Interactions between materials, their surfaces, and applied stresses are involved in every man-made construction in the world. Therefore, finding ways to interact without altering inherent properties of materials is of great interest. Surface spectroscopies, including second harmonic generation (SHG) and sum frequency generation (SFG), are inherently noninvasive testing methods. Both SHG and SFG are well-developed techniques that can be used in various applications including the characterization of material state. Both of these techniques allow for a noninvasive analysis of various materials, such as metals and polymers. We have used SHG as a method to characterize the change in signal strength before and after mechanical, chemical, and thermal stress. The results have allowed for comparisons to established methods such as electron backscatter diffraction (EBSD) and indenter testing. SHG shows great potential for a new nondestructive evaluation (NDE) technique to provide more information alongside current destructive and nondestructive methods. SFG has long been used to excite vibrations in the bulk and at interfaces. This allows for a deeper understanding of any molecular change induced by stress such as preferred orientation and new chemical interactions. Overall developments in surface specific methods deepens our understanding of how we interface with the universe.

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<p> The models derived from classical light scattering theory for predicting Rayleigh light scattering contain useful parameters such as polymer weight average molecular weight, z-average radius of gyration and virial coefficients. The methods used to estimate these model parameters have not been based on sound statistical principles. It is with improved statistical estimation methods for these parameters that this thesis is concerned with. The methods of linear least squares, non-linear least squares and error propagation were applied to the analysis of wide angle and low angle laser light scattering data and the results compared.</p> <p> From the theory of dynamic light scattering, methods have been developed to reconstruct particle size distributions of unimodal, bimodal and polydisperse polymer solutions from the data accumulated in a single experiment. Some of these methods of reconstruction are based upon the estimation of the coefficients in a sum of exponentials. Estimating sums of exponentials is a highly ill-conditioned problem and the problems encountered thereof are examined in this thesis. Linear least squares, non-linear least squares and exponential sampling techniques were applied to experimental data from a number of simulated polymer distributions and the final results compared.</p> / Thesis / Master of Engineering (MEngr)

<div>For over 20 years, biaxially oriented polypropylene (BOPP) has been used in capacitors as the dielectric material. BOPP has very high breakdown strength, low electric loss, and is relatively inexpensive however, it suffers from low dielectric constant and low usage temperature. The ever growing technology market requires more robust capacitors which can be used in high temperature and pulsed power applications, and the aim of this research is to meet or exceed dielectric properties of BOPP by combining specific polymer materials in layered structures, biaxially orienting the films, and heat setting the films to further improve thermal stability. Post-processing is done on custom built machines which track real-time true stress, true strain and birefringence values, allowing for a more complete picture of mechano-optical properties generated during the stretching process. These data, along with offline characterization techniques such as X-ray scattering and DSC, were coupled with dielectric property testing to help form relationships between polymer processing, morphology, and dielectric properties.</div><div><br></div><div>In Chapter 3, microlayer PET and PVDF (50:50 ratio) films with 32 total layers and thickness around 125 micron were provided by PolymerPlus. Films were first stretched uniaxially at varying temperatures in order to optimize processing conditions. Characterization confirmed PVDF crystal form transformation from alpha to beta form when films were stretched at 95^oC, and presence of - PVDF when stretched in molten state at 185^oC, sandwiched between solid PET layers. Dielectric properties were tested for films stretched at 150^oC, which exhibited low dielectric constant when PVDF spherulites or smaller, broken up fibrils were present, but improved dielectric constant when PVDF morphology consisted of long, highly ordered fibrils. Uniaxial drawing helped lower dielectric loss, and it further signicantly decreased at very high strains. In this case, morphology of uniaxially drawn PET did not have a strong correlation with dielectric constant, but higher PET crystallinity and orientation likely helps to lower dielectric losses.