Effects of multifunctional acrylates and thiols on the morphology and electro-optical properties of polymer-dispersed liquid crystal films

In the present paper, influence of the functionality of thiol monomers and acrylate crosslinkers, as well as crosslinker chain length on the polymer morphologies and electro-optical properties of the PDLC films, were systematically investigated. Results revealed that increasing the functionality of thiol monomers, both threshold voltage (Vth) and saturation voltage (Vsat) were increased due to the dense microstructures resulting from higher reactivity of thiol monomers. However, with increasing the functionality of acrylate monomers, Vth was increased evidently, but a relatively small rise of Vsat was found with moderate functionality monomer. Additionally, the increase in the chain length of flexible crosslinker resulted in an increase in the average size of LC droplets with a corresponding decrease in Vth and Vsat. On the whole, polymer morphology and electro-optical properties of the PDLC films can be artificially manipulated by adjusting the molecular structure of polymer matrix. A PDLC film exhibiting low driving voltage (24.0 V), moderately high contrast ratio (97.0) and fast response time (<8.0 ms), was found by employing the Pentaerythritol tetrakis (2-mercaptoacetate) (4SH), trimethylolpropane triacrylate (TMPTA) and polyethylene glycol diacrylate (PEGD 600).