Polymers capable of thermally controlled reversible bonding reactions are promising candidates for stimuli responsive materials, as required for self-healing or drug delivery materials. In order to investigate how the dynamic reactions can be controlled, effective analytical tools are demanded that are capable of analyzing not only the polymers but can also monitor the respective bonding reactions. Herein, we employ size exclusion chromatography in a newly developed temperature dependent mode (TD SEC) for the in situ characterization of polymers that undergo retro Diels-Alder (rDA) reaction at temperatures higher than 60 °C. Monitoring the evolution of the molar mass distribution of the polymers during the rDA reaction and evaluating the data quantitatively gives detailed information about the extent of the reaction and allows elucidating structural parameters that can be used for controlling the polymers debonding behavior. In contrast to spectroscopic techniques, TD SEC analyzes only the size of the polymers, hence the polymers do not need to fulfill any particular requirements (e.g. presence of detectable functional groups) but only need to be soluble in the TD SEC, which makes the method universally applicable. Side effects that might bias the results are minimized by using a high temperature chromatograph that allows performing the analysis in a broad temperature range (60 – 200 °C) and in different solvents. Thus, the analysis can be performed under the exact conditions that are required for the bonding reactions and an in situ image is provided.

In this research, two phases of work were conducted. First, an investigation into the durability concerns for precast prestressed concrete piles exposed to marine environments was conducted. The investigation characterized the durability concerns of chemical, biological, and physical deterioration mechanisms. The results of this study were used to develop potential high performance marine concretes (HPMC) that would be capable of 100+ year service lives in marine environments. Extensive durability testing and service life modeling of the HPMC was performed. Chloride ingress resistance was investigated using accelerated and long-term test procedures and the results used to perform service life modeling to predict the time before corrosion initiation. Sulfate resistance characterization was performed using multiple techniques to characterize the physical and chemical behavior of binder compositions containing binary or ternary mixes containing cement and supplementary cementitious materials (SCM's) subjected to a sulfate-laden environment. Accelerated carbonation testing and material characterization led to the finding of relationships in the chemical composition of mix designs and the observed durability and the results used to perform corrosion initiation service life modeling. An investigation into the influence of self-healing of cracked concrete led to fundamental findings on the behavior of chloride ingress for cracked concrete structures in marine environments. The results of this research led to the development of concrete mix designs capable of providing service lives over 100 years in Georgia's marine environments, as well as the advancement of the current state of knowledge on the durability characteristics of ternary mix designs.

Orientador: Prof. Dr. Jeverson Teodoro Arantes Junior / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2017. / Uma estrutura que pode autorregenerar em condições ambiente é um desafio enfrentado atualmente e é uma das áreas mais promissoras na ciência de materiais inteligentes. O presente projeto visa a utilização de métodos teóricos para o estudo das propriedades estruturais e funcionais de nanocompósitos intrinsecamente autorregenerativos, permitindo estratégias mais eficientes para o desenvolvimento de novos materiais. As simulações são baseadas na Teoria do Funcional da Densidade (DFT). Estudamos os componentes isolados que constituem o nanocompósito funcional: diarilbibenzofuranona (DABBF), SHP e nanopartículas de (óxido de) níquel. Estudando a formação da DABBF contra a reação da arilbenzofuranona (ABF) e O2 (auto-oxidação), vemos que a reação de formação sem barreira da DABBF é preferida à auto-oxidação porque existe um processo de transferência de carga que resulta no superóxido fracamente ligado. Realizamos um estudo sistemático por meio de cálculos ab initio para investigar a reação de clusters de Ni13 com moléculas de O2. Avaliamos dinamicamente o efeito sobre as propriedades estruturais, eletrônicas e magnéticas e compreendemos o mecanismo de quimissorção do oxigênio (primeiro estágio da oxidação). Finalmente, estudamos as interações entre os oligômeros do SHP e as nanopartículas, levando ao nanocompósito autorregenerativo. Sugerimos como trabalhos futuros simular as interações entre todos esses materiais levando ao nanocompósito autorregenerativo por meio de uma abordagem multiescala via métodos DFT e de dinâmica molecular (MD). / A structure that can sustain self-healing repair under standard conditions is a challenge faced nowadays and is one of the most promising areas in smart materials science. The present project aims at the use of theoretical methods for the study of structural and functional properties of intrinsically self-healing nanocomposites, allowing improved design strategies for novel materials. The simulations are based on Density Functional Theory (DFT). We studied the isolated components that constitute the functional nanocomposite network: diarylbibenzofuranone (DABBF), SHP, and oxidated nickel nanoparticles. Studying DABBF bond formation against arylbenzofuranone (ABF) and O2 reaction (autoxidation), we see that the barrierless DABBF bond formation is preferred over autoxidation because there is a charge transfer process that results in the weakly bonded superoxide. We performed a systematic study by means of ab initio calculations to investigate Ni13 clusters reaction with O2 molecules. We evaluate dynamically the effect on structural, electronic, and magnetic properties and understand the oxygen chemisorption (first oxidation stage) mechanism. Finally, we study the interactions between SHP oligomers and the nanoparticles, leading to the selfhealing nanocomposite. We suggest as future work simulating the interactions between all these materials leading to the self-healing nanocomposite through a multiscale approach via DFT and molecular dynamics (MD) methods.

