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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

The polymer wall thickness of lattice-patterned LC-polymer composites containing non-functionalized and functionalized SiO2 nanoparticles.
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Figure 4: The polymer wall thickness of lattice-patterned LC-polymer composites containing non-functionalized and functionalized SiO2 nanoparticles.

Mentions: Figure 2 presents polarized optical microscope images of the lattice-patterned LC-polymer composites prepared by using mixtures of the LC and UV-curable prepolymers containing untreated SiO2 nanoparticles (SiNP-7 and SiNP-14) as an additive. All the images show cells of LC molecules surrounded by UV-cured polymer walls. From the polarized optical microscope images, it can be seen that the dependence of the phase separation structure on the quantities of SiNP-7 and SiNP-14 is small. The polymer wall thickness decreased slightly with an increase in the quantities of SiNP-7 and SiNP-14. In the cases of the functionalized SiO2 nanoparticles, BTMA-SNP and MPS-SNP, the LC-polymer composites also showed a similar phase separation structure regardless of the quantities of BTMA-SNP and MPS-SNP (Figure 3). However, the polymer wall thickness did not change with the quantities of BTMA-SNP and MPS-SNP. The wall thickness reduction in the lattice-patterned LC-polymer composites with an increase in the quantities of SiNP-7 and SiNP-14 could be interpreted as being due to untreated SiO2 nanoparticles diffusing in the direction opposite to that of the polymerizing regions [14,15]. Thus, SiNP-7 and SiNP-14 migrated into the LC domains during photoinduced phase separation, resulting in a loss of volume for SiNP-7 and SiNP-14 and a loss in their free volume in the polymeric region. The reduction in the volume of the polymer walls corresponded to an increase in the quantities of SiNP-7 and SiNP-14, and thus, the polymer wall thickness also decreased. However, in the case of the functionalized SiO2 nanoparticles, the presence of alkyl chains gave the nanoparticles a hydrophobic character, which resulted in the particles being sequestered within the polymeric region [15]. BTMA-SNP and MPS-SNP were expected to remain in the polymeric region during photoinduced phase separation, and the volume of the polymer walls containing BTMA-SNP or MPS-SNP should not have changed with the quantities of BTMA-SNP and MPS-SNP. Therefore, there was no change in the polymer wall thickness regardless of the quantity of the surface-treated inorganic nanoparticles. Figure 4 summarizes the changes in the polymer wall thickness with the size and surface functional groups of the SiO2 nanoparticles. As can be clearly seen in the polarized optical microscope images, the polymer wall thickness decreased with an increase in the quantities of SiNP-7 and SiNP-14, whereas no difference was observed for the cases of BTMA-SNP and MPS-SNP. Thus, the functional groups of SiO2 nanoparticles were closely related to the phase separation behavior of the lattice-patterned LC-polymer composites, and the polymer wall thickness was affected only by the inclusion of untreated SiO2 nanoparticles.


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)

The polymer wall thickness of lattice-patterned LC-polymer composites containing non-functionalized and functionalized SiO2 nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: The polymer wall thickness of lattice-patterned LC-polymer composites containing non-functionalized and functionalized SiO2 nanoparticles.
Mentions: Figure 2 presents polarized optical microscope images of the lattice-patterned LC-polymer composites prepared by using mixtures of the LC and UV-curable prepolymers containing untreated SiO2 nanoparticles (SiNP-7 and SiNP-14) as an additive. All the images show cells of LC molecules surrounded by UV-cured polymer walls. From the polarized optical microscope images, it can be seen that the dependence of the phase separation structure on the quantities of SiNP-7 and SiNP-14 is small. The polymer wall thickness decreased slightly with an increase in the quantities of SiNP-7 and SiNP-14. In the cases of the functionalized SiO2 nanoparticles, BTMA-SNP and MPS-SNP, the LC-polymer composites also showed a similar phase separation structure regardless of the quantities of BTMA-SNP and MPS-SNP (Figure 3). However, the polymer wall thickness did not change with the quantities of BTMA-SNP and MPS-SNP. The wall thickness reduction in the lattice-patterned LC-polymer composites with an increase in the quantities of SiNP-7 and SiNP-14 could be interpreted as being due to untreated SiO2 nanoparticles diffusing in the direction opposite to that of the polymerizing regions [14,15]. Thus, SiNP-7 and SiNP-14 migrated into the LC domains during photoinduced phase separation, resulting in a loss of volume for SiNP-7 and SiNP-14 and a loss in their free volume in the polymeric region. The reduction in the volume of the polymer walls corresponded to an increase in the quantities of SiNP-7 and SiNP-14, and thus, the polymer wall thickness also decreased. However, in the case of the functionalized SiO2 nanoparticles, the presence of alkyl chains gave the nanoparticles a hydrophobic character, which resulted in the particles being sequestered within the polymeric region [15]. BTMA-SNP and MPS-SNP were expected to remain in the polymeric region during photoinduced phase separation, and the volume of the polymer walls containing BTMA-SNP or MPS-SNP should not have changed with the quantities of BTMA-SNP and MPS-SNP. Therefore, there was no change in the polymer wall thickness regardless of the quantity of the surface-treated inorganic nanoparticles. Figure 4 summarizes the changes in the polymer wall thickness with the size and surface functional groups of the SiO2 nanoparticles. As can be clearly seen in the polarized optical microscope images, the polymer wall thickness decreased with an increase in the quantities of SiNP-7 and SiNP-14, whereas no difference was observed for the cases of BTMA-SNP and MPS-SNP. Thus, the functional groups of SiO2 nanoparticles were closely related to the phase separation behavior of the lattice-patterned LC-polymer composites, and the polymer wall thickness was affected only by the inclusion of untreated SiO2 nanoparticles.

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