Estimation of the lateral dimensions of cellulose crystallites using NMR signal strengths

Newman, Roger H.

doi:10.1016/s0926-2040(99)00043-0

Cited by 241 publications

(203 citation statements)

References 26 publications

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“…For example, with increasing crystallinity, tensile strength, dimensional stability, and density increase, while properties such as chemical reactivity and swelling decrease. Some of the frequently used techniques for estimating cellulose crystallinity are wide-angle X-ray scattering (WAXS) (Segal et al 1959;Jayme and Knolle 1964;Leppänen et al 2009), solid state 13 C cross-polarization/magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy (Horii et al 1987;Newman and Hemmingson 1990;Newman 1999), and Fourier transform-infrared (FT-IR) spectroscopy (Richter et al 1991;Hulleman et al 1994). Although WAXS is the most extensively used technique, the X-ray method involves isolation of amorphous background from the diffraction pattern, which in the case of cellulose crystallites is not always easy for reasons that have to do with cellulose crystallites being small and, at lower crystallinities, the diffraction pattern being poorly defined (weak broad features).…”

Section: Introductionmentioning

confidence: 99%

“…However, if in addition to cellulose the sample includes hemicellulose and lignin (e.g., in wood) the 13 C solid state NMR spectra contain overlapping peaks, and in such cases the crystallinity calculation is based upon first separating the total NMR signal into two components, one belonging to cellulose and the other to the other non-cellulose contributors (Newman and Hemmingson 1990;Newman 1999). However, it was found that the accuracy of the NMR method depends not only upon how well the spectra can be separated into the contributions of cellulose and non-cellulose components but also upon the lateral dimensions of the crystallites (Newman 1999). Additionally, NMR crystallinity determination involves use of curvefitting methods that have shortcomings (Maddams 1980;Meier 2005).…”

Section: Introductionmentioning

confidence: 99%

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Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

2010

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Two new methods based on FT-Raman spectroscopy, one simple, based on band intensity ratio, and the other using a partial least squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1,096 cm -1 bands. For calibration purposes, 80.5% crystalline and 120-min milled (0% crystalline) Whatman CC31 and six cellulose mixtures produced with crystallinities in the range 10.9-64% were used. When intensity ratios were plotted against crystallinities of the calibration set samples, the plot showed a linear correlation (coefficient of determination R 2 = 0.992). Average standard error calculated from replicate Raman acquisitions indicated that the cellulose Raman crystallinity model was reliable. Crystallinities of the cellulose mixtures samples were also calculated from X-ray diffractograms using the amorphous contribution subtraction (Segal) method and it was found that the Raman model was better. Additionally, using both Raman and X-ray techniques, sample crystallinities were determined from partially crystalline cellulose samples that were generated by grinding Whatman CC31 in a vibratory mill. The two techniques showed significant differences. In the second approach, successful Raman PLS regression models for crystallinity, covering the 0-80.5% range, were generated from the ten calibration set Raman spectra. Both univariateRaman and WAXS determined crystallinities were used as references. The calibration models had strong relationships between determined and predicted crystallinity values (R 2 = 0.998 and 0.984, for univariateRaman and WAXS referenced models, respectively). Compared to WAXS, univariate-Raman referenced model was found to be better (root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) values of 6.1 and 7.9% vs. 1.8 and 3.3%, respectively). It was concluded that either of the two Raman methods could be used for cellulose I crystallinity determination in cellulose samples.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

2010

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“…These details have been elusive. The determination of microfibril diameters in wood has been addressed frequently by a variety of techniques, particularly wide-angle X-ray scattering (WAXS) and solid-state 13 C NMR (19)(20)(21)(22). However each technique has drawbacks and agreement has not been generally good.…”

