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Polymer laboratory: teaching polymer chemistry

Ferreira, Olga; Plasencia, Paula; Afonso, Maria João A.P.S.; Silva, A.; Barreiro, M.F.
Fonte: Pixel Publicador: Pixel
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
36.67%
This work aims to present the results achieved within the science communication project CV/PVI/1386-Laboratório de Polímeros (Polymer Laboratory), financed by Ciência Viva - Agência Nacional para a Cultura Científica e Tecnológica (2006-2008). Several demonstration/experimental kits were developed concerning three main thematics: (1) Polymer concepts; (2) Polymer synthesis and (3) Polymer properties. Additionally, a fourth module entitled “Technological aspects” was also put into practice by taking advantage from the LSRE-IPB installed capacity in the area of Polymer Chemistry. The various modules were designed to reach a wide target public, including students from primary and secondary schools to undergraduate levels, and general society. Polymer architecture (linear, branched and crosslinked) and polymer synthesis procedures (step versus chain growth polymerization) can be demonstrated by using the “Kit-models” to construct simplified molecular models that illustrate those concepts. Synthesis examples include the preparation of linear polymers and networks. In the first case, Nylon 6,6 synthesis is proposed and, in the second one, a polyurethane foam and a PVA polymer slime can be experienced. Among polymer properties...

Surface characterization of absorbing polymer films deposited on transparent glasses

GONCALVES, Debora; TRAVAIN, Silmar A.; GIACOMETTI, Jose A.; IRENE, Eugene A.
Fonte: EUROPEAN POLYMER FEDERATION Publicador: EUROPEAN POLYMER FEDERATION
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.41%
PANI films were deposited on glass substrates by in-situ polymerization and characterized by UV-VIS spectroscopy and atomic force microscopy. A method is developed to accurately analyze ellipsometric data obtained for transparent glass substrates before and after modification with absorbing polymer films. Surface modification was made with an overlayer such as polyaniline ( PANI), which exhibits different optical properties by varying its oxidation state. First, the issue of using transparent substrates for ellipsometry studies was examined and then, spectroscopic ellipsometry was used to characterize absorbing overlayers on transparent glasses. The same methodologies of data analysis can be also applied to other absorbing films on transparent substrates, and deposited by different techniques.

Preparação, caracterização e aplicação de eletrólitos polímericos gel em células solares TiO2/corante; Preparation, characterization and application of gel polymer electrolyte in dye sensitized solar cells

João Eduardo Benedetti
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/12/2010 PT
Relevância na Pesquisa
36.66%
Este trabalho consistiu na preparação, caracterização e posterior aplicação de eletrólitos poliméricos gel em celulas solares de TiO2/corante. No Capítulo I, e apresentado uma introdução geral sobre células solares e eletrólitos poliméricos. O Capítulo II contém os objetivos deste trabalho. No Capítulo III, são preparados os eletrólitos polimérico gel utilizando a matriz polimérica de poli(oxido de etileno-co-2-(2-metoxietoxi) etil glicidil eter) (P(EO/EM)) contendo I2 e várias concentrações de g-butirolactona (GBL) e LiI. Esses eletrólitos foram caracterizados por medidas de calorimetria exploratória diferencial (DSC), ressonância magnética de Li (RMN), termogravimetria (TGA), difração de raios-X (DRX), condutividade e voltametria cíclica (VC). O eletrólito polimérico gel P(EO/EM)/GBL/LiI/I2 apresentou excelentes propriedades químicas e eletroquímicas. Esses eletrólitos foram aplicados nas células solares de TiO2/corante, conforme e apresentado no Capítulo IV. As células solares foram caracterizadas por meio das curvas de corrente-potencial (J-V), estimativa do tempo de vida do eletron e espectroscopia de absorção transiente (TAS). De modo geral, os dispositivos montados com o eletrólito polimérico (P(EO/EM)/GBL/LiI/I2 apresentaram um aumento da fotocorrente com a incorporação de GBL no eletrólito. Esse resultado e influência da maior difusão das especies redox no meio. Em contrapartida...

