Near-surface alignment of polymers in rubbed films

Toney, Michael F.; Russell, Thomas P.; Logan, J. A.; Kikuchi, Hirotsugu; Sands, James M.; Kumar, Sanat K.

doi:10.1038/374709a0

Cited by 373 publications

(296 citation statements)

References 20 publications

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“…18,19 The rubbing process induces orientational order in polymer chains, and the relaxation of this order provides a sensitive probe of the relaxation process of the surface chains. 18,20 Although NEXAFS has excellent molecular sensitivity, it lacks a high enough signal-to-noise ratio to do rapid kinetic measurements of relaxation dynamics.…”

Section: Introductionmentioning

confidence: 99%

Surface Dynamics in Rubbed Polymer Thin Films Probed with Optical Birefringence Measurements

et al. 2000

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Measurements of the optical birefringence were used to probe the relaxation of rubbed ultrathin polystyrene (PS) films on glass substrates. It was found that the glass transition temperature, T g, of the films dropped by 15-20 K as the film thickness decreased from 10 µm to 5.8 nm. Experiments on thick films (∼10 µm) revealed that molecules closer to the polymer-air interface relax more quickly than molecules farther from the interface. These results are explained in the context of past experimental studies of thermal properties of similar ultrathin polymer films.

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Section: Introductionmentioning

confidence: 99%

Surface Dynamics in Rubbed Polymer Thin Films Probed with Optical Birefringence Measurements

et al. 2000

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“…This means that the photo-dimerized side chains do not have well-defined orientation in the film and thus may only give a very weak azimuthal anchoring force to LC molecules. It was also reported [3] that the groove formed on a rubbed polymer surface did not become the dominant azimuthal LC alignment force. Therefore, these two mechanisms may not be responsible for the reorientation phenomenon shown in Fig.2.…”

Section: Resultsmentioning

confidence: 99%

“…Papers on polymer buffing predicated that the oriented polymer chains induced LC alignments by the orientational epitaxy. [1][2][3][4] On the other hand, a photo-alignment method has attracted a good deal of theoretical and experimental attentions. This is not only due to the improvement of the production yield of LCDs, but also due to the fundamentals of LC alignment physics.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Photo-Induced Liquid Crystal Alignment on Poly(vinyl cinnamate) Surface.

Shinmoto

Nakamura

et al. 1997

J. Photopol. Sci. Technol.

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The photopolymer material of polyvinyl cinnamate) (PVCi) has been used to align liquid crystal molecules using linearly-polarized UV light, and the LC alignment mechanism on the films has been investigated. Comparing the LC alignment on rubbed PVCi films with that on UV-exposed PVCi film, it is shown that the side chains of PVCi molecules strongly interact with the LC molecules on the PVCi films and thus the alignment mechanism on linearly-polarized UV-exposed PVCi films is due to the anisotropic van der Waals interaction between LC molecules and optically-anisotropic PVCi films arising from the photo-induced anisotropic side chain distribution on the films. We also study the thermal stability of UVexposed PVCi films, and clarify the improvement of the thermal stability with increasing UV exposure energy.

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“…This is beautifully illustrated by orienting molecular chains at the surface by simply rubbing the surface of a vitrified ͑or crystalline͒ polymer with a soft material. [1][2][3] The polymer molecular segments at the film/substrate interface, in contrast to the bulk, experience stronger dispersive forces from the substrate molecules that are more polarizable and/or packed denser. This additional interaction may be modeled as the ''tail end'' of a van der Waals long-range interaction emanating from the substrate.…”

mentioning

confidence: 99%

Solid-like dynamics in ultrathin films of polymeric liquids

Singh¹,

Saraf²,

Martin³

2003

Applied Physics Letters

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In this letter, we demonstrate that, at mesoscales, nonferroelectric liquid films of poly(dimethyl siloxane) exhibit significant electrostriction not present in the corresponding bulk state. Remarkably, the observed electrostrictive effect has a response time <20 μs in contrast to >5 ms recorded in conventional bulk (ferroelectric) polymers. The emergence of this fast electrostrictive strain in thin films is explained in terms of the amalgamation of two contrasting dynamic features—the influence of a highly mobile, viscous layer (at the air/film interface) on the less-mobile, but fast responding, solid-like layer at the film/substrate interface. The effect is observed for thickness below 200 nm.

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Near-surface alignment of polymers in rubbed films

Cited by 373 publications

References 20 publications

Surface Dynamics in Rubbed Polymer Thin Films Probed with Optical Birefringence Measurements

Surface Dynamics in Rubbed Polymer Thin Films Probed with Optical Birefringence Measurements

Mechanism of Photo-Induced Liquid Crystal Alignment on Poly(vinyl cinnamate) Surface.

Solid-like dynamics in ultrathin films of polymeric liquids

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