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Lattice-patterned LC-polymer composites containing various nanoparticles as additives.

Sim K, Sung SJ, Jung EA, Son DH, Kim DH, Kang JK, Cho KY - Nanoscale Res Lett (2012)

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Green Energy Research Division, DGIST, 50-1 Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 711-873, Republic of Korea. sjsung@dgist.ac.kr.

ABSTRACT
In this study, we show the effect of various nanoparticle additives on phase separation behavior of a lattice-patterned 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 LC-polymer 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.

No MeSH data available.


Related in: MedlinePlus

Electro-optical properties of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives. The contrast ratio for a driving voltage of 12.5 V and the driving voltage corresponding to a contrast ratio of 30 in the case of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives.
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Figure 5: Electro-optical properties of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives. The contrast ratio for a driving voltage of 12.5 V and the driving voltage corresponding to a contrast ratio of 30 in the case of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives.

Mentions: In addition to the phase separation behavior of the LC-polymer composites, it is important to investigate the electro-optical properties of the composites when SiO2 nanoparticles are included in the prepolymer systems from the viewpoint of the applications of the composites. To this end, we measured the contrast ratio and driving voltage of the lattice-patterned LC-polymer composites. The contrast ratio of the LC is the ratio of light transmittance between the on-state and the off-state of the LC, and the driving voltage is the intensity of external electric field required to obtain the contrast ratio of the LC. The contrast ratio and driving voltage are known to affect the electro-optical properties of conventional LCDs. Figure 5 illustrates the contrast ratio and driving voltage of the LC-polymer composites containing SiNP-7 or SiNP-14. The contrast ratio decreased with the quantities of SiNP-7 and SiNP-14, and the range over which the contrast ratio decreased was more apparent for SiNP-14. When an external electric field was applied to the composites, the LC molecules rotated. In terms of driving the LC molecules, the SiO2 nanoparticles can hinder the movement of LC molecules, and thus, the contrast ratio of the LC would decrease with an increase in the quantity of SiO2 nanoparticles. These results also support the view that the untreated SiO2 nanoparticles, SiNP-7 and SiNP-14, were mainly located in the LC regions after photoinduced phase separation. In the case of the driving voltage, the SiO2 nanoparticles can have a similar hindrance effect on the movement of the LC molecules, and thus, the driving voltage of the LC molecules would increase with an increase in the quantity of SiO2 nanoparticles. In the case of SiNP-14, SiO2 nanoparticles with larger diameters can disturb the movement of the LC molecules more easily than those of SiNP-7, and thus, the changes in the contrast ratio and driving voltage were more evident than in the case of SiNP-7.


Lattice-patterned LC-polymer composites containing various nanoparticles as additives.

Sim K, Sung SJ, Jung EA, Son DH, Kim DH, Kang JK, Cho KY - Nanoscale Res Lett (2012)

Electro-optical properties of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives. The contrast ratio for a driving voltage of 12.5 V and the driving voltage corresponding to a contrast ratio of 30 in the case of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3275447&req=5

Figure 5: Electro-optical properties of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives. The contrast ratio for a driving voltage of 12.5 V and the driving voltage corresponding to a contrast ratio of 30 in the case of lattice-patterned LC-polymer composites containing non-functionalized SiO2 nanoparticles as additives.
Mentions: In addition to the phase separation behavior of the LC-polymer composites, it is important to investigate the electro-optical properties of the composites when SiO2 nanoparticles are included in the prepolymer systems from the viewpoint of the applications of the composites. To this end, we measured the contrast ratio and driving voltage of the lattice-patterned LC-polymer composites. The contrast ratio of the LC is the ratio of light transmittance between the on-state and the off-state of the LC, and the driving voltage is the intensity of external electric field required to obtain the contrast ratio of the LC. The contrast ratio and driving voltage are known to affect the electro-optical properties of conventional LCDs. Figure 5 illustrates the contrast ratio and driving voltage of the LC-polymer composites containing SiNP-7 or SiNP-14. The contrast ratio decreased with the quantities of SiNP-7 and SiNP-14, and the range over which the contrast ratio decreased was more apparent for SiNP-14. When an external electric field was applied to the composites, the LC molecules rotated. In terms of driving the LC molecules, the SiO2 nanoparticles can hinder the movement of LC molecules, and thus, the contrast ratio of the LC would decrease with an increase in the quantity of SiO2 nanoparticles. These results also support the view that the untreated SiO2 nanoparticles, SiNP-7 and SiNP-14, were mainly located in the LC regions after photoinduced phase separation. In the case of the driving voltage, the SiO2 nanoparticles can have a similar hindrance effect on the movement of the LC molecules, and thus, the driving voltage of the LC molecules would increase with an increase in the quantity of SiO2 nanoparticles. In the case of SiNP-14, SiO2 nanoparticles with larger diameters can disturb the movement of the LC molecules more easily than those of SiNP-7, and thus, the changes in the contrast ratio and driving voltage were more evident than in the case of SiNP-7.

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Green Energy Research Division, DGIST, 50-1 Sang-ri, Hyeonpung-myeon, Dalseong-gun, Daegu, 711-873, Republic of Korea. sjsung@dgist.ac.kr.

ABSTRACT
In this study, we show the effect of various nanoparticle additives on phase separation behavior of a lattice-patterned 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 LC-polymer 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.

No MeSH data available.


Related in: MedlinePlus