Amorphous—Liquid-Crystalline Side-Chain AB Block Copolymers

Adams, J.LaMonte; Gronski, W.

doi:10.1021/bk-1990-0435.ch013

Cited by 16 publications

(9 citation statements)

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“…In addition to the polymer-analogous method of synthesizing side group LC−coil block copolymers, − living polymerization of mesogenic monomers by various mechanisms has been widely used. Generally these living methods give modest molecular weights due to the difficulties of monomer purification.…”

Section: Introductionmentioning

confidence: 99%

Molecular Design, Synthesis, and Characterization of Liquid Crystal−Coil Diblock Copolymers with Azobenzene Side Groups

Mao¹,

Wang²,

Clingman³

et al. 1997

Macromolecules

226

294

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The synthesis and characterization of a family of well-defined liquid crystal−coil (LC−coil) diblock copolymers have been carried out. The block copolymers in this study have been designed to have nearly identical molecular weight azobenzene-containing LC blocks in order to eliminate possible variations in LC behavior caused by the differences in the LC block molecular weight. Quantitative hydroboration chemistry was used to convert the pendent double bonds of an isoprene block to hydroxyl groups to which the mesogenic groups were attached via acid chloride coupling. The LC homopolymer and the block copolymers (LC volume fraction from f LC = 0.82 to f LC = 0.20) all exhibited smectic mesophases with similar clearing transition temperatures. The clearing transition enthalpies strongly depend on the block composition ratio and decrease as the LC block volume fraction decreases. Solvent-casting of a lamellar LC−coil copolymer (SICN5-66/60) resulted in an oriented bulk film in which both the axes of the mesogenic groups and the lamellar interfaces lie parallel to the film surfaces. A LC cylinder morphology was observed with a f LC = 0.22 LC-containing block (SICN5-176/55) using TEM and confirmed by SAXS measurements. This is the first observation with the LC block in a cylinder microdomain. Other morphologies (bicontinuous, LC sphere) were observed by TEM while retaining the smectic order in the LC microphase.

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Section: Introductionmentioning

confidence: 99%

Molecular Design, Synthesis, and Characterization of Liquid Crystal−Coil Diblock Copolymers with Azobenzene Side Groups

Mao¹,

Wang²,

Clingman³

et al. 1997

Macromolecules

226

294

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“…In recent years, several groups have consolidated the ordering phenomena of block copolymers and liquid crystals by creating a new class of materials, liquid crystalline block copolymers. − The impetus has been not only to understand the interplay between order but also to employ the block copolymer interface to stabilize LC phases, namely the S C * phase, to realize bistable ferroelectric switching. − The glassy block forms a continuous matrix enabling free-standing LC films. Such self-supporting, switchable materials have great potential for display applications or electrooptic memory storage devices.…”

Section: Introductionmentioning

confidence: 99%

A SAXS Study of Microstructure Ordering Transitions in Liquid Crystalline Side-Chain Diblock Copolymers

Anthamatten

Hammond

1999

Macromolecules

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For a series of side-chain liquid crystalline (LC) diblock copolymers we have investigated the overlap of liquid crystalline and morphological phase behaviors. LC thermal transitions were identified using polarized optical microscopy combined with calorimetry. Order−disorder and order−order transitions (ODT's and OOT's) associated with the diblock copolymer morphology were located using elevated temperature SAXS and TEM microscopy. At low LC fractions, samples exhibit pure lamellar morphologies, and the ODT temperature, T ODT, is correlated to the LC isotropization temperature, T iso. For samples with higher LC volume fractions, morphologies were found to have curvature at room temperatures, and the T ODT was found to exceed T iso. In one sample, we observed a thermoreversible OOT transition between a predominately lamellar morphology with cylindrical defects and a completely lamellar morphology. The loss of curvature occurs upon heating, which is unusual for a block copolymer OOT and may be related to the conformational asymmetry of the diblocks. Finally, the sample with the longest LC block has a morphology of hexagonally close-packed PS cylinders which remains ordered well above isotropization. Discussion includes aspects on the coexistence of morphology and LC superstructure. Our analysis indicates that the length of the LC block and the related block copolymer morphology are key parameters to controlling both mesophase order and morphology.

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“…16. Here, the orientation of the smectic layers is perpendicular to the orientation of the lamellae as already described previously by Adams et al [42,43] for two different types of diblock copolymers and later by Watanabe et al for diblock copolymers [35] (all for samples exhibiting a lamellar morphology (see Fig. The outer reflections indicate the orientation of the smectic layers, the mesogen orientation is perpendicular to the layer orientation [52].…”

Section: Interaction Between Morphology and Lc Phase Structurementioning

confidence: 79%

“…Other authors report a substantial drop in the A Hcl of the block copolymers compared to the homopolymers which is attributed to a rather extended interface [35,39,40,[42][43][44]. However, there are no experimental results provided concerning the dimensions of the interfaces.…”

Section: Interaction Between Morphology and Lc Phase Structurementioning

confidence: 98%

“…The first synthesis of a LC side group block copolymer overall was successful carried out by Adams and Gronski [41] in 1989 using polymeranalogous reactions at a preformed block copolymer. The first synthesis of a LC side group block copolymer overall was successful carried out by Adams and Gronski [41] in 1989 using polymeranalogous reactions at a preformed block copolymer.…”

Section: Monomermentioning

confidence: 99%

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Liquid crystalline block and graft copolymers

Fischer

Poser

1996

Acta Polymerica

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FRG +tSince the first reports on the combination of liquid crystalline polymers in block (1985) and graft (1986) copolymers with amorphous and semi-crystalline polymers, the scientific interest has been focused on understanding how the size and type of the mesophase displayed by the liquid crystalline part(s) affects the LC + isotropic transition and the order in the LC domains themselves with respect to the morphology displayed. An overview of the work that has been done so far will be given, as well as a closer discussion of the interaction between morphology and LC phase behavior as evaluated on a large number of very well defined LC side group block copolymers. Furthermore, applications and results of mechanical and optical investigations are discussed.

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Amorphous—Liquid-Crystalline Side-Chain AB Block Copolymers

Cited by 16 publications

References 0 publications

Molecular Design, Synthesis, and Characterization of Liquid Crystal−Coil Diblock Copolymers with Azobenzene Side Groups

Molecular Design, Synthesis, and Characterization of Liquid Crystal−Coil Diblock Copolymers with Azobenzene Side Groups

A SAXS Study of Microstructure Ordering Transitions in Liquid Crystalline Side-Chain Diblock Copolymers

Liquid crystalline block and graft copolymers

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