This thesis focuses on understanding the factors that affect the properties of polyetherimide (PEI) and improving the properties. As a high-performance thermoplastic resin, the first challenge in PEI application is its high processing temperature and viscosity. Therefore, two supramolecular strategies were applied to not only solve the problem of high processing temperature or viscosity but also enhance the mechanical and flame retardancy. In addition, the yellow to amber color of PEIs limits its applications in high-tech fields such as microelectronics and optoelectronics. Thus, a fundamental study of how end group and molecular weight affect the optical properties of PEIs provides a better knowledge of the mechanism and an effective strategy for designing PEIs. To lower the processing viscosity while maintaining or even improving the mechanical properties of PEI, the first strategy was to synthesize PEI oligomers, and incorporate self-complementary quadruple hydrogen bonding ureidopyrimidinone (UPy) units at the chain ends. Surprisingly, the UPy imparted PEI with a Mn as low as 8 kDa (8k-PEI) with great film formability. Excitingly, 8k-PEI-UPy exhibited an outstanding Young's modulus higher than those of state-of-the-art high-molecular-weight (high-MW) commercial PEIs. Therefore, the incorporation of UPy was proved to be an effective method to synthesize low-molecular-weight, high-mechanical-strength PEIs. Although low-molecular-weight PEI-UPy had high mechanical properties, its limited thermal stability and potentially low flame retardancy, however, restricted its applications in areas such as aerospace and aircrafts. Hence in another strategy, which utilize the phosphonium ionic groups were incorporated into PEI oligomers targeting at achieving high thermal stability, flame retardancy, and mechanical properties simultaneously. Functionalization of dianhydride-terminated PEI by tetraphenylphosphonium bromide afforded the synthesis of phosphonium bromide terminated PEI (PEI-PhPPh3Br), which simultaneously exhibited excellent thermal stability up to ~400°C, outstanding flame retardancy evidenced by high char yield and extremely high limiting oxygen index, and a very high mechanical strength. The study thus provides an efficient strategy to simultaneously enhance the thermal and mechanical properties as well as flame retardancy. Furthermore, the low-molecular-weight PEI-PhPPh3Br had good processability due to its strong shear thinning. In addition to the thermal and mechanical properties and flame retardancy, the end groups affect the optical properties, especially the yellowness, of PEIs. Understanding how end group and molecular weight affect the yellowness, of PEIs is critical for their applications in fields including optoelectronics and microelectronics. Thereby, PEIs with different Mn and various end groups including electron-withdrawing and electron-donating were prepared and characterized. Electron-withdrawing end groups reduced the yellowness and increased the transparency of PEI, regardless of the Mn. Electron-donating end groups increased the yellowness of PEIs with dependence on the Mn. The Mn affected the yellowness of PEIs by changing end group density and the probability of charge-transfer complex formation. The systematic study reveals the correlations among yellowness, end group, and molecular weight of PEIs. / MS / One small step for end groups, one giant leap for properties. Simply tuning the repeating units at the polymer chain ends drastically changes the properties of the polymers. This thesis focuses on the modification of the end groups in low-molecular-weight polyetherimides, a class of high-temperature high-performance engineering thermoplastics, to achieve improved and tunable properties, such as mechanical strength, flame retardancy, and optical properties. On one hand, low-molecular-weight polyetherimides enabled low processing temperatures to decrease the processing cost. On the other hand, the incorporation of noncovalent hydrogen bonding interactions improved the mechanical strength of low-molecular-weight polyetherimides and maintained their thermal stability. This study for the first time showed the incorporation of multiple hydrogen bonds was effective to generate low-molecular weight but high-mechanical-strength polyetherimides. Although multiple hydrogen bonds improved the mechanical properties of polyetherimides, the thermal stability was inadequate for industrial melt processing at elevated temperatures. Alternatively, by incorporating noncovalent electrostatic interaction groups, the polyetherimides showed not only improved mechanical properties but also high thermal stability. Excitingly, their flame retardancy and melt processability were also significantly improved. This polyetherimide has great potential for applications such as aircrafts and aerospace. The end groups affected not only the thermal, mechanical, and rheological properties, but also the optical properties of polyetherimide. Polyetherimide has an intrinsic yellow color originated from the charge transfer complexes that are formed between electron-rich and electron-deficient moieties in the polymer chains. By tuning the concentrations of the different end groups, we controlled the strength of the charge transfer complexes and thus the yellowness of the films. Through a systematic study, a 3D contour was constructed and revealed the relations among the yellowness, the end group, and the molecular weight of polyetherimides. The 3D contour provides guidelines for designing polyetherimides with suitable molecular weights and adequately low yellowness.

