Preparation of nanocomposites based on thermoplastic polymers and influence of titanium and iron oxides nanoparticles on their properties

U ovoj disertaciji prikazan je postupak dobijanja polimernih nanokompozita in situ polimerizacijom monomera u prisustvu čestica punila. Kao punilo korišćene su nanočestice TiO2 i α-Fe2O3. Polimerni nanokompoziti poli(metil metakrilata) i TiO2 dobijeni su polimerizacijom metil metakrilata preko slobodnih radikala u rastvoru, u masi i u suspenziji, dok su nanokompoziti poli(metil metakrilata) i α-Fe2O3 dobijeni polimerizacijom preko slobodnih radikala u masi. Nanokompoziti poli(stirena) i TiO2 su dobijeni polimerizacijom stirena preko slobodnih radikala u masi. Površinska modifikacija nanočestica TiO2, dobijenih kontrolisanom hidrolizom TiCl4, izvršena je sa pet različitih jedinjenja - palmitatom askorbinske kiseline, oktil galatom, decil galatom, lauril galatom i cetil galatom. Kao punilo su korišćene dve vrste α-Fe2O3 čestica, u obliku štapića i u obliku kocki, dobijene forsiranom hidrolizom FeCl3. Površinskom modifikacijom nanočestica TiO2 izvršena je njihova hidrofobizacija što je omogućilo njihovo prebacivanje iz vodene sredine u organsku fazu, odnosno monomere metil metakrilat i stiren. Palmitat askorbinske kiseline i estri galne kiseline su se preko OH grupa hemijski vezali za površinu TiO2 čestica, što je rezultiralo pomeranjem apsorpcionog spektra površinski modifikovanih čestica TiO2 ka većim talasnim dužinama u odnosu na spektar TiO2 koloida. Karakterizacija površinski modifikovanih čestica TiO2 izvršena je apsorpcionom UV i FTIR spektroskopijom. Kristalna struktura sintetisanih α-Fe2O3 čestica određena je na osnovu difrakcije rendgenskih zraka, a veličina i oblik čestica su određeni pomoću transmisione elektronske mikroskopije. Karakterizacija dobijenih polimernih kompozita izvršena je UV i NMR spektroskopijom i transmisionom elektronskom mikroskopijom. Molarne mase poli(metil metakrilata) i poli(stirena), čistih i ekstrahovanih iz kompozitnih uzoraka, određene su korišćenjem gel propusne hromatografije i viskozimetrijske metode. Termička svojstva dobijeni polimernih nanokompozita ispitivana su termogravimetrijskom analizom i diferencijalnom skenirajućom kalorimetrijom. Cilj ovog rada je bio da se ispita uticaj načina sinteze polimerne matrice, vrste, veličine, oblika, načina površinske modifikacije i koncentracije oksidnih čestica punila na svojstva dobijenih polimernih nanokompozita. Dobijeni rezultati su pokazali da su površinski modifikovane nanočestice TiO2 i nanočestice α-Fe2O3 u obliku štapića, prisutne u toku polimerizacije MMA, uticale na reakcije terminacije pa samim tim i na molarne mase dobijenog PMMA. Čestice α-Fe2O3 u obliku kocki, prisutne u toku polimerizacije MMA, nemaju uticaj na reakcije terminacije pa ni na molarne mase dobijenog PMMA. Nanočestice TiO2 i α-Fe2O3 nisu dovele do značajnije promene vrednosti temperature ostakljivanja PMMA, što je ukazalo na slabu interakciju između čestica punila i PMMA matrice. Površinski modifikovane nanočestice TiO2, prisutne u toku polimerizacije stirena, nisu uticale na molarne mase dobijenog PS. Dodatak nanočestica TiO2-PAA u PS matricu dovodi do povećanja temperature ostakljivanja, dok nanočestice TiO2 modifikovane estrima galne kiseline ne utiču na temperaturu ostakljivanja PS matrice. Dodavanje nanočestica TiO2 u PMMA i PS matricu je povećalo njihovu termičku i termooksidativnu stabilnost.The synthesis