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Aqueous two-phase extraction using thermoseparating copolymer: a new system for phenolic compounds removal from hemicelullosic hydrolysate

HASMANN, Francislene A.; SANTOS, Valeria C.; GURPILHARES, Daniela B.; PESSOA-JUNIOR, Adalberto; ROBERTO, Ines C.
Fonte: JOHN WILEY & SONS LTD Publicador: JOHN WILEY & SONS LTD
Tipo: Artigo de Revista Científica
ENG
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BACKGROUND: The hydrolysis of hemicellulosic material can provide liquor with high xylose concentration (which can be used as a fermentation medium) and phenolic compounds (Phs), potentially immunostimulating compounds. However, these hydrolysates must be detoxified in order to remove the Phs that can act as inhibitors in bioconversions. RESULTS: Aqueous two-phase systems composed of thermoseparating copolymers were used for rice straw hydrolysate detoxification. The hydrolysis process was able to promote chemical breakdown of 85% of the total hemicellulose content, 14% of the cellulose, and 2% of the lignin. The hydrolysate obtained contained 19.7 g L-1 of xylose and several phenolic compounds, such as vanillin, vanillic acid, ferullic acid, etc. The phenolics extraction was studied as a function of copolymer molar mass (1100 g mol(-1), 2000 g mol(-1) and 2800 g mol(-1)), their percentages (from 5% to 50%) and Phs initial concentration. Phenolic compounds extraction of around 80% was obtained under the following conditions: 20% (w/w) and 35% (w/w) copolymer 1100 g mol-1, 35% (w/w) copolymer 2000 g mol(-1) and 35% (w/w) copolymer 2800 g mol(-1) at 25 degrees C. CONCLUSIONS: The results demonstrated the viability of this method for the removal of Phs from rice straw hydrolysate...

Dynamic formation of SEBS copolymer submicrometric structures

SALVADOR, Michele A.; BIANCHI, Andrea G. C.; PEREIRA-DA-SILVA, Marcelo A.; CARVALHO, Antonio J. F.; FARIA, Roberto M.
Fonte: ELSEVIER SCI LTD Publicador: ELSEVIER SCI LTD
Tipo: Artigo de Revista Científica
ENG
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Highly ordered A-B-A block copolymer arrangements in the submicrometric scale, resulting from dewetting and solvent evaporation of thin films, have inspired a variety of new applications in the nanometric world. Despite the progress observed in the control of such structures, the intricate scientific phenomena related to regular patterns formation are still not completely elucidated. SEBS is a standard example of a triblock copolymer that forms spontaneously impressive pattern arrangements. From macroscopic thin liquid films of SEBS solution, several physical effects and phenomena act synergistically to achieve well-arranged patterns of stripes and/or droplets. That is, concomitant with dewetting, solvent evaporation, and Marangoni effect, Rayleigh instability and phase separation also play important role in the pattern formation. These two last effects are difficult to be followed experimentally in the nanoscale, which render difficulties to the comprehension of the whole phenomenon. In this paper, we use computational methods for image analysis, which provide quantitative morphometric data of the patterns, specifically comprising stripes fragmentation into droplets. With the help of these computational techniques, we developed an explanation for the final part of the pattern formation...

Fractured Orbital Wall Reconstruction With an Auricular Cartilage Graft or Absorbable Polyacid Copolymer

