Origin of orientation phenomena observed in layered Langmuir-Blodgett structures of hairy-rod polymers

Schwiegk, S.; Vahlenkamp, Thomas; Xu, Yong; Wegner, Gerhard

doi:10.1021/ma00035a034

Cited by 147 publications

(146 citation statements)

References 16 publications

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“…This lateral orientation is due to monolayer How during the dipping process. 44 Only two crown ether phthalocyanine derivatives have been applied so far in LB films, i.e. an octa(15-crown-5)-lutetium bisphthalocyanine45 and the dihydroxysilicon derivative of the previously mentioned liquid crystalline Pc shown in Fig.…”

Section: Chem Commun 1996mentioning

confidence: 99%

Functional supramolecular materials: self-assembly of phthalocyanines and porphyrazines

Nostrum¹,

Nolte²

1996

Chem. Commun.

236

108

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Phthalocyanines and related compounds can self-assemble into columnar structures in the solid and liquid crystalline state, in Langmuir-Blodgett films and in solution. This paper presents an overview of supramolecular architectures that have been constructed using several phthalocyanine and porphyrazine building blocks substituted with hydro carbon chains and/or crown ether units. The most interesting applications of such highly organized columnar assemblies are in the field of one-dimensional transport of energy, charge and ions.

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Section: Chem Commun 1996mentioning

confidence: 99%

Functional supramolecular materials: self-assembly of phthalocyanines and porphyrazines

Nostrum¹,

Nolte²

1996

Chem. Commun.

236

108

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“…[28][29][30][31][32][33] The interest in LMs of ␣-helical polypeptides also arises from the fact that many of them can be transferred onto solid substrates as multilayers using the Langmuir-Blodgett ͑LB͒ technique. In recent years, various ␣-helical poly͑L-glutamates͒ have been studied both as LMs on water 23,25,26,[34][35][36][37] and as LB films on solid substrates. 26,34,[37][38][39][40][41][42][43][44][45][46][47][48][49] In most of these studies the primary objective has been to achieve good-quality LB films that possess technologically important properties, 50 such as lateral homogeneity, 23,45 thermal 37,44,47,49 and mechanical 45,48 stability, low defect density, 38,45 and optical anisotropy; 38,39,42 in addition, potential applications, 50,51 for example, as optical wave guides, 38,…”

Section: Introductionmentioning

confidence: 99%

Structure of poly(γ-benzyl-L-glutamate) monolayers at the gas–water interface: A Brewster angle microscopy and x-ray scattering study

Fukuto

Heilmann

Pershan

et al. 1999

The Journal of Chemical Physics

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. 1999. Structure of poly(\(\gamma\)-benzyl-L-glutamate) monolayers at the gas-water interface: A Brewster angle microscopy and x-ray scattering study. Journal of Chemical Physics 111 (21) This paper reports Brewster angle microscopy ͑BAM͒, x-ray specular reflectivity ͑XR͒, grazing incidence diffraction ͑GID͒ and off-specular diffuse scattering ͑XOSDS͒ measurements of Langmuir monolayers formed on water by both mono-and polydisperse samples of ␣-helical poly͑␥-benzyl L-glutamate͒ ͑PBLG͒ as a function of area/monomer A. The microscopic behavior does not exhibit any discernible effects due to differing dispersity. At low surface densities ͑A Ͼϳ21 Å 2 /monomer, surface pressure ⌸ϭ0͒, BAM images reveal partial surface coverage by solidlike monolayer islands. GID measurements show an interhelix peak corresponding to a local parallel alignment of rodlike PBLG molecules, indicating their tendency to aggregate laterally without external pressure. Compression to AϽ21 Å 2 /monomer first leads to full and uniform surface coverage by the monolayer, followed by a steep rise in ⌸ that is accompanied by a decrease in the interhelix distance. Further compression results in a plateau of constant ⌸ in the ⌸-A isotherm ͑ϳ11.5ϽAϽϳ18.5 Å 2 /monomer, ⌸ϳ9 dyn/cm͒, which has previously been attributed to a first-order monolayer-bilayer transition. The interfacial electron density profiles determined by the XR measurements on both sides of the coexistence plateau provide direct evidence for this transition. On the basis of x-ray scattering results, the film on the high-density side of the plateau is shown to consist of a newly formed incomplete and incommensurate second layer that sits on top of and has lower average density than a homogeneous first layer. GID measurements indicate that the second layer can be characterized by larger interhelix d-spacing than the first layer, while XOSDS measurements on the bilayer suggest that the second layer is microscopically inhomogeneous. For both mono-and bilayers, the analysis of observed GID peak widths indicates that the extent of lateral positional correlations between parallel PBLG rods ranges from a few to no more than ϳ15 interhelix distances, implying short-range order.

