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Artículos de revistas sobre el tema "High molar mass"

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Publicado: 25 de mayo de 2024

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1

Matsuda, Yasuhiro, Fumitada Sugiura, Kazuya Okumura y Shigeru Tasaka. "Renaturation behavior of xanthan with high molar mass and wide molar mass distribution". Polymer Journal 48, n.º 5 (27 de enero de 2016): 653–58. http://dx.doi.org/10.1038/pj.2015.128.

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2

Tsinas, Zois, Sara V. Orski, Viviana R. C. Bentley, Lorelis Gonzalez Lopez, Mohamad Al-Sheikhly y Amanda L. Forster. "Effects of Thermal Aging on Molar Mass of Ultra-High Molar Mass Polyethylene Fibers". Polymers 14, n.º 7 (24 de marzo de 2022): 1324. http://dx.doi.org/10.3390/polym14071324.

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Ultra-high molar mass polyethylene (UHMMPE) is commonly used for ballistic-resistant body armor applications due to the superior strength of the fibers fabricated from this material combined with its low density. However, polymeric materials are susceptible to thermally induced degradation during storage and use, which can reduce the high strength of these fibers, and, thus, negatively impact their ballistic resistance. The objective of this work is to advance the field of lightweight and soft UHMMPE inserts used in various types of ballistic resistant-body armor via elucidating the mechanisms of chemical degradation and evaluating this chemical degradation, as well as the corresponding physical changes, of the UHMMPE fibers upon thermal aging. This is the first comprehensive study on thermally aged UHMMPE fibers that measures their decrease in the average molar mass via high-temperature size exclusion chromatography (HT-SEC) analysis. The decrease in the molar mass was further supported by the presence of carbon-centered free radicals in the polyethylene that was detected using electron paramagnetic resonance (EPR) spectroscopy. These carbon-centered radicals result from a cascade of thermo-oxidative reactions that ultimately induce C–C ruptures along the backbone of the polymer. Changes in the crystalline morphology of the UHMMPE fibers were also observed through wide-angle X-ray diffraction (WAXS), showing an increase in the amorphous regions, which promotes oxygen diffusion into the material, specifically through these areas. This increase in the amorphous fraction of the highly oriented polyethylene fibers has a synergistic effect with the thermo-oxidative degradation processes and contributes significantly to the decrease in their molar mass.
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3

Duguet, Etienne, Michele Schappacher y Alain Soum. "High molar mass polysilazane: a new polymer". Macromolecules 25, n.º 19 (septiembre de 1992): 4835–39. http://dx.doi.org/10.1021/ma00045a001.

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4

Qiu, Wulin y Bernhard Wunderlich. "Reversible melting of high molar mass poly(oxyethylene)". Thermochimica Acta 448, n.º 2 (septiembre de 2006): 136–46. http://dx.doi.org/10.1016/j.tca.2006.07.005.

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5

Fadeyeva, I. V., S. M. Staroverov, G. V. Lisichkin, A. V. Gaida, Yu V. Magerovskii y V. A. Monastyrskii. "Gel-chromatography of high molar mass thromboplastin complexes". Polymer Science U.S.S.R. 29, n.º 8 (enero de 1987): 1829–33. http://dx.doi.org/10.1016/0032-3950(87)90052-9.

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6

Monnery, Bryn D., Valentin V. Jerca, Ondrej Sedlacek, Bart Verbraeken, Rachel Cavill y Richard Hoogenboom. "Defined High Molar Mass Poly(2‐Oxazoline)s". Angewandte Chemie 130, n.º 47 (19 de noviembre de 2018): 15626–30. http://dx.doi.org/10.1002/ange.201807796.

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7

Monnery, Bryn D., Valentin V. Jerca, Ondrej Sedlacek, Bart Verbraeken, Rachel Cavill y Richard Hoogenboom. "Defined High Molar Mass Poly(2‐Oxazoline)s". Angewandte Chemie International Edition 57, n.º 47 (19 de noviembre de 2018): 15400–15404. http://dx.doi.org/10.1002/anie.201807796.

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8

Blain, Marine, Adrien Cornille, Bernard Boutevin, Rémi Auvergne, Dominique Benazet, Bruno Andrioletti y Sylvain Caillol. "Hydrogen bonds prevent obtaining high molar mass PHUs". Journal of Applied Polymer Science 134, n.º 45 (13 de febrero de 2017): 44958. http://dx.doi.org/10.1002/app.44958.

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9

Snyder, Chad R., Ryan C. Nieuwendaal, Dean M. DeLongchamp, Christine K. Luscombe, Prakash Sista y Shane D. Boyd. "Quantifying Crystallinity in High Molar Mass Poly(3-hexylthiophene)". Macromolecules 47, n.º 12 (3 de junio de 2014): 3942–50. http://dx.doi.org/10.1021/ma500136d.

