- I do reseach on polymers from renewable resources.edit
This paper provides an overview of the recent progress in research and development dealing with polymers derived from plant oils. It highlights the widening interest in novel approaches to the synthesis, characterization, and properties... more
This paper provides an overview of the recent progress in research and development dealing with polymers derived from plant oils. It highlights the widening interest in novel approaches to the synthesis, characterization, and properties of these materials from renewable resources and emphasizes their growing impact on sustainable macromolecular science and technology. The monomers used include unmodified triglycerides, their fatty acids or the corresponding esters, and chemically modified triglycerides and fatty acid esters. Comonomers include styrene, divinylbenzene, acrylics, furan derivatives, epoxides, etc. The synthetic pathways adopted for the preparation of these materials are very varied, going from traditional free radical and cationic polymerizations to polycondensation reactions, as well as metatheses and Diels–Alder syntheses. In addition to this general appraisal, the specific topic of the use of tung oil as a source of original polymers, copolymers, and (nano)composite...
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... Whenever pentoses are the saccharide units (as, eg, in sugarcane bagasse, rice hulls, corn cobs, etc ... In the former study (20) the foam could be readily removed by 1-butanol at ... The report thatpoly(N-acetylethyleneimine)s... more
... Whenever pentoses are the saccharide units (as, eg, in sugarcane bagasse, rice hulls, corn cobs, etc ... In the former study (20) the foam could be readily removed by 1-butanol at ... The report thatpoly(N-acetylethyleneimine)s bearing either maleimide or furancarbonyl side groups ...
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This essay introduces the subject and interpretative perspective of the monograph ‘Unboxing the Sharing Economy’, and is divided into three parts. The first part illustrates the evolution of the concept of the ‘sharing economy’ and the... more
This essay introduces the subject and interpretative perspective of the monograph ‘Unboxing the Sharing Economy’, and is divided into three parts. The first part illustrates the evolution of the concept of the ‘sharing economy’ and the main analytical implications. The second part outlines the key findings of a systematic review of the literature, which indicates both that academic research on the sharing economy has expanded considerably since 2013, and that sociology’s contribution to this debate remains underdeveloped and somewhat incoherent. The final part both locates the contributions to the monograph in the context of other studies and summarizes its content.
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Este estudo descreve uma série de reações envolvendo os grupos isocianatos (NCO) e os grupos hidroxílicos do acetato de celulose com grau de substituição (DS) igual a 2,4. As reações foram realizadas em meio homogêneo e utilizaram dois... more
Este estudo descreve uma série de reações envolvendo os grupos isocianatos (NCO) e os grupos hidroxílicos do acetato de celulose com grau de substituição (DS) igual a 2,4. As reações foram realizadas em meio homogêneo e utilizaram dois isocianatos estruturalmente diferentes: o 3-isopropenil-<img width=32 height=32 src="http://img/fbpe/po/v8n3/8303s5.gif">,<img width=32 height=32 src="http://img/fbpe/po/v8n3/8303s5.gif">'-dimetilbenzil isocianato (TMI) e o 2-isocianato-etil metacrilato (IEM). Um acompanhamento cinético das reações foi realizado por espectroscopia na região do infravermelho, onde acompanhou-se o desaparecimento da banda típica de isocianato a aproximadamente 2260 cm-1. Filmes de acetato de celulose modificados foram obtidos após as reações, sendo posteriormente caracterizados por análises de ângulos de contato, espectroscopia na região do infravermelho e ensaios de tração.
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The conventional vulcanization process applied to elastomers is irreversible and hinders therefore their useful recycling. We demonstrate here that natural rubber can be reversibly crosslinked via the Diels-Alder coupling of furan and... more
The conventional vulcanization process applied to elastomers is irreversible and hinders therefore their useful recycling. We demonstrate here that natural rubber can be reversibly crosslinked via the Diels-Alder coupling of furan and maleimide moieties. The furan-modified natural rubber used in this strategy was also exploited to bind it to maleimide-modified nanocellulose, thus generating a covalently crosslinked composite of these two renewable polymers.
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The main purpose of this study was to investigate the potential of suberin (a naturally occurring aromatic-aliphatic polyester ubiquitous to the vegetable realm) as a renewable source of chemicals and, in particular, to assess their... more
The main purpose of this study was to investigate the potential of suberin (a naturally occurring aromatic-aliphatic polyester ubiquitous to the vegetable realm) as a renewable source of chemicals and, in particular, to assess their physical properties. A comparison between cork and birch suberin fragments obtained by conventional depolymerisation processes (hydrolysis or methanolysis) is provided, focusing essentially on their thermal and crystallinity properties. It was found that suberin fragments obtained by the hydrolysis depolymerisation of birch had a high degree of crystallinity, as indicated by their thermal analysis and corroborated by the corresponding XRD diffractions, as opposed to hydrolysis-depolymerised cork suberin counterparts, which were essentially amorphous.
