Self-Assembling Behavior of Cellulose Nanoparticles during Freeze-Drying: Effect of Suspension Concentration, Particle Size, Crystal Structure, and Surface Charge

Abstract

Cellulose nanocrystals and cellulose nanofibers with I and II crystalline allomorphs (designated as CNC I, CNC II, CNF I, and CNF II) were isolated from bleached wood fibers by alkaline pretreatment and acid hydrolysis. The effects of concentration, particle size, surface charge, and crystal structure on the lyophilization-induced self-assembly of cellulose particles in aqueous suspensions were studied. Within the concentration range of 0.5 to 1.0 wt %, cellulose particles self-organized into lamellar structured foam composed of aligned membrane layers with widths between 0.5 and 3 μm. At 0.05 wt %, CNC I, CNF I, CNC II, and CNF II self-assembled into oriented ultrafine fibers with mean diameters of 0.57, 1.02, 1.50, and 1.00 μm, respectively. The size of self-assembled fibers became larger when more hydroxyl groups and fewer sulfates (weaker electrostatic repulsion) were on cellulose surfaces. Possible formation mechanism was inferred from ice growth and interaction between cellulose nanoparticles in liquid-crystalline suspensions.

Cellulose nanocrystals/poly(methyl methacrylate) nanocomposite films: Effect of preparation method and loading on the optical, thermal, mechanical, and gas barrier properties

“…And the corresponding aspect ratio was 17.10. Comparing with the previous work [11,25], which also used MCC to produce the CNCs by sulfuric acid (64 wt%) at 458C, the length and width of the obtained CNCs were smaller, but the aspect ratio was higher.…”

Composite Hydrogels with Tunable Anisotropic Morphologies and Mechanical Properties

“…While the A-CNC components of the aerogel could be aligned by shear forces imposed by the growing ice front during uni-directional freezing, as previously suggested for freeze-cast CNC aerogels; 69 it is difficult to prove such an alignment by low-angle SAXS measurements. This is because the scattering of small cylinder-like objects such as CNCs is concealed by the scattering from larger mesoscopic fibrils, columnar walls, and lamellae.…”

Transitional Properties of Cotton Fibers from Cellulose I to Cellulose II Structure

“…This could be related to the fact that the mercerized cellulose fibers possessed more -OH groups on their surfaces, which may lead to a stronger interaction between the fibers and polymer matrix. However, it is also noted that the size and aspect ratio of cellulose II were smaller than those of cellulose I, resulting in a less entanglement of cellulose II fibers (Han et al 2013b).…”