Doctor of Philosophy / Enhancing and recycling plastic are two important focuses in plastics research. In this dissertation, enhancing the property of polyetherimide (PEI) is first discussed, and two methods are introduced. Later, a new recycling strategy, the degradation-upcycling (Deg-Up) strategy, is presented. The potential of Deg-Up is evaluated on three plastics: polystyrene (PS), polyethylene (PE), and polypropylene (PP). These plastics serve broad applications in daily life, such as Styrofoam, food containers, shopping bags, garden decorations, and furniture. PEI, a powerful plastic resilient to high temperature and strength, is broadly used in aerospace, defense technology, space exploration, and transportation. However, PEI can only be processed at high temperatures, and PEI films can be easily dissolved or compromised in many solvents, such as solmethine, chloroform, and furanidin. Water is not permeable in PEI, and therefore, it is strongly demanded to modify the PEI structure, giving PEI new and improved properties for water filtration and purification. We have investigated two methods for modifying PEI. Influencers affecting the PEI film's performance are also studied. Plastic upcycling, which converts low-value wastes to high-value chemical products, is a vital technology that mitigates the environmental crisis and the plastic recycling problem. However, effective plastic upcycling improving waste value with good selectivity toward products with ten-fold or even greater value is uncommon due to the lack of upcycling theories/methodologies. This dissertation presents a new upcycling strategy; the degradation-upcycling strategy (Deg-Up) comprises degradation reactions yielding preliminary chemicals and upcycling reactions converting the preliminary chemicals to desired high-value products. Based on the Deg-Up strategy, PS is converted to fragrances and drug precursors, and PE and PP are Deg-Up to fats and soaps. The economic and industrial possibilities are also discussed through a preliminary industrial design and an economic analysis.

Techn. Universiẗat, Diss., 2004--Berlin.

Orientador: Maria Isabel Felisberti / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T14:29:50Z (GMT). No. of bitstreams: 1 Alexandrino_EvandroMendes_M.pdf: 5484383 bytes, checksum: 6b7a12479a8a08d807230df845e7bd12 (MD5) Previous issue date: 2012 / Resumo: A combinação de polianilina (PAni) com termoplásticos, elastômeros e termorrígidos na forma de compósitos e blendas tem sido amplamente estudada nas últimas duas décadas. Entretanto, a utilização de termoplásticos de alto desempenho térmico em compósitos ou blendas com polianilina tem sido pouco explorada devido às altas temperaturas de processamento destes termoplásticos e no fato de que, nestas condições, a PAni se apresenta termicamente instável de acordo com a natureza do dopante utilizado. A poli(éter imida) (PEI) é um termoplástico de engenharia que apresenta boas propriedades térmicas e mecânicas, porém apresenta altas temperaturas de processamento. Nesta dissertação de Mestrado, PAni foi sintetizada em escala laboratorial através de oxidação química, gerando a PAni dopada com ácido clorídrico (PAni HCl). A PAni HCl foi desdopada e redopada para obtenção de PAni dopada com ácido p-tolueno sulfônico (PAni APTS) ou com um complexo de cobalto com acetonitrila (PAni CoAcn). Foram preparados compósitos de PEI com PAni APTS, com teor de PAni entre 2,5 a 20% em massa, por extrusão em uma mini-extrusora dupla rosca. Compósitos de PEI plastificada (PEIR) com resorcinol bis(difenil fosfato) (RDP) também foram preparados com PAni APTS ou PAni CoAcn, com a mesma faixa de concentração em massa. As PAni sintetizadas e os compósitos foram caracterizados por métodos térmicos, morfológicos, mecânicos e elétricos. Os compósitos apresentam boas propriedades mecânicas e térmicas, principalmente os compósitos com PAni CoAcn, porém eles apresentam características de materiais isolantes / Abstract: The combination of polyaniline (PAni) with thermoplastics, thermosets and elastomers as composites and blends has been widely studied in the last two decades. However, the use of high thermal performance thermoplastic in composites or blends with polyaniline has been little explored due to the high processing temperatures of these thermoplastics and the fact that under these conditions the PAni presents thermal instability according to the nature of the dopant used. The polyetherimide (PEI) is an engineering thermoplastic presenting good thermal and mechanical properties, however, it is processed in the melting state at high temperatures. In this dissertation, PAni was synthesized in laboratory scale by chemical oxidation, leading to hydrochloric acid doped PAni (PAni HCl) was dedoped and redoped to obtain p-toluene sulfonic acid doped PAni (PAni APTS) or a cobalt - acetonitrile complex doped PAni (PAni CoAcn). PEI composites were prepared with PAni APTS, in the composition range of 2.5 to 20wt%, by extrusion in a twin screw mini-compounder. PEI plasticized composites (PEIR) with resorcinol bis(diphenyl phosphate) (RDP), were also prepared with PAni APTS and PAni CoAcn, at the same composition range. The PAni synthesized and the composites were characterized by thermal, morphological, mechanical and electrical methods. The composite exhibited good mechanical and thermal properties, especially those with PAni CoAcn, nevertheless they still stand as insulating materials / Mestrado / Físico-Química / Mestre em Química

