Optimizing polarization efficiency of optically anisotropic films cast from lyotropic chromonic liquid crystals on surface-modified triacetyl cellulose films

• Published in: Progress in organic coatings 2015-08, Vol.85, p.38-45
• Main Authors: Chang, Eugene, Cho, Jin Ku, Shin, Seunghan
• Format: Article
• Language: English
• Subjects: Anisotropy; Atmospheric pressure plasma; Cellulose; Hydrolysis; Liquid crystals; Lyotropic chromonic liquid crystal; Optically anisotropic film; Optimization; Polarization; Polarization efficiency; Shear; Substrates; Surface energy; Triacetyl cellulose
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2015.03.001

•Optically anisotropic films cast from LCLCs were developed on TAC substrate.•TAC films were modified by combined treatment by NaOH solution and Ar/O2 plasma.•Effects of surface properties of TAC on polarization efficiency were studied.•Polarization efficiency of anisotropic film on TAC was nearly equal to that on glass. Optically anisotropic films by shear coating of a lyotropic chromonic liquid crystal (LCLC) aqueous solution were developed on a triacetyl cellulose (TAC) film instead of a glass substrate. The TAC film surface was treated using a sodium hydroxide (NaOH) solution to increase its surface energy for wetting ability. Although the desired surface energy, which is competitive with glass, was achieved, the TAC film surface became rougher during NaOH hydrolysis, which aggravated the alignment of LCLC aggregates, especially for those with a small length-to-width ratio. To alleviate the surface roughness without compensating the surface energy, further treatment of the NaOH-hydrolyzed TAC film was performed using atmospheric pressure Ar/O2 plasma. After optimization of the treatment conditions, the combined method could enhance the polarization efficiency (Peff) of the anisotropic film on the TAC substrate from 91.2% to 95.9%, which was nearly equal to that on a glass substrate.