KRUSCHEWSKY, Leonardo de Souza; NOVAIS, Tatiana; DALTRO, Carla; BRANCO, Bruno Castelo; LESSA, Marcus; KRUSCHEWSKY, Marinella Benez; MELLO-FILHO, Francisco Verissimo de
Fonte: LIPPINCOTT WILLIAMS & WILKINS Publicador: LIPPINCOTT WILLIAMS & WILKINS
Tipo: Artigo de Revista Científica
ENG
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Objective: The objective of the study was to compare the functional and aesthetic results of fractured orbital wall reconstruction with an auricular cartilage graft or absorbable polyacid copolymer. Materials and Methods: Twenty patients with blow-out orbital fracture/orbital floor associated or not with the medial wall were assessed by the same craniofacial surgical group. All were evaluated preoperatively and postoperatively by an ophthalmologist for diplopia, enophthalmos, exophthalmos, sensitivity, ophthalmic reflexes, intraocular pressure, and visual field. The patients were subjected to a preoperative facial multislice computed tomographic scan, repeated 6 months after surgery. Eight patients underwent reconstruction with an auricular cartilage graft, and 12 patients, with blade absorbable polyacid copolymer. Subtarsal access was used for all patients. Results: Two patients showed temporary ectropion, 1 in each group. All patients presented satisfactory ocular function, and all tests revealed good orbital delineation, orbital symmetry, periorbital sinus individualization, and reduction of blow-out. Conclusions: The blow-out orbital wall reconstruction can be performed with the use of an auricular cartilage or with a blade absorbable copolymer without differences regarding functional or aesthetic complications and sequelae.

Langmuir and Langmuir-Blodgett films of a quinoline-fluorene based copolymer

Correia, Fabio Conte; Wang, Shu H.; Peres, Laura O.; Caseli, Luciano
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
ENG
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The fabrication of Langmuir-Blodgett (LB) films of synthetic polymers allows the control of molecular architecture in order to optimize physical properties. In this paper, the surface chemistry of a quinoline-fluorene based copolymer spread on the air-water interface is investigated. Surface pressure-area isotherms as well as Polarization-Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) were employed to characterize the films, which could be transferred to solid supports by the LB technique. Atomic force microscopy as well as UV-Vis and fluorescence spectroscopies have shown a regular deposition of the polymers, and the luminescence properties could be controlled with the number of layers deposited on the solid support. As a result, the photoluminescence of the LB films was considerably higher than that observed for the spin coated film, and the maximum emission peak was shifted to higher energies, which is attributed to the molecular-level interactions within the layer-ordered structure of the LB film. The luminescence response would possibly be tuned to approach the highest level, which allows the films to be employed in future applications in efficient optical devices such as organic light-emitting diodes (OLEDs). (C) 2011 Elsevier B.V. All rights reserved.

Replication of submicrometric organized structures of block copolymer from coordination-polymer templates

Longaresi, R. H.; Travençolo, B. A. N.; Silva, L. C.; Silva, Marcelo de Assumpcao Pereira da; Carvalho, A. J. F.; Costa, Luciano da Fontoura; Faria, Roberto Mendonça
Fonte: American Scientific Publishers - ASP; Valencia Publicador: American Scientific Publishers - ASP; Valencia
Tipo: Artigo de Revista Científica
ENG
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This paper presents fabrication of a submicrometric template obtained from self-organized well-ordered pattern of nanostructured (poly(styrene)-b-poly(ethene-co-butene)-b-poly(styrene) (SEBS) copolymer. The SEBS ordered structure was formed on mica substrate, in which a thin liquid film of SEBS/Toluene solution was deposited by dip-coating procedure, and after the solvent evaporation, SEBS droplets are spontaneously displayed in a hexagonal arrangement. The molding template was made of PDMS by a soft lithography process and replicas of epoxy forming the original hexagonal pattern with reasonable accuracy. All structures were studied by AFM images, using quantitative computational analyses: hexagonality index and radial distribution functions. The computational analyses showed that the high spacial order in the SEBS nanostructures was followed by the produced mold although and the replica. Also we observed that the original pattern presented 1.7% of dislocation defects (from the hexagonality), while the replica reached 5% showing the success of soft lithography process of nano templates.

"Propriedades da pasta de cimento portland com adições do copolímero Va/VeoVa e fibras de poliamida - estudo da interface fibra-matriz" ; properties of va/veova copolymer modified cement pastes reinforced by polyamide fibers - study of interface fiber-matrix