Polyetherimides are an important class of engineering thermoplastics used in a broad range of industries and applications because of their high heat resistance and stability, high strength and moduli, excellent electrical properties over a wide range of temperatures and frequencies, good processability, good adhesive properties, and chemical stability. All-atom molecular dynamics (MD) simulation is a useful tool to study polymers, but the accessible length and time scales are limited. In this thesis, we explore several computational methods that go beyond all-atom MD simulations to investigate polyetherimides. First, we have developed a transferable coarse-grained MD model of polyetherimides that captures their mechanical and thermal expansion properties. Our results show that in order to make the model transferable, it is critical to include an entropic correction term in the coarse-grained force field and require the coarse-grained model to capture the thermal expansion property of polyetherimides. Secondly, we have constructed a predictive model of the glass transition temperature (Tg) for polyimides by using machine-learning algorithms to analyze existing data on Tg reported in the literature. The predictive model is validated by comparing its predictions to experimental data not used in the training process of the model. We further demonstrate that the diffusion coefficients of small gas molecules can be quickly computed with all-atom MD simulations and used to determine Tg. Finally, we have developed a Monte Carlo (MC) program to model the polymerization process of branched polyetherimides and to compute their molecular weight distribution for a wide range of systems, including fully reacted, partially reacted, stoichiometric, and nonstoichiometric ones. The MC results are compared to the predictions of the Flory-Stockmayer theory of branched polymers and an excellent agreement is found below the gel point of the system under consideration. Above the gel point, the Flory- Stockmayer theory starts to fail but the MC method can still be used to quickly determine the molecular weight distribution of branched polyetherimides under very general conditions. / Doctor of Philosophy / Polyetherimides are an important category of engineering plastics with wide applications in many fields because of their superior mechanical, thermal, chemical, and electrical properties. All-atom molecular dynamics simulations serve as a useful tool to study the properties of polyetherimides in silico. However, such simulations are computationally expensive and therefore limited to small system sizes and short time scales. To overcome these issues, we employed various computational techniques in this thesis to model polyetherimides. First, we have developed a coarse-grained model of polyetherimides where atoms are grouped into beads. We show that molecular dynamics simulations on the basis of the coarse-grained model can be used to provide a reasonable description of the mechanical and thermal expansion properties of polyetherimides. Secondly, we have constructed a predictive model of the glass transition temperature, which is the temperature at which a material enters a glassy state when cooled rapidly, of polyimides using machine-learning algorithms. This model is capable of estimating the glass transition temperature of polyimides within an accuracy of ± 15 K even for those not synthesized yet. We further show that the diffusion coefficients of gas molecules, in addition to the polymer density, can be computed accurately with all-atom molecular dynamics simulations and used to determine the glass transition temperature of polyimides. Finally, we have developed a Monte Carlo scheme to efficiently model the polymerization and compute the chain-length distribution of branched polyetherimides under very general conditions. The results from Monte Carlo simulations are compared to the predictions of the Flory-Stockmayer theory of branched polymers. The range of applicability of the theory is revealed. Overall, we have demonstrated several computational techniques that can be used to efficiently model polyetherimides, potentially other polymers as well, beyond the widely-used all-atom molecular dynamics simulations.

