Abstract: Poly (vinylidene fluoride) (PVDF), thanks to its versatile properties, finds many applications ranging from water purification membranes (thermal and chemical stability) to electronic devices (piezoelectric, pyroelectric and ferroelectric properties). Block copolymers of PVDF with other polymers further expand its properties and, consequently, its applications. Toward this line, my thesis investigates the synthesis, molecular characterization and properties of novel PVDF-based copolymers mainly with poly(tert-butyl acrylate) (PtBuA), poly(methyl methacrylate) (PMMA) and polystyrene (PSt). To prepare the block copolymers a living polymerization is needed, which is compatible with the VDF and the comonomer (tBuA, MMA, St). For this purpose, we used iodine transfer polymerization (ITP) with the difunctional chain transfer agent (CTA) C4F8I2. Difunctional macroinitiator (I-PVDF-I) was first obtained by ITP of VDF monomer with C4F8I2, followed by addition of the comonomer tBuA, MMA or St to afford the triblock copolymers poly(tert-butyl acrylate)-block-poly(vinylidene fluoride)-block-poly(tert-butyl acrylate) (PtBuA-b-PVDF-b-PtBuA), poly(methyl methacrylate)-block-poly(vinylidene fluoride)-block-poly(methyl methacrylate) (PMMA-b-PVDF-b-PMMA) and polystyrene-block-poly(vinylidene fluoride)-block-polystyrene (PSt-b-PVDF-b-PSt). The structure of all intermediates and final products were characterized by Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC). The microstructure and polymorphism of all triblock copolymers, characterized by XRD, shown that the PVDF in the first two copolymers exhibits the electroactive β-phase, while in the third copolymer there is the coexistence of α- and γ-phases. Linear PVDF homopolymers, using the free radical and IT polymerizations, were prepared for comparison purposes. All linear polymers possess the α-phase. The thesis is divided into the following five chapters: 1. Introduction, where the scope of this thesis is given with a brief background on PVDF; 2. Literature Review, where a summary of previously published works on PVDF synthesis and polymorphism is presented; 3. Experimental Section, where detailed procedures and characterization methods are given; 4. Results and Discussion, where outcomes of successful experiments are discussed; and 5. Conclusion and Perspective, where the outcomes of this work are summarized and perspective are discussed.

RESUME Les alliages Cu-Al-Ni sont les seuls à posséder une température de transformation allant jusque 200°C. Ceci leur confère un avantage par rapport aux alliages Cu-Al-Zn ou Ti-Ni dont les températures de transformation ne dépassent pas 100°C. Néanmoins, un chauffage temporaire au dessus de 200°C peut provoquer une perte de l’effet mémoire des alliages Cu-Al-Ni. Nous avons étudié trois alliages aves des teneurs en nickel comprises entre 3 % et 5 %. L’objectif de notre étude est double : • Étudier la cinétique des transformations structurales au cours d’un vieillissement en phase β dans le domaine de températures 200°C-350°C ; • Quantifier la perte de l’effet mémoire au cours du vieillissement afin de déterminer les possibilités d’utilisation de ces alliages au dessus de 200°C. La caractérisation structurale a été effectuée par microscope optique, diffraction des rayons X, microscopie électronique à balayage et microscopie électronique en transmission. Les caractéristiques de la transformation martensitique ont été déterminées par analyse thermomécanique (TMA), par calorimétrie différentielle à balayage (DSC) et par des mesures de résistivité électrique. La perte de l’effet mémoire simple sens a été quantifiée à partir des courbes de transformations obtenues par analyse thermomécanique(TMA) sur des échantillons comprimés. Les résultats principaux sont :  Au dessus de 300°C, la précipitation de la phase d’équilibre у₂ se produit au cours du vieillissement. Elle entraîne une augmentation de la température Mѕ. Nous avons montré que cette augmentation de Ms peut être reliée à la fraction transformée par une loi de puissance.  Il n’y a pas de relation directe, en revanche, entre la perte de l’effet mémoire et la fraction transformée. Cela indique que le nombre et la taille des précipités ont une influence sur la perte de l’effet mémoire.  