Gomes, Carlos Eduardo Marmorato
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/09/2005 PT
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O crescente emprego de compósitos fibrosos pela indústria da construção civil, nos últimos anos, comprova a eficiência da adoção de fibras como reforço de matrizes frágeis, a exemplo das pastas, argamassas e concreto de cimento Portland. Com o desenvolvimento de novas fibras sintéticas em suas propriedades, com custo similar ao das fibras comuns, faz-se supor que os produtos reforçados por essas fibras tenham grande avanço nos próximos anos. Especificamente em relação à fibra poliamida 6.6, constata-se que a mesma possui módulo de elasticidade menor em relação às matrizes de cimento Portland convencionais e pobre interface fibra/matriz. O incremento do módulo de elasticidade dessas fibras constitui grande desafio à industria têxtil devido às características de seu processo de fabricação, especificamente no que se refere à fiação, porém, isso não bastaria, havendo também a necessidade de aumentar sua aderência com as matrizes cimenticias. Dessa maneira, o presente trabalho buscou, pela adição de um copolímero redispersável (Va/VeoVa – vinil acetato/ vinil éster do ácido versático), tornar compatível o valor do módulo de elasticidade da matriz cimentícia ao das fibras de poliamida...

Síntese e caracterização do copolímero tribloco anfifílico biodegradável poli(L, L-lactídeo-stat-e-caprolactona)-bloco-poli(óxido de etileno)-bloco-poli(L, L-lactídeo-stat-e-caprolactona).; Synthesis and characterization of triblock anfiphilic biodegradable copolymer poly(l,l-lactide-stat-e-caprolactone)-b-poly(ethylene oxide)-b-poly(l,l-lactide-stat-e-caprolactone).

Lili, Zhao
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/04/2007 PT
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Este trabalho apresenta um estudo sobre a síntese e propriedades do copolímero poli(l,l-lactídeo-stat-e-caprolactona)-bloco-poli(óxido de etileno)-bloco-poli(l,l-lactideostat-e-caprolactona). Poli(óxido de etileno) de massa molar 20.000 u.m.a. e poli(óxido de etileno) modificado, preparado a partir de poli(glicol etilênico) de massa molar 4.000 u.m.a., foram selecionados para o processo da síntese. A reação foi feita pela polimerização por abertura de anel em massa a 120ºC usando octoanato de estanho como iniciador. A composição química de cada amostra foi determinada com auxílio de RMN-1H e RMN-13C e suas propriedades mecânicas foram verificadas e comparadas utilizando análises térmicas como DMTA, DSC, TG e a aplicação da MEV como análise complementar. A observação pelas fotos de MOLP permitiu a visualização do comportamento de nucleação dos copolímeros e as características de sua cristalinidade. Seu grau de cristalinidade e as fases cristalinas foram identificados por difração de raios X (WAXS). A biocompatibilidade do material também foi examinada pela cultura de células. Os resultados de caracterização indicam o sucesso da copolimerização, as propriedades elastoméricas e, sua não citotoxidade comprovaram a possibilidade do uso destes copolímeros como biomateriais. Contudo...

Efeito da adição de ácidos fosfóricos no comportamento reológico de ligantes asfálticos puros e modificados com copolímero SBS; Effect of phosphoric acid in the rheological behavior of pure and modified asphalt binders with SBS copolymer

Sobreiro, Fernanda Pilati
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/03/2014 PT
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A adição de modificadores no ligante asfáltico visando melhorar o seu comportamento é uma prática comum atualmente. Existem vários tipos de modificadores, entre eles o mais utilizado nas rodovias federais brasileiras é o copolímero SBS. Além dos polímeros, o ácido polifosfórico (PPA) é outro tipo de modificador que produz boas características quando adicionado ao ligante asfáltico. Apesar do efeito positivo, sabe-se que este material é importado, o que dificulta sua aquisição e pode tornar o produto final muito caro. Tendo em vista a possibilidade de se trabalhar com um produto de mesma base, mas de origem nacional, o que o tornaria o modificador mais acessível, optou-se por verificar o comportamento da adição de ácido fosfórico (PA85) ao ligante asfáltico. Sendo assim, o propósito desta tese é analisar o efeito da adição de ácidos fosfóricos no comportamento reológico de ligantes asfálticos puros e modificados com o copolímero SBS. Para tanto, realizou-se ensaios empíricos e reológicos com o intuito de verificar o comportamento destes materiais. Na primeira parte da pesquisa, dois ligantes asfálticos de base, CAP50/70 de classificação PG64-XX, (Replan e Lubnor), foram modificados somente com a adição dos dois ácidos (PPA e PA85)...