Polyetherimide/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (PEI/BSTZ8291) composites are fabricated using PEI, dispersant, solvents, and BSTZ powder. The effects of the content of BSTZ8291 filler on the chemical, physical, mechanical and dielectric properties of PEI/BSTZ8291 composites are studied in this paper. As the content of BSTZ filler increases from 10 wt% to 70 wt%, the relative permittivity of PEI/BSTZ8291 composites at 1 MHz increase from 2.58 to 17.71. The measurement of relative permittivity of PEI/BSTZ8291 composites is developed using the ¡§Rectangular Cavity Resonator¡¨ method from 1 GHz to 13.5 GHz. The relative permittivity is calculated by observing the frequencies of resonant cavity modes. The relative permittivity of PEI/BSTZ8291 composites is almost unchanged as the measured frequency increases from 1 GHz to 13.5 GHz. The presented characteristics are better than those of polymer/BaTiO3 composites. The improvement in the tensile strength of PEI/BSTZ8291 composites may be caused by the increased interactions between neat PEI and BSTZ8291 ceramic powder, and no phase separation phenomenon occurred. The Young¡¦s modulus of the PEI/BSTZ8291 composites is improved by about 58% as the content of BSTZ8291 filler from 0 to 50 wt% and the elongation at break of the composites decreases as the content of BSTZ8291 filler increases, indicating that the composite becomes somewhat brittle as compared with neat PEI. PEI/BSTZ8291 composite substrates are developed for the applications of circularly polarized (CP) antennas. A CP antenna with a simple structure is developed as the ultra high frequency (UHF) band radio frequency identification (RFID) reader application. The fabricated antenna has an impedance bandwidth spanning from 901 to 949 MHz, which covers the entire band of Taiwan UHF-RFID frequency. The measured return loss, Smith chart, axial ratio, radiation patterns and CP gain characteristics of antennas fabricated on PEI/BSTZ8291 composites are excellent in the band of Taiwan UHF-RFID frequency. It is demonstrated that the CP antenna fabricated on PEI/BSTZ substrate has the better characteristics and small size than those fabricated on FR4 substrate.

No description available.

Facile monomer synthesis provided routes towards novel step-growth polymers for emerging applications. Adjustment of reaction conditions enabled green synthetic strategies, and promising scalability studies offered impetus for industrial funding. Engineering thermoplastics, such as linear polyetherimides (PEIs), had carefully targeted molecular weights for analysis of the effect of molecular weight and regiochemistry on the thermomechanical and rheological properties of PEIs. The design of linear, high performance PEIs comprising 3,3'- and 4,4'-bisphenol-A dianhydride (bis-DA) and m-phenylene diamine (mPD) provided an opportunity to elucidate the influence of dianhydride regiochemistry on thermomechanical and rheological properties. This unique pair of regioisomers allowed the tuning of the thermal and rheological properties for high glass transition temperature polyimides for engineering applications. The selection of the dianhydride regioisomer influenced the weight loss profile, entanglement molecular weight, glass transition temperature (Tg), tensile strain-at-break, zero-shear melt viscosity, average hole-size free volume, and the plateau modulus prior to viscous flow during dynamic mechanical analysis (DMA). The 3,3'-PEI composition interestingly exhibited a ~20 °C higher Tg than the corresponding 4,4'-PEI analog. Moreover, melt rheological analysis revealed a two-fold increase in Me for 3,3'-PEI, which pointed to the origin of the differences in mechanical and rheological properties as a function of PEI backbone geometry. The frequently studied 4,4'-PEI exhibited exceptional thermal, mechanical, and rheological properties, yet the 3,3'-PEI regioisomer lacked significant study in the industrial and academic sectors due to its 'inferior' properties, namely poor mechanical properties. Introduction of long-chain branching (LCB) into PEIs provided a unique comparison between a commercially relevant PEI (Ultem® 1000) and a regioisomer infrequently found in the literature. Thermal stability remained consistent for each regioisomer, and Tgs for the 3,3'- and 4,4'-LCB-PEIs agreed well with prior literature. Rheological analysis demonstrated typical shear thinning and low-shear viscosity trends for LCB systems. The targeted molecular weights for the 3,3'-LCB-PEIs were well below the Me cutoff for "high molecular weight," and for this reason the rheological properties demonstrated inconsistent trends. Further study of PEIs led to the incorporation of ionic endgroups. These