Orientador: Antonio Riul Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-02T14:50:41Z (GMT). No. of bitstreams: 1 Ly_KallyCheinSheng_M.pdf: 2442128 bytes, checksum: 86716c6c19fa3a9db425b32c36463141 (MD5) Previous issue date: 2017 / Resumo: Materiais biomiméticos são inspirados em estruturas biológicas para a obtenção de propriedades e funcionalidades específicas. Dentre os materiais biomiméticos, os que são capazes de se regenerar (self-healing) despertaram grande interesse pelo potencial de aplicação em diversas áreas. Para ilustrar, alguns materiais autorregeneráveis poliméricos apresentam regeneração múltipla, necessitando apenas de água para que a regeneração ocorra em alguns minutos, aumentando consideravelmente a proteção mecânica da superfície contra desgastes, danos mecânicos entre outros. Entretanto, múltiplas imersões em água ou em meios aquosos pode degradar o material e neste contexto este projeto visa incorporar a hidrofobicidade a um sistema regenerável. Desta forma, o material regenerável hidrofóbico, durante sua regeneração imersa em água, poderá diminuir a interação da superfície não danificada com a água, reduzindo corrosões e degradações devido a meios aquosos. Estudamos a nanoestruturação de materiais através da técnica de automontagem por adsorção física (LbL, do inglês Layer-by-Layer) utilizando os polieletrólitos poli(etileno imina) (PEI) e poli(ácido acrílico) (PAA), a fim de produzir revestimentos capazes de se regenerar a danos mecânicos micrométricos. Adicionalmente, foram incorporados a estes dois materiais nanofolhas de óxido de grafeno reduzido (rGO) funcionalizados com poli(cloridrato de alilamina) (GPAH) e poli(estireno-sulfonato de sódio) (GPSS), com o intuito de verificarmos um aumento de resistência a abrasão do material e alterações nas propriedades elétricas na nanoestrutura formada para aumentar o potencial de aplicação em eletrônica flexível. A arquitetura molecular (GPAH-PEI/GPSS-PAA)60 foi caracterizada com espectroscopia Raman, medidas de ângulo de contato, microscopia de força atômica, medidas elétricas e nanoindentação. Foi observada boa regeneração do material após 15 minutos de imersão em água a temperatura ambiente em um dano mecânico da ordem de 10 micrômetros. Também observamos boa hidrofobicidade do filme LbL (GPAH-PEI/GPSS-PAA)60 ( teta = 136º), e medidas de microscopia de força atômica e perfilometria indicaram, respectivamente, rugosidade superficial de 55 nm em uma área de (2 ?m x 2 ?m) e espessura de filme de 30 ?m. A análise Raman apontou para uma forte interação das nanofolhas de rGO com os polímeros, corroborando o tem caráter elétrico isolante do filme (GPAH-PEI/GPSS-PAA)60, que apresentou função trabalho ~ 5,2 eV e condutividade elétrica da ordem de 10-7 S/cm, que acreditamos resultar das fortes interações das nanofolhas com os polímeros. Por fim, medidas de nanoindentação indicaram que a incorporação de nanofolhas de GPSS e GPAH aumentou em 10 vezes a dureza do nanocompósito formado, sem comprometer a regeneração / Abstract: Biomimetic materials are inspired in biological structures to obtain specific properties and functionalities and among them, those capable of self-healing brought great interest due to high potential of application in different areas. To illustrate, some polymeric self-healing materials present multiple regeneration in the presence of water, with the regeneration occurring within a few minutes, increasing considerably the mechanical protection of a surface against wear and mechanical damage among others. Nevertheless, multiple immersions in water or in aqueous media can degrade the material and in this context this project aims the incorporation of hydrophobicity to a self-healing system. In this way, the self-healing, hydrophobic material during its immersion in water may decrease the interaction of the damaged surface with water, reducing corrosion and degradation due to aqueous media. We study the nanostructuration f materials through the layer-by-layer (LbL) technique using poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA) in order to produce self-healing coatings from micrometric mechanical damages. In addition, we also incorporate to these materials reduced graphene oxide (rGO) functionalized with poly(allylamine hydrochloride) (GPAH) and poly(styrene-sodium sulfonate) (GPSS), with the purpose of verifying an increase in the mechanical abrasion resistance of the material and changes in the electrical properties of the nanostructures formed to increase the potential application in flexible electronics. The molecular architecture (GPAH-PEI/GPSS-PAA)60 was characterized by Raman spectroscopy, contact angle measurements, atomic force microscopy, electrical measurements and nanoindentation. It was observed good self-healing capacity after 15 min f immersion in water at room temperature in a mechanical scratch of the order of 10 micrometers. It was also observed good hydrophobicity in the (GPAH-PEI/GPSS-PAA)60 LbL film ( teta = 136º) and atomic force microscopy and perfilometer indicate, respectively, surface roughness of 55 nm in a (2 ?m x 2 ?m) area and film thickness of 30 ?m. Raman analysis pointed out to a strong physical interaction between the rGO nanoplatelets with the polymeric materials, corroborating the strong insulating nature of (GPAH-PEI/GPSS-PAA)60 film that displayed a work function of 5.2 eV and electrical conductivity of 10-7 S/cm, which we believe results from the strong interactions of the nanosheets with the polymers. Finally, nanoindentation measurements indicated that the incorporation of GPAH and GPSS nanoplatelets increased hardness by 10 times, without compromising the regeneration / Mestrado / Física / Mestra em Física / 1543078/2015 / CAPES

