosanado mediante el cierre de fisuras puede llevar a una sobreestimación de la capacidad de sanación, comparada con los resultados obtenidos mediante permeabilidad. Los ensayos de sorptividad resultaron fáciles de implementar, sin embargo, los resultados obtenidos mostraron una alta dispersión y sensibilidad a las variaciones en las fisuras producidas durante el proceso de prefisuración. En cuanto a la evaluación de la recuperación mecánica, los resultados muestran que la evolución de las propiedades del hormigón con el tiempo es un parámetro que debe considerarse, especialmente en fisuras de edades tempranas. En este trabajo se ha obtenido que los aditivos cristalinos potencian las reacciones de autosanación, pero tienen una capacidad limitada. La proximidad de los CA a la industria es un punto positivo para su inclusión como un nuevo tipo de aditivo de hormigón. Sin embargo, los resultados obtenidos en esta tesis indican que se necesitan más análisis para determinar sus efectos completos en hormigón, especialmente con respect / Self-healing materials are materials with the capability to repair their damage autonomously or with minimal help from an external stimulus. In the construction field, the development of self-healing elements will increase the durability of structures and reduce their maintenance and repair actions. Reinforced concrete elements frequently suffer small cracks (< 0.3 mm), not relevant mechanically, but they can be an entrance point for aggressive agents. Concrete has a natural self-healing capability able to seal small cracks, produced by the continuing hydration and carbonation processes. Recent studies have attempted to improve that healing capability and to design specific products to achieve it. These products include, among others: crystalline admixtures, micro- or macro-encapsulated agents, and even the use of bacteria. Crystalline admixtures (CA) are a concrete admixture that is claimed to provide self-healing properties. However, the lack of knowledge on their behavior and self-healing properties limits their usage. In addition, the methods to evaluate the self-healing capability of mortar and concrete are not standardized yet. This complicates the performance of a critical analysis of the different self-healing products and evaluation methods found in the literature. In order to answer to this lack of knowledge, the objectives of this thesis are: 1) to study and propose experimental procedures in order to evaluate self-healing in concrete and, 2) to evaluate experimentally the self-healing enhancements produced when introducing crystalline admixtures. This thesis includes the following tests for the determination of the self-healing: the evaluation of crack closing, water permeability, three point bending tests and capillary absorption test. In addition, several experimental campaigns have been performed with the objective of validating the proposed tests. Afterwards, these methods have been used to analyze the influence of several parameters, including among others: the presence of crystalline admixtures, the damage extent, healing time needed, concrete composition and healing conditions. Finally, the effects that crystalline admixtures produce in concrete are analyzed in terms of slump, strength and hydration. The results show that crack closing is an effective and simple method to evaluate self-healing. However, the orientation of the crack during healing is of great importance, and disregarding this aspect may lead to misleading conclusions. The water permeability method proposed in this work has good stability and it is easy to implement in concrete laboratories. Moreover, the relations obtained between crack parameters and water permeability confirmed the cubic relation, as reported in the literature. This work shows that analyzing healing efficiency by means of crack closing tends to overestimate self-healing if compared with the results obtained by means of water permeability. Sorptivity analysis tests were easy to implement, however, the results obtained in this work showed high dispersion and sensitivity to the variations of the cracks introduced during the precracking process. Regarding the evaluation of mechanical recoveries, the results show that the evolution of concrete properties with time is a parameter of importance that, therefore, should be considered, especially for early age cracks. In this work, crystalline admixtures have been reported as an enhancer of self-healing reactions, but with a limited capacity of enhancement. The proximity of CA to the industry is a positive point to their inclusion as a new type of admixture for concrete. However, the results obtained in this thesis indicate further analyses are needed to determine their full effects on concrete, especially regarding self-healing. / Els materials autosanables són materials amb la capacitat de reparar els seus danys de forma autònoma o amb ajuda mínima d'estímuls externs. En el camp de la construcció, el desenvolupament d'elements autosanables augmentarà la durabilitat de les estructures i reduirà les accions de manteniment i reparació. Els elements de formigó armat presenten freqüentment fissures menudes (< 0.3 mm), no rellevants des del punt de vista mecànic, però poden suposar un punt d'entrada per a agents agressius. El formigó té una capacitat de autosanació capaç de tancar fissures menudes, produïda principalment per la hidratació continuada i la carbonatació. Estudis recents han intentat millorar eixa capacitat i dissenyar productes específics per aconseguir-la. Aquests productes inclouen, entre d'altres, additius cristal·lins, agents micro- o macroencapsulats, i fins i tot l'ús de bacteris. Els additius cristal·lins (CA) són un tipus d'additiu reductor per formigó que es considera que proporciona propietats de autosanació. No obstant, la manca de coneixement sobre el seu comportament limita el seu ús. A més, els mètodes per