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ABSTRACT Styrene copolymers containing various amounts of a novel comonomer bearing a pendant furan ring were synthesized and characterized before being submitted to Diels−Alder reactions with either a monomaleimide or a bismaleimide.... more
ABSTRACT Styrene copolymers containing various amounts of a novel comonomer bearing a pendant furan ring were synthesized and characterized before being submitted to Diels−Alder reactions with either a monomaleimide or a bismaleimide. Spectroscopic evidence, supported by data from model compounds, indicated that the resulting linear and cross-linked products contained extensive percentages of adduct structures formed from the furan moieties. Both types of materials were then heated in a solvent containing a large excess of 2-methylfuran in order to induce the retro-Diels−Alder and the coupling of the released maleimides with the furanic additive. The reaction proceeded as expected and the original copolymers could be recovered from the treatment. The interest in the general strategy reported here resides in the possibility of recycling cross-linked polymers by a simple thermal treatment conducted in the presence of a suitable trap.
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ABSTRACT A two-step transesterification procedure was applied to combinations of difuranic diesters and both aliphatic and furanic diols. The reaction parameters (including the nature of the catalyst) were varied in both phases of the... more
ABSTRACT A two-step transesterification procedure was applied to combinations of difuranic diesters and both aliphatic and furanic diols. The reaction parameters (including the nature of the catalyst) were varied in both phases of the process and the results compared with those published for similar systems based on aromatic diesters. The best results related to the first phase of the synthesis were obtained using Zn(AcO)2, Pb(AcO)2 or Ti(OBu)4 at 200°C with a large excess of diol. The second phase, which led to the actual polymer at 200–240°C, called upon the catalytic action of SnC2O4, Sb2O3 and Ti(OBu)4 and was prolonged until the viscosity of the media ceased to increase. Specific problems, related to some fragile moieties, limited the success of these polymerizations to a number of combinations which gave polyesters bearing regular structures and molecular weights in the tens of thousands.
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Several monomers were submitted to pulsed TEA-CO2 laser radiation. In the condensed phase neither polymerization nor decomposition was observed. In the vapour phase, polymerization did not take place but extensive decomposition occurred,... more
Several monomers were submitted to pulsed TEA-CO2 laser radiation. In the condensed phase neither polymerization nor decomposition was observed. In the vapour phase, polymerization did not take place but extensive decomposition occurred, mainly through molecular elimination reactions. Possible reasons for the lack of polymerization are discussed.
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Several furanic polyazines and polyazomethines were prepared by solution condensation of 2,5-furandicarboxaldehyde (FDC) with hydrazine, 1,4-phenylene diamine and OO′(bis-2-aminopropyl )polyethylene oxide (Jeffamine) and thoroughly... more
Several furanic polyazines and polyazomethines were prepared by solution condensation of 2,5-furandicarboxaldehyde (FDC) with hydrazine, 1,4-phenylene diamine and OO′(bis-2-aminopropyl )polyethylene oxide (Jeffamine) and thoroughly characterized. Their thermal and ...
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ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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A brief review is given of the fundamental features determining the behavior of amorphous PEO-based networks as polymer electrolytes containing ionic moieties in terms of two basic issues affecting the ultimate optimum ionic conductivity,... more
A brief review is given of the fundamental features determining the behavior of amorphous PEO-based networks as polymer electrolytes containing ionic moieties in terms of two basic issues affecting the ultimate optimum ionic conductivity, viz. the factors determining the extent of ionic dissociation and those influencing the ionic mobility. These generalizations deduced from previous studies on a variety of systems
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A new synthetic pathway for the production of p-toluic acid has been developed starting from reagents derived from renewable resources. A Diels-Alder reaction between sorbic and acrylic acids is followed by a combined dehydrogenation/... more
A new synthetic pathway for the production of p-toluic acid has been developed starting from reagents derived from renewable resources. A Diels-Alder reaction between sorbic and acrylic acids is followed by a combined dehydrogenation/ decarboxylation process, providing p-toluic acid in high yields. This route permits to use milder conditions compared to other Diels-Alder approaches reported in the literature, and therefore can contribute to a more sustainable terephthalic acid production.