of polymer nanocomposites by in situ polymerization of monomers in the presence of filler particles is presented in this dissertation. Nanoparticles of TiO2 and α-Fe2O3 were used as fillers. Polymer nanocomposites of poly(methyl methacrylate) and TiO2 were obtained by radical polymerization of methyl methacrylate in solution, bulk and suspension, while nanocomposites of poly(methyl methacrylate) and α-Fe2O3 and poly(styrene) and TiO2 were prepared by radical polymerization in bulk. Surface modification of TiO2 nanoparticles, obtained by control hydrolysis of TiCl4, was performed using five different compounds- ascorbic acid palmitate, octyl gallate, decyl gallate, lauryl gallate and cetyl gallate. The α-Fe2O3 particles were obtained by forced hydrolysis of FeCl3 and depending on the conditions of the reaction they were in the shape of rods or cubes. Surface modification of TiO2 nanoparticles allows the extraction of the TiO2 nanoparticles from water into organic phase, methyl methacrylate and styrene, due to the increased hydrophobic character of the modified particles. Ascorbic acid palmitate and gallic acid esters were chemically bonded to the surface of TiO2 particles through –OH groups, which resulted in the red-shift of the absorption spectrum of the surface modified TiO2 particles compared to the non-modified ones. Characterization of surface modified TiO2 particles was performed using absorption UV and FTIR spectroscopy. Crystal structure of the synthesized α-Fe2O3 particles was determined from the X-ray diffraction measurements, while size and shape of the particles were determined using transmission electron microscopy. Characterization of the obtained polymer composites was done using UV and NMR spectroscopy and transmission electron microscopy. Molar masses of poly(methyl methacrylate) and poly(styrene) samples, pure and extracted from the composites, were determined by gel permeation chromatography and viscosimetry. Thermal properties of the synthesized polymer nanocomposites were investigated by thermogravimetric analysis and differential scanning calorimetry, The goal of this study was to examine the influence of methods of synthesis of polymer matrix, and the influence of nature, size, shape, surface modification method and concentration of filler particles on the properties of the obtained polymer nanocomposites. The obtained results showed that surface modified TiO2 nanoparticles and α-Fe2O3 nanorods, present during the polymerization of MMA, influenced the termination reactions and thus the molar masses of the obtained PMMA. Cubic α-Fe2O3 particles, present during the polymerization of MMA, did not have the influence on the termination reactions and molar masses of obtained PMMA. The presence of TiO2 and α-Fe2O3 nanoparticles did not lead to significant changes of glass transition temperature of PMMA, indicating weak interactions between filler particles and PMMA matrix. Surface modified TiO2 nanoparticles, present during the polymerization of styrene, did not influence molar masses of obtained PS. Incorporation of TiO2 nanopraticles modified with ascorbic acid palmitate in PS matrix led to an increase of glass transition temperature of PS, while the TiO2 nanoparticles, surface modified by gallic acid esters, did not influence the glass transition temperature of PS matrix. Incorporation of TiO2 nanoparticles in PMMA and PS matrix increased their thermal and thermo-oxidative stability