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confidence: 99%

“…However each technique has drawbacks and agreement has not been generally good. Diameters suggested have ranged from 2.2 nm to 3.6 nm (20,23). These upper and lower limits correspond to about 12 and 32 chains (πr 2 ∕0.317) if it is assumed that the wood microfibrils are approximately circular in crosssection and each chain occupies 0.317 nm 2 as in cellulose Iβ (9).…”

mentioning

confidence: 99%

“…A 36-chain model is frequently suggested (25), although the evidence on which this was originally based is very indirect (26) and a 36-chain microfibril would be larger than the spectroscopic and WAXS evidence suggests, about 3.8 nm diameter (2 p ð36 × 0.317Þ∕π) or 3 × 5 nm (27). Microfibrils synthesized in a matrix with few noncellulosic polymers, as in cotton, flax, and angiosperm tension wood, have considerably larger and apparently variable dimensions (20,28,29) suggesting coalescence of newly synthesized microfibrils. Microfibrils appeared to split apart along the 002 crystal plane when subjected to vigorous acoustic degradation (30) and there is evidence that in some fruits the primary-wall microfibrils are less than 2 nm thick in their native state (31).…”

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confidence: 99%

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Nanostructure of cellulose microfibrils in spruce wood

Fernandes

Thomas

Altaner

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

627

693

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The structure of cellulose microfibrils in wood is not known in detail, despite the abundance of cellulose in woody biomass and its importance for biology, energy, and engineering. The structure of the microfibrils of spruce wood cellulose was investigated using a range of spectroscopic methods coupled to small-angle neutron and wide-angle X-ray scattering. The scattering data were consistent with 24-chain microfibrils and favored a "rectangular" model with both hydrophobic and hydrophilic surfaces exposed. Disorder in chain packing and hydrogen bonding was shown to increase outwards from the microfibril center. The extent of disorder blurred the distinction between the I alpha and I beta allomorphs. Chains at the surface were distinct in conformation, with high levels of conformational disorder at C-6, less intramolecular hydrogen bonding and more outward-directed hydrogen bonding. Axial disorder could be explained in terms of twisting of the microfibrils, with implications for their biosynthesis.crystallinity | infrared | deuterium exchange | nuclear magnetic resonance | spin diffusion

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Fibrous long-chain organic acid cellulose esters and their characterization by diffuse reflectance FTIR spectroscopy, solid-state CP/MAS13C-NMR, and X-ray diffraction

Jandura

Kokta

Riedl

2000

J. Appl. Polym. Sci.

107

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Unsaturated and saturated organic acids with 11 and 18 carbon atoms, respectively, were used in a heterogeneous esterification reaction in the pyridine/toluene sulfonyl chloride system to prepare fibrous cellulose esters with different degrees of substitution. Highly bleached sulfite cellulose fibers were esterified during a 1‐ or 2‐h reaction time with the following organic acids: undecylenic acid, undecanoic acid, oleic acid, and stearic acid. In all cases, the heterogeneous esterification yielded partially substituted cellulose esters retaining their fibrous structure. The substitution reaction was confirmed by diffuse reflectance infrared spectroscopy and the chemical structures of cellulose esters were identified by solid‐state CP/MAS 13C‐NMR (75.3 MHz). X‐ray diffraction analyses showed broadening of the diffraction peaks with a higher degree of substitution of cellulose esters, which suggests structural changes within the cellulose fibers. Because the broadening peaks of X‐ray spectra or the unassigned C‐4 region of substituted cellulose chains in NMR spectra do not allow the calculation of dimensional changes of cellulose crystallites in cellulose esters, the lateral dimensions of crystallites in only cellulose fibers were calculated. The value derived from NMR (4.6 nm) differs by about 11% when compared with the value calculated from X‐ray diffraction data (4.1 nm). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1354–1365, 2000

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Estimation of the lateral dimensions of cellulose crystallites using NMR signal strengths

Cited by 241 publications

References 26 publications

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Cellulose I crystallinity determination using FT–Raman spectroscopy: univariate and multivariate methods

Nanostructure of cellulose microfibrils in spruce wood

Fibrous long-chain organic acid cellulose esters and their characterization by diffuse reflectance FTIR spectroscopy, solid-state CP/MAS13C-NMR, and X-ray diffraction

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