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10

Braendle, Andreas, Carina Vidovič, Nadia Mösch-Zanetti, Markus Niederberger y Walter Caseri. "Synthesis of High Molar Mass Poly(phenylene methylene) Catalyzed by Tungsten(II) Compounds". Polymers 10, n.º 8 (7 de agosto de 2018): 881. http://dx.doi.org/10.3390/polym10080881.

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Poly(phenylene methylene)s (PPMs) with high molar masses were isolated by polymerization of benzyl chloride catalyzed with tungsten(II) compounds and subsequent fractionation. Four different tungsten(II) catalysts were successfully exploited for the polymerization, for which a strict temperature profile was developed. The PPMs possessed roughly a trimodal molar mass distribution. Simple fractionation by phase separation of 2-butanone solutions allowed to effectively segregate the products primarily into PPM of low molar mass (Mn = 1600 g mol−1) and high molar mass (Mn = 167,900 g mol−1); the latter can be obtained in large quantities up to 50 g. The evolution of the trimodal distribution and the monomer conversion was monitored by gel permeation chromatography (GPC) and 1H NMR spectroscopy, respectively, over the course of the polymerization. The results revealed that polymerization proceeded via a chain-growth mechanism. This study illustrates a new approach to synthesize PPM with hitherto unknown high molar masses which opens the possibility to explore new applications, e.g., for temperature-resistant coatings, fluorescent coatings, barrier materials or optical materials.
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11

Kennedy, J. C., J. R. MacCallum y D. H. MacKerron. "Synthesis and characterization of a series of poly(α,ω-alkyldiynes) and copoly(α,ω-alkyldiynes)". Canadian Journal of Chemistry 73, n.º 11 (1 de noviembre de 1995): 1914–23. http://dx.doi.org/10.1139/v95-236.

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A series of poly(α,ω-alkyldiynes) and copoly(α,ω-alkyldiynes) were synthesized by catalytic Glaser coupling reactions. Two routes were investigated and developed. These routes were chosen in anticipation that high molar mass, linear and polydisperse, polymers would be achieved. GPC (gel permeation chromatography) curves revealed that this was possible for the majority of polymers synthesized by the first route. However, a wide range of molar masses were obtained by the second route with a significant low molar mass tail present in almost all GPC curves. Very low Mn (number average molar mass) values by GPC gave correspondingly very high Mn values by end-group analysis (EGA). Hence, it was proposed that the low molar mass tail was a consequence of cyclic structures. From these results and observations a mechanism for the polymerization of the α,ω-alkyldiynes was proposed. Keywords: poly(α,ω-alkyldiynes), Glaser coupling, molar mass.
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12

Li, Ying, Ulrich Pöschl y Manabu Shiraiwa. "Molecular corridors and parameterizations of volatility in the chemical evolution of organic aerosols". Atmospheric Chemistry and Physics 16, n.º 5 (14 de marzo de 2016): 3327–44. http://dx.doi.org/10.5194/acp-16-3327-2016.

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Abstract. The formation and aging of organic aerosols (OA) proceed through multiple steps of chemical reaction and mass transport in the gas and particle phases, which is challenging for the interpretation of field measurements and laboratory experiments as well as accurate representation of OA evolution in atmospheric aerosol models. Based on data from over 30 000 compounds, we show that organic compounds with a wide variety of functional groups fall into molecular corridors, characterized by a tight inverse correlation between molar mass and volatility. We developed parameterizations to predict the saturation mass concentration of organic compounds containing oxygen, nitrogen, and sulfur from the elemental composition that can be measured by soft-ionization high-resolution mass spectrometry. Field measurement data from new particle formation events, biomass burning, cloud/fog processing, and indoor environments were mapped into molecular corridors to characterize the chemical nature of the observed OA components. We found that less-oxidized indoor OA are constrained to a corridor of low molar mass and high volatility, whereas highly oxygenated compounds in atmospheric water extend to high molar mass and low volatility. Among the nitrogen- and sulfur-containing compounds identified in atmospheric aerosols, amines tend to exhibit low molar mass and high volatility, whereas organonitrates and organosulfates follow high O : C corridors extending to high molar mass and low volatility. We suggest that the consideration of molar mass and molecular corridors can help to constrain volatility and particle-phase state in the modeling of OA particularly for nitrogen- and sulfur-containing compounds.
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13

Chen, Chuangbi, Mehdihasan I. Shekh, Shuming Cui y Florian J. Stadler. "Rheological Behavior of Blends of Metallocene Catalyzed Long-Chain Branched Polyethylenes. Part I: Shear Rheological and Thermorheological Behavior". Polymers 13, n.º 3 (20 de enero de 2021): 328. http://dx.doi.org/10.3390/polym13030328.