</div><div><br></div><div>Polymer microlayer fims consisting of 32 layers, 50:50 ratio PET to PVDF films were also studied extensively using thermal heat setting technique. Samples with good thickness uniformity after stretching were selected for these experiments, and offline characterization techniques were applied to study morphology. Films were annealed at temperatures around PVDF melting peak, which caused transformation of PVDF polymorphs from primarily alpha to combined gamma and/or gamma' forms. When oriented at 150^oC to 1.5X1, and ' -PVDF were detected in small amounts (via DSC) after annealing at 172^oC, and only ' after higher temperature annealing. Stretching at 150^oC to higher strains produced high amounts of '-PVDF only when annealed at 155^oC for films stretched to 3.5X1, and annealed at 150^oC for films stretched to 2.5X1. Offline characterization led to development of a structural model for PVDF layers alone, by de-laminating film layers. Then, morphology was correlated with dielectric properties by testing lms at room temperature, and at constant frequency, in temperature ramping experiments. Temperature ramping dielectric experiments showed that high percent crystallinity of PET may also help improve loss behavior at high temperatures. Furthermore, samples containing gamma and/or gamma'-PVDF had increasing dielectric constant with increasing temperature, however dielectric loss also greatly increased with increasing temperature. A significant conclusion was that the annealed sample without gamma or gamma'-PVDF present had only a slightly lower dielectric constant at high temperature testing, but also had much lower loss, making it a potential candidate for high temperature capacitor applications.</div><div><br></div><div>Other materials for potential dielectric film applications were studied as well. Two fluoropolymer films consisting of monolayers of ETFE and THV were uniaxially oriented and their morphology was characterized offline to elucidate structure-process-property relationships. Film samples produced were not large enough to be tested for dielectric properties, however morphology development during uniaxial orientation was evaluated. Both films showed nearly affine stretching behavior, and mechano-optical properties were studied during stretching at several temperatures. Combinations of X-ray scattering experiments and AFM led to proposed morphological structure models for each material at varying levels of deformation.</div><div><br></div><div>Finally, in collaboration with A. Schulman, Inc., PET and EVOH compounded blend and three layer PET-EVOH-PET films were oriented uniaxially and the morphology of the two was compared to each other. Potential applications include high barrier food packaging applications, due to the very high oxygen barrier but poor water vapor barrier of EVOH, which can be complimented by PET's high water vapor barrier. Uniaxial orientation of these two film systems showed that mechano-optical behavior was significantly different for blend versus layered films. Crystalline orientation factors were calculated from 1D WAXS data, which showed PET orientation was largely unaffected by increasing EVOH content in blend films, but blending decreased orientation of EVOH. PET's orientation in layered films was also largely unaffected by amount of EVOH in inner layer. EVOH's orientation factor was higher in all layered film compositions compared to neat EVOH film after stretching, suggesting that the coextrusion process is beneficial to increasing orientation of EVOH.</div><div><br></div>

An experimental and modelling investigation of a tetrafunctional initiator designed for free radical polymerizations is presented. Multifunctional initiators are believed to provide two advantages over traditional monofunctional initiators. With a higher number of functional sites per molecule, they are able to increase polymer production while simultaneously maintaining or increasing polymer molecular weight. Examination of the literature indicates the majority of academic and industrial published studies have investigated difunctional initiators with most focusing on styrene. In this thesis, a tetrafunctional initiator, JWEB50, was systematically investigated for a variety of monomer systems in order to develop a better understanding of the behaviour of multifunctional initiators in free radical polymerizations. <br /><br /> A kinetic study comparing the tetrafunctional initiator to a monofunctional counterpart, TBEC, demonstrated that the impact of a multifunctional initiator is dependent upon monomer type. Regardless of the homo- or copolymer system examined, it was observed that the tetrafunctional initiator could produce higher rates of polymerization due to the greater number of labile groups per initiator molecule. However, the influence of the tetrafunctional initiator on the polymer molecular weight was dictated by the polymerization characteristics of the system in question. In the case of styrene, the tetrafunctional initiator maintained similar molecular weights compared to the monofunctional initiator while for methyl methacrylate (MMA), switching from a mono- to a tetrafunctional initiator actually decreased the polymer molecular weight. Other monomers such as butyl acrylate and vinyl acetate and copolymers of MMA and styrene or alpha-methyl styrene were examined to study the effect of initiator functionality in free radical polymerizations. <br /><br /> Subsequent to the kinetic investigation, polystyrene and poly(methyl