Morphology of Nylon 6/Acrylonitrile-Butadiene-Styrene Blends Compatibilized by a Methyl Methacrylate/Maleic Anhydride Copolymer

Araújo, E. M.; Hage, E.; Carvalho, A. J. F.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 3512-3518
ENG
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The morphologies of nylon 6/acrylonitrile-butadiene-styrene blends compatibilized with a methyl methacrylate/maleic anhydride copolymer, with 3-20 wt % maleic anhydride, were examined by transmission electron microscopy. Some staining techniques were employed for identifying the various phases. The binary blends were immiscible and exhibited poor mechanical properties that stemmed from the unfavorable interactions among their molecular segments. This produced an unstable and coarse phase morphology and weak interfaces among the phases in the solid state. The presence of the copolymer in the blends clearly led to a more efficient dispersion of the acrylonitrile-butadiene-styrene phase and consequently optimized Izod impact properties. © 2003 Wiley Periodicals, Inc.

Electrochemical synthesis of the copolymer poly(2-methoxy-5-bromo-p-phenylenevinylene)/(2,5-dicyano-p-phenylenevinylene) (MB-PPV/DCN-PPV): tuning properties

Klider,Karine C. C. W. S.; Santos,Fábio S.; Péres,Laura O.; Wohnrath,Karen; Garcia,Jarem R.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
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The present work describes an electrochemical method to produce the copolymer poly(2-methoxy-5-bromo-p-phenylenevinylene)/(2,5-dicyano-p-phenylenevinylene) (cop-MB-PPV/DCN-PPV). This copolymer was proposed due to its D-A characteristic produced by the presence of the electron-donating methoxy moiety and the electron-withdrawing dicyano moiety. The copolymer was electrochemically synthetized by cathodic reduction of the convenient starting materials dissolved in a DMF/LiClO4 using a mercury pool acting as working electrode. The copolymer was characterized by infrared (IR), UV-Vis and fluorescence (FL) spectroscopy and cyclic voltammetry (CV). All the results were compared to the MB-PPV homopolymer. The analysis of electrochemical measurements and IR indicated that the cop-MB-PPV/DCN-PPV was obtained through the formation of blocks containing DCN-PPV units linked by blocks containing MB-PPV units. The electronic structure, performed by CV, UV-Vis and FL showed that the conduction band is more stabilized in the copolymer than in homopolymer. Furthermore, the FL spectra indicated that the light emission of the cop-MB-PPV/DCN-PPV in chloroform solution occurs by means of excimer formation.

Analyses of microstructural properties of VA/VeoVA copolymer modified cement pastes

Gomes,Carlos Eduardo M.; Ferreira,Osny P.
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2005 EN
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Recently, modern techniques have been applied for analysis of the influence of polymers on microstructural properties of Portland cement, such as Thermogravimetric Analyses (TG), Scanning Electronic Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Mercury Intrusion Porosimetry (MIP). In this study, thermogravimetric analyses were used to study the influence of vinyl acetate-versatic vinylester copolymer (VA/VeoVA) in seven pastes of 28-day old Portland cement, in which distinct polymer contents and water/cement ratios were employed. In addition, analyses of FT-IR and MIP on Portland cement pastes modified by the copolymer were employed. The results showed that the addition of polymer interferes significantly in the reduction of Portlandite formation and increases the porosity of the matrices. A possible chemical interaction between the copolymer and hydrated products of Portland cement was also observed.

