Effects of silicone monomer on the grating formation of holographic PDLC

To augment polymer-LC phase separation and driving characteristics of holographic polymer dispersed liquid crystals (HPDLCs), various types and contents of silicone monomer viz. vinyloxytrimethylsilane (VOTMS), 1,3-divinyltetramethyldisiloxane (DVTMDS) and 3-dicyclohexyl-1,1,3,3-tetrakis (dimethylvinylsilyloxy) disiloxane (DCHTDS) were added to the conventional formulations for HPDLC in a broad range of content. It was found that grating formation becomes fast in proportion to its content regardless of the type of silicon monomer due to the enhanced polymer-LC phase separation driven by the increased immiscibility. SEM and AFM showed that DCHTDS gave by far the greatest extent of phase separation. VOTMS and DVTMDS preferentially migrated toward the surface or polymer-LC interface, which effectively lowered the surface anchoring and reduced driving voltage. Due to the droplet coalescence and poor migration of DCHTDS toward the interfaces, DCHTDS gave low diffraction efficiency and high driving voltage in spite of its great and fast phase separation with LC molecules.