Molecular Changes during Tensile Deformation of Single Wood Fibers Followed by Raman Microscopy

In this study we demonstrate that bacterial cellulose (BC) networks can be crosslinked via glyoxalization. Modified BC networks are found to not dissolve in a typical cellulose solvent comprising a DMAc/LiCl mixture, whereas unmodified BC networks readily dissolve. The crystal structure of unmodified BC networks was investigated and found to not significantly change after glyoxalization, indicating heterogeneous modification occurs. No significant difference in moisture content between unmodified and glyoxalized BC networks is found using thermogravimetric analysis.

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“…This band is thought to be representative of C-O ring stretching modes 35 and/or the C-O-C glycosidic bond stretching 36,37 .…”

Section: Resultsmentioning

confidence: 99%

Cross-Linked Bacterial Cellulose Networks Using Glyoxalization

Quero

Nogi

Lee

et al. 2010

ACS Appl. Mater. Interfaces

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“…The Raman band located at ~1095 cm -1 seen in the composite samples is characteristic of cellulose and has been attributed to vibrational modes of C-O and C-O-C moieties. 29, 49 As these bonds are present in the backbone structure of cellulose, the shift in the position of this band can be used to quantify stress in the cellulose fibrils. 32 This technique has been widely used to 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 In Figure 8, a typical shift in the peak position towards a lower wavenumber of the Raman band initially located at ~1095 cm -1 at 0 and 5% strain is reported.…”

Section: Morphological Analysis Of Gelatin and Bc-gelatin Compositesmentioning

confidence: 99%

Stress Transfer Quantification in Gelatin-Matrix Natural Composites with Tunable Optical Properties

et al. 2015

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This work reports the preparation and characterization of natural composite materials prepared from bacterial cellulose (BC) incorporated into a gelatin matrix. Composite morphology was studied using SEM and 2D Raman imaging revealing an inhomogeneous dispersion of BC within the gelatin matrix. The composite materials showed controllable degrees of transparency to visible light and opacity to UV light depending on BC weight fraction. By adding a 10 wt.% fraction of BC in gelatin, visible (λ = 550 nm) and UV (λ = 350 nm) transmittances were found to decrease by ~35 and 40 %, respectively. Additionally, stress transfer occurring between the gelatin and BC fibrils was quantified using Raman spectroscopy. This is the first report for a gelatin-matrix composite containing cellulose. As a function of strain, two distinct domains, both showing linear relationships, were observed for which an average initial shift rate with respect to strain of -0.63 ± 0.2 cm -1 % -1 was observed, followed by an average shift rate of -0.25 ± 0.03 cm -1 % -1 . The average initial Raman band shift rate value corresponds to an average effective Young's modulus of 39 ± 13 GPa and 73 ± 25 GPa, respectively for either a 2D and 3D network of BC fibrils embedded in the gelatin matrix. As a function of stress, a linear relationship was observed with a Raman band shift rate of -27 ± 3 cm -1 GPa -1 . The potential use of these composite materials as a UV blocking food coating is discussed.

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“…Currently easier to use and increasingly available, Raman microscopy is being used more frequently. In the investigations of wood and pulp fibers, Raman stud ies range from investigating tensile deformation of single wood fibers [55,56] to detailed investigations, at the subcellular level, of composition and ultrastructure of native woody tissue [7][8][9].…”

Section: Microscope Studiesmentioning

confidence: 99%

“…In other studies of wood fibers [55,56], Raman microscopy was used to show that during tensile deformation the ∼1095 cm −1 Raman band shifts towards a lower wave number due to molecular deformation of cellulose. This shift has been shown to be useful in under standing the micromechanisms of deformation in wood and pulp fibers.…”

Section: Molecular Changes During Tensile Deformationmentioning

confidence: 99%

“…This shift has been shown to be useful in under standing the micromechanisms of deformation in wood and pulp fibers. In one study [56], isolated fibers of spruce latewood were mechanically strained and molecular changes due to deformation were monitored by stress-strain curves and changes in band positions and intensities. Frequency changes for the 1097 cm −1 band correlated well with the applied stress and strain.…”

Section: Molecular Changes During Tensile Deformationmentioning

confidence: 99%

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Raman Spectroscopic Characterization of Wood and Pulp Fibers

Agarwal

2008

Characterization of Lignocellulosic Materials

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This chapter reviews applications of Raman spectroscopy in the field of wood and pulp fibers. Most of the literature examined was published between 1998 and 2006. In addi tion to introduction, this chapter contains sections on wood and components, mechanical pulp, chemical pulp, modified/treated wood, cellulose I crystallinity of wood fibers, and the "self-absorption" phenomenon in near-infrared (IR) Fourier-transform (FT)-Raman spectroscopy. When needed, the sections are further categorized into various subsections. For example, the section on wood and components contains a variety of topics ranging from Raman band assignments to molecular changes during tensile deformation. From this review it will become clear that Raman spectroscopy has become an essential analytical technique in the field of wood and pulp fibers. IntroductionTechniques that can provide information on the chemical constitution of wood and pulp fibers and on processing-related changes of these materials are of great interest. Raman spectroscopy [1] is one such technique that provides fundamental knowledge on a molecu lar level and does not require chemical treatment of the sample (contrary to the case, for example, in fluorescence and electron microscopy). It has become an important analyt ical technique for nondestructive, qualitative, and quantitative analysis of materials. The technique is useful in a number of areas, including analytical measurements, mechan istic studies, and structural determinations. Studying a sample is very simple and usually involves sampling an area of interest by directing a laser excitation beam and analyzing the collected molecularly specific scattered light [2]. Although initially, obtaining good-quality Raman data required operator skill and training, this has started to change as a result of the commercial availability of compact, easy-to-use, integrated instruments at reasonable cost.Nevertheless, although the specificity of Raman spectroscopy is very high, its sensitivity is somewhat poor. Considering that only a small number of the incident laser photons are inelastically scattered, the detection of analytes present in very low concentrations is limited. To overcome this problem, special Raman signal-enhancing techniques can be applied. The two most prominent approaches are the resonance Raman effect [3] and the

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Molecular Changes during Tensile Deformation of Single Wood Fibers Followed by Raman Microscopy

Cited by 131 publications

References 29 publications

Cross-Linked Bacterial Cellulose Networks Using Glyoxalization

Cross-Linked Bacterial Cellulose Networks Using Glyoxalization

Stress Transfer Quantification in Gelatin-Matrix Natural Composites with Tunable Optical Properties

Raman Spectroscopic Characterization of Wood and Pulp Fibers

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