Crosslinkable potato starch-based graft copolymer emulsion for humidity controlling coatings

Wang,Rong-Min; Wang,Xiao-Wen; Guo,Jun-Feng; He,Yu-Feng; Jiang,Meng-Lan
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2013 EN
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A new kind of crosslinkable potato starch-based graft copolymer emulsion (PoSt-g-BMD) has been prepared using butyl acrylate (BA) and methyl methacrylate (MMA) as main monomers, and diacetone acrylamide (DAAM) as functional monomer. The keto-carbonyl group of DAAM in PoSt-g-BMD copolymer could react with adipic dihydrazide (ADH) at ambient temperature to form cross-linked copolymer. The PoSt-g-BMD had been characterized by the FT-IR spectra and thermogravimetric analysis (TGA). It was applied to prepare the humidity-controlling coatings (PoSt-g-BMD-C). The water absorption of PoSt-g-BMD-C was 105%. The humidity controlling properties were also measured, and the PoSt-g-BMD-C exhibited humidity sensitivity and humidity retention because fillers of porous structure combined with PoSt-g-BMD copolymer emulsion based on scanning electron microscopy images (SEM). It could be widely applied in indoor coating for controlling humidity.

ABC block copolymer as "smart" pH-responsive carrier for intracellular delivery of hydrophobic drugs

Yao, J.; Ruan, Y.; Zhai, T.; Guan, J.; Tang, G.; Li, H.; Dai, S.
Fonte: Elsevier Sci Ltd Publicador: Elsevier Sci Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
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Amphiphilic triblock copolymer of poly(ethylene glycol)-block-poly(dimethylaminoethyl methacrylate)-block-poly(ε-caprolatone) (PEG-PDMA-PCL) was synthesized using a one-pot sequential oxyanionic polymerization of DMA and ε-CL, associated with a PEG-O−K+ macroinitiator. The pH-responsive micellization behavior of the copolymer was studied using dynamic light scattering (DLS), steady–state fluorescence and TEM techniques. The anti-cancer drug of doxorubicin (DOX) was chosen as a model drug to investigate the potential application of this triblock copolymer in drug controlled release. The results indicated the important roles of the PCL block for drug loading, the PDMA block for pH-responsive release, and PEG block for good bio-affinity. Cell cytotoxicity tests showed that the DOX-loaded PEG-PDMA-PCL micelles were pharmaceutically active to suppress the growth of SKOV-3 cells. This novel stimuli–responsive block copolymer is an attractive candidate as the "smart" pH-responsive carrier for intracellular delivery of hydrophobic drugs.; Jia Yao, Yuelei Ruan, Tao Zhai, Jun Guan, Guping Tang, Haoran Li, Sheng Dai

Mucoadhesive Amphiphilic Methacrylic Copolymer-Functionalized Poly(epsilon-caprolactone) Nanocapsules for Nose-to-Brain Delivery of Olanzapine

Fonseca, Francisco N.; Betti, Andresa H.; Carvalho, Flavia C.; Gremiao, Maria P. D.; Dimer, Frantiescoli A.; Guterres, Silvia S.; Tebaldi, Marli L.; Rates, Stela M. K.; Pohlmann, Adriana R.
Fonte: Amer Scientific Publishers Publicador: Amer Scientific Publishers
Tipo: Artigo de Revista Científica Formato: 1472-1481
ENG
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Nose-to-brain drug delivery has been proposed to overcome the low absorption of drugs in central nervous system due to the absence of brain-blood barrier in the olfactory nerve pathway. However, the presence of a mucus layer and quick clearance limit the use of this route. Herein, amphiphilic methacrylic copolymer-functionalized poly(epsilon-caprolactone) nanocapsules were proposed as a mucoadhesive system to deliver olanzapine after intranasal administration. In vitro evaluations showed that these nanocapsules were able to interact with mucin (up to 17% of increment in particle size and 30% of reduction of particle concentration) and nasal mucosa (2-fold higher force for detaching), as well as to increase the retention of olanzapine (about 40%) on the nasal mucosa after continuous wash. The olanzapine-loaded amphiphilic methacrylic copolymer-functionalized PCL nanocapsules enhanced the amount of drug in the brain of rats (1.5-fold higher compared to the drug solution). In accordance with this finding, this formulation improved the prepulse inhibition impairment induced by apomorphine, which is considered as an operational measure of pre-attentive sensorimotor gating impairment present in schizophrenia. Besides...