Otimização do eletrolito polimerico baseado no complexo poli (epicloridrina-co-oxido de etileno) com NaI/I2 para celulas solares de TiO2/corante; Optimization of the polymer electrolyte based on the complex poly (epichlorohydrin-co-ethylene oxide) with NaI/I2 for application in dye sensitized solar cells

Viviane Carvalho Nogueira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 23/05/2005 PT
Relevância na Pesquisa
36.64%
As células solares de TiO2 sensibilizadas por corante, DSSC, são constituídas por um filme nanoporoso de TiO2 modificado por um corante fotosensibilizador, um eletrólito no qual está presente o par redox I¨/I3¨, e um contra-eletrodo de platina. Desde 1996 o Laboratório de Polímeros Condutores e Reciclagem (LPCR) do Instituto de Química da Unicamp vem se dedicando ao desenvolvimento de células solares de TiO2/corante de estado sólido, através do emprego de eletrólitos poliméricos. A substituição do eletrólito líquido por um eletrólito polimérico visa minimizar os problemas decorrentes de vazamento ou evaporação do solvente, além de facilitar a montagem dos dispositivos. Estudos anteriores mostraram que as DSSC com eletrólito polimérico apresentam uma baixa estabilidade. Como a durabilidade de um dispositivo é um fator fundamental visando sua produção e uso em larga escala, o objetivo desta dissertação foi investigar as possíveis causas da baixa estabilidade das DSSC e otimizar a composição do eletrólito polimérico baseado em poli(epicloridrina-co-óxido de etileno), P(EO-EPI)84:16, NaI e l2, visando obter células solares com maior eficiência e estabilidade. Os resultados obtidos mostraram que a baixa estabilidade destas células está relacionada com a elevada quantidade de solvente residual presente no dispositivo após o término de sua montagem. A primeira parte do trabalho consistiu em eliminar esta interferência. O eletrólito polimérico foi otimizado através da adição do plastificante poli(etileno glicol) metil éter...

Recuperação de óleo por injeção de polímeros : abordagens experimental, analítica e numérica em pequena escala; Oil recovery by polymer flooding - experimental, analytical and numerical approaches

Vinicius de Souza Rios
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/07/2014 PT
Relevância na Pesquisa
36.66%
Dadas as práticas atuais de gerenciamento de reservatórios, motivadas pelos altos preços do petróleo e baixa eficiência de métodos convencionais de recuperação, as empresas operadoras têm considerado a aplicação de métodos de recuperação avançada (EOR) cada vez mais cedo na vida produtiva dos seus campos. Neste contexto, a importância de pesquisas e desenvolvimento de métodos avançados como injeção de polímeros tem aumentado fortemente nas últimas décadas. A injeção de polímero é um método químico de recuperação indicado para casos de reservatórios heterogêneos ou em que a razão de mobilidades entre água e o óleo é alta, dita desfavorável. Este método mostra-se bastante eficaz, atuando no aumento da viscosidade da água, que reflete em deslocamentos mais eficientes devido à redução da razão de mobilidades. Visando avaliar o desempenho deste método de recuperação, este trabalho apresenta um estudo da técnica de injeção de polímeros através de três abordagens: experimental, analítica e numérica. O trabalho experimental envolveu testes utilizando uma amostra de arenito, em que se realizou o deslocamento de óleo mineral grau SAE 15W-40, com viscosidade acima de 200 cP em condição ambiente. Como fluido deslocante...