Surface modification of TiO2 nanoparticles with catechol

Surface modification of nanocrystalline TiO2 particles with catechol was found to result in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The undercoordinated defect sites at TiO2 surface are the source of novel enhanced and selective reactivity of the nanoparticle toward bidentate ligand binding. Catechol, an enediol ligand, have the optimal geometry for chelating surface Ti atoms, resulting in a five-membered ring coordination complex and restoration of six-coordinated octahedral geometry of surface Ti atoms.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Influence of alkyl gallate surface modified TiO2 nanoparticles on the rheological properties of alkyd resin

The influence of alkyl gallate surface modified TiO2 nanoparticles on the rheological properties of long oil alkyd resin, based on soybean oil, was investigated. Surface modification of TiO2 nanoparticles, obtained by acid catalyzed hydrolysis of titanium tetraisopropoxide, was performed with propyl, lauryl or cetyl gallate. The average particle size and the crystal structure of synthesized nanoparticles were estimated by transmission electron microscopy and X-ray diffraction. The gallate chemisorption onto surface of TiO2 nanoparticles was confirmed by FTIR and UV spectroscopy. The examined dispersions were prepared by the addition of modified TiO2 nanoparticles to the commercial alkyd resin. The viscosity of the prepared dispersions was higher than viscosity of the pure resin and it increased with increasing length of hydrophobic part of the gallate used for surface modification of TiO2 nanoparticles. This occurred because the increase of their hydrodynamic volume led to the increase of the effective volume fraction of particles in dispersion

Mechanical Properties of UV Cured Mixture of Linear and Hyperbranched Urethane Acrylates

Ispitivane su smeše uretan akrilata na bazi linearnog poliestra i dva uretan akrilata, sa istim stepenom akrilovanja, na bazi alifatskih hiperrazgranatih poliestara (HRP). Linearni poliestar sintetisan je od neopentil glikola i adipinske kiseline. HRP treće generacije dobijen je od 2,2- bis(hidroksimetil)propionske kiseline i di-trimetilol propana. Modifikacija 60 % završnih OH grupa HRP-a izvedena je masnim kiselinama sojinog ulja ili izononskom kiselinom. Linearni uretan akrilat (LUA) i hiperrazgranati uretan akrilat (HUA) na bazi HRP modifikovanog masnim kiselinama sojinog ulja i HUA na bazi HRP modifikovanog izononskom kiselinom dobijeni su reakcijom određenog poliestra i izocijanatnog adukta, prethodno dobijenog reakcijom ekvimolarnih količina izoforon diizocijanata i 2-hidroksietil akrilata. Procena mešljivosti smeša LUA i HUA izvršena je na osnovu viskozimetrijskih merenja koristeći metodu koju je ustanovio Chee. Ovako pripremljenim smešama dodato je 20 mas. % heksandioldiakrilata i 4 mas. % fotoinicijatora, Irgacure 184, i umrežene su pod dejstvom UV zračenja. Umreženi uzorci ispitivani su u ogledima dinamičkog uvijanja i jednoosnog istezanja. Mehanička svojstva umreženih uzoraka zavise od mešljivosti komponenata smeše i od njenog sastava.The mixtures of urethane acrylate resin based on linear polyester and two urethane acrylates, with the same degree of acrylation, prepared from partially modified aliphatic hyperbranched polyesters (HBP), were examined. Linear polyester was obtained from neopentil glycol and adipic acid. HBP of the third generation was synthesized from 2,2-bis(hydroxymethyl)propionic acid and ditrimethylol propane. The modification of 60 % OH end-groups of HBP was carried out with soybean fatty acids or isononanoic acid. Linear urethane acrylate (LUA) and hyperbranched urethane acrylate (HUA) based on the HBP modified with soy been faty acid and HUA based on the HBP modified with isononanoic acid were obtained by reaction of appropriate polyester and NCO adduct, previously obtained by reaction of equimolar amount of isophorone diisocyanate and 2-hydroxyethyl acrylate. The miscibility of the prepared mixtures of LUA and HUAs was estimated according to viscosity measurements using the approach developed by Chee. UV curable formulation was obtained by adding hexanediol diacrylate (20 wt. %) and photoinitiator, Irgacure 184, (4 wt. %) to the prepared LUA and HUA mixtures. The UV cured samples were examined by dynamic torsion and uniaxial tension. It was obtained that mechanical properties of the UV cured samples depend on miscibility of mixture’s constituents and on its composition

Uticaj veličine nanočestica TIO2 i njihove površinske modifikacije na reološka svojstva alkidne smole