The covalent bond formed between a N-heterocyclic carbene and an aryl-isothiocyanate was discovered to be thermally-reversible. This bond was incorporated into the backbone of an aromatic polymer which, when subjected to heat and excess monomer, would depolymerize to smaller oligomers. In addition these small molecules contain active chain ends and could be repolymerized to reform the original polymer. The high molecular weight material was made into freestanding sheets with desirable mechanical properties and could be made conductive by treatment with iodine. A new poly(triazene) was formed from the reaction of a facially opposed, annulated, bis-N-heterocyclic carbene (NHC) and an organic bis-azide. The NHC as well as the azide were varied and combined to produce a series of polymers which were characterized by GPC, TGA, and NMR. These thermally robust polymers were also coated onto glass slides and rendered electrically conductive by exposure to iodine vapor. A new reagent for Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT) is described. This imidazolium based reagent shows unusually fast kinetics which allows it to control polymerizations at significantly reduced loadings compared to the more traditional neutral dithiocarbamates or dithioesters. The fast kinetics is explained by the rapid rotation of the dithioester about the plane of the cationic N-heterocycle. Sulfonated poly(ether ether ketone) (sPEEK) membranes were blended with imidazoles with varying pKas. The proton conductivity of the membranes was evaluated as a function of pKa and temperature. Interestingly, the conductivity of the dry membranes showed a non-monotonous profile over a temperature range of 25 – 150 C. We use a theoretical model to better understand the mechanistic origins of the observed temperature–conductivity profiles. This model is based on the reaction equilibria between sPEEK’s sulfonic acid groups and the basic sites of the added heterocycles. Using the copper-catalyzed 1,3-dipolar “click” cycloaddition reaction, poly(sulfone)s containing pendant azide moieties were functionalized with various amounts of sodium 3-(prop-2-ynyloxy)propane-1-sulfonate and crosslinked with 1,7-octadiyne. The degree of sulfonation as well as the degree of cross-linking was systematically varied by changing the ratios of the aforementioned reagents. The polymers were cast into membranes, acidified, and then tested for proton conductivity, methanol permeability, and membrane-electrode assembly (MEA) performance. / text

Polymers capable of thermally controlled reversible bonding reactions are promising candidates for stimuli responsive materials, as required for self-healing or drug delivery materials. In order to investigate how the dynamic reactions can be controlled, effective analytical tools are demanded that are capable of analyzing not only the polymers but can also monitor the respective bonding reactions. Herein, we employ size exclusion chromatography in a newly developed temperature dependent mode (TD SEC) for the in situ characterization of polymers that undergo retro Diels-Alder (rDA) reaction at temperatures higher than 60 °C. Monitoring the evolution of the molar mass distribution of the polymers during the rDA reaction and evaluating the data quantitatively gives detailed information about the extent of the reaction and allows elucidating structural parameters that can be used for controlling the polymers debonding behavior. In contrast to spectroscopic techniques, TD SEC analyzes only the size of the polymers, hence the polymers do not need to fulfill any particular requirements (e.g. presence of detectable functional groups) but only need to be soluble in the TD SEC, which makes the method universally applicable. Side effects that might bias the results are minimized by using a high temperature chromatograph that allows performing the analysis in a broad temperature range (60 – 200 °C) and in different solvents. Thus, the analysis can be performed under the exact conditions that are required for the bonding reactions and an in situ image is provided.

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