methacrylate) samples produced with the tetrafunctional initiator were characterized in detail in order to examine the effects of initiator functionality on polymer properties. Samples generated with the monofunctional initiator were used for comparison purposes. Chromatographic and dilute solution methods were able to detect significant levels of branching in the polystyrene sample produced with JWEB50, while poly(methyl methacrylate) samples showed no evidence of branching. Rheological tests involving a combination of oscillatory and creep shear measurements were completed in order to detect differences between samples. The presence of branching using rheological techniques was clearly observed for both polystyrene and poly(methyl methacrylate) samples produced with the tetrafunctional initiator. <br /><br /> In order to explain the experimental results observed in the kinetic and polymer properties studies, a reaction mechanism for polymerizations initiated with a tetrafunctional initiator was proposed and used in the development of a mathematical model. Reactions involving the fate/efficiency of functional groups are properly accounted for, while in the past this had been ignored by modelling work in the literature. Based on model predictions, di-radical concentrations were estimated to be several orders of magnitude smaller than mono-radical concentrations and their contribution in the reaction mechanism was found to be negligible. Modelling results also demonstrated that the concentration and chain length of various polymer structures (i. e. , linear, star or coupled stars) depend upon monomer type and reaction conditions.

An experimental and modelling investigation of a tetrafunctional initiator designed for free radical polymerizations is presented. Multifunctional initiators are believed to provide two advantages over traditional monofunctional initiators. With a higher number of functional sites per molecule, they are able to increase polymer production while simultaneously maintaining or increasing polymer molecular weight. Examination of the literature indicates the majority of academic and industrial published studies have investigated difunctional initiators with most focusing on styrene. In this thesis, a tetrafunctional initiator, JWEB50, was systematically investigated for a variety of monomer systems in order to develop a better understanding of the behaviour of multifunctional initiators in free radical polymerizations. <br /><br /> A kinetic study comparing the tetrafunctional initiator to a monofunctional counterpart, TBEC, demonstrated that the impact of a multifunctional initiator is dependent upon monomer type. Regardless of the homo- or copolymer system examined, it was observed that the tetrafunctional initiator could produce higher rates of polymerization due to the greater number of labile groups per initiator molecule. However, the influence of the tetrafunctional initiator on the polymer molecular weight was dictated by the polymerization characteristics of the system in question. In the case of styrene, the tetrafunctional initiator maintained similar molecular weights compared to the monofunctional initiator while for methyl methacrylate (MMA), switching from a mono- to a tetrafunctional initiator actually decreased the polymer molecular weight. Other monomers such as butyl acrylate and vinyl acetate and copolymers of MMA and styrene or alpha-methyl styrene were examined to study the effect of initiator functionality in free radical polymerizations. <br /><br /> Subsequent to the kinetic investigation, polystyrene and poly(methyl methacrylate) samples produced with the tetrafunctional initiator were characterized in detail in order to examine the effects of initiator functionality on polymer properties. Samples generated with the monofunctional initiator were used for comparison purposes. Chromatographic and dilute solution methods were able to detect significant levels of branching in the polystyrene sample produced with JWEB50, while poly(methyl methacrylate) samples showed no evidence of branching. Rheological tests involving a combination of oscillatory and creep shear measurements were completed in order to detect differences between samples. The presence of branching using rheological techniques was clearly observed for both polystyrene and poly(methyl methacrylate) samples produced with the tetrafunctional initiator. <br /><br /> In order to explain the experimental results observed in the kinetic and polymer properties studies, a reaction mechanism for polymerizations initiated with a tetrafunctional initiator was proposed and used in the development of a mathematical model. Reactions involving the fate/efficiency of functional groups are properly accounted for, while in the past this had been ignored by modelling work in the literature. Based on model predictions, di-radical concentrations were estimated to be several orders of magnitude smaller than mono-radical concentrations and their contribution in the reaction mechanism was found to be negligible. Modelling results also demonstrated that the concentration and chain length of various polymer structures (i. e. , linear, star or coupled stars) depend upon monomer type and reaction conditions.