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Long-chain branched metallocene-catalyzed high-density polyethylenes (LCB-mHDPE) were solution blended to obtain blends with varying degrees of branching. A high molecular LCB-mHDPE was mixed with low molecular LCB-mHDPE at varying concentrations. The rheological behavior of those low molecular LCB-mHDPE is similar but their molar mass and molar mass distribution are significantly different. Those blends were characterized rheologically to study the effects of concentration, molar mass distribution, and long-chain branching level of the low molecular LCB-mHDPE. Owing to the ultra-long relaxation times of the high molecular LCB-mHDPE, the blends exhibited a clearly more long-chain branched behavior than the base materials. The thermorheological complexity analysis showed an apparent increase in the activation energies Ea determined from G′, G″, and especially δ. Ea(δ), which for LCB-mHDPE is a peak function, turned out to produce even more pronounced peaks than observed for LCB-mPE with narrow molar mass distribution and also LCB-mPE with broader molar mass distribution. Thus, it is possible to estimate the molar mass distribution from the details of the thermorheological complexity.
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14

ONO, HIROSHI y NOBUHIRO KAWATSUKI. "HIGH- AND LOW-MOLAR-MASS LIQUID CRYSTAL MIXTURES FOR PHOTOREFRACTIVE APPLICATIONS". Journal of Nonlinear Optical Physics & Materials 08, n.º 03 (septiembre de 1999): 329–40. http://dx.doi.org/10.1142/s0218863599000230.

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We describe a highly efficient photorefractive material possessing high-molar-mass liquid crystal (H-LC), low-molar-mass liquid crystal (L-LC), and photoconductive agent. These photorefractive high- and low-molar-mass liquid crystal mixtures (HL-LCMs) show high-performance in a thick grating regime (Bragg regime) under low dc electric fields (< 1 V/μm). The photorefractive properties are strongly dependent on the concentration of the H-LC. The fastest response time of 70 ms is achieved with a gain coefficient of 213 cm-1 in the case of 10 wt% of the H-LC with 0.18 V/μm. The largest gain coefficient of over 600 cm-1 is achieved with the response time of 2.6 s in the case of 40 wt% of the H-LC with 0.7 V/μm. In addition, our future directions in this research area are also presented.
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15

Li, Y., U. Pöschl y M. Shiraiwa. "Molecular corridors and parameterizations of volatility in the evolution of organic aerosols". Atmospheric Chemistry and Physics Discussions 15, n.º 19 (15 de octubre de 2015): 27877–915. http://dx.doi.org/10.5194/acpd-15-27877-2015.

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Abstract. The formation and aging of organic aerosols (OA) proceed through multiple steps of chemical reaction and mass transport in the gas and particle phases, which is challenging for the interpretation of field measurements and laboratory experiments as well as accurate representation of OA evolution in atmospheric aerosol models. Based on data from over 30 000 compounds, we show that organic compounds with a wide variety of functional groups fall into molecular corridors, characterized by a tight inverse correlation between molar mass and volatility. We developed parameterizations to predict the volatility of organic compounds containing oxygen, nitrogen and sulfur from the elemental composition that can be measured by soft-ionization high-resolution mass spectrometry. Field measurement data from new particle formation events, biomass burning, cloud/fog processing, and indoor environments were mapped into molecular corridors to characterize the chemical nature of the observed OA components. We found that less oxidized indoor OA are constrained to a corridor of low molar mass and high volatility, whereas highly oxygenated compounds in atmospheric water extend to high molar mass and low volatility. Among the nitrogen- and sulfur-containing compounds identified in atmospheric aerosols, amines tend to exhibit low molar mass and high volatility, whereas organonitrates and organosulfates follow high O : C corridors extending to high molar mass and low volatility. We suggest that the consideration of molar mass and molecular corridors can help to constrain volatility and particle phase state in the modeling of OA particularly for nitrogen- and sulfur-containing compounds.
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16

Ono, Hiroshi y Nobuhiro Kawatsuki. "High-performance photorefractivity in high- and low-molar-mass liquid crystal mixtures". Journal of Applied Physics 85, n.º 5 (marzo de 1999): 2482–87. http://dx.doi.org/10.1063/1.369609.

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17

Gervais, Matthieu, Anne-Laure Brocas, Gabriel Cendejas, Alain Deffieux y Stephane Carlotti. "Linear High Molar Mass Polyglycidol and its Direct α-Azido Functionalization". Macromolecular Symposia 308, n.º 1 (octubre de 2011): 101–11. http://dx.doi.org/10.1002/masy.201151014.

