Solid-State C-13 NMR Studies of Vulcanized Elastomers X. N-t-Butyl-2-Benzothiazole Sulfenamide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75.5 MHz

1992 ◽  
Vol 65 (2) ◽  
pp. 427-443 ◽  
Author(s):  
M. R. Krejsa ◽  
J. L. Koenig
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Chain Scission ◽  
Sulfur Concentration ◽  
Nmr Studies ◽  
Double Bond Migration ◽  
Sulfur Vulcanization ◽  
Equilibrium Swelling ◽  
Cis And Trans ◽  
Good Agreement

Abstract Accelerated sulfur vulcanized cis-polyisoprene was analyzed using C-13 solid-state NMR to determine the chemical microstructure of the network. Three formulations were analyzed consisting of varying accelerator/sulfur ratios. All formulations yielded similar network structures, but the amount of sulfurization varied with sulfur concentration. At low percent cure, only polysulfidic A-type cis-structures were found. For longer cure times, the A-type structures shortened to monosulfldic, and B-type polysulfidic structures, both cis and trans, were formed. The amount of trans-sulfurized product was constant with cure once this resonance appeared. No isomerization, chain scission, saturation, or double bond migration was detected. The NMR measurements appeared to show fairly good agreement with equilibrium swelling measurements.

Solid State Carbon-13 NMR Studies of Elastomers. XL N-t-Butyl Benzothiazole Sulfenimide Accelerated Sulfur Vulcanization of cis-Polyisoprene at 75 MHz

1993 ◽  
Vol 66 (1) ◽  
pp. 73-82 ◽  
Author(s):  
M. R. Krejsa ◽  
J. L. Koenig
Keyword(s):  
Solid State ◽  
Network Structure ◽  
Solid State Nmr ◽  
Cyclic Structure ◽  
Sulfur Concentration ◽  
Nmr Studies ◽  
Maturation Period ◽  
Sulfur Vulcanization

Abstract The network structure of TBSI-accelerated vulcanization of cis-polyisoprene was studied using C-13 solid-state NMR. The initial crosslink products consisted of A1c (cis) and A2c (cis) polysulfides. As the percent cure is increased, the A1c and A2c structures reduce in rank to monosulfides, and polysulfidic B1c (cis) and B1t (trans) structures are formed. During the maturation period C1c (cis) polysulfidic structures are also formed. The percent of sulfurization was shown to vary directly with sulfur concentration, while the efficiency of sulfurization (crosslink/cyclic-structure ratio) was shown to vary with accelerator content. TBSI-accelerated vulcanization was found to be more inefficient (lower crosslink/cyclic-structure ratio) than TBBS-accelerated vulcanization during the initial cure region. However, this results in shorter sulfur chains, which decreases the reactivity of TBSI vulcanizates as compared to TBBS vulcanizates during the reversion regime.

Solid-State C-13 NMR Studies of Vulcanized Elastomers XIII. TBBS Accelerated, Sulfur-Vulcanization of Carbon Black Filled Natural Rubber

1995 ◽  
Vol 68 (4) ◽  
pp. 551-562 ◽  
Author(s):  
Makio Mori ◽  
Jack L. Koenig
Keyword(s):  
Double Bond ◽  
Solid State ◽  
Carbon Black ◽  
Natural Rubber ◽  
Main Chain ◽  
Chain Scission ◽  
Nmr Studies ◽  
Double Bond Migration ◽  
Sulfur Vulcanization ◽  
Basic Network

Abstract Solid state C-13 NMR has been used to compare the chemistry of accelerated vulcanization of natural rubber using N-t-butyl-2-benzothiazole sulfenamide in the presence and absence of carbon black. The carbon black filler has an influence on the vulcanization chemistry in addition to its accepted role in reinforcment and stabilization. The basic network structure formation is modified to the extent that crosslink desulfurization from poly to monosulflde structures occurs earlier in the cure in the presence of carbon black. No main chain scission or double bond migration was detected.

Gold complexes of ditelluridoimidodiphosphinate ligands — Reversible oxidation of Au(I) to Au(III) via insertion of gold into a phosphorus–tellurium bond

2009 ◽  
Vol 87 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Dana J Eisler ◽  
Stuart D Robertson ◽  
Tristram Chivers
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Trans Isomers ◽  
Nmr Studies ◽  
Gold Complexes ◽  
X Ray ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Insertion Process

The reaction of (THT)AuCl with (TMEDA)Na[N(TePR2)2] (R = Ph, i-Pr, t-Bu) produces a series of gold (III) complexes of the type [{R2PNP(Te)R2}Au(µ-Te)]2 (4a, R = i-Pr; 4b, R = Ph; 4c, R = t-Bu) rather than the expected homoleptic Au(I) complexes of the ditelluridoimidodiphosphinate ligands. A combination of solution- and solid-state NMR studies shows that both cis and trans isomers of 4a–4c are formed in these reactions. X-ray structural determinations of the trans isomers of 4a–4c reveal a centrosymmetric arrangement with a central four-membered Au2Te2 ring formed by the formal insertion of gold into a P–Te bond; this insertion process was shown to be reversible upon addition of PPh3 to 4a to give the monomeric gold(I) complex Ph3PAu[N{TeP(i-Pr)2}2]. The X-ray structure of cis-4b is also described.Key words: gold, tellurium, redox, X-ray structures, imidodiphosphinate.

scholarly journals Solid-State NMR Studies of HIV-1 Capsid Protein Assemblies

2010 ◽  
Vol 132 (6) ◽  
pp. 1976-1987 ◽  
Author(s):  
Yun Han ◽  
Jinwoo Ahn ◽  
Jason Concel ◽  
In-Ja L. Byeon ◽  
Angela M. Gronenborn ◽  
...  
Keyword(s):  
Solid State ◽  
Capsid Protein ◽  
Solid State Nmr ◽  
Protein Assemblies ◽  
Nmr Studies ◽  
Hiv 1

Solid-state NMR studies of the molecular structure of Taxol

2006 ◽  
Vol 44 (6) ◽  
pp. 581-585 ◽  
Author(s):  
Yu Ho ◽  
Der-Lii M. Tzou ◽  
Feng-I Chu
Keyword(s):  
Molecular Structure ◽  
Solid State ◽  
Solid State Nmr ◽  
Nmr Studies
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