Polymer-encapsulated liquid crystals comprising montmorillonite clay

The morphologies of polymer-dispersed liquid crystals (PDLCs) and holographic PDLC (HPDLC) composites consisting of nematic liquid crystals filled with inorganic nanoparticles of either pristine montmorillonite (MMT) clay or organically modified MMT (OMMT) clay in polymer matrices are described. Different curing processes with ultraviolet irradiation and an Ar+ laser were applied to make the PDLCs and HPDLCs, respectively. In order to gain some prior knowledge of the dispersion of the inorganic nanoparticles in the polymer-encapsulated systems, wide-angle x-ray diffraction patterns from an MMT clay suspension in liquid crystal were observed at variable temperatures. Differential scanning photocalorimetry was carried out to observe the monomer conversion. The morphology of liquid-crystal droplets of the PDLCs was investigated by optical polarizing microscopy. The holographic nature of the HPDLCs was confirmed by both scanning electron microscopy and atomic force microscopy. It was found that the diffraction efficiency is markedly enhanced by doping a small amount of pristine clay platelets in the HPDLC. This preliminary study demonstrates the potential of a new optical device, which is made of MMT clay hybridized with liquid crystal in a PDLC system.