Maria Helena Godinho (CENIMAT): Twisted structures in cellulose nanocrystal (CNC) solid films

Much attention has been devoted to solid iridescent films made from cellulose nanocrystal self-assembly. The films’ structural color is attributed to a helicoidal structure that selectively reflects left and transmits circularly polarized light. These solid structures retain the characteristics associated with the cholesteric liquid crystalline phase. In this sense, the defects that appear parallel and perpendicular to the optical axis should be present in the CNC solid films. In cholesterics, different dislocations can be observed: λ parallel to the helical axis, χ parallel to the director, and τ orthogonal to both the helical axis and the director. While the λ and τ dislocations were identified in the cross-section of CNC solid films, χ lines were never reported. Here, we give evidence of χ dislocations and right-handed bundles in left-handed CNC solid film structures.