Spherical TiO2 particles of different size were dispersed in alkyd resin based on soybean oil. Four samples of TiO2 particles were used, three commercial and one obtained by acid catalyzed hydrolysis of titanium tetraisopropoxide. The size of the synthesized nanoparticles was determined by transmission electron microscopy. Surface modification of TiO2 nanoparticles was performed with propyl gallate and lauryl gallate. The influence of the size of TiO2 nanoparticles, their concentration and type of the surface modification on the rheological properties of alkyd resin was investigated. The obtained results have shown that the viscosity of the prepared dispersions was higher than the viscosity of the pure resin, increases with decreasing particle diameter and decreases with frequency increase. Surface modified particles showed higher influence on the viscosity of alkyd resin than unmodified, because their hydrodynamic volume is higher due to the presence of the adsorbed gallates, leading to the increase of effective volume fraction of particles in dispersion. For the lowest TiO2 concentration, the viscosity was higher for the sample modified with lauryl gallate, due to the higher thickness of the adsorbed layer. The increase of concentration, because of less dispersion stability of the particles modified with propyl gallate, leads to particle agglomeration. The presence of agglomerates, which was confirmed by a change in the slope of the functional dependence of storage modulus on loss modulus, leads to a rapid increase in viscosity.Sferne čestice TiO2 različitih veličina dispergovane su u alkidnoj smoli. Površinska modifikacija nanočestica TiO2 izvedena je propil galatom i lauril galatom. Ispitivan je uticaj veličine nanočestica TiO2, koncentracije, kao i vrste površinske modifikacije na reološka svojstva alkidne smole. Dobijeno je da je viskoznost pripremljenih disperzija veća od viskoznosti čiste smole, da raste sa smanjenjem prečnika čestica i opada sa povećanjem frekvencije. Površinski modifikovane čestice imaju veći uticaj na viskoznost alkidne smole nego nemodifikovane zbog povećanja efektivnog zapreminskog udela čestica u disperziji. Za najmanju koncentraciju TiO2 viskoznost je veća kada je modifikacija izvršena lauril galatom, dok sa povećanjem koncentracije, zbog manje disperzione stabilnosti čestica modifikovanih propil galatom, dolazi do njihove aglomerizacije i naglog povećanja viskoznosti

Uticaj samodopovanja na elektrohemijsku sintezu i svojstva polianilina

Electrochemical synthesis was used to polymerize aniline and copolymerize aniline and m-aminobenzoic from aqueous acidic electrolyte containing aniline and aniline with different amount of m-aminobenzoic acid. These materials were obtained galvanostatically at graphite electrode at current density of 1.0 mA cm-2 from aqueous electrolyte containing 1.0 mol dm-3 HCl and different amount of monomers. The effect of self-doping due to meta positioned carboxylic group was observed in both synthesis parameters, morphology, degree of oxidation and electrochemical behaviour. The presence of m-aminobenzoic acid led higher copolymerization increasing with the increase of amount of m-aminobenzoic acid if comparing to polymerization potential of aniline. Moreover, the copolymer with equal amount of aniline/m-aminobenzoic acid showed electrochemical activity in neutral electrolyte which might be due to possibility of proton exchange process which can be expelled from the copolymer during oxidation process together by insertion of anions, making this material promising for use in electrochemical biosensors.Elektrohemijski postupak korišćen je za polimerizaciju anilina i kopolimerizaciju anilina i m-aminobenzoeve kiseline iz kiselog vodenog rastvora elektrolita sa različitim molskim odnosima anilina i m-aminobezoeve kiseline. Ovi materijali dobijeni su uslovima konstantne gustine struje od 1,0 mA cm-2 iz kiselog vodenog elektrolita koji je sadržavao 1,0 mol dm-3 HCl, anilin i m-aminobenzoevu kiselinu. Uticaj samo-dopovanja koji je posledica prisustva karboskilne grupe u meta položaju ispoljavao se u različitim parametrima sinteze, morfologiji dobijenih materijala, stepenu oksidacije i elektrohemijskom ponašanju. Prisustvo m-aminobenzoeve kiseline uslovilo je veći potencijal sinteze kopolimera u odnosu na polianilin koji je rastao sa porastom udela m-aminobezoeve kiseline. Kopolimer koji je dobijen iz elektrolita sa jednakim molskim odnosom anilina i m-aminobenzoeve kiseline pokazao je elektrohemijsku aktivnost u neutralnom elektrolitu koja može biti posledica razmene protona što ovaj materijal čini perspektivnim za praktičnu primenu u elektrohemijskim biosenzorima

