Colorfully Patterned Epoxy Resin Films with a Cholesteric Structure Prepared through a Photopolymerization Approach
Xiaoli Zhang, Yongxing Guo, Yi Li, Wei Liu, Hongkun Li, Yonggang Yang
Abstract
Structurally colored epoxy resin films were prepared using a liquid crystalline (LC) epoxy monomer of E11M and a chiral additive of CA-iso through a photopolymerization approach. With the addition of the co-photoinitiator isopropyl thioxanthone and comonomer 3′,4′-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, the polymerization rate was increased. Since the epoxy resin films can be obtained within several seconds, they are feasible for large-area preparation on the coating line. The reflective wavelength was tunable by changing the concentration of CA-iso in the LC mixture. Diffuse-reflectance circular dichroism spectra indicated a right-handed helical supramolecular structure. Field-emission scanning electron microscopy images indicated a multilayer structure. Since the LC mixtures were thermochromic, colorfully patterned epoxy resin films were prepared by controlling the polymerization temperature. Moreover, LC gratings were also prepared, which were expected to be applied for anticounterfeiting.