Nanocomposites of Hairy‐Rod Macromolecules: Concepts, Constructs, and Materials

Wegner, Gerhard

doi:10.1002/macp.200290081

Cited by 101 publications

(91 citation statements)

References 70 publications

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“…By examining Langmuir films and LB or LS films, it is possible to obtain information about the mechanical, electrical, optical, and chemical properties of oriented molecules at the interface as well as information about structural properties, such as the size and shape of molecules. [5][6][7][8][9][10][11] Poly(ethylene glycol) (PEG) and poly(ethylene oxide) (PEO) are widely studied polymers [12][13][14] with applications in a variety of technological fields such as drug delivery, 15,16 batteries, 17 and biotechnology. 18 Even though PEG and PEO are completely water-soluble at room temperature, PEO of sufficient molar mass can still form Langmuir monolayers at the A/W interface.…”

Section: Introductionmentioning

confidence: 99%

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Lee

Deng

et al. 2007

Macromolecules

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Combining two non-surface-active building blocks, oligomeric poly(ethylene glycol) (PEG) and a completely hydrophobic polyhedral oligomeric silsesquioxane (POSS) cage, creates amphiphilic telechelic polymers (POSS-PEG-POSS), which exhibit surface activity at the air/water (A/W) interface. POSS moieties serve as the hydrophobic groups for hydrophilic PEG chains of different number-average molar mass (1, 2, 3.4, 8, and 10 kg mol -1 ). For short PEG chains (1, 2, and 3.4 kg mol -1 ), insoluble monolayers form, whereas POSS end groups were not sufficiently hydrophobic to keep higher molar mass hydrophilic PEG blocks (8 and 10 kg mol -1 ) at the A/W interface. Thermodynamic analyses of the 1, 2, and 3.4 kg mol -1 POSS-PEG-POSS via surface pressurearea per monomer isotherms indicate that the POSS end groups reside at the A/W interface and that the PEG chains are squeezed into the subphase with increasing surface pressure. This conclusion is supported by X-ray reflectivity studies on Y-type Langmuir-Blodgett multilayer films which reveal a double-layer structure with a double-layer spacing of about 3.52 nm. These findings provide a strategy for producing new surface active species from non-surface-active precursors.

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Section: Introductionmentioning

confidence: 99%

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Lee

Deng

et al. 2007

Macromolecules

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“…in photooptics), rigid two-dimensional oligomers are relatively unexplored. [4][5][6][7][8] However, this approach has numerous potential benefits as these structures are molecularly defined and well characterizable, allow introduction of functionality at the rim as well as above and below the molecular plane, and can be obtained in different sizes (Figure 1). [9] Although some defined rigid 2D structures have already been described, an approach towards objects in a size range of the inorganic counterparts can be rarely found.…”

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Molecularly Defined Shape‐Persistent 2D Oligomers: The Covalent‐Template Approach to Molecular Spoked Wheels

et al. 2007

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“…Hairy-rod polymers 1 are one important example and, among those with -conjugated backbones 2 ͓e.g., poly͑p-phenylenes͒, 3 polyfluorenes ͑PFs͒, 4 and ladder derivatives 5 ͔, the nature of the main chain conformation and interchain packing are crucial factors in ultimately determining optical and transport properties. The structural characteristics at larger length scales are equally as important, and this has been the main emphasis in a number of recent studies.…”

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Influence of star-like iridium complexes in the graphoepitaxy of polyfluorene thin films

et al. 2006

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We report on the impact on the equatorial and meridional orientation in hairy-rod poly͓9,9-bis͑2-ethylhexyl͒-fluorene-2,7-diyl͔ thin films when blended with tris-cyclometalated oligo-fluorenylpyridine iridium͑III͒ complex. The presence of this transition-metal complex does not alter the underlying helical motif of the polymer chain or the hexagonal unit-cell intermolecular packing. However, systematic changes in the resulting texture patterning of the crystallites are observed. Crystallites with two preferred a-b orientations, so called type I and II and differing by 30 degrees, are superimposed on an isotropic background that is designated as type III. The extent of meridional alignment for all three is found to be similar. DOI: 10.1103/PhysRevB.74.214203 PACS number͑s͒: 61.10.Ϫi, 82.35.Lr, 81.07.Bc, 81.16.Dn Manipulating and controlling the molecular-level structure of functionalized polymers in bulk and at surfaces is central to the science and applications of these materials. Hairy-rod polymers 1 are one important example and, among those with -conjugated backbones 2 ͓e.g., poly͑p-phenylenes͒, 3 polyfluorenes ͑PFs͒, 4 and ladder derivatives 5 ͔, the nature of the main chain conformation and interchain packing are crucial factors in ultimately determining optical and transport properties. The structural characteristics at larger length scales are equally as important, and this has been the main emphasis in a number of recent studies. A classic example is the poly͑3-alkylthiophene͒ family 6 in which the extent of structural isomorphism or regioregularity strongly affects the internal crystallite structure 7 and the subsequent structural evolution when intercalated or doped. 8 Among PFs, important blue emitting polymers, even small differences in the molecular structure can influence the charge carrier mobility 9 and fluorescence. 10 Poly͓9,9-bis͑2-ethylhexyl͒-9H-fluorene-2,7-diyl͔ ͑or PF2/6͒ ͑Ref. 11͒ is a well-known helical PF polymer functionalized with branched alkyl side chains. PF2/6's optical properties 12 are relatively insensitive to either changes in the molecular weight ͑MW͒ or processing history, and so it is an excellent model system for studies of intermolecular self-organization. 13 However, this intermolecular assembly is affected by changes in the MW ͑or number averaged MW, M n ͒. In PF2/6, there is a threshold MW, M n * , at which there is a crossover in the phase behavior. 14 Low MW samples exhibit only a single nematic liquid crystal phase ͑n-LC and M n Ͻ M n * ͒ while high MW samples ͑M n Ͼ M n * ͒ include a distinctive thermotropic transition between this n-LC phase and a hexagonal crystalline phase. This threshold MW also marks sharp changes in both meridional alignment 15 and surface morphology. 16 In aligned films on rubbed polyimide ͑PI͒, the rigid PF2/6 lies on the substrate with the helical axes pointing along the rubbing direction ͑denoted z here͒. Consequently, meridional alignment leads to a large absorption and dispersion of the refractive index in the ͑xy0͒ plane along the z...

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Nanocomposites of Hairy‐Rod Macromolecules: Concepts, Constructs, and Materials

Cited by 101 publications

References 70 publications

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Telechelic Poly(ethylene glycol)−POSS Amphiphiles at the Air/Water Interface

Molecularly Defined Shape‐Persistent 2D Oligomers: The Covalent‐Template Approach to Molecular Spoked Wheels

Influence of star-like iridium complexes in the graphoepitaxy of polyfluorene thin films

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