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18

D’Elia, Marco F., Yingying Yu, Melvin Renggli, Madeleine A. Ehweiner, Carina Vidovic, Nadia C. Mösch-Zanetti, Markus Niederberger y Walter Caseri. "Synthesis of Soluble High Molar Mass Poly(Phenylene Methylene)-Based Polymers". Polymers 16, n.º 7 (2 de abril de 2024): 967. http://dx.doi.org/10.3390/polym16070967.

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Poly(phenylene methylene) (PPM) is a multifunctional polymer that is also active as an anticorrosion fluorescent coating material. Although this polymer was synthesized already more than 100 years ago, a versatile synthetic route to obtain soluble high molar mass polymers based on PPM has yet to be achieved. In this article, the influence of bifunctional bis-chloromethyl durene (BCMD) as a branching agent in the synthesis of PPM is reported. The progress of the reaction was followed by gel permeation chromatography (GPC) and NMR analysis. PPM-based copolymers with the highest molar mass reported so far for this class of materials (up to Mn of 205,300 g mol−1) were isolated. The versatile approach of using BCMD was confirmed by employing different catalysts. Interestingly, thermal and optical characterization established that the branching process does not affect the thermoplastic behavior and the fluorescence of the material, thus opening up PPM-based compounds with high molar mass for applications.
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19

Liu, Yang, Kaihu Xian, Zhongxiang Peng, Mengyuan Gao, Yibo Shi, Yunfeng Deng, Yanhou Geng y Long Ye. "Tuning the molar mass of P3HT via direct arylation polycondensation yields optimal interaction and high efficiency in nonfullerene organic solar cells". Journal of Materials Chemistry A 9, n.º 35 (2021): 19874–85. http://dx.doi.org/10.1039/d1ta02253a.

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20

Sågfors, P. E. y B. Starck. "High Molar Mass Lignin in Bleached Kraft Pulp Mill Effluents". Water Science and Technology 20, n.º 2 (1 de febrero de 1988): 49–58. http://dx.doi.org/10.2166/wst.1988.0045.

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The proportion of high molar mass (M &gt; 1000D*) substances (HMM) in acid and alkaline bleaching effluents from kraft pulping has been studied by means of analytical gel permeation chromatography, GPC. The amount of HMM substances in alkaline effluents was found to be 65 - 75 % and in acid stage effluents 20 % of the UV-absorbing (A280 nm) components. Lignin is the precursor of the HMM substances in the alkaline stage, and lignin and carbohydrates are the precursors of the acid stage HMM substances. For the purpose of characterization the HMM compounds were separated from low molar mass substances by preparative GPC. The IR spectra of both alkaline and acid stage substances in their neutral form had strong bands characteristic of carboxylic salts. There were no aromatic bands in the spectra of softwood HMM substances. In the spectra of hardwood substances a narrow aromatic band of low intensity was found in two alkaline stage HMM samples originating from mills using a high proportion of ClO2 to chlorine. Elemental analysis of the alkaline stage HMM substances showed that the chlorine content was as high as 9.8 % when the ClO2 charge had been small and less than 4 % with a large ClO2 charge. The low methoxyl group content and high oxygen content showed that the substances were largely oxidized. The LC50 test with water flea indicated no acute toxicity.
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21

Tamsilian, Yousef, Mahsa Shirazi, James J. Sheng, Amaia Agirre, Mercedes Fernandez y Radmila Tomovska. "Advanced oil recovery by high molar mass thermoassociating graft copolymers". Journal of Petroleum Science and Engineering 192 (septiembre de 2020): 107290. http://dx.doi.org/10.1016/j.petrol.2020.107290.

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22

Šoltés, L., G. Kogan, M. Stankovská, R. Mendichi, J. Schiller y P. Gemeiner. "Degradation of High-Molar-Mass Hyaluronan and Characterization of Fragments". Biomacromolecules 8, n.º 9 (septiembre de 2007): 2697–705. http://dx.doi.org/10.1021/bm070309b.

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23

Cevada, E., K. Roos, F. Alvarez, S. Carlotti y F. Vázquez. "High molar mass polyethers as defoamers of heavy crude oil". Fuel 221 (junio de 2018): 447–54. http://dx.doi.org/10.1016/j.fuel.2018.02.136.

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24

Jamróz-Piegza, M., A. Utrata-Wesołek, B. Trzebicka y A. Dworak. "Hydrophobic modification of high molar mass polyglycidol to thermosensitive polymers". European Polymer Journal 42, n.º 10 (octubre de 2006): 2497–506. http://dx.doi.org/10.1016/j.eurpolymj.2006.04.017.

