In situ polarized micro-Raman investigation of periodic structures realized in liquid-crystalline composite materials

Abstract

In situ polarized micro-Raman Spectroscopy has been utilized to determine the liquid crystal configuration inside a periodic liquid crystalline composite structure made of polymer slices alternated to films of liquid crystal. Liquid crystal, Norland Optical Adhesive (NOA-61) monomer and its polymerized form have been investigated separately. The main Raman features, used as markers for the molecular orientation estimation, have been identified. In situ polarized Raman spectra indicate that the orientation of the liquid crystal director inside the structure is perpendicular to its polymeric slices. Results show the usefulness of in situ polarized micro-Raman spectroscopy to investigate liquid crystalline composite structures.

Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings

“…Surface-based patterning is typically obtained by the use of striped electrodes that generate a periodic electric field within the LC medium or by patterning of alignment layers that govern the LC orientation in contact with the surrounding surfaces [ 10 , 23 , 25 , 26 ]. Volume-based patterning relies on the use of mixtures of LCs with photopolymeric materials and patterning is achieved by photolithographic methods, such as conventional mask-based optical lithography, holographic lithography and direct laser writing [ 27 , 28 , 29 , 30 ].…”

Chitosan as matrix for bio-polymer dispersed liquid crystal systems

“…In the Raman spectra of this compound four bands can be evidenced at 1180 cm −1 , assigned to aromatic CH in-plane deformation, 1286 cm −1 to C C stretching of the biphenyl link, 1606 cm −1 to C C stretching of the aromatic rings and 2228 cm −1 to C N stretching (Buyuktanir, Zhang, Gericke, & West, 2008;Kachynski, Kuzmin, Prasad, & Smalyukh, 2008). The assignment of such modes has been performed by taking into account the fact that biphenyl belongs to the C2v point group and their skeletal vibrational modes can be described in four symmetry species (Castriota et al, 2011). According to this assumption, the vibrations at 1184, 1609 and 2228 cm −1 occur in the molecular plane, while all other vibrations occur out of the molecular plane.…”

Dynamic in-situ sensing of fluid-dispersed 2D materials integrated on microfluidic Si chip

“…Such a method is pivotal to the confirmation of the integration of composites in the device and to enable determination of parameters, such as spatial alignment of incorporated 2D materials, dynamically during device operation. Conventional characterisation methods such as Raman spectroscopy 5 27 28 , coherent anti-Stokes Raman spectroscopy (CARS) 29 and Fourier Transform Infrared Spectroscopy (FTIR) 30 are not suitable for studies of fluid nanocomposites with relatively low concentrations of nanoparticles dispersed. In this case, the significantly greater scattering volume of the host fluid compared to that of the dispersed nanoparticles always dominates the vibrational signal intensity, rendering the monitoring of the considerably weaker bands of dispersed nanoparticles impossible.…”