Effect of molecular properties on the performance of polymer light-emitting diodes

Ramos, Marta M. D.; Almeida, A. M.; Correia, Helena M. G.; Ribeiro, R. M.; Stoneham, A. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /11/2004 ENG
Relevância na Pesquisa
36.62%
The performance of a single layer polymer light-emitting diode depends on several interdependent factors, although recombination between electrons and holes within the polymer layer is believed to play an important role. Our aim is to carry out computer experiments in which bipolar charge carriers are injected in polymer networks made of poly(p-phenylene vinylene) chains randomly oriented. In these simulations, we follow the charge evolution in time from some initial state to the steady state. The intra-molecular properties of the polymer molecules obtained from self-consistent quantum molecular dynamics calculations are used in the mesoscopic model. The purpose of the present work is to clarify the effects of intra-molecular charge mobility and energy disorder on recombination efficiency. In particular, we find that charge mobility along the polymer chains has a serious influence on recombination within the polymer layer. Our results also show that energy disorder due to differences in ionization potential and electron affinity of neighbouring molecules affects mainly recombinations that occur near the electrodes at polymer chains parallel to them.; Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência...

Theoretical study of the influence of the morphology in polymer-based devices functioning

Barbosa, Helder M. C.; Ramos, Marta M. D.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em /01/2009 ENG
Relevância na Pesquisa
36.66%
It is well known that the morphology of polymer-based optoelectronic devices can influence their efficiency, since the ways that polymer chains pack inside the active layer can influence not only the charge transport but also the optic properties of the device. By using a mesoscopic model we carried out computer experiments to study the influence of the polymer morphology on the processes of charge injection, transport, recombination and collection by the electrodes opposite to those where the injection of bipolar charge carriers take place. Our results show that for polymer layers where the conjugated segments have perpendicular and random orientation relative to the electrodes surface, the competition between charge collection and charge recombination is affected when the average conjugation length of the polymer strands increase. This effect is more pronounced with the increase of the potential barrier at polymer/electrode interfaces that limit charge injection and increase charge collection. For these molecular arrangements the intra-molecular charge transport plays a major role in device performance, being this effect negligible when the polymer molecules have their axis parallel to the electrodes. Although the polymer morphology modelled in this work is far from real...

The effect of the intramolecular properties in single-carrier polymer diodes

Barbosa, Helder M. C.; Ramos, Marta M. D.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /12/2009 ENG
Relevância na Pesquisa
36.66%
The electric behaviour of polymer diodes has the influence of several factors such as the electrodes work function, the experimental conditions used to deposit the active component or the chemistry of the polymer. Although experimentally it is possible to study the effect of some of these factors on the device performance, for instance by changing the chemical structure of the polymer used or the type of electrodes, it is impossible to study individually each one of these effects because changing one of them can influence the others. Quantum mechanical calculations have shown that depending on the chemical structure of the polymer, its intramolecular properties (e.g. ionization potential, electron affinity or intramolecular charge mobility) can be changed. To understand the effect of the intramolecular properties in the performance of polymer diodes we use a generalized dynamical Monte Carlo method that considers the nanostructure of the polymer layer and the main electronic processes involved in diode functioning. Our results show that the influence of the intramolecular properties on the electric behaviour of pristine polymer-diodes with ohmic contacts depends on the morphology of the polymer layer at nanoscale that can alter not only hole and electron current density for the same applied electric field but also charge density and charge distribution inside the polymer layer.; Fundação para a Ciência e a Tecnologia (FCT) – POCTI/CTM/41574/2001; CONC-REEQ/443/EEI/2005; SFRH/BD/22143/2005; FEDER