Pour un vieillissement de 256 minutes à 275°C, la perte de l’effet mémoire est inférieure à 15%. Par contre, au dessus de 300°C, la perte de l’effet mémoire est très rapide. Nous pouvons donc considérer que 275°C est une température limite à ne pas dépasser pour ces alliages. ABSTRACT The shape memory alloys Cu-Al-Ni are the only ones to have a transformation temperature of up to 200°C. This gives them an advantage compared to shape memory alloys Cu-Zn-Al or Ti-Ni whose transformation temperatures do not exceed 100 ° C. However, a temporary heating above 200 ° C can cause a loss of memory effect alloys Cu-Al-Ni. We studied three alloys with nickel content between 3% and 5%. The aim of our study is twofold: • Studying the kinetics of structural changes during aging in β phase in the temperature range 200 °C-350 °C. • Quantifying the loss of memory effect with aging in order to determine the potential use of these alloys above 200°C. The structural characterization was carried out by optical microscope, XR-ray diffraction, scanning electron microscopy and transmission electron microscopy. The characteristics of the martensitic transformation were determined by thermomechanical analysis (TMA), differential scanning calorimetry (DSC) and by measuring the electrical resistivity. The loss of one way shape memory was quantified from the curves obtained by thermomechanical analysis (TMA) on compressed samples. The main results are:  Above 300 ° C, the precipitation of equilibrium phase γ2 occurs during aging. It causes an increase in temperature Mѕ. We showed that this increase of Ms may be related to the fraction transformed by a power law.  There is no direct relationship between the loss of memory effect and the fraction transformed. This indicates that the number and size of the precipitates have an influence on the loss of memory effect.  For 256 minutes of aging at 275°C, loss of memory effect is less than 15%. On the other hand, above 300 ° C, loss of memory effect is very fast. We can therefore consider that 275°C is the temperature limit that not may be exceeded for these alloys.

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Agradecemos on 2018-05-22T17:55:29Z (GMT) / Submitted by Mariana Luna Lourenço (marianaluna92@hotmail.com) on 2018-05-24T18:33:57Z No. of bitstreams: 1 Dissertacao_Mariana.pdf: 3768608 bytes, checksum: ba977fb3d77d80f3207df693713d4d8c (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-05-24T18:59:05Z (GMT) No. of bitstreams: 1 lourenco_ml_me_Bauru.pdf: 3718025 bytes, checksum: 6999d85c58ed3fa2a14ec911f0de0e93 (MD5) / Made available in DSpace on 2018-05-24T18:59:05Z (GMT). No. of bitstreams: 1 lourenco_ml_me_Bauru.pdf: 3718025 bytes, checksum: 6999d85c58ed3fa2a14ec911f0de0e93 (MD5) Previous issue date: 2018-03-27 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Com o aumento da população mundial, o crescimento dos acidentes de trânsito e o aumento da expectativa de vida crescem cada vez mais a necessidade do uso de implantes, dentários e ortopédicos. Pesquisadores vêm trabalhando para o aperfeiçoamento dos biomateriais utilizados, melhorando a funcionalidade e aumentando a vida útil no corpo humano. O módulo de Young das ligas já utilizadas é ainda cerca de 2 a 4 vezes maior que o do osso humano. A liga de titânio mais utilizada para aplicações biomédicas é a Ti-6Al-4V, porém, estudos anteriores mostraram que o vanádio causa reações alérgicas nos tecidos humanos e o alumínio tem sido associado com desordens neurológicas. Assim, novas ligas de titânio sem a presença desses elementos estão sendo desenvolvidas, geralmente com elementos β-estabilizadores, que diminuem o módulo de elasticidade. O manganês é um forte candidato como elemento de liga para o desenvolvimento de novas ligas de titânio do tipo β, em razão de sua abundância e baixa citotoxicidade. O objetivo deste trabalho foi preparar e caracterizar novas ligas do sistema Ti-Mo-Mn, visando aplicações biomédicas. As ligas foram projetadas utilizando as teorias do Orbital Molecular e do molibdênio equivalente, foram obtidas por fusão a arco e caracterizadas química, estrutural, microestrutural, mecânica, e