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Your search keyword '"4-polyisoprene"' showing total 4 results
Start Over Descriptor "4-polyisoprene" Topic organic chemistry
4 results on '"4-polyisoprene"'

1. Properties of carbon nanotubes reinforced natural rubber/trans-1,4-polyisoprene shape memory composites

Author

WANG Qi; LIU Xun-cong; Ma Yuan; MENG Jia-feng; XIA Lin

Subjects
natural rubber, trans-1, 4-polyisoprene, composite, carbon nanotube, reinforcement, shape memory, curing characteristics, mechanical property, Organic chemistry, QD241-441, Chemical engineering, TP155-156, Chemicals: Manufacture, use, etc., TP200-248
Abstract

Natural rubber （NR）/trans-1,4-polyisoprene （TPI） composites with shape memory effect were prepared, and the effect of carbon nanotubes （CNTs） amount on the properties of the composites was studied. The results showed that with the increase of CNTS, the scorch time and curing time of the composites were shortened, and the curing rate and crosslinking density were slightly increased, and the tensile strength, modulus and hardness all showed an obvious upward trend, while the elongation at break did not change significantly, indicating that CNTs played a reinforcing role. However, the shape fixation rate decreased from 91.83% to 86.64%, and the shape recovery rate dropped from 95.43% to 90.76% in the shape memory properties. When the amount of CNTs was 6 phr（mass） and the DC voltage was above 80 V, the composites exhibited good electrical stimulation shape memory behavior.

Published
2022
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2. Polymerization of isoprene catalyzed by high active and thermo-stable iminopyridine-titanium complexes

Author

ZHNAG Jun-hua, KUANG Jia, WANG Liang, LIANG Hong-wen, WANG Qing-gang

Subjects
iminopyridine-titanium complex, cis-1, 4-polyisoprene, catalytic activity, selectivity, thermo-stability, Organic chemistry, QD241-441, Chemical engineering, TP155-156, Chemicals: Manufacture, use, etc., TP200-248
Abstract

A series of well-defined iminopyridine-titanium complexes were prepared and characterized by nuclear magnetic resonance spectroscopy, X-ray diffraction analysis and elemental analysis. Isoprene polymerization was carried out by using those complexes as main catalyst and dried methylaluminoxane as cocatalyst.The results showed that the iminopyridine-titanium complexes with strong electron-donating group possessed high activity （up to 6.3×104 g/（mol·h））, high cis-1,4 -unit selectivity (up to 74%) and excellent thermo-stability（up to 90 ℃）. The increased steric hindrance of substituent groups would significantly reduce the catalytic acti-vity, molecular weight and cis-1,4-unit selectivity. These results indicated that the ligand structure had more effects on activity than stereo-selectivity.

Published
2022
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3. Natural rubber biosynthesis—A living carbocationic polymerization?

Author

Emilie Gautriaud, Joseph P. Kennedy, Judit E. Puskas, Alain Deffieux, Univ Akron, Dept Polymer Sci, Univ Akron, Laboratoire de Chimie des polymères organiques (LCPO), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Université Sciences et Technologies - Bordeaux 1-Institut de Chimie du CNRS (INC), Team 1 LCPO : Polymerization Catalyses & Engineering, Laboratoire de Chimie des Polymères Organiques (LCPO), and Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Université de Bordeaux (UB)-Institut de Chimie du CNRS (INC)

Subjects
Reaction mechanism, Polymers and Plastics, Stereochemistry, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, chemistry.chemical_compound, Natural rubber, Biosynthesis, Materials Chemistry, Organic chemistry, cis-1, chemistry.chemical_classification, Organic Chemistry, Cationic polymerization, Surfaces and Interfaces, Polymer, 021001 nanoscience & nanotechnology, 4-polyisoprene, 0104 chemical sciences, [CHIM.POLY]Chemical Sciences/Polymers, chemistry, Polymerization, visual_art, Ceramics and Composites, visual_art.visual_art_medium, natural rubber biosynthesis, 0210 nano-technology, Natural Living Carbocationic Polymerization NLCP
Abstract

International audience; An exhaustive in-depth review of the biochemical literature concerning the biosynthesis of polyisoprenes, including natural rubber (NR, cis-1,4-polyisoprene cPIP) by rubber-producing plants, and the polymer chemical literature on biomimetic and related syntheses, leads us to postulate that the biosynthesis of polyisoprenoids in general and that of NR in particular, may proceed by a living carbocationic polymerization process. Our analysis led to the formulation of a "Natural Living Carbocationic Polymerization" (NLCP) mechanism in terms of accepted polymer chemical formalism, i.e., initiation, propagation, and equilibria between active and dormant species. A thorough analysis of the intermediates known to be involved in the biosynthesis of NR is consistent with our postulate. (c) 2006 Elsevier Ltd. All rights reserved.

Published
2006

4. Metathetic degradation of trans-1,4-polyisoprene with ruthenium catalysts

Author

Samira Ouardad, Frédéric Peruch, Laboratoire de Chimie des Polymères Organiques (LCPO), Université de Bordeaux (UB)-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Team 1 LCPO : Polymerization Catalyses & Engineering, and Université de Bordeaux (UB)-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Ecole Nationale Supérieure de Chimie, de Biologie et de Physique (ENSCBP)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Ethylene, Materials science, Polymers and Plastics, chemistry.chemical_element, 010402 general chemistry, 01 natural sciences, Catalysis, chemistry.chemical_compound, Ruthenium catalysts, Metathetic degradation, Materials Chemistry, Organic chemistry, Octene, Molar mass, 010405 organic chemistry, Regioselectivity, Condensed Matter Physics, Toluene, 4-polyisoprene, 0104 chemical sciences, Ruthenium, Grubbs' catalyst, [CHIM.POLY]Chemical Sciences/Polymers, chemistry, Trans-1, Mechanics of Materials
Abstract

International audience; Degradation study of trans-1,4-polyisoprene (trans-1,4-PI), that can be produced by the nature, was performed using first and second generation Grubbs and Hoveyda Grubbs catalysts with olefins (ethylene or 1-octene) as transfer agents in toluene at 60 C. While first generation Grubbs catalyst afforded low degradation, highlighting the presence of catalyst decomposition and/or inter-chain cross-metathesis reactions, an almost complete metathetic degradation could be reached using the second generation Grubbs catalyst in few minutes. Nevertheless, the synthesis of well-defined polyisoprenes with a targeted molar mass revealed to be difficult with Grubbs catalysts. On the contrary, Hoveyda Grubbs catalysts were found to be more efficient to control the degradation of trans-1,4-PI. Indeed, regioselective degradation afforded pure trans-1,4-PI with a range of molar mass from 50 000 g/mol to 10 000 g/mol. However, polyisoprenes of lower molar masses (M-n < 10 000 g/mol) contained some cis units, highlighting the presence of isomerization reactions, which could be due to the catalyst decomposition into hydride specie and/or pi-allyl metal hydride

Published
2014

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