scholarly journals Unravelling Main- and Side-Chain Motions in Polymers with NMR Spectroscopy and Relaxometry: The Case of Polyvinyl Butyral

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2686
Author(s):  
Lucia Calucci ◽  
Silvia Pizzanelli ◽  
Alessandro Mandoli ◽  
Artur Birczyński ◽  
Zdzisław T. Lalowicz ◽  
...  
Keyword(s):  
Glass Transition ◽  
Nmr Spectroscopy ◽  
Main Chain ◽  
Amorphous Polymer ◽  
Polyvinyl Butyral ◽  
Side Chains ◽  
Nmr Relaxometry ◽  
Field Cycling ◽  
Nmr Methods ◽  
First Time

Polyvinyl butyral (PVB) is an amorphous polymer employed in many technological applications. In order to highlight the relationships between macroscopic properties and dynamics at a microscopic level, motions of the main-chain and of the propyl side-chains were investigated between Tg − 288 °C and Tg + 55 °C, with Tg indicating the glass transition temperature. To this aim, a combination of solid state Nuclear Magnetic Resonance (NMR) methods was applied to two purposely synthesized PVB isotopomers: one fully protonated and the other perdeuterated on the side-chains. 1H time domain NMR and 1H field cycling NMR relaxometry experiments, performed across and above Tg, revealed that the dynamics of the main-chain corresponds to the α-relaxation associated to the glass transition, which was previously characterized by dielectric spectroscopy. A faster secondary relaxation was observed for the first time and ascribed to side-chains. The geometry and rate of motions of the different groups in the side-chains were characterized below Tg by 2H NMR spectroscopy.

Ultrasound Devulcanization of SBR: Molecular Mobility of Gel and Sol

1997 ◽  
Vol 70 (2) ◽  
pp. 183-193 ◽  
Author(s):  
S. T. Johnston ◽  
J. Massey ◽  
E. von Meerwall ◽  
S. H. Kim ◽  
V. Yu Levin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Main Chain ◽  
Molecular Level ◽  
Spin Echo ◽  
Mean Diffusivity ◽  
Nmr Relaxation ◽  
Butadiene Rubber ◽  
Ultrasound Technique ◽  
Large Molecules ◽  
Nmr Methods

Abstract In an effort to support the recycling of rubbery polymers and composites, 1H NMR relaxation and pulsedgradient spin echo diffusion measurements have been performed on virgin and unfilled vulcanized strene-butadiene rubber (SBR), and networks after various extents of devulcanization using an ultrasound technique. The NMR methods recognize unentangled light molecules (e.g. sol), but do not distinguish between unattached entangled large molecules and chemical network segments. Devulcanization generates additional sol with a wide mass distribution, thus increasing both sol and gel mobility, but decreasing sol mean diffusivity. The latter effect is accounted for by the increasing mean sol molecular mass but also by the increasing glass transition temperature, which is related to main-chain stiffening seen in our earlier 13C NMR experiments. In addition to improving the molecular-level understanding of devulcanization, this study provides guidance for the optimization of the devulcanization parameters.

Reactions of Carbenes with Unsaturated Polymers

1967 ◽  
Vol 40 (3) ◽  
pp. 934-935 ◽  
Author(s):  
M. S. Lishanskii ◽  
V. A. Tsitokhtsev ◽  
N. D. Vinogradova
Keyword(s):  
Ethyl Ester ◽  
Trichloroacetic Acid ◽  
Main Chain ◽  
Sodium Methylate ◽  
Side Chains ◽  
Copper Salts ◽  
Chain Reactions ◽  
Decomposition Reactions ◽  
Polar Substituents ◽  
First Time

Abstract The literature has a limited amount of data on chain reactions of unsaturated polymers, in particular diene polymers. The appearance of a paper dealing with addition of dichlorocarbene to polyisoprene and to polybutadiene has impelled us to publish results of studies we made on reactions of unsaturated polymers with carbenes, which have made it possible for the first time to obtain polymers containing in the main chain, or in the side chains, cyclopropane groups with polar substituents. Addition of carbenes to cis-1, 4-polyisoprene, trans-1, 4-polyisoprene, 1, 4-polybutadiene, and 1, 2-polybutadiene was accomplished through decomposition reactions of diazoacetic esters catalyzed by copper salts (for carbethoxycarbene and carbomethoxycarbene) and the reaction of the ethyl ester of trichloroacetic acid with sodium methylate (for dichlorocarbene).

Dynamics of PPI Dendrimers: A Study by Dielectric and 2H NMR Spectroscopy and by Field-Cycling 1H NMR Relaxometry

2015 ◽  
Vol 48 (10) ◽  
pp. 3294-3302 ◽  
Author(s):  
F. Mohamed ◽  
M. Hofmann ◽  
B. Pötzschner ◽  
N. Fatkullin ◽  
E. A. Rössler
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
2H Nmr ◽  
2H Nmr Spectroscopy ◽  
Nmr Relaxometry ◽  
Field Cycling ◽  
1H Nmr Relaxometry

Dissolution Mechanism of Crystalline Cellulose in H3PO4As Assessed by High-Field NMR Spectroscopy and Fast Field Cycling NMR Relaxometry

2009 ◽  
Vol 57 (19) ◽  
pp. 8748-8752 ◽  
Author(s):  
Pellegrino Conte ◽  
Antonella Maccotta ◽  
Claudio De Pasquale ◽  
Salvatore Bubici ◽  
Giuseppe Alonzo
Keyword(s):  
Nmr Spectroscopy ◽  
High Field ◽  
Crystalline Cellulose ◽  
Dissolution Mechanism ◽  
Nmr Relaxometry ◽  
Field Cycling ◽  
Fast Field

The Total Synthesis of Rhabdastrellic Acid A

2018 ◽  
Author(s):  
Yaroslav Boyko ◽  
Christopher Huck ◽  
David Sarlah
Keyword(s):  
Total Synthesis ◽  
Late Stage ◽  
Cross Coupling ◽  
Side Chains ◽  
General Strategy ◽  
Modular Approach ◽  
Linear Sequence ◽  
Generating Sequence ◽  
First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained <i>trans-syn-trans</i>-perhydrobenz[<i>e</i>]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a <i>p</i>-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

Sign in / Sign up

Export Citation Format

Share Document