title: Tuning the iridescence of chiral nematic cellulose nanocrystal films with a vacuum-assisted self-assembly technique.
abstract: Iridescent films composed of the chiral nematic liquid crystal phase of cellulose nanocrystals (CNC) have attracted significant interest due to their fascinating optical properties. However, the current fabrication method, i.e., solution casting with a subsequent evaporation process, has significant limitations and therefore hinders the application of CNC iridescent films. In the present study, we demonstrate, for the first time, that vacuum-assisted self-assembly (VASA) can be used to fabricate highly oriented, large area, smooth, and structurally homogeneous CNC iridescent films. It was found that a long ultrasonic pretreatment is necessary for obtaining CNC iridescent films via VASA. Furthermore, it was also found that the iridescent color of the CNC films can be tuned by the sonication time, suspension volume, and degree of vacuum. By combining CD spectroscopy, SEM, and WAXD techniques, the internal structure of CNC iridescent films prepared by VASA has been investigated in detail. Moreover, the origin of the ultrasonic pretreatment effect on the self-assembly behavior of CNCs is also discussed.
authors.affiliation: Key Laboratory of Rubber-Plastics, Ministry of Education/Shandong Provincial Key Laboratory of Rubber-Plastics, Qingdao University of Science & Technology , Qingdao City 266042, People's Republic of China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Fuchun
authors.initials: F
authors.lastname: Nan
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhou
authors.forename: Jianming
authors.initials: J
authors.lastname: Zhang
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D014618:Vacuum
chemical_list: D002482:Cellulose