Orientador: Maria Isabel Felisberti / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T18:00:04Z (GMT). No. of bitstreams: 1 Trinca_RafaelBergamo_D.pdf: 7109183 bytes, checksum: 36f8cbad69a4e17b2adb60ccbc082e94 (MD5) Previous issue date: 2015 / Resumo: Este trabalho teve como objetivo a síntese e a caracterização de poliuretanas segmentadas (SPUs), baseadas em macrodióis de baixa massa molar (2 kDa) ¿ poli(etileno glicol), poli(L-lactídeo) e poli(carbonato de trimetileno) (PEG, PLLA e PTMC, respecti- vamente) ¿ e diferentes diisocianatos (2,4-diisocianato-tolueno e 1,6-diisocianato-hexano, 2,4-TDI e HDI, respectivamente) e extensores de cadeia (1,4-butanodiol e ácido-2,2-bis(hidroximetil)-propanóico BDO e DMPA, respectivamente). Os macrodióis PLLA e PTMC foram sintetizados por polimerização por abertura de anel (ROP). As SPUs foram obtidas por uma rota de duas etapas: pré-polimerização dos macrodióis com diisocianatos e extensão de cadeia. Estudou-se os efeitos da razão mássica entre os macrodióis sobre as propriedades físico-químicas e morfológicas de SPUs mono, bi e tricomponentes baseadas em 2,4-TDI e BDO. Análises de ¹H NMR e GPC revelaram diferenças na reatividade dos macrodióis, que resultaram em diferenças de composição das SPUs em relação ao meio reacional e na distribuição de massa molar. Análises por DSC, DMTA, AFM e ensaios de intumescimento revelaram que as propriedades intrínsecas dos precursores foram combinadas e moduladas nas SPUs. A combinação dos três macrodióis resultou em SPUs com propriedades únicas, não encontradas nas SPUs binárias e monocomponentes. Os efeitos da natureza de diisocianatos e extensores de cadeia sobre as propriedades de SPUs ternárias também foram estudados. As SPUs baseadas em diisocianatos simétricos (HDI) apresentam temperatura de transição vítrea inferior aos baseados em 2,4-TDI, além disso, essas SPUs são semicristalinas, enquanto as baseadas em 2,4-TDI são essencialmente amorfas. A morfologia das SPUs, tipicamente de fase dispersa em uma matriz, é afetada pela proporção entre os macrodióis e pela natureza dos diisocianatos e dos extensores de cadeia. A capacidade das SPUs em intumescer em água é governada pelo teor de PEG e varia com a temperatura (SPUs termo-responsivas) enquanto as SPUs baseadas em DMPA apresentaram intumescimento dependente do pH do meio (SPUs responsivas ao pH). SPUs com menor teor de PEG e ricas em PLLA foram processadas pela técnica de eletrofiação, resultando em filmes nano fibrosos e porosos com propriedades elastoméricas / Abstract: This study aimed at the synthesis and characterization of segmented polyurethanes (SPUs), based on low molecular weight (2 kDa) macrodiols ¿ poly(ethylene glycol), poly(L-lactide) and poly(trimethylene carbonate) (PEG, PLLA and PTMC, respectively) - and different diisocyanates (2,4-diisocyanato-toluene and 1,6-diisocyanato-hexane, 2,4-TDI and HDI, respectively) and chain extenders (1,4-butanediol and 2,2-bis-hydroxymethyl-propanoic acid, DMPA and BDO respectively). The PLLA and PTMC macrodiols were synthesized by ring-opening polymerization (ROP). The SPUs were obtained by a two-step route: synthesis of prepolymers from diisocyanates and macrodiols, followed by a chain extension step. The effects of the weight ratio of macrodiols on the physico-chemical and morphological properties of SPUs based on 2,4-TDI and BDO were studied. The ¹H NMR and GPC analysis revealed differences in reactivity of macrodióis, which resulted in differences in composition of the SPUs in relation to the reaction medium and in the molar mass distribution. Analysis by DSC, DMTA, AFM and swelling assays revealed that the intrinsic properties of the precursors were combined and modulated in SPUs. The combination of the three macrodiols results in SPUs with unique properties not found in binary and single component SPUs. The effects of the nature of the chain extenders and diisocyanates on the properties of ternary SPUs were also studied. The SPUs based on symmetrical diisocyanates (HDI) presents lower glass transition temperatures than those based on 2,4-TDI. Moreover, they are semi crystalline while SPUs based on 2,4-TDI are essentially amorphous. The morphology of the SPUs, typically of a dispersed phase in a matrix, is affected by the macrodiols ratio and by the nature of diisocyanates and chain extenders. The water swelling capability of the SPUs is governed by the PEG content and varies with temperature (temperature responsive SPUs) as well as with pH (pH responsive SPUs) when BDO is replaced with DMPA. SPUs with low PEG content and rich in PLLA were processed by electrospinning technique, resulting in nanofibrous porous films with elastomeric properties / Doutorado / Físico-Química / Doutor em Ciências