provided physical crosslinks, which enhanced mechanical and rheological properties of branched PEIs compared to their non-ionic analogs. The Tgs decreased with an increase in branching concentration for the phenyl-terminated PEI, while it remained unchanged for the ionically-endcapped PEIs. The divalent salts demonstrated higher mechanical strength and melt viscosities compared to the monovalent salt and the non-ionic PEIs. Interestingly, the zinc-endcapped PEI series exhibited decreased high-shear viscosities compared to the other PEIs, lending to promising industrial applications for the zinc-endcapped branched and linear PEIs for high temperature applications. Additional engineering thermoplastics in the form of bio-based polyureas exhibited mechanical properties similar to those of non-bio-based polyureas. The isocyanate-free synthetic route incorporated an essential urea degradation mechanism at elevated temperatures to produce isocyanic acid, which then reacted with amines to produce linear polyurea thermoplastics. Urea provided a sustainable and bio-friendly reagent for high molecular weight, isocyanate-free polyureas. Poly(propylene glycol) triamine enabled the long-chain branching of thermoplastic polyureas. Differential scanning calorimetry (DSC) showed no change in Tg for the series; however, melting peaks decreased in intensity as the branching concentration increased, indicating a reduction in crystallinity. Tensile testing eluded to a decrease in ultimate stress values for higher branching concentrations, while melt rheology showed significant differences in melt viscosities. Viscosities increased markedly with an increase in branching concentration, signifying greater entanglement and stronger physical crosslinks for the branched polyureas. Further analysis of possible isocyanate-free routes led to the use of 1,1'-carbonyldiimidazole (CDI) to generate polyureas and polyurethanes. CDI, known in the literature for its use in amidation and functionalization reactions, enabled the production of well-defined and stable polyurethane monomers. The functionalization of butanediol with CDI yielded an electrophilic biscarbamate monomer, bis-carbonylimidazolide (BCI), suitable for further step-growth polymerization in the presence of amines. The reaction of this novel monomer with aliphatic diamines produced thermoplastic polyurethanes with high thermal stability, tunable glass transition temperatures based on incorporation of flexible polyether segments, and creasable thin films. It is envisioned that CDI functionalized diols will afford access to various polymeric backbones without the use of toxic isocyanate-containing strategies. Additionally, non-isocyanate polyurethane (NIPU) foams were produced from BCI monomers without the need of blowing agents, catalysts, or solvents. These materials offered an alternative to existing foaming technology, which typically employed isocyanates. Polyurethanes were foamed through a CO2 thermal decomposition mechanism involving the BCI monomers. We investigated two series of polyurethane foams with a tunable Tg range from ~0 °C to ~110 °C. We found that the incorporation of aromatic amines vastly altered the foam thermomechanical properties, and the resulting foams were closed-cell in nature. / Doctor of Philosophy / Step-growth polymers play a significant role in commercial and industrial applications. On-going work in this field focuses on sustainability, biodegradability, and improved processability. This dissertation encompasses the improvement and innovation of current and novel engineering thermoplastics and foams. The careful purification and step-growth synthetic strategies herein, afforded targeted molecular weights for analysis of linear and long-chain branched (LCB) polyetherimides (PEIs). Further analysis of LCB-PEIs, with monovalent and divalent ionic endgroups, provided an opportunity to study the effect of ionic interactions and physical crosslinks at high temperatures (>300 °C). The long branches improved the melt processability compared to linear analogues at equivalent molecular weights. The challenge to investigate polyurethanes using non-isocyanate methodologies offered an opportunity to apply fundamental small-molecule, organic synthesis to macromolecular science. 1,1'-Carbonyldiimidazole (CDI) provided a platform to generate polymeric chains from industrially relevant monomers. Additional testing serendipitously discovered the generation of CO2 upon thermal degradation of the novel monomers. Harnessing the release of CO2, during the gelation of polyurethanes, provided an isocyanate-, catalyst-, and solvent-free synthetic route towards polyurethane foams that boasts scalability and industrial relevance.