Diffusion through Reversibly Associating Polymer Networks

Anthamatten, Mitchell ; Park, Helen
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Artigo de Revista Científica Formato: Number of Pages:5
ENG
Relevância na Pesquisa
36.64%
Many natural macromolecules, like proteins and DNA, are equipped with site-specific, non-covalent molecular interactions. These interactions lead to intricate secondary structures such as the double helix, self-assembled phospholipid membrane bilayers, and precisely folded protein structures that are vital to life and rely on non-covalent interactions to "guide" molecular organization. Mankind has begun to borrow such concepts from nature to engineer responsive materials. In recent years, for example, the use of strong, highly directional hydrogen bonds has enabled polymers with temperature-tunable architectures to be engineered. Site-specific hydrogen bonding and ionic interactions in solution can lead to aggregation, gelatin, or sudden viscosity changes that are triggered by slight changes in polymer concentration, pH, or temperature.3·5 In the melt, rigid and elastic polymer networks can be reversibly transformed into a low viscosity polymer melt simply by heating. This new materials concept is playing an important role in the development of recyclable (thermoplastic) elastomers. The quest to fully understand structure-property relationships of polymers decorated with hydrogen bonding groups has opened a new field at the interface of polymers and supramolecular chemistry. Our laboratory has synthesized novel polymer networks which contain both covalent crosslinks and non-covalent crosslinks (Figure 1). Non-covalent crosslinks arise from the presence of ureidopyrimidone (UPy) sidegroups...

Diffusion through Reversibly Associating Polymer Networks

Anthamatten, Mitchell ; Park, Helen
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Artigo de Revista Científica Formato: Number of Pages:5
ENG
Relevância na Pesquisa
36.64%
Many natural macromolecules, like proteins and DNA, are equipped with site-specific, non-covalent molecular interactions. These interactions lead to intricate secondary structures such as the double helix, self-assembled phospholipid membrane bilayers, and precisely folded protein structures that are vital to life and rely on non-covalent interactions to "guide" molecular organization. Mankind has begun to borrow such concepts from nature to engineer responsive materials. In recent years, for example, the use of strong, highly directional hydrogen bonds has enabled polymers with temperature-tunable architectures to be engineered. Site-specific hydrogen bonding and ionic interactions in solution can lead to aggregation, gelatin, or sudden viscosity changes that are triggered by slight changes in polymer concentration, pH, or temperature.3·5 In the melt, rigid and elastic polymer networks can be reversibly transformed into a low viscosity polymer melt simply by heating. This new materials concept is playing an important role in the development of recyclable (thermoplastic) elastomers. The quest to fully understand structure-property relationships of polymers decorated with hydrogen bonding groups has opened a new field at the interface of polymers and supramolecular chemistry. Our laboratory has synthesized novel polymer networks which contain both covalent crosslinks and non-covalent crosslinks (Figure 1). Non-covalent crosslinks arise from the presence of ureidopyrimidone (UPy) sidegroups...

The role of polymer flocculants in microfiltration of surface water

Wang, Sen
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.72%
Polymer flocculants, traditionally used with primary coagulant to enhance flocculation and sedimentation, are used in the coagulation-/microfiltration process as well assuming they can improve membrane performance similarly. However, there are several uncertainties concerning the use of polymer flocculants in the coagulation-microfiltration process. First, polymer flocculants may not have measurable effect on turbidity removal, because microfiltration membranes can remove significantly smaller particles than those removed by the conventional treatment process. Second, the effect of using polymer flocculants on NOM removal has been controversial. Although a number of studies reported improved NOM removal when polymers were used, others reported no or negative impact of polymers on NOM removal. Third, polymer flocculants are high molecular weight organic compounds. When carried over to membrane residual polymers can potentially foul the membranes. Finally, the use of polymer flocculants will change floc properties (i.e. size, fractal dimension, and stickiness) and subsequently bring uncertain effect on cake layer resistance. Therefore, the role of polymer flocculants in coagulation-microfiltration system needs to be carefully assessed for system optimization. In the reported research...

Density Functional Theory Study of Microstructure and Phase Behavior of Stimuli-Responsive Polymer Brushes