Among the myraid energy storage technologies, polymer electrolytes have been widely employed in diverse applications such as fuel cell membranes, battery separators, mechanical actuators, reverse-osmosis membranes and solar cells. The polymer electrolytes used for these applications usually require a combination of properties, including anisotropic orientation, tunable modulus, high ionic conductivity, light weight, high thermal stability and low cost. These critical properties have motivated researchers to find next-generation polymer electrolytes, for example ion gels. This dissertation aims to develop and characterize a new class of ion gel electrolytes based on ionic liquids and a rigid-rod polyelectrolyte. The rigid-rod polyelectrolyte poly (2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT) is a water-miscible system and forms a liquid crystal phase above a critical concentration. The diverse properties and broad applications of this rigid-rod polyelectrolyte may originate from the double helical conformation of PBDT molecular chains. We primarily develop an ionic liquid-based polymer gel electrolyte that possesses the following exceptional combination of properties: transport anisotropy up to 3.5×, high ionic conductivity (up to 8 mS cm⁻¹), widely tunable modulus (0.03 – 3 GPa) and high thermal stability (up to 300°C). This unique platform that combines ionic liquid and polyelectrolyte is essential to develop more advanced materials for broader applications. After we obtain the ion gels, we then mainly focus on modifying and then applying them in Li-metal batteries. As a next generation of Li batteries, the Li-metal battery offers higher energy capacity compared to the current Li-ion battery, thus satisfying our requirements in developing longer-lasting batteries for portable devices and even electric vehicles. However, Li dendrite growth on the Li metal anode has limited the pratical application of Li-metal batteries. This unexpected Li dendrite growth can be suppressed by developing polymer separators with high modulus (~ Gpa), while maintaining enough ionic conductivity (~ 1 mS/cm). Here, we describe an advanced solid-state electrolyte based on a sulfonated aramid rigid-rod polymer, an ionic liquid (IL), and a lithium salt, showing promise to make a breakthrough. This unique fabrication platform can be a milestone in discovering next-generation electrolyte materials. / Ph. D. / Among the myraid energy storage technologies, polymer-based electrolytes have been widely employed in diverse applications such as fuel cell membranes, battery electrolytes, “artificial muscle” mechanical actuators, reverse-osmosis membranes and solar cells. The materials used for each of these applications usually require a specific combination of properties, which include anisotropic orientation, tunable mechanical stiffness (modulus), high ionic conductivity, light weight, high thermal stability and low cost. These critical properties have motivated researchers to find next-generation polymer-based electrolytes, for example “ion gels” that consist of a polymer combined with ionic liquids or salts. This thesis describes development of an ion gel that possesses the following exceptional combination of properties: high ionic conductivity (up to 8 mS cm^-1), widely tunable modulus (0.03 ‒ 3 GPa), ion transport anisotropy up to 3.5×, and high thermal stability (up to 300°C). Thus, this unprecedented material shows liquid-like ion motions inside a matrix with solid-like stiffness, and in a material that can