Lattice-patterned LC-polymer composites containing various nanoparticles as additives
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NANO EXPRESS
Open Access
Lattice-patterned LC-polymer composites containing various nanoparticles as additives Kyoseung Sim1, Shi-Joon Sung1*, Eun-Ae Jung1, Dae-Ho Son1, Dae-Hwan Kim1, Jin-Kyu Kang1 and Kuk Young Cho2
Abstract In this study, we show the effect of various nanoparticle additives on phase separation behavior of a latticepatterned liquid crystal [LC]-polymer composite system and on interfacial properties between the LC and polymer. Lattice-patterned LC-polymer composites were fabricated by exposing to UV light a mixture of a prepolymer, an LC, and SiO2 nanoparticles positioned under a patterned photomask. This resulted in the formation of an LC and prepolymer region through phase separation. We found that the incorporation of SiO2 nanoparticles significantly affected the electro-optical properties of the lattice-patterned LC-polymer composites. This effect is a fundamental characteristic of flexible displays. The electro-optical properties depend on the size and surface functional groups of the SiO2 nanoparticles. Compared with untreated pristine SiO2 nanoparticles, which adversely affect the performance of LC molecules surrounded by polymer walls, SiO2 nanoparticles with surface functional groups were found to improve the electro-optical properties of the lattice-patterned LC-polymer composites by increasing the quantity of SiO2 nanoparticles. The surface functional groups of the SiO2 nanoparticles were closely related to the distribution of SiO2 nanoparticles in the LC-polymer composites, and they influenced the electro-optical properties of the LC molecules. It is clear from our work that the introduction of nanoparticles into a lattice-patterned LCpolymer composite provides a method for controlling and improving the composite’s electro-optical properties. This technique can be used to produce flexible substrates for various flexible electronic devices. Keywords: phase separation, nanoparticle, LC-polymer composite, photopolymerization, lattice pattern.
Introduction Owing to its impact on device performance, the phase separation behavior of materials and its effect on the device morphology have attracted considerable attention as one of the powerful methods for fabricating flexible electronic devices, such as organic photovoltaics, organic field effect transistors, organic nonvolatile memory devices, and liquid crystal displays [LCDs] [1-6]. The phase separation of a mixture is attributed to the difference in surface free energy among the components and their interactions with each other. Lattice-patterned liquid crystal [LC]-polymer composites, which are characterized by phase separation of the mixture of LC and the miscible photoreactive monomers upon UV light irradiation under a patterned mask, are one of the most * Correspondence: [email protected] 1 Green Energy Research Division, DGIST, 50-1 Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 711-873, Republic of Korea Full list of author information is available at the end of the article
important fabrication materials for flexible substrate
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