citotoxicamente, com o propósito de melhor compreender a relação entre a microestrutura e propriedades da liga. As ligas estudadas Ti-10Mo-5Mn e Ti-15Mo-5Mo apresentaram valores próximos dos valores nominais, boa estequiometria e homogeneidade. A estrutura e microestrutura apresentaram apenas a fase β em todas as condições de processamento. As propriedades mecânicas apresentaram bons valores, a dureza se manteve alta e o módulo de elasticidade com valores abaixo das ligas comerciais. Tais ligas não se mostraram citotóxicas para células fibroblásticas em curto período de tempo. A associação destes bons resultados as credencia para uma possível aplicação biomédica. / LOURENÇO, M.L. Development and c haracterization of n ew a lloys containing Titanium, Molybdenum and Manganese for b iomedical a pplications. 2018. 6 2 p. Dissertation (Master in M a terials Science and Tec h n o logy) UN ESP, Bauru (SP) , 2018 . ABSTRACT With the increase of the world population, the growth of traffic accidents and the increase in life expectancy, the need for the use of implants, dental and orthopaedics, is growing more and more. Researchers have been wor king towards the improvement of the used biomaterials, improving the functionality and increasing the useful life in the human body. Young's modulus of the alloys already used is still about 2 to 4 times larger than the human bone. The most commonly used t itanium alloy for biomedical applications is Ti - 6Al - 4V, but previous studies have shown that vanadium causes allergic reactions in human tissues and aluminum has been associated with neurological disorders. Thus, new titanium alloys without the presence of these elements are being developed, usually with β - stabilizers, which diminish the elastic modulus. Manganese is a strong candidate as an alloy element for the development of new β - type titanium alloys, due to its abundance and low cytotoxicity. The aim of this work was to prepare and characterize new al loys of the Ti - Mo - Mn system, aiming at biomedical applications. The alloys were designed using the the molecular orbital and the equivalent molybdenum theories, were obtained by arc - melting and characterized chemical, structural, microstructural, mechanica l, and cytotoxically, with the purpose of better understanding the relationship among the microstructure and properties of the alloy. The studied alloys, TI - 10Mo - 5Mn and Ti - 15Mo - 5Mo, presented values close to nominal values, good stoichiometry and homogene ity. The structure and microstructure presented only the β phase in all processing conditions. The mechanical properties showed good values, the hardness remained high and the modulus of elasticity with values below the commercial alloys. Such alloys did n ot show cytotoxicity for fibroblastic cells in a short time period. The association of these good results the make these alloys adequate for a possible biomedical application / 2015/25248-0

In this work phase transformations in metastable β Ti-15Mo alloy were studied using electrical resistivity measurements. The alloy was subjected to a solution treatment at a temperature higher than β- transus and quenched in water. In this condition, the microstructure of Ti-15Mo alloy consists of a metastable β - matrix and ω-phase particles. During in-situ electrical resistivity measurement in a specially designed furnace, significant temperature points which indicate phase transformations in the material were detected. The dependence of electrical resistivity on the temperature changes during heating between increasing and decreasing according to the ongoing phase transformation. The changes were observed at temperatures 225, 356 and 560 řC. A further study of these phase transformations using electrical resistivity measurements was performed on various heat treated specimens. In order to control the microstructure evolution in the material, scanning and transmission electron microscopy was used. Mechanical properties were studied using Vickers microhardness testing. The obtained results serve to identify the type and sequence of phase transformations which take place in the Ti-15Mo alloy. Powered by TCPDF (www.tcpdf.org)