Gong, Kai
Fonte: Universidade Rice Publicador: Universidade Rice
Relevância na Pesquisa
36.67%
Stimuli-responsive polymer materials can change their structure and physical properties drastically on external signals like a change in temperature, solvent properties (pH, ionic strength), the magnetic or electrical field etc. Such "smart" polymer materials play an important role in various fields such as biology, medicine, and soft materials. However, it is a great challenge to investigate such "smart" polymer materials due to highly inhomogeneous structure at the molecular scale and the complex interactions. In this thesis, we have systematically studied three common types of stimuli-responsive polymer brushes such as temperature responsive polymer brushes, copolymer brushes, and mixed polymer brushes by using classical density functional theory. We find a surface outer layer switch for both copolymer brushes and mixed polymer brushes with a selective solvent. Without using any temperature-dependent parameter, our theory successfully captures the lower critical solution temperature behavior of the associating polymer brushes. Related parameters such as molecular weight, grafting density, and solvent properties that affect the phase behavior of these stimuli-responsive polymer brushes have been also investigated. Qualitatively consistent with experimental observations...

Properties of absorbent polymer polymer extractants for the selective removal of target molecules from fermentation systems

Dafoe, JULIAN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.66%
This thesis investigated polymer properties for their application as extractants in two-phase partitioning bioreactors (TPPBs), which are intended to remove inhibitory fermentation products as they are produced. Three applications of polymer TPPB extractants were studied, followed by an investigation into poly(ether)-based polymers’ affinity toward representative target molecules, to identify properties which confer improved extraction performance. The first investigation aimed to replace a liquid extractant (silicone oil) using a block copolymer, Hytrel® 8206, in the biotransformation of indene to cis-(1S,2R)-indandiol, a chiral pharmaceutical intermediate, by Pseudomonas putida ATCC55687. The polymer simultaneously delivered substrate and removed the product and by-products to alleviate inhibition, improving operability and productivity relative to silicone oil, which could only deliver substrate. Subsequently, soft segment composition and proportion were varied in different block copolymers to selectively extract product or by-product(s) from the same biotransformation, altering the cells’ production profile. This demonstrated selective polymer extraction to help direct substrate utilization toward the product rather than by-product(s) in complex biotransformations. The next study was on absorptive extraction of a hydrophilic target molecule...

Fotofísica e eletroluminescência de dispositivos poliméricos emissores de luz branca : uma nova estratégia para a produção de luz branca; Photophysics and electroluminescence of polymer-light emitting diodes : a new strategy to produce white light

Fernando Júnior Quites
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/11/2013 PT
Relevância na Pesquisa
36.66%
Nesta Tese as propriedades foto e eletroluminescentes de diferentes polímeros conjugados foram abordadas: poli[(9,9-dioctilfluoreno-2,7-diil)-alt-co-(9,9-di-{5f-pentanil}-fluoreno-2,7-diil)] (PFP) emissor na região do azul, poli[(9,9-dihexilfluoreno-2,7-diil)-alt-co-(bitiofeno)] (F6T2) emissor na região do verde e poli[2-metóxi-5(3f,7f-dimetiloctilóxi)1-,4-fenilenovinileno] (MDMO-PPV) emissor na região do vermelho. Primeiramente foram preparados materiais híbridos orgânico-inorgânico baseados em PFP e siliconas (polímeros de silício). Devido à presença de grupos vinílicos laterais na cadeia do PFP, estes foram ligados quimicamente às siliconas através da reação de hidrossililação produzindo dois tipos de siliconas: uma com menor grau (PDHS-PDVS-l-PFP-X) e outra com maior (PDHSS-PDVS-h-PFP-X) grau de reticulação. As propriedades fotofísicas destes materiais híbridos foram comparadas com o polímero PFP na forma de filme e em soluçõoes de THF e de diferentes polissiloxanos usados na reação de hidrossililação. Através de medidas de fotoluminescência no estado estacionário e medidas dinâmicas verificou-se que as cadeias de PFP estão desordenadas em solução e no filme fino e nas siliconas com menor grau de reticulação (PDHS-PDVS-l-PFP-X) independente da quantidade de PFP usada. Entretanto...

