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Song P.,University of Science and Technology Beijing | Yu L.,Dalian University | Cao H.,University of Science and Technology Beijing | Wang F.,University of Science and Technology Beijing | And 4 more authors.
Liquid Crystals | Year: 2012

Epoxy polymer dispersed liquid crystal (PDLC) films based on ethyleneglycol diglycidyl ether (EGDE)/nematic liquid crystal (SLC1717) composites were prepared by ultraviolet-initiated cationic polymerisation using triphenylsulfonium hexafluoroantimonate (Ar 3S +SbF 6 -) as the photoinitiator. The effect of the composition of the mixture and curing temperature on the microstructure of the polymer network and the electro-optical properties was investigated. It was found that the liquid crystal (LC) domain size of the polymer network could be regulated by adjusting the LC content and the curing temperature. The electro-optical properties of PDLC films could then be optimised. © 2012 Copyright Taylor and Francis Group, LLC. Source


Song P.,University of Science and Technology Beijing | Yu L.,Dalian University | Jiao A.,Dalian Urban Construction Expert Co. | Wang F.,University of Science and Technology Beijing | And 5 more authors.
Journal of Applied Physics | Year: 2012

Polymer-dispersed liquid crystal (PDLC) films based on epoxy resins were prepared by UV-initiated cationic polymerization using UVI-6974 as UV-initiator. The charged ions arose from photolysis of the UV-initiator remained in the liquid crystal (LC) droplet of the polymer matrix. Optical devices based on PDLC films derive their functional properties from the electric field induced reorientation of LC droplets. These PDLC films doped with ions showed different reorientation of LC molecules and electro-optical properties than those prepared without ionic dopants. When an electric field was applied across these PDLC films, the charged ions in the LC droplet migrated along the direction of the electric field in inducement of the electric field and assembled at the LC droplet/polymer interface. According to the situation mentioned above, the model of charged double layers at the LC droplet/polymer interface was set up in our study. The behavior was attributed to the charged double layers that cancel the field strength within the bulk of the liquid crystal in time. By using this model, the electric field and initiator concentration dependent results and the difference of the PDLC with and without ions were investigated and explained. © 2012 American Institute of Physics. Source


Zhang C.,University of Science and Technology Beijing | Wang D.,University of Science and Technology Beijing | Cao H.,University of Science and Technology Beijing | Song P.,University of Science and Technology Beijing | And 4 more authors.
Polymers for Advanced Technologies | Year: 2013

In this paper, polymer dispersed liquid crystals (PDLC) films with LC content as low as 40wt% were prepared, and the electro-optical properties were carefully investigated. To accomplish this, different (meth)acrylate copolymerizaiton monomers have been used. The electro-optical properties and morphologies of the PDLC films were strongly influenced by the chemical structure of copolymerization monomers (hydroxypropyl methacrylate (HPMA), glycidyl methacrylate, hydroxypropyl acrylate) and their feed ratio. Lower driven voltage and higher contrast ratio were achieved when the PDLC films showed a morphology with suitably LC domain size. At high HPMA content, a thin polymer film was formed on the surface of PDLC samples, which is beneficial to decrease the total LC content in PDLC devices. © 2013 John Wiley & Sons, Ltd. Source

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