Synthesis of a Novel Diblock Copolymer and Preparation of Highly Selective Molecularly Imprinted Polymer Nanospheres from It

Peng, BOLU
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
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Crosslinking monomers or a polymer around template molecules and the subsequent removal of the templates yield a polymer matrix containing cavities that resemble the shape of the templates and bear binding groups that complement those on the template molecules. However, a key challenge facing those molecularly imprinted polymers (MIPs) is the infidelity of the pores generated to the original templates and thus non-specific binding of the pores to analytes other than the template. I report in this thesis a method to improve the selectivity of MIP particles. I prepared an MIP for a chiral analyte relying not only on the traditional H-bonding interactions between the polymer matrix and the template but also on the - stacking interactions. Specifically, I synthesized a novel diblock copolymer poly(ethylene oxide)226-block-poly[(2-pentafluorocinnamoyloxyethyl methacrylate)75%-ran-[2-(2’-carboxybenzoyloxy)ethyl methacrylate]25%]100 or PEO226-b-P(FEMA75%-r-CA25%)100. While the CA groups were introduced because of their H-bond interactions with carbonyl oxygen and amino group of the chiral template D-phenylalanine anilide, the FEMA units were introduced for their ability to crosslink under the UV irradiation and also for the π-π stacking interactions of the fluorinated FEMA phenyl rings with the phenyl rings of D-phenylalanine anilide. To prepare MIP nanoparticles...

BLOCK COPOLYMER SELF-ASSEMBLY, HIERARCHICAL ASSEMBLY, AND APPLICATION

Li, XIAOYU
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
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This thesis addresses three issues. These are the self-assembly of block copolymer in selective solvents, hierarchical assembly of micelles or crosslinked micelles of block copolymers, and the application of block copolymers as solid state compatibilizers in polymer-based photovoltaic cells. Poly(acrylic acid)-block-(2-cinnamoyloxylethyl methacrylate)-block-poly(perfluorooctylethyl methacrylate) or PAA-b-PCEMA-b-PFOEMA self-assembles in solvent mixtures of α,α,α-trifluorotoluene (TFT) and methanol, which are selective towards PAA. At TFT volume fraction (fTFT) of 40 %, the copolymer forms vesicles at 70 oC and cylinders at 21 oC. These two structures inter-convert via meta-stable intermediates including jellyfish-like, tethered vesicular, and bilayer sheet-like structures. These structures occur in kinetic experiments involving quick temperature swing from 21 to 70 oC or vice versa and also in experiments involving annealing samples long at temperatures between 21 to 70 oC. Thus, they are meta-stable and point to complex pathways for the morphological transition. At fTFT = 10 %, the polymer forms vesicles with bumpy surface at 70 oC and toroids with sharp angles at 21 oC. Closely examined is how the liquid crystalline nature of the PFOEMA block affects the formation of these unique morphologies and their morphological transitions. Two types of hierarchical assembly of cylindrical micelles (cylinders) or crosslinked cylindrical micelles (fibers) of block copolymers are examined. First...

Nanostructured thermosetting systems modified with poly (isoprene-b-methyl metacrylate) diblock copolymer and polyisoprene grafted carbon nanotubes

Espósito, Leandro Hernan; Ramos, José A.; Mondragon, Iñaki; Kortaberria, Galder
Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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Nanostructured thermosetting composites based on an epoxy matrix modified with poly(isoprene-b-methyl methacrylate) (PIb-PMMA) block copolymer were prepared through PI block segregation. Morphological structures were examined by means of atomic microscopy force microscopy. As epoxy/pristine multi-walled carbon nanotubes (MWCNT) systems were found to present big agglomerations, with a very poor dispersion of the nanofiller, epoxy/PI-b-PMMA/MWCNT systems were prepared by using polyisoprene-grafted carbon nanotubes (PI-g-CNT) to enhance compatibility with the matrix and improve dispersion. It was found that the functionalization of MWCNT with grafted polyisoprene was not enough to totally disperse them into the epoxy matrix but an improvement of the dispersion of carbon nanotubes was achieved by nanostructuring epoxy matrix with PI-b-PMMA when compared with epoxy/MWCNT composites without nanostructuring. Nevertheless, some agglomerates were still present and the complete dispersion or confinement of nanotubes into desired domains was not achieved. Thermomechanical properties slightly increase with PI-g-CNT content for nanostructured samples, whereas for nonnanostructured epoxy/PI-g-CNT composites they appeared almost constant and even decreased for the highest nanofiller amount due to the presence of agglomerates. Compression properties slightly decreased with block copolymer content...