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“…Both for polyphthalocyanine and polyglutamate LB films , their main chains align along the dipping direction [13,14,15], which fact was away from rubbing or ctrine direction _ The angular dependence of the polarized light absorption of the polyphthalocyanine on the PTFE rubbed surface and on the PMMA stripe pattern is shown in Fig.4 and Fig.5, respectively. Polyphthalocyanine has a transition moment perpendicular to the polymer main chain direction.…”

Section: Resultsmentioning

confidence: 99%

“…Polyphthalocyanine and polyglutamate were synthesized and were characterized as published [13,14,15]. High molecular weight polymethylmethacrylate (PMMA) (molecular weight:9.5x 105) was purchased from KTI Chemicals.…”

Section: Methodsmentioning

confidence: 99%

Relation between the orientations of polymer alignment layer and liquid crystal molecules.

Suzuki

1995

J. Photopol. Sci. Technol.

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Effects of surface topology and polymer molecule orientation on the liquid crystal(LC) orientation have been examined using photolithography and Langmuir-Blodgett techniques. It has been clarified that the polymer orientation in the alignment layer affects more effectively than surface topology. UV/Visible spectroscopy has shown that the elevation angle of the polymer main chain in the alignment layer from the substrate plane does not correspond to the LC pretilt angle, which suggests that long alkyl side chains produce high pretilt angle for some polyimides. (.Introduction Liquid crystal(LC) materials are successfully used in display devices. Controlling the liquid crystal molecules orientation is quite important for producing good quality LC diveces(LCD). A rubbing technique is commonly used to achieve an LC alignment. The substrate surface is rubbed with a cloth or other polishing material prior to introducing the LC material and the director of the liquid crystals aligns along this rubbing direction. The pretilt angle, which is defined as the angle between the LC director and the substrate surface plane, is also an important factor for LCD production. The mechanism how liquid crystal molecules are aligned on the rubbed surface has not been fully understood, yet. Both surface topology [1,2] and molecular orientation [3,4,5,6] are discussed to affect the alignment of LCs. In these studies, Langmuir-Blodgett(LB) technique is effectively used to examine the relation between the orientations of the alignment polymer layer and LC molecules [4,5,6]. Factors affecting the pretilt angle are also studied extensivelly [7,8,9]. Long alkyl chains seem to influence the pretilt angle. Another study shows the asymmetric triangles in polymer backbone generated through the rubbing process plays an important role for giving a pretilt angle [10].In this paper, I report how LC molecules align 1)on PTFE rubbed surfaces [1 1 ], 2) on fine stripe patterns, 3)on highly anisotropic polymer LB films, 4)on the surfaces where fine patterns are fabricated in highly anisotropic polymer LB films such that the groove/ridge direction is oblique to the polymer's main chain direction, 5)on surfaces where highly anisotropic polymer LB films are obliquely deposited with regard to the direction of the fine patterns [12]. I also

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Origin of orientation phenomena observed in layered Langmuir-Blodgett structures of hairy-rod polymers

Cited by 147 publications

References 16 publications

Functional supramolecular materials: self-assembly of phthalocyanines and porphyrazines

Functional supramolecular materials: self-assembly of phthalocyanines and porphyrazines

Structure of poly(γ-benzyl-L-glutamate) monolayers at the gas–water interface: A Brewster angle microscopy and x-ray scattering study

Relation between the orientations of polymer alignment layer and liquid crystal molecules.

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