Influence of film thickness on the reorientation structure of photoalignable liquid crystalline polymer films

Taniguchi, Yusuke; Kondo, Mizuho; Haruyama, Yuichi; Matsui, Shinji; Kawatsuki, Nobuhiro

doi:10.1016/j.polymer.2016.03.025

Cited by 5 publications

(3 citation statements)

References 19 publications

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“…The structure-property relationships of polymeric materials become more complex with decreasing material thickness due to the influence of the polymer-substrate and polymer-air interfaces when there is little bulk material, which usually occurs for thin films with thicknesses of less than 100 nm. [29] To date, a number of characterization techniques have been employed to study the molecular orientation in polymer thin films including Fourier transform infrared spectroscopy, [30,31] near edge X-ray absorption fine structure spectroscopy, [32,33] and variable angle spectroscopic ellipsometry (VASE). [34,35] VASE is a powerful technique that measures the change in the polarization of light interacting with the thin film sample in order to elucidate the anisotropic optical properties and thickness of a film and has enjoyed great success as a characterization technique for semiconductors, [36] liquid crystals, [37] and has emerged as a key analytical technique in polymer thin films.…”

Section: Introductionmentioning

confidence: 99%

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Kushner

Kusoglu

Podraza

et al. 2019

Adv Funct Materials

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The effects of film thickness and substrate composition on the ionomer structure in porous electrodes is critical in understanding pathways towards developing higher performance electrochemical devices, including fuel cells and batteries. Insights are gained into the molecular and nanostructural orientation dependence for thin Nafion films (12 to 300 nm thick) on gold, platinum, and SiO 2 model substrates. Molecular orientation is determined from the birefringence measured using spectroscopic ellipsometry, while the nanostructural orientation of the ionic domains was measured using grazing-incidence smallangle X-ray scattering. Density functional theory calculations for the molecular polarizability of the Nafion backbone and side chain show complimentary contributions to the measured birefringence values for the material. Nafion films prepared on SiO 2 substrates exhibit a nearly isotropic molecular and nanostructural orientation. Films on gold and platinum display parallel backbone orientations, relative to the substrate, with decreasing film thickness. However, a birefringence transition towards molecular isotropy is observed for 30 nm thick films on Au and Pt; while the ionic nanostructured domains continuously align parallel to the substrate. This apparent isotropic molecular orientation with increasing domain orientation highlights the difference between the backbone and side chain orientation, a key finding for elucidating transport in confined films at the interfaces.

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Section: Introductionmentioning

confidence: 99%

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Kushner

Kusoglu

Podraza

et al. 2019

Adv Funct Materials

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“…After thermal annealing, their UV-vis absorption and CD signals were decreased (Figure 3b), probably due to the partial conversion of in-plane orientation to out-of-plane orientation of mesogenic units during the thermal annealing process. [23] Because of the small doping amount of PTZ, its absorption and induced Cotton effect peaks were not detected at 425 nm. It should be noticed that R-PB2 had a positive CD signal at 626 nm from the selective reflection of chiral nematic LC.…”

Section: Resultsmentioning

confidence: 99%

Strong Circularly Polarized Luminescence Promoted by AIE‐active Chiral Co‐assemblies in Liquid Crystal Polymer Films

Li,

Luo,

Liu

et al. 2024

Chemistry A European J

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Recently, extensive works have focused on increasing the dissymmetry factors (glum) of various circularly polarized luminescence (CPL) materials, which is one of the most important factors for future applications of CPL. Herein, we designed a chiral co‐assembled liquid crystal polymer (LCP) PTZ@R/S‐PB2, which was prepared by chiral binary co‐polymer (R/S‐PB2) doped with achiral phenothiazine derivation dye (PTZ). For comparison, ternary co‐polymerized LCP (R/S‐PT) was synthesized by co‐polymerizing with mesogenic monomer, chiral monomer and emissive monomer. Both PTZ@R/S‐PB2 and R/S‐PT showed aggregation‐induced emission (AIE) properties. Interestingly, the CPL signals of both PTZ@R/S‐PB2 and R/S‐PT were reversed and amplified after thermal annealing treatment. The |glum| values of the co‐assembled PTZ@R/S‐PB2 were up to 0.13 at a 32 nm thickness, which was 5.4 times that of R/S‐PT (|glum| = 0.024). This is due to PTZ@R/S‐PB2 could form more orderly chiral co‐assembly structures. Noticeably, increasing the LCP film thickness could further improve the glum value, and the maximum glum of PTZ@R/S‐PB2 could be enhanced to 0.91 at a 220 nm thickness.

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“…The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.7b00417. The writing dynamics of the photoalignment films with different thickness (Figure S1); ordering comparison of the photoalignment films induced by 1 J/cm 2 and 3 J/cm 2 365 nm LPUV at different relative humidities (Figure S2); film alignment before and after LPUV excitation with increasing humidity from 20%RH to 80%RH (Figure S3); aligned SD1 observed under depolarized optical microscope (Figure S4) (PDF) …”

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confidence: 99%

Exotic Property of Azobenzenesulfonic Photoalignment Material Based on Relative Humidity

Shi

Zhao

et al. 2017

Langmuir

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Azobenzene photoalignment materials are highly effective for liquid crystal alignment with high sensitivity and rewritability. A strong relationship between relative humidity and the alignment quality of a thin layer of azobenzenesulfonic dye has been investigated, where the photoinduced phase retardation, order parameter, and anchoring strength of the alignment layer are influenced dramatically by relative humidity. Our results provide fabrication guidance for the photoalignment process in both display and photonic applications. In addition, an exotic substantial ordering enhancement is observed by increasing the relative humidity without further light illumination, where the self-assembly of the photoaligned material incorporated with water molecules is the underlying reason for the enhanced high ordering (S > 0.8). Based on X-ray diffraction and depolarized optical microscopy observation, together with the photoalignment quality, a semicrystalline structure of the humidified azobenzenesulfonic material is proposed. The transition from amorphous solid at low relative humidity to semicrystal at high relative humidity provides a new perspective of understanding the hydrophilic photoalignment materials.

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Influence of film thickness on the reorientation structure of photoalignable liquid crystalline polymer films

Cited by 5 publications

References 19 publications

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Substrate‐Dependent Molecular and Nanostructural Orientation of Nafion Thin Films

Strong Circularly Polarized Luminescence Promoted by AIE‐active Chiral Co‐assemblies in Liquid Crystal Polymer Films

Exotic Property of Azobenzenesulfonic Photoalignment Material Based on Relative Humidity

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