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... Olvido García Valdés La narración y el paisaje: Andréi Tarkovski. Blanca Montalvo ... Blanca Montalvo Page 22. La primera película que recuerdo haber visto de Tarkovski fue Solaris. Mi pasión por la ciencia ficción y las novelas de... more
... Olvido García Valdés La narración y el paisaje: Andréi Tarkovski. Blanca Montalvo ... Blanca Montalvo Page 22. La primera película que recuerdo haber visto de Tarkovski fue Solaris. Mi pasión por la ciencia ficción y las novelas de Stanislaw Lem me arrastró a la Filmoteca ...
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ABSTRACT Various attempts to induce the anionic polymerisation of 2-vinylfuran and some of its homologues were carried out. Negative results were obtained, except with sodium biphenyl in hexamethylphosphotriamide, a system which gave... more
ABSTRACT Various attempts to induce the anionic polymerisation of 2-vinylfuran and some of its homologues were carried out. Negative results were obtained, except with sodium biphenyl in hexamethylphosphotriamide, a system which gave limited yields and not a living polymerisation. The results are interptreted on the basis of side reactions of the furan ring marring the normal vinyl propagation, A critical discussion of previous conflicting reports is also given.
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ABSTRACT Grafting of cellulosic materials, including bleached kraft pulp, has been achieved by electrophilic polymerization. The process involves two steps, (i) the tosylation of the cellulosic substrate by reaction with tosyl chloride,... more
ABSTRACT Grafting of cellulosic materials, including bleached kraft pulp, has been achieved by electrophilic polymerization. The process involves two steps, (i) the tosylation of the cellulosic substrate by reaction with tosyl chloride, (ii) polymerization of 2-methyl-2-oxazoline in contact with the esterified cellulose. The grafting efficiency was generally in the range of 20 to 50 %, which was attributed to the occurrence of a transfer reaction specific to the cellulose.
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ABSTRACT The homopolymerisation of 2-furaldehyde, 5-methyl-2-furaldehyde and 2-furyl methyl ketone and their cationic copolymerisation (BF3. Et2) with olefins were investigated. All attempts to obtain homopolymers failed because of... more
ABSTRACT The homopolymerisation of 2-furaldehyde, 5-methyl-2-furaldehyde and 2-furyl methyl ketone and their cationic copolymerisation (BF3. Et2) with olefins were investigated. All attempts to obtain homopolymers failed because of thermodynamic restrictions. 2-Furaldehyde and α-methylstyrene gave an alternating copolymer of low degree of polymerisation, 2-methyl-2-furaldehyde and α-methylstyrene gave copolymers rich in 5-methyl-2-furaldehyde, indicating a penultimate effect in the growth mechanism. The use of less basic comonomers (cyclopentadiene, styrene, isoprene, etc.) resulted in inhibition or strong retardation of the polymerisation. The use of more basic comonomers (acenaphthy-lene, N-vinylcarbazole) resulted in their homopolymerisation. Furyl methyl ketone inhibited the polymerisation of all comonomers tried. A complex between BF3. Et2O and 2-furaldehyde was isolated and characterised. A general mechanism is offered to explain the behaviour of these systems.
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Surface functionalization of cellulose nanocrystals (CNCs) aims to improve their properties. The main objective of this study was the esterification of the surface of CNCs using nontoxic resin acids, rosin. The structural and... more
Surface functionalization of cellulose nanocrystals (CNCs) aims to improve their properties. The main objective of this study was the esterification of the surface of CNCs using nontoxic resin acids, rosin. The structural and morphological modifications of CNC nanorods were characterized by (13)C NMR and Fourier transform infrared spectroscopy, atomic force microscopy, and X-ray diffraction analyses. The properties of functionalized CNCs were evaluated by thermogravimetric analysis and contact-angle measurements. The results indicate that the esterification proceeded from the surface of the CNC. The antimicrobial activities of the modified and neat CNC were investigated; the rosin-grafted CNC exhibited a strong antibacterial activity against Gram-negative bacteria and a modest antibacterial activity against Gram-positive bacteria.
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After the end of World War II, science and technology related to polymers underwent a spectacular development that resulted in the production of a wide variety of materials covering a vast domain of applications. These thermoplastic and... more
After the end of World War II, science and technology related to polymers underwent a spectacular development that resulted in the production of a wide variety of materials covering a vast domain of applications. These thermoplastic and thermoset materials ...