Coupling between mean curvature and textures in block copolymer thin films deposited on curved substrates

Vega, Daniel Alberto; Gomez, Leopoldo Raimundo; Pezzutti, Aldo Daniel; Pardo, Flavio; Chaikin, Paul M.; Register, Richard A.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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We study the dynamics of coarsening in a cylinder-forming polystyrene-block-poly(ethylene-alt-propylene) block copolymer thin film deposited on a topographically patterned substrate. Thermal annealing leads to highly ordered arrays of polystyrene cylinders embedded in the poly(ethylene-alt-propylene) matrix, lying in-plane and oriented perpendicular to the trenches of the substrate. We show that this configuration corresponds to an equilibrium state. The coupling between the block copolymer morphology and the mean curvature of the substrate is dictated by the out-of-plane deformations of the block copolymer structure. Thus, with appropriate control over the substrate features, it should be possible to obtain novel structures with controlled orientation.; Fil: Vega, Daniel Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina;; Fil: Gomez, Leopoldo Raimundo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina;; Fil: Pezzutti, Aldo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina;; Fil: Pardo...

Charge Transfer in Single Chains of a Donor?Acceptor Conjugated Tri-Block Copolymer

Hooley, Emma N.; Jones, David J.; Greenham, Neil C.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Article; accepted version
EN
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This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/jp510769p.; The photophysics of a conjugated tri-block copolymer comprising poly(9,9-dioctylfluorene-co-bis- N,N?-(4-methylphenyl)-bis-N,N?-phenyl-1,4-phenylenediamine (PFM) electron donor and poly-(4-(9,9- dioctyl-9H-fluoren-2-yl)benzo[c][1,2,5]-thiadiazole) (F8BT) electron acceptor blocks has been studied in solution, in films and as single chains. While an additional long-wavelength emission apparent in neat films of the copolymer is attributed to inter-chain exciplex formation, no such long-wavelength emission is apparent in solution or from single molecules. However, in these cases, time-resolved fluorescence measurements indicate the presence of a delayed fluorescence. The kinetics of the delayed emission can be interpreted in terms of an equilibrium between a locally-excited and a charge-transfer state at the interface of the copolymer block components. Rate constants and thermodynamic quantities associated with these processes have been evaluated. The single molecule results allow the assignment of an intramolecular charge-transfer state in an isolated conjugated block copolymer chain.; We thank the Australian Research Council (ARC) for financial support of this research through grants DP0986166...

Cyclic olefin copolymer: An Alternative plastic film for pharmaceutical blister packages

Trombley, Kurt
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
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This thesis paper will provide data to show that cyclic olefin copolymer blister film can be used as a beneficial alternative to polyvinyl chloride film which is more commonly used in the pharmaceutical market today. Polyvinyl chloride continues to be a highly controversial packaging material due to potential environmental concerns. Cyclic olefin copolymer is shown to have properties which result in fewer environmental concerns and also can provide the added benefit of an improved barrier to moisture permeation when compared to polyvinyl chloride film. This paper documents a summary of the data on both sides of the polyvinyl chloride environmental debate. It also documents cyclic olefin copolymer's mechanical properties, small and large scale manufacturing data, and potential future developments which will improve the manufacturing of many new film opportunities for cyclic olefin copolymer as well as reduce the manufacturing costs. To date, very little public information could be found documenting data on cyclic olefin copolymer for use as a replacement for polyvinyl chloride, currently used for blister packaging. Most of the data available today has been provided by cyclic olefin copolymer manufacturers instead of industry and/or institutions. The null hypothesis for this thesis is as follows: Cyclic olefin copolymer will not be a beneficial alternative blister film to polyvinyl chloride. It will not address environmental concerns...