No description available.

Cette thèse traite de la modification de surface des nanotubes de carbone avec des polymères Le chapitre I présente l'état de l'art des matériaux hybrides associant des liquides ioniques avec des nanotubes de carbone (NTC) ou du graphenes. Le chapitre II commence par un aperçu général de l'adsorption non-covalente de polymères sur la surface de NTC, suivi d'une description détaillée de l'étude réalisée sur la fonctionnalisation non covalente des nanotubes de carbone avec divers liquides ioniques polymérisable (LIP) à base d'imidazolium. Dans ce cadre, nous avons comparé deux méthodes expérimentales: la polymérisation in situ et le mélange en solution. Une des applications les plus importantes des NTC se situe dans le domaine des nanocomposites polymères/NTC. Le chapitre III décrit la formation de composites polyetherimide/NTC à partir des NTC-LIP obtenue dans la chapitre II. La préparation des composites en utilisant la méthode dite « solvent casting » est détaillée. Les NTC bruts, oxydés à l'acide nitrique et fonctionnalisé par le LIP ont été comparés. Des mesures mécaniques, thermiques et électriques de ces composées ont été aussi réalisées. Le dernier chapitre, divisé en deux sections, traite de la fonctionnalisation covalente des nanotubes de carbone avec une variété de polymères en utilisant deux approches différentes: "grafting from" et "grafting to". En utilisant la première approche, nous avons réalisé la croissance de chaînes de polyamide (PA) à partir de la surface de nanotubes de carbone fonctionnalisés avec le caprolactame par polymérisation anionique par ouverture de cycle. Les propriétés de traction des composites à base de PA ainsi préparées ont été étudiées. La polymérisation radicalaire de monomères vinyliques à base de LI de type imidazolium greffés à la surface de NTC est également présentée dans cette partie. Dans la deuxième partie du chapitre IV, nous présentons plusieurs stratégies de fonctionnalisation, y compris l'addition radicalaire et le greffage sur les défauts de NTC, pour la préparation des NTC fonctionnalisés de manière covalente avec des polymères compatibles avec des matrices époxy / This thesis deals with the surface modification of multi-walled carbon nanotubes with polymers with the aim to achieve a high level of dispersion in polymer matrices. Chapter I gives a comprehensive review of the state of the art of hybrids of ionic liquids with carbon nanomaterials, particularly, nanotubes and more recently, graphene. Chapter II starts with a general overview of the non-covalent adsorption of polymers onto the CNT surfaces followed by a detailed description of the study carried out on the non-covalent functionalization of CNTs with various imidazolium based polymerized ionic liquids (PIL). For this purpose, we further compare the two experimental methods: in situ polymerization and solution mixing. One of the most important applications of CNT is in polymer/CNT composites. Chapter III describes the formation of polyetherimide/CNT composites starting from PIL-CNT hybrids obtained in Chapter II. The preparation and characterization of composites using solvent casting methods have been detailed. Pristine, acid oxidized and PIL functionalized CNTs have been compared. Mechanical, thermal and electrical property measurements on these composites have also been described. The last chapter – Chapter IV, divided into two sections, discusses the covalent functionalization of CNTs with a variety of polymers using two main approaches: “grafting from” and “grafting to”. Using the first approach we have grown polyamide (PA) chains from the surface of caprolactam grafted CNTs by anionic ring opening polymerization. The tensile properties of the PA based composites prepared therefrom containing pristine, amine- and PA-functionalized CNTs have been investigated. The radical polymerization of vinyl imidazolium based IL monomers attached to the activated CNT surface is also given in this section. In the second part of Chapter IV, we have reported several “grafting to” functionalization strategies including radical addition and “defect site” grafting used for the preparation of CNTs covalently attached with polymers intended to blend well with epoxy matrices