Electrochemical synthesis and characterization of poly(aniline-co-(maminobenzoic acid)

Kopolimerizacija anilina i m-aminobenzoeve kiseline ostvarena je elektrohemijskim postupkom u uslovima konstantne gustine struje od 1,0 mA cm-2 (galvanostatski). Kao elektrolit za sintezu korišćen je vodeni rastvora 1,0 mol dm-3 HCl sa dodatkom anilina i maminobenzoeve kiseline različitog odnosa koncentracija. Prisustvo karboskilne grupe u meta položaju uslovljava povećanje potencijala kopolimerizacije, drugačiju morfologiju i elektrohemijsko ponašanje kopolimera u poređenju sa polianilinom. Kopolimer polianilina i m-aminobenzoeve kiseline dobijen kopolimerizacijom iz rastvora koji je sadržao istu količinu anilina i m-benzoeve kiseline od 1.0 mol dm-3 pokazuje, za razliku od polianilina, elektrohemijsku aktivnost u neutralnoj sredini.Galvanostatic electrochemical syntheses of poly(aniline-co-(m-aminobenzoic acid)) was performed at graphite electrode at constant current density of 1.0 mA cm-2. Aqueous electrolyte used for synthesis was consisted of: 1.0 mol dm-3 HCl and different amounts of aniline and m-aminobenzoic acid. The presence of the meta positioned carboxylic group in m-aminobenzoic acid had influenced higher co-polymerization potential, different morphology and electrochemical behavior of copolymers compared to polyaniline. Poly(aniline-co-(m-aminobenzoic acid)) obtained from electrolyte with an equal amount of aniline and m-aminobenzoic acid exhibits electrochemical activity in neutral electrolyte which can be related to proton exchange process

The Effect of Glycol Derivatives on the Properties of Bio-Based Unsaturated Polyesters

The scope of the present study was to prepare fully bio-based unsaturated polyester resins (UPRs) with comparable properties to the commercial formulations. The focus was set on the determination of the optimal prepolymer formulation using the same set of diacids (itaconic and succinic acid) and different diols (propylene glycol, isosorbide and neopentyl glycol) or its equimolar mixtures, keeping the fixed molar ratio of 1:1:2.1 in all feed compositions. Instead of commonly used styrene, bio-based dimethyl itaconate was used as a reactive diluent (RD). The rheology of the obtained resins was studied in detail. The effect of the used diol on structural (FTIR), thermal (DSC), thermomechanical (DMA), and mechanical (tensile) properties was explained. The properties of UPRs were found to be highly dependent on the diol used in the prepolymer formulation. The UPR with an equimolar ratio of propylene glycol and neopentyl glycol was shown to be the most promising candidate to compete with the commercial petroleum-based resins

New Hybrid Properties of TiO2 Nanoparticles Surface Modified With Catecholate Type Ligands

Surface modification of nanocrystalline TiO2 particles (45 Å) with bidentate benzene derivatives (catechol, pyrogallol, and gallic acid) was found to alter optical properties of nanoparticles. The formation of the inner-sphere charge–transfer complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The binding structures were investigated by using FTIR spectroscopy. The investigated ligands have the optimal geometry for chelating surface Ti atoms, resulting in ring coordination complexes (catecholate type of binuclear bidentate binding–bridging) thus restoring in six-coordinated octahedral geometry of surface Ti atoms. From the Benesi–Hildebrand plot, the stability constants at pH 2 of the order 103 M−1 have been determined

Ficção e sociedade em Guimarães Rosa: interpretação dos contos “A volta do marido pródigo” e “Minha gente”