withstand extreme temperatures and will not burn. After obtaining these ion gels, we are then mainly focusing on modifying them for application in safe and high density Li-metal batteries. As a next generation of Li batteries, the Li-metal battery offers higher energy capacity compared to the current Liion battery, thus satisfying our requirements in developing longer-lasting batteries for portable devices and even electric vehicles. However, Li dendrite growth on the Li metal anode has limited the pratical application of Li-metal batteries. This unexpected Li dendrite growth can be supressed by developing polymer electrolytes with high modulus (~ GPa), while maintaining sufficient ionic conductivity (~ 1 mS/cm) for efficient battery operation. In short, this thesis describes an advanced solid-state electrolyte based on a kevlar-like (sulfonated aramid) rigid-rod polymer, an ionic liquid (IL), and a lithium salt, showing promise to make a breakthrough and enable practical Li-metal batteries. Furthermore, the unique fabrication platform for these ion gels represents a new paradigm for discovering next-generation electrolyte materials for a wide variety of applications.

In response to the growing concerns surrounding pollution and sustainability, this research explores the possibility of recycling post-consumer polyester (PET) and nylon (PA6) waste for textile applications. By blending the polymers and analyzing the recyclability and thermomechanical properties of PET/PA6 blends, this study aims to contribute to the development of sustainable materials for textile applications. Virgin PET and PA6 polymers were utilized, with blending ratios ranging from 35% PET to 65% PET to assess the impact of composition on the material’s performance. Compounding and injection molding techniques were employed to prepare samples for characterization. Mechanical testing revealed that the blending of PET and PA6 increased tensile and flexural strengths, with higher PET content leading to increased stiffness. However, impact testing indicated a decrease in toughness with the incorporation of PET, which is attributed to increased crystallinity. Thermal analysis demonstrated that the blends retained sufficient thermal stability for industrial processing, despite slight reductions in degradation temperatures. Differential scanning calorimetry explained the crystallization behavior of the blends, revealing nuanced changes in PET's crystallization temperature. The dynamic mechanical analysis highlighted enhanced elastic modulus and improved rigidity and adhesion. These findings may have significant implications for polymer blend research and applications. Understanding the mechanical and thermal behavior of PET/PA6 blends is crucial for optimizing their performance in textiles and various other sectors. The study contributes to the development of sustainable materials with improved mechanical properties, offering potential solutions to environmental challenges and promoting the adoption of recyclable polymers in society. Future research should focus on optimizing blend compositions with compatibilizers to enhance impact strength and fully integrate these materials into textile production processes.

This dissertation deals with the potential of thermal field-flow fractionation (ThFFF) for the multidetection-based analysis of polymers with complex topology to prove its capability in resolving polymer branching characteristics from measured thermophoretic properties. For that, not yet existent but necessary profound advances in the theory of ThFFF and as well, thermophoresis of branched polymers were generated to allow a full exploitation of the method in the elucidation of polymer topology. Exemplary, two different libraries of branched polymer model systems based on aliphatic-aromatic polyesters and on a new type of short chain branched polyethylene were investigated. On top, the potential of the optimized ThFFF theory was assessed in the context of crosslinked polymer architectures and shines light onto the so far controversially debated topic of electron beam irradiation effects on thermoplastic polyurethane.