avaluar la autosanació de formigons encara no estan estandarditzats. Açò complica la realització d'una anàlisi crítica dels diferents productes i mètodes d'avaluació proposats a la literatura. Per respondre a aquesta manca de coneixement, els objectius d'aquesta tesi són: 1) estudiar i proposar procediments experimentals per avaluar els fenòmens d'autosanació en formigó i, 2) avaluar experimentalment les millores produïdes en introduir additius cristal·lins. Aquesta tesi inclou com assajos per a la determinació de l'autosanació: l'avaluació del tancament de fissures, la permeabilitat a l'aigua, flexió a tres punts i absorció capil·lar. A més, s'han realitzat diverses campanyes experimentals per validar els assajos proposats. Posteriorment, aquests assajos s'han utilitzat per analitzar la influència de diversos paràmetres: presència d'additius cristal·lins, nivell de dany, temps necessari per a la sanació, composició del formigó i condicions de sanació. Finalment, s'analitzen els efectes produïts en afegir additius cristal·lins en formigó en fluïdesa, resistència i hidratació. Els resultats mostren que el tancament de fissures és un assaig eficaç i senzill per avaluar l'autosanació. No obstant això, l'orientació de la fissura durant la sanació ha resultat ser de gran importància, i no considerar aquest aspecte pot portar a conclusions enganyoses. L'assaig de permeabilitat a l'aigua proposat presenta una bona estabilitat i és fàcil d'implementar en laboratoris. A més, les relacions obtingudes entre els paràmetres de fissura i la permeabilitat a l'aigua han confirmat la relació cúbica de la literatura. Aquest treball mostra que analitzar l'eficiència de l'autosanació amb el tancament de fissures pot sobreestimar la capacitat de sanació, comparada amb els resultats obtinguts-dues mitjançant permeabilitat a l'aigua. Els assajos de sorptivitat van resultar fàcils d'implementar, però, els resultats obtinguts en aquest treball van mostrar una alta dispersió i sensibilitat a les variacions en les fissures produïdes durant el procés de prefissuració. Pel que fa a l'avaluació de la recuperació mecànica, els resultats mostren que l'evolució de les propietats del formigó amb el temps és un paràmetre d'importància que, per tant, s'ha de considerar, especialment per fissures primerenques. En aquest treball s'ha obtingut que els additius cristal·lins potencien les reaccions d'autosanació, però tenen una capacitat limitada. La proximitat dels CA a la indústria és un punt positiu per a la seva inclusió com un nou tipus d'additiu de formigó. Tanmateix, els resultats obtinguts en aquesta tesi indiquen que calen més anàlisis per determinar els seus efectes complets en formigó, especialment pel que fa a l'autosanació. / Roig Flores, M. (2018). Self-healing concrete: efficiency evaluation and enhancement with crystalline admixtures [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/100082

A self-sensing and self-healing bolted joint has been developed. This concept encompasses the areas of health monitoring, joint dynamics and smart materials. In order to detect looseness in a joint the impedance health monitoring method is used. A new method of making impedance measurements for health monitoring that greatly reduces the equipment cost and equipment size was developed. This facilitates implementation of the impedance technique in real-life field applications. Several proof of concept experiments are presented and compared to the traditional method of making impedance measurements. Investigations of bolted joint dynamics were conducted. A literature review of bolted joints and their diagnostics is presented. The application of the transfer impedance method is compared to standard modal tests on various bolt tensions. An investigation of damping in bolted joints was also made comparing a bolted and monolithic beam. Practical issues in adaptive bolted joints are investigated. This includes issues on activating/heating SMA actuators, connecting the actuators to the power source, size selection of SMA actuators and insulations. These issues are examined both experimentally and theoretically. / Master of Science

Poly(ethylene-co-methacrylic acid) (EMAA) ionomer polymers carry great potential for use in a wide variety of unique applications due to their property of “self-healing” following projectile impact. Following puncture, certain films based on these materials are observed to “heal”, with the penetration opening recovering to an air-tight condition. Specifically, four polymers of this class were examined, including DuPont™ Surlyn® 8920, Surlyn® 8940, Nucrel® 925, and Nucrel® 960. Though these differ in their amount of ionic content, all expressed a certain degree of self-healing. Thin films were prepared by a compression molding process and punctured at temperatures ranging from room up to that of the melt using a pellet gun. Samples were then assessed for self-healing. A quantitative post-puncture burst-test method examined the strength or quality of the healed site in the four examples. A comparison of this data provided an understanding of the importance of ionic content and the mechanism of puncture healing. Additional damage modes were also examined to determine other cases where healing occurs and the requirements necessary to elicit the healing response. In addition, interesting composite materials consisting of carbon nanotube filled ionomers were fabricated by a melt-mixing process which produced potentially self-healing composites with superior mechanical properties. By comparing peel testing, projectile testing, the quantitative healed strength, and other characteristics, it was determined that healing is not a function of the ionic content of the materials involved. Further, healing was determined to occur due to a synergy of thermomechanical properties facilitated by the addition of the methacrylic acid groups to the polymer backbone. / Master of Science