The Effect of Polymer Chain Mobility on Protein Adsorption and Subsequent Cell Behavior

Vyner, Moira
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.64%
Many cell types are known to respond to the stiffness of polymeric biomaterial substrates. However, the mechanism by which cells sense this stiffness is still under investigation. Cell response to a material is believed to be mediated by the composition and/or configuration of the protein layers that adsorb to the biomaterial surfaces prior to cell contact. It is, therefore, hypothesized that polymer stiffness, and specifically, the flexibility of the polymer chains at the polymer aqueous interface, affects the composition and configuration of the adsorbed protein layer, which is responsible for influencing cell response. In this thesis, two biomaterials known to induce stiffness dependent cell responses are used as model systems to determine whether polymer chain flexibility influences cell behavior via differences in the protein adsorption. The first is an elastomer formed from an acrylated star-poly(D,L-lactide-co-ϵ-caprolactone) (ELAS) which has been shown to support higher NIH3T3 fibroblast proliferation on a less stiff version of the elastomer despite minimal differences in surface chemistry. The second is poly(trimethylene carbonate) (PTMC) which has been shown to degrade in vivo via macrophage mediated erosion at molecular weights higher than 100 kg/mol...

Electroluminescence in ion gel gated organic polymer semiconductor transistors

Bhat, Shrivalli
Fonte: University of Cambridge; Department of Physics; Optoelectronics Group, Cavendish Laboratory; Queens' College Publicador: University of Cambridge; Department of Physics; Optoelectronics Group, Cavendish Laboratory; Queens' College
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
36.64%
This thesis reports the light emission in ion gel gated, thin film organic semiconductor transistors and investigates the light emission mechanism behind these devices. We report that ion gel gated organic polymer semiconductor transistors emit light when the drain source voltage is swept slightly beyond the energy gap of the polymer divided by the elementary charge (Vds > Eg/e). In particular, the light emission in poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) polymer semiconductor, with 1-ethyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide/ poly(styrene-block-ethylene oxide-block-styrene (EMIM TFSI/ SOS) ion gel as dielectric material is reported. The current-voltage characteristics corresponding to the light emission, where the systematic increase of the drain current, correlated with light emission is reported. In low voltage regime, (Vds < Eg/e), well saturated transistor characteristics are observed. By charge modulation spectroscopy (CMS) study we show that there is a prominent electrochemical doping occurring with gate voltages. Further, owing to the movement of ions with voltages, irrespective of the location of electrodes, we show that the ion gel, bilayer planar devices emit light in Vds > Eg/e regime (without any gate voltages)...

Polymer Remodeling Enabled by Covalent Mechanochemistry

Ramirez, Ashley Lauren Black
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2013
Relevância na Pesquisa
36.64%

Material failure is a ubiquitous problem, and it is known that materials fail at much lower stresses than the theoretical maximum calculated from the number and strength of the individual bonds along the material cross-section. The decreased strength is attributed to inhomogeneous stress distributions under load, thus causing the stress to accumulate at localized regions, initiating microcrack formation and subsequent propagation. In many cases, these initiation and propagation steps involve covalent bond scission.

Over the past decade there has been increased interest in channeling the mechanical forces that typically trigger destructive processes (e.g., chain scission) during use into constructive chemical transformations. In an ideal system, these stress-induced chemical transformations would redistribute load prior to material failure, thus extending material lifetime. In this Dissertation, the work of developing constructive transformations through the response of a small molecule "mechanophore" is discussed.

The gem-dihalocyclopropane mechanophore is capable of undergoing a non-scissile electrocyclic ring opening reaction under molecular scale tensile load. The mechanochemistry is demonstrated both in solution via pulsed ultrasound (Chapter 2) and in the bulk via extrusion and uniaxial tension (Chapter 3). In solution...

