Separation and characterization of cellulose nanocrystals by multi-detector asymmetric flow field-flow fractionation
Arnab K. Mukherjee, Vincent A. Hackley
Cellulose nanocrystals (CNCs) are renewable, naturally derived polymeric nanomaterials that are receiving substantial attention for a wide range of potential applications. The recent availability of high quality reference materials will facilitate the development and validation of measurement methods needed to advance the scientific and commercial use of CNCs. In the present study, we demonstrate an optimized method to fractionate CNCs with narrow size dispersion based on multi-detection asymmetric flow field-flow fractionation (AF4) coupled with on-line multi-angle light scattering (MALS), dynamic light scattering (DLS), and differential refractometry (dRI). A stable suspension of CNC (CNCD-1, NRC-Canada) in deionized water was prepared using a dispersion method provided by NRC and adopted from a protocol originally developed at the National Institute of Standards and Technology. The as-prepared material was initially characterized in batch mode to validate the dispersion method. AF4 was then optimized for channel and cross flow, mobile phase composition, and injection volume, among other parameters. Additionally, suspensions containing (1.25 - 10) mg/mL CNC were injected directly into the dRI detector (off-line), yielding a dn/dc value of 0.148 ± 0.003 g/mL. dRI was then used as an on-line mass sensitive detector to quantify recovery. Results show that maximum recovery (≈ 99 %) was achieved under optimized conditions. The weight-averaged molar mass (Mw) was estimated by applying the Zimm equation to MALS data, and was roughly 10E7. The root mean square radius of gyration, Rg, was also obtained from the Zimm analysis, while the hydrodynamic radius, Rh, was measured on-line using DLS and cumulants analysis at a scattering angle of 99.9 °. Finally, the shape factor (Rg/Rh) for fractionated CNCs was determined during elution, and ranged from 1.5 to 1.9. A shape factor of in this range is indicative of rod-like morphology.
and Hackley, V.
Separation and characterization of cellulose nanocrystals by multi-detector asymmetric flow field-flow fractionation, Analyst, [online], https://doi.org/10.1039/c7an01739a, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924059
(Accessed September 22, 2023)