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25

Petton, Lionel, Edwin P. C. Mes, Hanno Van Der Wal, Sven Claessens, Freddy Van Damme, Sam Verbrugghe y Filip E. Du Prez. "High molar mass segmented macromolecular architectures by nitroxide mediated polymerisation". Polymer Chemistry 4, n.º 17 (2013): 4697. http://dx.doi.org/10.1039/c3py00600j.

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26

Qiu, W., M. Pyda, E. Nowak-Pyda, A. Habenschuss y B. Wunderlich. "Reversible melting and crystallization of high-molar-mass poly(oxyethylene)". Journal of Polymer Science Part B: Polymer Physics 45, n.º 4 (2007): 475–89. http://dx.doi.org/10.1002/polb.21067.

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27

Zhang, Afang. "High-Molar-Mass, First and Second GenerationL-Lysine Dendronized Polymethacrylates". Macromolecular Rapid Communications 29, n.º 10 (19 de mayo de 2008): 839–45. http://dx.doi.org/10.1002/marc.200800145.

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28

Losio, Simona, Fabio Bertini, Adriano Vignali, Taiga Fujioka, Kotohiro Nomura y Incoronata Tritto. "Amorphous Elastomeric Ultra-High Molar Mass Polypropylene in High Yield by Half-Titanocene Catalysts". Polymers 16, n.º 4 (14 de febrero de 2024): 512. http://dx.doi.org/10.3390/polym16040512.

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Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp’TiCl2(N=CtBu2) [Cp’ = C5H5 (1), C5Me5 (2), Me3SiC5H4 (3)], with MAO as a cocatalyst, were investigated. The obtained polymers were studied in detail by determining their microstructure, molar masses, thermal, and mechanical properties. The Cp*-ketimide, (C5Me5)TiCl2(N=CtBu2) (2), exhibited higher catalytic activities than Cp’TiCl2(N=CtBu2) (1,3), yielding higher molar mass polymers, Mw up to 1400 Kg/mol. All the synthesized polypropylenes (PP) are atactic and highly regioregular, with predominant rrrr pentads, especially PP prepared with catalyst 1. Differential scanning calorimetry (DSC) established that the polymers are fully amorphous aPP, and no melting endotherm events are detected. Glass transition temperatures were detected between −2 and 2 °C. These polypropylenes have been established to be high-performance thermoplastic elastomers endowed with remarkably high ductility, and a tensile strain at break higher than 2000%.
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29

Di Lorenzo, Maria Laura y René Androsch. "Accelerated crystallization of high molar mass poly( l / d -lactic acid) by blending with low molar mass poly( l -lactic acid)". European Polymer Journal 100 (marzo de 2018): 172–77. http://dx.doi.org/10.1016/j.eurpolymj.2018.01.030.

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30

Galland, Sylvain, Fredrik Berthold, Kasinee Prakobna y Lars A. Berglund. "Holocellulose Nanofibers of High Molar Mass and Small Diameter for High-Strength Nanopaper". Biomacromolecules 16, n.º 8 (20 de julio de 2015): 2427–35. http://dx.doi.org/10.1021/acs.biomac.5b00678.

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31

Alasonati, Enrica, Stephane Dubascoux, Gaetane Lespes y Vera I. Slaveykova. "Assessment of metal - extracellular polymeric substances interactions by asymmetrical flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry". Environmental Chemistry 7, n.º 2 (2010): 215. http://dx.doi.org/10.1071/en09148.

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Environmental context. Extracellular polymeric substances (EPS) are soluble polymers that are liberated from microorganisms and represent an important component of the natural organic matter in the aquatic and terrestrial environment. These substances affect nutrient and toxic metal cycling, both owing to their metal binding properties and their effect on aggregation and sedimentation. In order to obtain more information on their role in metal transport, EPS size (molar mass) distributions and the associated Ca, Cd and Pb were measured by using asymmetrical flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry. Abstract. Extracellular polymeric substances (EPSs) excreted by the bacterium Sinorhizobium meliloti and associated Ca, Cd and Pb were characterised by asymmetrical flow field-flow fractionation coupled with UV spectrophotometry and inductively coupled plasma mass spectrometry in terms of molar-mass distributions, number- and weight-average molar masses and polydispersity index. Two major populations with weight-average molar masses of 74 × 103 and 1.35 × 106 g mol–1 were obtained for the EPS. Characterisation of the whole EPS–metal interactions evidenced the preferential binding of Ca and Cd to the low molar mass fraction, whereas Pb associated mainly with the high molar mass (HMM) fraction. Comparison with the EPS produced by exoY-mutant, deficient in HMM-EPS excretion, confirmed the preferential binding of Pb to the high molar mass fraction. Enrichment of the EPS with increasing metal concentrations induced the formation of aggregates, which was most pronounced in the presence of 10–4 mol L–1 Pb.
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32

Sedlacek, Ondrej, Bryn D. Monnery y Richard Hoogenboom. "Synthesis of defined high molar mass poly(2-methyl-2-oxazoline)". Polymer Chemistry 10, n.º 11 (2019): 1286–90. http://dx.doi.org/10.1039/c9py00013e.