This work has as theoretical and methodological basis the Aesthetic of Reception, the school of literary theory that emerged in the late sixties in opossition to the dogmas Marxist and formalist, to the extent that they ignore the role of the reader as the main recipient of the literary work. The research is focused on a hermeneutic approach and grounded in an analisis that relates literature and society, considering that is possible to find echoes of humanist ideals in this book, mainly within the tales that form the corpus for our analysis. Thus, following the methodological bias postulated by Jauss (1921-1997), in which the sense of a literary work should be sought into a dialetic constitution between the text and the reader, this paper outlines a survey of short stories “A volta do marido pródigo” and “Minha gente” of Sagarana, especially when it cames to the tematic and formal ties and to the analysis of the characters. In these narratives, it is possible to identify political and amorous disputes wich are developed at the same time along the plot, in general, is depicted the form of the assignment partisan politics and the family relationships in Brazil at the beginning of last century, each tale casts these thematics in their own way, one more comic, focusing on political and social issues and the other emphasizing family relations. In “A volta do marido pródigo” we found a hero with a obvious folk origination within a narrative that dialogues with the parable of the prodigal son and the Aesopian fable of turtle and toad. “Minha gente” tells a story of a relation between the characters lives and the game of chess. Although they retain significant differences between them, those stories have much in common. We took into acount studies already stablished about Sagarana as it is the Mortos de sobrecasaca of Álvaro Lins, as well as others, more recent, of researchers such as Luiz Roncari (O Brasil de Rosa: o amor e o poder), Gilca Seidinger (Guimarães Rosa ou a paixão de contar: narrativas de Sagarana), Nildo Benedetti (Sagarana: o Brasil de Guimarães Rosa) and Sílvio Holanda (Rapsódia Sertaneja: leituras de Sagarana).CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorO presente trabalho tem como base teórico-metodológica a Estética da Recepção, corrente de teoria literária surgida no final da década de 1960 em oposição aos dogmas marxistas e formalistas, na medida em que eles ignoram o papel do leitor enquanto principal destinatário da obra literária. A pesquisa está centrada em uma abordagem hermenêutica e embasada em uma leitura que relaciona a literatura e a sociedade, tendo em vista que é possível encontrar ecos de ideais humanistas dentro da obra como um todo, mas, principalmente, dentro dos contos que serviram de corpus para este estudo. Desse modo, seguindo o viés metodológico postulado por Jauss (1921-1997), no qual o sentido da obra deve ser buscado dentro de uma constituição dialética entre o próprio texto e o leitor, este trabalho traça um exame dos contos “A volta do marido pródigo” e “Minha gente” de Sagarana, sobretudo no que concerne aos vínculos temático-formais e à análise da construção dos personagens dos contos mencionados. Nestas narrativas, é possível identificar lides políticas e amorosas que se desenvolvem paralelamente ao longo da trama, em linhas gerais, é retratada a forma do exercício da política partidária e das relações familiares no Brasil do início do século passado, cada conto molda essas temáticas à sua própria maneira, um de forma mais cômica, privilegiando os aspectos políticos e sociais, outro enfatizando as relações familiares. Em “A volta do marido pródigo”, depara-se com um protagonista de evidente procedência folclórica, dentro de uma narrativa que dialoga com a parábola do filho pródigo e com a fábula esópica do cágado e do sapo. Em “Minha gente” encontra-se uma história em que é estabelecida uma relação entre a vida dos personagens e o jogo de xadrez. Embora guardem diferenças significativas entre si, as narrativas que aqui nos servem de corpus possuem muitos aspectos em comum. Este trabalho levou em consideração estudos já consolidados acerca de Sagarana como o é o de Álvaro Lins em Mortos de sobrecasaca, bem como outros, mais recentes, de pesquisadores como Luiz Roncari (O Brasil de Rosa: o amor e o poder), Gilca Seidinger (Guimarães Rosa ou a paixão de contar: narrativas de Sagarana), Nildo Benedetti (Sagarana: o Brasil de Guimarães Rosa) e Sílvio Holanda (Rapsódia Sertaneja: leituras de Sagarana)