Chiral Structure Formation during Casting of Cellulose Nanocrystalline Films

Abstract

A Landau-de Gennes formulation coupled with a mass-transfer equation was used to track the evaporation front and the development of chiral microstructures during the casting of sulfuric acid-hydrolyzed cellulose nanocrystal (CNC) films. These simulations are compared to thin-film casting experiments that used analogous processing parameters and environments. The results show that the initial concentration, chiral strength, surface anchoring, speed of drying, and the influence of initial shear alignment all affect the uniformity of the microstructure and the orientation of the chiral director. In this report, we aim to show that under optimal casting conditions, the lateral size of planar microstructural domains that exhibit uniform selective reflection can be achieved on the order of millimeters.

Self-assembly of cellulose nanocrystals confined to square capillaries

“…Between parallel glass surfaces, CNCs align with the nematic director parallel to the surfaces, forming vertical helices that propagate perpendicular to the glass plates, owing to shape anisotropy of the nanoparticles. 55 In contrast, thin-walled rectangular capillaries (thickness of 50 μm and width of 1000 μm) containing biphasic CNC suspensions resulted in ChN nematic layers anchored parallel to an upper isotropic phase with the helical axis perpendicular to the wall. 42 In both instances, the CNC suspensions were studied under drying conditions with continuous shear perpendicular to the helical axis.…”

Structure and Pattern Formation in Biological Liquid Crystals: Insights From Theory and Simulation of Self-Assembly and Self-Organization

“…Hence starting from a paranematic well-oriented phase with an order parameter S close to the target one, one can in principle obtain defect-free films with directed evaporation, where the mass transfer drives the order in a controlled way (Gutierrez and Rey, 2017). Hence if we look at the open system examples, we find evaporation examples such as in (Chu et al, 2018;Pospisil et al, 2020).…”