Molecular orientation distribution of regenerated cellulose fibers investigated with rotor synchronized solid state NMR spectroscopy

Abstract

A regenerated cellulose fiber is, in contrast to cotton, a man-made fiber. In the fiber production, the cellulose polymer is subject to various processing steps, affecting the underlying molecular orientation distribution, which is a determining factor for mechanical properties of the fiber. In this work, the molecular orientation distribution was determined in a 13 C natural abundance Lyocell regenerated cellulose fiber bundle using rotor synchronized magic angle spinning NMR spectroscopy (ROSMAS) to investigate the chemical shift anisotropy (CSA). The recorded signal intensities were compared with an analytical model of the experiment to find the order parameters reflecting the orientation of the fiber. The CSA tensor was calculated using density functional theory for the crystalline cellulose II structure, commonly found in regenerated cellulose, and is required as an input parameter. The expected order parameter values were only found when approximating the glycosidic bond and its CSA tensor as being parallel to the molecular frame with the order parameter P 2 ¼ 0:45 AE 0:02 compared to P 2 ¼ 0:46 AE 0:02 obtained with wide angle X-ray scattering on a fiber bundle. To make this method accessible to the community, we distribute the Matlab script for the simulation of spectra obtained by the ROSMAS experiment at github.com/LeoSvenningsson/ROSMAS.

A Combined Theoretical and Experimental Study of the Polymer Matrix-Mediated Stress Transfer in a Cellulose Nanocomposite

“…The orientation of CNC occurs already upon extrusion and is further enhanced by the draw down experienced during melt spinning. Wide-angle X-ray scattering (WAXS; Figure S7) and solid-state nuclear magnetic resonance (solid-state NMR) spectroscopy in combination with the rotor-synchronized magic angle spinning (ROSMAS) technique , confirm that CNC orients already upon extrusion and ROSMAS NMR further shows that alignment of EAA 15 requires solid-state drawing (Figures S8–S9).…”

Molecular Orientation Distribution of Regenerated Cellulose Fibers Investigated with Polarized Raman Spectroscopy

“…However, we have recently found, using ROSMAS solid-state NMR spectroscopy, no or negligible differences in orientation for these two phases. 11 In the same study, a wrapped Lorentzian-based ROSMAS method was also successfully applied, with the results summarized in Table 1, which shows that the wrapped Lorentzian model is a good approximation also for fiber bundles. Consequently, we are confident in claiming to have constructed a methodology that yields quantitative results across three techniques, i.e., Raman spectroscopy, NMR spectroscopy, and WAXS, based on different physical phenomena.…”

“… a Rotor synchronized MAS solid-state NMR experiments by Svenningsson et al P 4 * is implicit by assuming a wrapped Lorentzian ODF. …”

“…Potentially, more structural information could be achieved if several order parameters are known. A handful of experimental methods exist to investigate molecular orientations, such as rotor synchronized magic angle spinning − (ROSMAS) or DECODER NMR spectroscopy, , wide angle X-ray scattering (WAXS), infrared (IR) dichroism, birefringence, and polarized Raman spectroscopy, ,− each method having advantages and limitations. The NMR techniques have the potential to measure all structural contributions of the material as well as high moment order parameters, but require the use of a bundle of fibers that may introduce a macroscopic orientation distribution and hence obscure the uniaxial fiber symmetry.…”

Effect of Nonisoprene Degradation and Naturally Occurring Network during Maturation on the Properties of Natural Rubber

“…Due to obvious superiorities to its counterparts, NR has been employed in versatile solutions to satisfy the demanding requirements in the characteristics of high-performance, production efficiency, sustainability, etc. [ 3 , 4 , 5 , 6 ]. Nowadays, NR is an increasingly important elastomeric material for our daily life applications spanning many domains of military, chemistry, hygiene and medical sectors.…”