Carbon-13 NMR analysis of propene-butene copolymer. Steric structure of chain end groups and inhomogeneity of isotactic sites

1990 ◽  
Vol 23 (8) ◽  
pp. 2406-2409 ◽  
Author(s):  
P. Locatelli ◽  
M. C. Sacchi ◽  
I. Tritto ◽  
F. Forlini
Keyword(s):  
Steric Structure ◽  
Nmr Analysis ◽  
End Groups

scholarly journals A New Insight into the Comonomer Effect through NMR Analysis in Metallocene Catalysed Propene–co–1-Nonene Copolymers

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1266
Author(s):  
Qiong Wu ◽  
Alberto García-Peñas ◽  
Rosa Barranco-García ◽  
María Luisa Cerrada ◽  
Rosario Benavente ◽  
...  
Keyword(s):  
Active Sites ◽  
Nmr Analysis ◽  
Reaction Parameters ◽  
Transfer Processes ◽  
Detailed Explanation ◽  
Selective Interaction ◽  
End Groups ◽  
Alpha Olefin ◽  
Kinetic Phenomenon ◽  
Insight Into

The “comonomer effect” is an intriguing kinetic phenomenon in olefin copolymerization that still remains without a detailed explanation. It typically relates to the rate of enhancement undergone in ethylene and propene catalytic polymerization just by adding small fractions of an alpha-olefin. The difficulty lies in the fact that changes caused by the presence of the comonomer in reaction parameters are so conspicuous that it is really difficult to pin down which of them is the primary cause and which ones are side factors with marginal contribution to the phenomenon. Recent investigations point to the modification of the catalyst active sites as the main driving factor. In this work, the comonomer effect in the metallocene copolymerization of propene and 1-nonene is analysed and correlated to the comonomer role in the termination of the chain-growing process. The associated termination mechanisms involved furnish most of chain-free active sites, in which the selective interaction of the comonomer was proposed to trigger the insertion of monomers. A thorough characterisation of chain-end groups by means of the 1H NMR technique allows for detailing of specific transfer processes, ascribed to comonomer insertions, as well as evidencing the influence of the growing chain’s microstructure over the different termination processes available.

NMR Analysis of Polyester Urethane End Groups and Solid-Phase Hydrolysis Kinetics

2000 ◽  
Vol 33 (10) ◽  
pp. 3569-3576 ◽  
Author(s):  
David M. LeMaster ◽  
Griselda Hernández
Keyword(s):  
Solid Phase ◽  
Hydrolysis Kinetics ◽  
Nmr Analysis ◽  
Polyester Urethane ◽  
End Groups

Stereochemistry of living poly(methyl methacrylate) anions as determined by carbon-13 NMR analysis of carbon-13-labeled methyl end groups

1992 ◽  
Vol 25 (13) ◽  
pp. 3553-3560 ◽  
Author(s):  
Raymond Volpe ◽  
Thieo E. Hogen-Esch ◽  
Friedhelm Gores ◽  
Axel H. E. Mueller
Keyword(s):  
Methyl Methacrylate ◽  
Nmr Analysis ◽  
Poly Methyl Methacrylate ◽  
End Groups

scholarly journals NMR Analysis of Hydroxyl-Terminated Polybutadiene End Groups and Reactivity Differences with Monoisocyanates

2018 ◽  
Vol 56 (23) ◽  
pp. 2665-2671 ◽  
Author(s):  
Timothy S. Haddad ◽  
Levi M. J. Moore ◽  
Josiah T. Reams ◽  
Michael D. Ford ◽  
Jacob C. Marcischak ◽  
...  
Keyword(s):  
Nmr Analysis ◽  
End Groups

Solid State NMR Analysis of β-13C-Enriched Lignocellulosic Material During Light-Induced Yellowing

Holzforschung ◽  
2001 ◽  
Vol 55 (3) ◽  
pp. 276-282 ◽  
Author(s):  
Jim Parkås ◽  
Magnus Paulsson ◽  
Ulla Westermark ◽  
Noritsugu Terashima
Keyword(s):  
Cell Wall ◽  
Solid State ◽  
Structural Changes ◽  
Coniferyl Alcohol ◽  
Enzymatic System ◽  
Nmr Analysis ◽  
End Groups ◽  
A New Technique ◽  
Dehydrogenation Polymer ◽  
C Nmr

Summary Photoyellowing of lignocellulosic materials has been studied with a new technique based on solid state 13C-NMR analysis of 13C-enriched DHP in cell wall tissue. The selectively 13C-enriched cell wall-dehydrogenation polymer (CW-DHP) was prepared directly on differentiating xylem from spruce (Picea abies) at pH 6.0 by administering β-13C-enriched coniferin in an enzymatic system consisting of glucose oxidase, β-glucosidase, and the naturally occurring water-insoluble enzymes remaining in the cell wall. The bonding pattern of the formed CW-DHP was found to be: 42% β-β, β-5, and β-1 substructures; 36% β-O-4 derived substructures; and 22% coniferyl alcohol and coniferaldehyde end-groups. The 13C-NMR analysis of unirradiated and irradiated tissue revealed a decrease in the relative amount of coniferaldehyde and/or coniferyl alcohol end-groups during irradiation. Prolonged irradiation also introduced new signals centered at 37, 70, and 102 ppm. The results indicate that the present technique, with the formation of DHP in a naturally lignifying carbohydrate environment, has the potential of being a valuable tool for the study of structural changes of lignin during light-induced yellowing.

Photoyellowing behavior of non-phenolic lignin models representative of end groups and β-ether structures

2004 ◽  
Vol 19 (2) ◽  
pp. 146-154
Author(s):  
Jim Parkås ◽  
Magnus Paulsson ◽  
Shiming Li ◽  
Knut Lundquist ◽  
Ulla Westermark
Keyword(s):  
End Groups

Synthesis, Characterization, and Dynamic Behavior of Well-defined Dithiomaleimide-functionalized Maltodextrins

2020 ◽  
Vol 17 (2) ◽  
pp. 85-89
Author(s):  
Francisco J. Hidalgo ◽  
Nathan A.P. Lorentz ◽  
TinTin B. Luu ◽  
Jonathan D. Tran ◽  
Praveen D. Wickremasinghe ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Dynamic Behavior ◽  
Industrial Applications ◽  
19F Nmr ◽  
Nmr Studies ◽  
Synthetic Pathway ◽  
End Groups ◽  
Sugar End

: Maltodextrins have an increasing number of biomedical and industrial applications due to their attractive physicochemical properties such as biodegradability and biocompatibility. Herein, we describe the development of a synthetic pathway and characterization of thiol-responsive maltodextrin conjugates with dithiomaleimide linkages. 19F NMR studies were also conducted to demonstrate the exchange dynamics of the dithiomaleimide-functionalized sugar end groups.

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