High resolution, magic angle sampling spinning carbon-13 NMR of solid cellulose I

Earl, William L.; VanderHart, David L.

doi:10.1021/ja00529a064

Cited by 228 publications

(93 citation statements)

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“…The somewhat broad, high-field shoulders, on the cellulose C-4 and C-6 signals, correspond to amorphous cellulose regions. 26 The cluster of resonances from 70 to 81 ppm is assigned to C-2, C-3, and C-5 cellulose carbons. Thus, chemical shift data allow qualitative and quantitative identification of the three major components of wood, plus determination of the cellulose crystallinity.…”

Section: Solid-state 13c Nmr Spectroscopymentioning

confidence: 99%

Physical characterization of wood and wood‐polymer composites: An update

Wright

Mathias

1993

J of Applied Polymer Sci

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SYNOPSISNew and reliable test methods have been developed, and are under development, for the physical characterization of wood and whole wood-polymer composites ( WPC is used in this article to refer to polymer-impregnated whole wood). The methods described here have been designed for smaller samples than are required for most ASTM tests. It should be stressed that, when comparing treated samples to untreated samples in any type of testing, the initial density or specific gravity (density before treatment) of the treated sample should be the same as the untreated control sample. If possible, measurements should be made on a given sample before and after treatment; on a split sample, half should be treated and compared with the untreated half. If there is much variation in density between samples within a group, the effectiveness of the treatment cannot be determined with an acceptable degree of accuracy, since whole wood varies greatly between specimens and density is a major factor contributing to property variability. For example, swelling (due to moisture uptake), modulus, toughness, surface hardness, and compressive strength of wood all increase dramatically with increasing density for both untreated whole wood and WPCs.Scanning electron microscopy, coupled with x-ray energy analysis, indicated the presence or absence of good interaction between wood components and in situ formed polymer. For example, poly (EHMA) (the homopolymer of ethyl a-hydroxymethylacrylate) and wood components were seen to be strongly bonded, and x-ray activation elemental analysis confirmed the presence of poly (EHMA) and its copolymers within the wood cell walls. On the other hand, proton spin-lattice relaxation in the rotating frame ( Tin) measurements (by I3C solid-state NMR) for balsa/EHMA WPCs gave two separate sets of relaxation times, one each for unique peaks corresponding to either the polymer or the wood components.It is probable that the region of interaction between poly( EHMA) and the wood component in the balsa/EHMA WPC (the interphase region) is small, as compared to the individual components, and is not observed. This result is consistent with a two-parameter relaxation process for the peak a t ca. 61 ppm, which includes overlapping peaks for the hydroxymethyl carbons of poly (EHMA) and cellulose.

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Section: Solid-state 13c Nmr Spectroscopymentioning

confidence: 99%

Physical characterization of wood and wood‐polymer composites: An update

Wright

Mathias

1993

J of Applied Polymer Sci

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“…16, No. 12, 1984 (8) where m 0 denotes the amount of cellulose originally used in this test. Figure 1 shows the X-ray diffraction patterns of the cellulose samples.…”

Section: N M R Spectroscopymentioning

confidence: 99%

Study on the Solubility of Cellulose in Aqueous Alkali Solution by Deuteration IR and 13C NMR

Kamida

Okajima

Matsui

et al. 1984

Polym J

167

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ABSTRACT:A correlation of the solubility of cellulose in aqueous alkali solution was established with its so-called "amorphous" content. To achieve this end, cellulose was regenerated under different preparative conditions from its cuprammonium solution and cotton linter was acidhydrolyzed into a fibrous form and the pulp was physically milled to powder. Cellulose having a relatively large molecular weight was found to completely dissolve in aqueous NaOH solution at 4°C. The solubility of cellulose in a 10 wt% aqueous NaOH at 4°C, s. could generally be correlated to the relative amount of the high magnetic field envelope of the C4 carbon NMR peak, xh (NMR). xh (NMR) was assigned to the region where intramolecular hydrogen bonds are at least partly broken. The intramolecular hydrogen bond was found to have an important influence on the solubility behavior of cellulose.

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“…This lack of understanding is largely attributed to the complex nature of the interactions between cellulose and other PCW components. Since the first two high-resolution solid-state NMR studies of cellulose were published in 1980 (Atalla et al 1980;Earl and VanderHart 1980), solidstate NMR spectroscopy has been an important tool in the study of the 3D architecture of PCWs. Solid-state NMR spectroscopy not only revealed the polymorphic structure of cellulose but also detailed the interactions between cellulose and other macromolecules in intact plant cell walls (Dick-Pérez et al 2011;Earl and VanderHart 1981;Larsson et al 1999;Newman and Hemmingson 1995;Wang and Hong 2016;Wang et al 2016a).…”

Section: Introductionmentioning

confidence: 99%

“…Two d 13 C4 peaks, centered at * 89 and * 85 ppm, have been assigned to ordered (crystalline) and disordered (amorphous) regions, respectively (Atalla et al 1980;Earl and VanderHart 1980). This assignment was based on the dominance of 89-ppm signals in highly crystalline cellulose and was tested by ball-milling microcrystalline cellulose sample which led to increased intensity of the 85 ppm peak and a simultaneous decrease in the intensity of the 89 ppm peak (Maciel et al 1982).…”

Section: Introductionmentioning

confidence: 99%

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

et al. 2017

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The doublet C4 peaks at * 85 and * 89 ppm in solid-state 13 C NMR spectra of native cellulose have been attributed to signals of C4 atoms on the surface (solvent-exposed) and in the interior of microfibrils, designated as sC4 and iC4, respectively. The relative intensity ratios of sC4 and iC4 observed in NMR spectra of cellulose have been used to estimate the degree of crystallinity of cellulose and the number of glucan chains in cellulose microfibrils. However, the molecular structures of cellulose responsible for the specific surface and interior C4 peaks have not been positively confirmed. Using density functional theory (DFT) methods and structures produced from classical molecular dynamics simulations, we investigated how the following four factors affect 13 C NMR chemical shifts in cellulose: conformations of exocyclic groups at C6 (tg, gt and gg), H 2 O molecules H-bonded on the surface of the microfibril, glycosidic bond angles (U, W) and the distances between H4 and HO3 atoms. We focus on changes in the d 13 C4 value because it is the most significant observable for the same C atom within the cellulose structure. DFT results indicate that different conformations of the exocyclic groups at C6 have the greatest influence on d 13 C4 peak separation, while the other three factors have secondary effects that increase the spread of the calculated C4 interior and surface peaks.

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High resolution, magic angle sampling spinning carbon-13 NMR of solid cellulose I

Cited by 228 publications

References 0 publications

Physical characterization of wood and wood‐polymer composites: An update

Physical characterization of wood and wood‐polymer composites: An update

Study on the Solubility of Cellulose in Aqueous Alkali Solution by Deuteration IR and 13C NMR

Structural factors affecting 13C NMR chemical shifts of cellulose: a computational study

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