Matrix-Assisted Pulsed Laser Evaporation of Conjugated Polymer and Hybrid Nanocomposite Thin Films: A Novel Deposition Technique for Organic Optoelectronic Devices

Pate, Ryan Jared
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
Relevância na Pesquisa
36.74%

This dissertation develops a novel application of the resonant-infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) technique toward the end goal of conjugated-polymer-based optoelectronic device fabrication. Conjugated polymers are attractive materials that are being investigated in the development of efficient optoelectronic devices due to their inexpensive material costs. Moreover, they can easily be combined with inorganic nanomaterials, such as colloidal quantum dots (CQDs), so as to realize hybrid nanocomposite-based optoelectronic devices with tunable optoelectronic characteristics and enhanced desirable features. One of the most significant challenges to the realization of optimal conjugated polymer-CQD hybrid nanocomposite-based optoelectronics has been the processes by which these materials are deposited as thin films, that is, conjugated polymer thin film processing techniques lack sufficient control so as to maintain preferred optoelectronic device behavior. More specifically, conjugated-polymer-based optoelectronics device operation and efficiency are a function of several attributes, including surface film morphology, internal polymer chain morphology, and the distribution and type of nanomaterials in the film bulk. Typical conjugated-polymer thin-film fabrication methodologies involve solution-based deposition...

Miscibility study of polymer blends by a novel phosphorescent quenching system

Qiao, L.; Langner, Andreas
Fonte: The American Chemical Society: Polymer Preprints Publicador: The American Chemical Society: Polymer Preprints
Tipo: Abstract Formato: 31371 bytes; application/pdf
EN_US
Relevância na Pesquisa
46.64%
New techniques, such as X-ray and neutron scattering, solid-state NMR, and fluorescence quenching, have attracted much research interest in probing miscibility of multicomponent polymer systems because of their capacity to determine the phase diagram of blends more precisely, and to obtain information at earlier stages of phase separation than the traditional methods. Among these new tools, the fluorescence quenching techniques are most often used owing to their great sensitivity to elucidate local molecular environments at sub-nanometer level. The technique is based on the fact that, the characteristic fluorescence signal of dye molecules attached to polymer chains will be influenced by the phase miscibility of a specific blend system. Although phosphorescence quenching has been used successfully to study the molecular interactions in solution between small molecule-small molecule, polymer-small molecule, and polymer-polymer, there is no report regarding miscibility studies of solid state polymer blends using phosphorescent probes. Because the lifetime of a chromophore in the triplet state is much longer than that in the singlet state, phosphorescence quenching techniques are expected to have the capacity to monitor large phase domains and therefore are able to bridge the gap between thermo-mechanical techniques and fluorescent methods. In this study...

Photoetching and modification of organic polymer surfaces with vacuum UV radiation

Takacs, Gerald; Vukanovic, V.; Tracy, D.; Chen, J.; Egitto, F.; Matienzo, L.; Emmi, F.
Fonte: Elsevier: Polymer Degradation and Stability Publicador: Elsevier: Polymer Degradation and Stability
Tipo: Abstract Formato: 37365 bytes; application/pdf
EN_US
Relevância na Pesquisa
46.41%
Commercially available organic polymer films were treated with radiation from 6·7 × 104 Pa He and Ar plasmas that were made to rotate inside a graphite tube by the application of an auxiliary magnetic field. To investigate modification with vacuum ultraviolet (VUV) photons, the films were covered with LiF, CaF2, fused silica, KBr and crown glass optical filters having different cut-off wavelengths. The weight loss for polytetrafluoroethylene (PTFE) was found to be linear with exposure time and dependent upon cut-off wavelength, inert gas, exposure temperature and arc current. Photoetch rates up to 105 nm min−1 were observed for PTFE using unfiltered radiation from a He arc with a current of 7 A and temperatures up to 240°C. Kapton-H® showed nearly linear weight loss, although there was some curvature at longer exposure times. Upilex-S® and -R® showed rapid initial weight loss that increased with decreasing wavelength and then negligible loss with increasing time of exposure. XPS analysis of treated samples revealed defluorination for PTFE and formation of SiO2, probably resulting from photo-oxidation of a Si, O, C-containing additive, on Upilex-S which prevented further photoetching. Receding contact angles of the polymers decreased rapidly with exposure time to minimum saturation values. In agreement with known photoabsorption spectra...