New Approach toward Reflective Films and Fibers Using Cholesteric Liquid-Crystal Coatings

Abstract

A new approach for the production of oriented films and fibers with angular-dependent reflective colors is presented. The process consists of spray coating a solution of cholesteric liquid-crystalline monomers onto a melt-processed and oriented polyamide-6 substrate followed by UV curing. Reflectivity measurements and optical microscopy show that a well-defined liquid-crystalline and planar alignment is obtained. It is further demonstrated that a reflection up to 80% is obtained by coating oriented films on both sides of the oriented substrate with a single-handedness cholesteric liquid-crystal coating. The high reflectivity is attributed to the close to half-wave retardation induced by the anisotropic polymer substrate. Also, polyamide-6 filaments are successfully coated and fibers are obtained with an angular-dependent color in a single dimension along the fiber direction, which originates from the planar cholesteric alignment on a curved surface.

Programmable helical twisting in oriented humidity-responsive bilayer films generated by spray-coating of a chiral nematic liquid crystal

“…S5 †). 29 The elegance of this system is further found in the self-organized coating: in principle, any chiral nematic LC mixture can be used to access helical twisting and its response to different stimuli can be tailored by changing the chemistry (Fig. S6 †).…”

Responsive Liquid‐Crystal‐Clad Fibers for Advanced Textiles and Wearable Sensors

“…Fibers clad with a chiral polymer LC have recently been reported. [22] In this case, a chiral prepolymer reflecting in the green at room temperature was airbrushed on the fiber followed by polymerization. While brilliantly colored, the resulting fibers do not respond to external stimuli, such as changes in temperature, because the helical pitch of a CLC polymer is frozen in the state where the mixture was polymerized.…”

“…Fibers clad with a chiral polymer LC have recently been reported . In this case, a chiral prepolymer reflecting in the green at room temperature was airbrushed on the fiber followed by polymerization.…”

Fisheye lens conoscopy

“…A wide variety of physical effects are being explored, ranging from anisotropic absorption [14] or reflection, [15] to the photonic tailoring of spatially modulated birefringence. [16] We have found the OiP system to be an effective tool for the study of the transmission characteristics of such sheet polarising systems, with several examples presented in Figure 18. The conoscopic images of pairs of standard absorptive O-type polarising films were imaged, with the polarizer and analyser parallel in Figure 18a-c, and crossed in Figure 18d.…”