Solid-State Polymerization of Poly(Ethylene Furanoate) Biobased Polyester, III: Extended Study on Effect of Catalyst Type on Molecular Weight Increase
Yosra ChebbiNejib KasmiMustapha MajdoubGeorge Z. PapageorgiouDimitris S. AchiliasDimitrios Ν. Bikiaris
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In this study, the synthesis of poly(ethylene furanoate) (PEF), catalyzed by five different catalysts-antimony acetate (III) (Sb Ac), zirconium (IV) isopropoxide isopropanal (Zr Is Ip), antimony (III) oxide (Sb Ox), zirconium (IV) 2,4-pentanedionate (Zr Pe) and germanium (IV) oxide (Ge Ox)-via an industrially common combination of melt polymerization and subsequent solid-state polymerization (SSP) is presented. In all reactions, proper amounts of 2,5-dimethylfuran-dicarboxylate (DMFD) and ethylene glycol (EG) in a molar ratio of DMFD/EG= 1/2 and 400 ppm of catalyst were used. Polyester samples were subjected to SSP procedure, under vacuum application, at different reaction times (1, 2, 3.5, and 5 h) and temperatures of 190, 200, and 205 °C. Carboxyl end-groups concentration (⁻COOH), intrinsic viscosity (IV), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polymers to study the effect of the used catalysts on the molecular weight increase of PEF during SSP process. As was expected, it was found that with increasing the SSP time and temperature, the intrinsic viscosity and the average molecular weight of PEF steadily increased. In contrast, the number of carboxyl end-groups content showed the opposite trend as intrinsic viscosity, that is, gradually decreasing during SSP time and temperature increase. It is worthy to note that thanks to the SSP process an obvious and continuous enhancement in the thermal properties of the prepared PEF samples was attained, in which their melting temperatures (Tm) and degree of crystallinity (Xc) increase progressively with increasing of reaction time and temperature. To predict the time evolution of polymers IV, as well as the hydroxyl and carboxyl content of PEF polyesters during the SSP, a simple kinetic model was developed. From both the theoretical simulation results and the experimental measurements, it was demonstrated that surely the Zr Is Ip catalyst shows the best catalytic characteristics compared to all other used catalysts herein, that is, leading in reducing-in a spectacular way-the activation energy of the involved both transesterification and esterification reactions during SSP.Keywords:
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Poly ethylene
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Polymerizations of styrene and methyl methacrylate (MMA) containing 1 wt % C60 initiated by 5 or 10 mol of azobis(isobutyronitrile)/mol of C60 in 1,2-dichlorobenzene solution produce brown polymers in 53−97% yield with all of the C60 incorporated, linear polymer equivalent molecular weights of Pn = 19 000−31 000, and Pw/Pn < 2. There are short induction periods before polymerization begins. All of the C60 is incorporated into the polymer after low conversion of the monomer. Multidetector size exclusion chromatography analyses measured polymer mass by differential refractive index, Mw by two-angle laser light scattering, intrinsic viscosity by differential viscometry, and mass of only C60 derivatives by UV. Molar chromatograms show that all of the polymer at the high end of the molecular weight distributions contains C60, and there are sizeable amounts of a lower molecular weight linear polymer. The high molecular weight polystyrene contains as many as 10−100 C60 units, but the high molecular weight PMMA contains an average of one C60 unit per macromolecule. All of the polymers have lower intrinsic viscosities and higher Mw than linear standards of the same retention volume due to branched or star structures. Calculations from a random branching model of Zimm and Stockmayer indicate that the PMMAs have an average branch number of five over the entire molecular weight distribution and systematically increasing average branch lengths with an increasing degree of conversion.
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Abstract Computations have been performed of the intrinsic viscosity of trifunctional, randomly branched whole polymers. Both the Thurmond‐Zimm and the Zimm‐Kilb treatments of the viscosity of branched polymers have been combined with the Beasley molecular weight distribution function. The Beasley distribution function has also been compared with a function derived by Flory for trifunctionally branched condensation polymers. The two functions are in good agreement at low extents of branching, but at higher branch contents the former function extends to significantly higher molecular weights.
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Abstract New polymer characterization capabilities have recently been added to our size exclusion chromatography (SEC) using an on-line viscosity detector. In addition to molecular weight distribution (MWD) capabilities, we now also can determine the intrinsic viscosity distribution (IVD), and the molecular size distribution, i.e., polymer radius-of-gyration, or Rg-distribution (RGD) of polymer samples. Polymer conformation and branching features can now be studied by the log(Rg) versus log(MW) results of a single SEC-viscometry experiment. Also added to our SEC-viscometry analyses is the absolute Mn method recently proposed by J. M. Goldwasser for handling the difficult problems of determining molecular weight (MW) of copolymers and polymer blends. In this new method, the number-average molecular weight (Mn) of a complex polymer sample can be determined by SEC using an on-line viscosity detector, without the need of an on-line concentration detector.
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Branching (polymer chemistry)
Gel permeation chromatography
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Nonconventional fluorescent polymers without π-aromatic structure have attracted extensive interest in recent years. Hyperbranched polyesters are generally known because of their industrial applications; however, the luminescent properties of the polyester has not been reported. Herein, we synthesized a series of fully biobased aliphatic hyperbranched polyesters via a one-pot A2 + B3 esterification reaction. Intriguingly, the resultant hyperbranched polyesters carrying no conventional fluorescent units exhibited unexpected bright blue fluorescence under 365 nm UV light. It was found that the fluorescence intensity was enhanced with increasing solution concentrations and molecular weights of the polyesters. Moreover, the results suggested that the luminescence of polyesters could be controlled by solvents and metal ions. In particular, the fluorescence of the polyesters was extremely sensitive to Fe3+. More interesting is that the fluorescence of the polyesters showed an aggregation-induced enhanced emission in the mixture system. Notably, the resulting polyesters displayed a remarkably enhanced quantum yield (16.75%) as compared with that of other types of these polymers. Preliminary results demonstrate that clustering of the carbonyl groups is responsible for the unusual fluorescence in the aliphatic hyperbranched polyesters, namely, clustering-induced emission (CIE). This study provides a novel perspective for the design of biobased luminescent materials to new application areas.
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Abstract BACKGROUND: Number‐average molecular weight, M̄ n , is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size‐exclusion chromatography (SEC) using on‐line viscometric detection and assuming the validity of the universal calibration concept. RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on‐line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M̄ n and weight‐average molecular weight, M̄ w . Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules. CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η] M , on elution volume, can differ in values of [η] M from those obtained for narrow molecular weight standards by 10–15%. The method studied is helpful for the determination of M̄ n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers. Copyright © 2008 Society of Chemical Industry
Molar mass distribution
Divinylbenzene
Gel permeation chromatography
Molecular mass
Branching (polymer chemistry)
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This paper summarized the structures of polyesters,separately introduced two kinds of polyesters,the saturated polyester and the unsaturated polyester,particularly described the properties of polyesters,especially showed the applications of electronics and research progress of the polyester film,polyester adhesive and polyester fiber.
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