Modification in diffusion kinetics and electro-optic behavior of holographic thin films with carbon nanotubes

Abstract

This work focuses on the study of the modification in formation and electro-optic behavior of holographically formed polymer -liquid crystal thin film gratings doped with multiwalled carbon nanotubes. Results indicate a time delay in the evolution of the first diffraction order in the presence of carbon nanotubes when compared to ones with no nanotubes. An analysis is presented based on the modification of the diffusion kinetics in terms of photo induced phase separation. This slow down is attributed to the non-participation of the carbon nanotubes in the phase separation process, and acting as physical barriers to the counter diffusing liquid crystals. The diffusion constant of nanotubes, incorporating its shape anisotropy, is computed in such a photo polymerizable system and compared with those of the participating polymers and liquid crystals. An optimal concentration of carbon nanotube doping is arrived at which helps in improve the switching speed while maintaining diffraction efficiency. Improvement is switching speed is attributed to reduction in size of the liquid crystal droplets. Scanning electron microscopy results indicate a change in morphology of the gratings doped with carbon nanotubes. In specific, smaller droplet size and, beyond the optimal level of nanotube doping, imperfect liquid crystal phase separation with scarcity of liquid crystal droplets across the sample is seen.