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33

Wagner, Manfred H., Esmaeil Narimissa y Taisir Shahid. "Elongational viscosity and brittle fracture of bidisperse blends of a high and several low molar mass polystyrenes". Rheologica Acta 60, n.º 12 (22 de octubre de 2021): 803–17. http://dx.doi.org/10.1007/s00397-021-01304-1.

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AbstractElongational viscosity data of four well-characterized blends consisting of 10% mass fraction of monodisperse polystyrene PS-820k (molar mass of 820 kg/mol) and 90% matrix polystyrenes with a molar mass of 8.8, 23, 34, and 73 kg/mol, respectively, as reported by Shahid et al. Macromolecules 52: 2521–2530, 2019 are analyzed by the extended interchain pressure (EIP) model including the effects of finite chain extensibility and filament rupture. Except for the linear-viscoelastic contribution of the matrix, the elongational viscosity of the blends is mainly determined by the high molar mass component PS-820k at elongation rates when no stretching of the lower molar mass matrix chains is expected. The stretching of the long chains is shown to be widely independent of the molar mass of the matrix reaching from non-entangled oligomeric styrene (8.8 kg/mol) to well-entangled polystyrene (73kg/mol). Quantitative agreement between data and model can be obtained when taking the interaction of the long chains of PS-820k with the shorter matrix chains of PS-23k, PS-34k, and PS-73k into account. The interaction of long and short chains leads to additional entanglements along the long chains of PS-820k, which slow down relaxation of the long chains, as clearly seen in the linear-viscoelastic behavior. According to the EIP model, an increased number of entanglements also lead to enhanced interchain pressure, which limits maximal stretch. The reduced maximal stretch of the long chains due to entanglements of long chains with shorter matrix chains is quantified by introducing an effective polymer fraction of the long chains, which increases with the increasing length of the matrix chains resulting in the excellent agreement of experimental data and model predictions.
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34

Kerr, Ryan W. F., Paul M. D. A. Ewing, Sumesh K. Raman, Andrew D. Smith, Charlotte K. Williams y Polly L. Arnold. "Ultrarapid Cerium(III)–NHC Catalysts for High Molar Mass Cyclic Polylactide". ACS Catalysis 11, n.º 3 (15 de enero de 2021): 1563–69. http://dx.doi.org/10.1021/acscatal.0c04858.

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35

Cauvin, Séverine, François Ganachaud, Michel Moreau y Patrick Hémery. "High molar mass polymers by cationic polymerisation in emulsion and miniemulsion". Chemical Communications, n.º 21 (2005): 2713. http://dx.doi.org/10.1039/b501489a.

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36

Besheer, Ahmed, Karsten Mäder, Sergej Kaiser, Jörg Kressler, Christine Weis y Erich K. Odermatt. "Tracking the urinary excretion of high molar mass poly(vinyl alcohol)". Journal of Biomedical Materials Research Part B: Applied Biomaterials 82B, n.º 2 (2007): 383–89. http://dx.doi.org/10.1002/jbm.b.30743.

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37

Turunen, Jani P. J., Matti Haukka y Tuula T. Pakkanen. "Cocatalyst-originated aluminum residues in fibrous, very high molar mass polyethylene". Journal of Applied Polymer Science 93, n.º 4 (2004): 1812–15. http://dx.doi.org/10.1002/app.20645.

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38

Walach, Wojciech, Agnieszka Kowalczuk, Barbara Trzebicka y Andrzej Dworak. "Synthesis of High-Molar Mass Arborescent-Branched Polyglycidol via Sequential Grafting". Macromolecular Rapid Communications 22, n.º 15 (1 de octubre de 2001): 1272. http://dx.doi.org/10.1002/1521-3927(20011001)22:15<1272::aid-marc1272>3.0.co;2-#.

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39

Kricheldorf, Hans R., Mikhail G. Zolotukhin y Jorge Cárdenas. "Non-Stoichiometric Polycondensations and the Synthesis of High Molar Mass Polycondensates". Macromolecular Rapid Communications 33, n.º 21 (24 de septiembre de 2012): 1814–32. http://dx.doi.org/10.1002/marc.201200345.

