Memory effect of polymer dispersed liquid crystal by hybridization with nanoclay

Jeong, Eunwook; Sun, K. R.; Kang, Minjee; Jeong, Han Mo; Kim, B. K.

doi:10.3144/expresspolymlett.2010.7

Cited by 8 publications

(4 citation statements)

References 20 publications

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“…The 3 440 cm −1 is associated with the OH stretching from the free water of the nanoclay 19. The 1 640 cm −1 is associated with the bending of the water OH adsorbed by the nanoclay 20. The band at 1 117 cm −1 corresponds to the Si–O stretching outside the plane, which is a characteristic of nanoclays because it is composed mainly of these two elements.…”

Section: Resultsmentioning

confidence: 99%

Surface Modification of Nanoclays by Plasma Polymerization of Ethylene

Neira‐Velázquez

Ramos-deValle

Hernández‐Hernández

et al. 2011

Plasma Processes & Polymers

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Sodium nanoclay was modified by plasma polymerization using ethylene gas. Due to the complexity of its lamellar morphology that prevents ethylene from entering into the clay galleries, a new two‐step strategy was employed. This method proved to be effective in overcoming the limited accessibility by first exposing the nanoclay to ethylene under a pressure of 0.14 MPa (1.4 kg · cm−2), followed by the ethylene plasma polymerization while within the clay galleries. Fourier transform infrared (FTIR)spectroscopy, dispersion tests in water, Raman spectroscopy, X‐ray photoelectronic spectroscopy (XPS), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HRTEM), and high‐annular angle dark field (HAADF) were used to characterize the modified nanoclay. XRD analysis indicated that the nanoclays layers were intercalated with polyethylene. Dispersion tests in water confirmed the nanoclays change from hydrophilic to organophilic. New chemical bondings (C–Si, C–O–Al, C–O, and C=O) were found by XPS. The presence of plasma polymer on the surface and inside the nanoclays galleries was corroborated by HRTEM.

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Section: Resultsmentioning

confidence: 99%

Surface Modification of Nanoclays by Plasma Polymerization of Ethylene

Neira‐Velázquez

Ramos-deValle

Hernández‐Hernández

et al. 2011

Plasma Processes & Polymers

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“…Decreasing A3DA content resulted in an increase of Vmax slightly to 7.6 and 9.8 V for 8.8 wt% and 8.0 wt% A3DA blends, respectively ( Figure S3 and Table S1, Supplementary Materials ). Whilst the impact of increasing A3DA concentration on voltage reduction was negligible, the decreased amount of cross-linker resulted in memory effect—a situation supported by the appearance of increased transparency even after the film was fully switched to OFF state ( Figure S3, Supplementary Materials ) [ 50 ].…”

Section: Resultsmentioning

confidence: 99%

High-Performance Polymer Dispersed Liquid Crystal Enabled by Uniquely Designed Acrylate Monomer

et al. 2020

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The widespread electro–optical applications of polymer dispersed liquid crystals (PDLCs) are hampered by their high-driving voltage. Attempts to fabricate PDLC devices with low driving voltage sacrifice other desirable features of PDLCs. There is thus a clear need to develop a method to reduce the driving voltage without diminishing other revolutionary features of PDLCs. Herein, we report a low-voltage driven PDLC system achieved through an elegantly simple and uniquely designed acrylate monomer (A3DA) featuring a benzene moiety with a dodecyl terminal chain. The PDLC films were fabricated by the photopolymerization of mono- and di-functional acrylate monomers (19.2 wt%) mixed in a nematic liquid crystal E7 (80 wt%). The PDLC film with A3DA exhibited an abrupt decline of driving voltage by 75% (0.55 V/μm) with a high contrast ratio (16.82) while maintaining other electro–optical properties almost the same as the reference cell. The response time was adjusted to satisfactory by tuning the monomer concentration while maintaining the voltage significantly low (3 ms for a voltage of 0.98 V/μm). Confocal laser scanning microscopy confirmed the polyhedral foam texture morphology with an average mesh size of approximately 2.6 μm, which is less in comparison with the mesh size of reference PDLC (3.4 μm), yet the A3DA-PDLC showed low switching voltage. Thus, the promoted electro–optical properties are believed to be originated from the unique polymer networks formed by A3DA and its weak anchoring behavior on LCs. The present system with such a huge reduction in driving voltage and enhanced electro–optical performance opens up an excellent way for abundant perspective applications of PDLCs.

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“…The main focus of these studies was to clarify the role of nanoparticle size, core material and functional coating on the thermal, chiral, [11,12] optical and electro-optic properties mainly of nematic liquid crystals, but also of T-shaped amphiphilic [13] and bent core liquid crystals. [14] Several other research labs also investigate dispersions of colloidal particles and nanoparticles in liquid crystal phases including studies on ferroelectric nanoparticles, [15][16][17][18][19] chemically modified nanoclay particles, [20][21][22][23] and carbon nanotubes, [24][25][26][27][28][29][30] among others.…”

Section: Introductionmentioning

confidence: 98%

Alignment and electrooptic effects in nanoparticle-doped nematic liquid crystals

Kinkead

Urbanski

et al. 2010

SPIE Proceedings

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It is well known that doping nematic liquid crystals with nanoparticles can alter the electrooptic response of the nematic host as well as the alignment of the liquid crystal molecules on various substrates. In addition, nanoparticles dispersed in a nematic matrix often induce defects and defect patterns justifying the necessity for more detailed optical and electrooptic investigations including effects of nanoparticle size, coating, concentration and core material. We studied the local alignment of nematic LC molecules in such dispersions by means of fluorescence confocal polarizing microscopy. The results of two-and three-dimensional imaging indicate that frequently observed birefringent stripes, which are induced by the presence of metal nanoparticles and semiconductor quantum dots, correspond to twist disclinations located at the LC/substrate interface. The luminescence of dispersed quantum dots shows that the ends of these disclination threads are pinned to conglomerates of nanoparticles that stabilize these line defects. By performing (x,z)-scans, it can be shown that the defects are not walls extending through the entire cell gap, but lines that are located at the substrate surface. Our experiments also confirm, as hypothesized before, that the nanoparticles preferably reside at the liquid crystal/substrate interfaces. Finally, detailed electrooptic investigations also revealed that a contrast inversion observed earlier is initiated by a change from parallel to homeotropic anchoring, thereby causing an instability, which in turn leads to the appearance of convection rolls (Kapustin-Williams domains). This electrohydrodynamic instability is likely an example for the behavior of (+, -) systems predicted by de Gennes, which was only recently experimentally observed for the first time.

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Memory effect of polymer dispersed liquid crystal by hybridization with nanoclay

Cited by 8 publications

References 20 publications

Surface Modification of Nanoclays by Plasma Polymerization of Ethylene

Surface Modification of Nanoclays by Plasma Polymerization of Ethylene

High-Performance Polymer Dispersed Liquid Crystal Enabled by Uniquely Designed Acrylate Monomer

Alignment and electrooptic effects in nanoparticle-doped nematic liquid crystals

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