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40

Munawar, Muhammad A. y Dirk W. Schubert. "Revealing Electrical and Mechanical Performances of Highly Oriented Electrospun Conductive Nanofibers of Biopolymers with Tunable Diameter". International Journal of Molecular Sciences 22, n.º 19 (24 de septiembre de 2021): 10295. http://dx.doi.org/10.3390/ijms221910295.

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The present study outlines a reliable approach to determining the electrical conductivity and elasticity of highly oriented electrospun conductive nanofibers of biopolymers. The highly oriented conductive fibers are fabricated by blending a high molar mass polyethylene oxide (PEO), polycaprolactone (PCL), and polylactic acid (PLA) with polyaniline (PANi) filler. The filler-matrix interaction and molar mass (M) of host polymer are among governing factors for variable fiber diameter. The conductivity as a function of filler fraction (φ) is shown and described using a McLachlan equation to reveal the electrical percolation thresholds (φc) of the nanofibers. The molar mass of biopolymer, storage time, and annealing temperature are significant factors for φc. The Young’s modulus (E) of conductive fibers is dependent on filler fraction, molar mass, and post-annealing process. The combination of high orientation, tunable diameter, tunable conductivity, tunable elasticity, and biodegradability makes the presented nanofibers superior to the fibers described in previous literature and highly desirable for various biomedical and technical applications.
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41

Shchetinin, Pyotr P. y Margarita Shurupova. "Study of Sorption on Natural Minerals under Environmental Conditions". Key Engineering Materials 683 (febrero de 2016): 358–62. http://dx.doi.org/10.4028/www.scientific.net/kem.683.358.

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This paper presents a comparative study of the adsorption activity of the grass meal of lady's mantle aerial part (Alchemilla vulgaris) and modern adsorption materials – activated carbon (carbolenum) and hydrolyzed lignin (polyphepane) towards model substances (markers of adsorption). The model substances were used to effectively simulate a group of toxic substances with different molar mass and degree of ionogenicity in the environment that simulates gastric and intestinal juices. It was shown that hydrolized lignin had the highest protein adsorption activity and activated carbon appeared the most active in sorbing toxicants with low molar mass. The grass meal of lady's mantle aerial parts (Alchemilla vulgaris) was able to moderately absorb both high-molar mass and low-molar mass substances at an average degree of dispersion of the raw material. It is supposed that it was mainly due to the high-porous structure of the material. This shows the versatility of the enterosorbent under development.
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42

Pasch, Harald, Lars-Christian Heinz, Tibor Macko y Wolf Hiller. "High-temperature gradient HPLC and LC-NMR for the analysis of complex polyolefins". Pure and Applied Chemistry 80, n.º 8 (1 de enero de 2008): 1747–62. http://dx.doi.org/10.1351/pac200880081747.

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The synthesis and characterization of polyolefins continues to be one of the most important areas for academic and industrial polymer research. One consequence of the development of new "tailor-made" polyolefins is the need for new and improved analytical techniques for the analysis of polyolefins with respect to molar mass and chemical composition distribution. The present article briefly reviews different new and relevant techniques for polyolefin analysis. Crystallization analysis fractionation is a powerful new technique for the analysis of short-chain branching in linear low-density polyethylene (LLDPE) and the analysis of polyolefin blends and copolymers regarding chemical composition. For the fast analysis of the chemical composition distribution, a new high-temperature gradient high-performance liquid chromatography (HPLC) system has been developed. The efficiency of this system for the separation of various olefin copolymers is demonstrated. The correlation between molar mass and chemical composition can be accessed by on-line coupling of high-temperature size exclusion chromatography (HT-SEC) and 1H NMR spectroscopy. It is shown that the on-line NMR analysis of chromatographic fractions yields information on microstructure and tacticity in addition to molar mass and copolymer composition.
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43

Claverie, Marion, Gianluca Cioci, Marlène Vuillemin, Pauline Bondy, Magali Remaud-Simeon y Claire Moulis. "Processivity of dextransucrases synthesizing very-high-molar-mass dextran is mediated by sugar-binding pockets in domain V". Journal of Biological Chemistry 295, n.º 17 (11 de marzo de 2020): 5602–13. http://dx.doi.org/10.1074/jbc.ra119.011995.

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The dextransucrase DSR-OK from the Gram-positive bacterium Oenococcus kitaharae DSM17330 produces a dextran of the highest molar mass reported to date (∼109 g/mol). In this study, we selected a recombinant form, DSR-OKΔ1, to identify molecular determinants involved in the sugar polymerization mechanism and that confer its ability to produce a very-high-molar-mass polymer. In domain V of DSR-OK, we identified seven putative sugar-binding pockets characteristic of glycoside hydrolase 70 (GH70) glucansucrases that are known to be involved in glucan binding. We investigated their role in polymer synthesis through several approaches, including monitoring of dextran synthesis, affinity assays, sugar binding pocket deletions, site-directed mutagenesis, and construction of chimeric enzymes. Substitution of only two stacking aromatic residues in two consecutive sugar-binding pockets (variant DSR-OKΔ1-Y1162A-F1228A) induced quasi-complete loss of very-high-molar-mass dextran synthesis, resulting in production of only 10–13 kg/mol polymers. Moreover, the double mutation completely switched the semiprocessive mode of DSR-OKΔ1 toward a distributive one, highlighting the strong influence of these pockets on enzyme processivity. Finally, the position of each pocket relative to the active site also appeared to be important for polymer elongation. We propose that sugar-binding pockets spatially closer to the catalytic domain play a major role in the control of processivity. A deep structural characterization, if possible with large-molar-mass sugar ligands, would allow confirming this hypothesis.
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44

Dinculescu, Daniel Dumitru, Manuela Rossemary Apetroaei, Cristiana Luminița Gîjiu, Mirela Anton, Laura Enache, Verginica Schröder, Raluca Isopescu y Ileana Rău. "Simultaneous Optimization of Deacetylation Degree and Molar Mass of Chitosan from Shrimp Waste". Polymers 16, n.º 2 (6 de enero de 2024): 170. http://dx.doi.org/10.3390/polym16020170.

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Shrimp waste is a valuable source for chitin extraction and consequently for chitosan preparation. In the process of obtaining chitosan, a determining step is the chitin deacetylation. The main characteristic of chitosan is the degree of deacetylation, which must be as high as possible. The molar mass is another important parameter that defines its utilizations, and according to these, high or low molar masses are required. The present study is an attempt to optimize the deacetylation step to obtain chitosan with a high degree of deacetylation and high or low molar mass. The study was carried out based on experimental data obtained in the frame of a central composite design where three working parameters were considered: NaOH concentration, liquid:solid ratio, and process duration. The regression models defined for the degree of deacetylation (DD) and for the mean molar mass (MM) of chitosan powders were used in the formulation of optimization problems. The objectives considered were simultaneous maximum DD and maximum/minimum MM for the final chitosan samples. For these purposes, multiobjective optimization problems were formulated and solved using genetic algorithms implemented in Matlab®. The multiple optimal solutions represented by trade-offs between the two objectives are presented for each case.
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45

Metzler, Lukas, Thomas Reichenbach, Oliver Brügner, Hartmut Komber, Florian Lombeck, Stefan Müllers, Ralf Hanselmann, Harald Hillebrecht, Michael Walter y Michael Sommer. "High molecular weight mechanochromic spiropyran main chain copolymers via reproducible microwave-assisted Suzuki polycondensation". Polymer Chemistry 6, n.º 19 (2015): 3694–707. http://dx.doi.org/10.1039/c5py00141b.

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46

Ogawa, Ryohei y Marc A. Hillmyer. "High molar mass poly(ricinoleic acid) via entropy-driven ring-opening metathesis polymerization". Polymer Chemistry 12, n.º 15 (2021): 2253–57. http://dx.doi.org/10.1039/d1py00185j.

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High molar mass poly(ricinoleic acid) was synthesized via entropy-driven ring-opening metathesis polymerization of mono-, di- and mixed macrolactones of ricinoleic acid using a Grubbs second-generation catalyst and fully characterized.
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47

Hardouin, F., G. Sigaud, P. Keller, H. Richard, Nguyen Huu Tinh, M. Mauzac y M. F. Achard. "Invited Lecture. Smectic A polymorphism from low to high molar mass systems". Liquid Crystals 5, n.º 2 (enero de 1989): 463–78. http://dx.doi.org/10.1080/02678298908045396.

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48

Ono, Hiroshi, Isao Saito y Nobuhiro Kawatsuki. "Photorefractive Bragg diffraction in high- and low-molar-mass liquid crystal mixtures". Applied Physics Letters 72, n.º 16 (20 de abril de 1998): 1942–44. http://dx.doi.org/10.1063/1.121230.

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49

Feng, X. J., J. T. Zhang, M. R. Moldover, I. Yang, M. D. Plimmer y H. Lin. "Determination of the molar mass of argon from high-precision acoustic comparisons". Metrologia 54, n.º 3 (8 de mayo de 2017): 339–47. http://dx.doi.org/10.1088/1681-7575/aa68c7.

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50

Rangelov, S., B. Trzebicka, M. Jamroz-Piegza y A. Dworak. "Hydrodynamic Behavior of High Molar Mass Linear Polyglycidol in Dilute Aqueous Solution". Journal of Physical Chemistry B 111, n.º 38 (septiembre de 2007): 11127–33. http://dx.doi.org/10.1021/jp074485q.

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