Synthesis of Side-Chain Liquid Crystalline Homopolymers and Block Copolymers with Well-Defined Structures by Living Anionic Polymerization and Their Thermotropic Phase Behavior

Yamada, Masayuki; Hirao, Akira; Nakahama, Seiichi; Iguchi, Tsukasa; Watanabe, Junji

doi:10.1021/ma00105a006

Cited by 117 publications

(155 citation statements)

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“…An essential breakthrough can be performed by controlled polymerization such as group-transfer polymerization and living polymerization, since these permit the control of several parameters given above because of the synthesis of welldefined structures. 3 -8 In the previous paper, 9 we succeeded to prepare a series of side-chain LC polymers with a well-controlled structure, by living anionic polymerization. Polymerization was attempted at an elevated temperature of -40oC since precipitation occurs during the polymerization at a usually applied temperature of -78oC.…”

mentioning

confidence: 99%

Side-Chain Liquid Crystal Block Copolymers with Well-Defined Structures Prepared by Living Anionic Polymerization I. Thermotropic Phase Behavior and Structures of Liquid Crystal Segment in Lamellar Type of Microphase Domain

Yamada

Iguchi

Hirao

et al. 1998

Polym J

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ABSTRACT:We have synthesized the A-B block copolymer with polystyrene as A segment and side-chain liquid crystal (LC) polymer as B segment by a sequential living polymerization. The copolymers were successfully prepared with quantitative yields, possessing the predictable M. values, compositions, and narrow molecular weight distributions. The thermotropic phase behavior and structures were examined for nine copolymers with the fraction of segments around 50 w% and with the various molecular weights ranged from 8000 to 34000. All the polymers exhibit the well-defined lamellar type of segregation and the side-chain LC segment in the microdomain forms crystal, smectic A (SA) and isotropic phases with increasing temperature. The lamellar segregation is maintained over the whole temperature region from crystal to isotropic phases, and the crystal and SA structures are formed with a preferential orientation to the microdomain interface such that the mesogenic side-chain groups lie parallel to the interface. The lamellar thickness depends on the SA temperatures. It gradually decreases from the value of crystal phase to that of isotropic phase. The reduction is around 2(}--25%, which can be explained in terms of the change in main-chain conformation of the LC block.KEY WORDS Block Copolymer I Liquid Crystal I Smectic Phase I Microphase Separation I Lamellar Structure I Living Polymerization I Liquid crystal (LC) polymers with mesogenic groups in the side chains (side-chain LC polymers) have been extensively studied. 1 • 2 More recently, the research interests have focused on a role of the main-chain backbone on liquid crystal structures and properties. The various parameters with respect to the main-chain backbone such as a degree of polymerization, molecular weight distribution, tacticity, and monomer unit distribution in copolymers can be considered. An essential breakthrough can be performed by controlled polymerization such as group-transfer polymerization and living polymerization, since these permit the control of several parameters given above because of the synthesis of welldefined structures. 3 -8 In the previous paper, 9 we succeeded to prepare a series of side-chain LC polymers with a well-controlled structure, by living anionic polymerization. Polymerization was attempted at an elevated temperature of -40oC since precipitation occurs during the polymerization at a usually applied temperature of -78oC. Irrespective of this unusual condition for the living anionic polymerization, the polymers were obtained with unimodal distribution of less than 1, 1 when the molecular weights are less than 12000. Their thermotropic phase behavior and structures were examined as a function of the molecular weight.

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confidence: 99%

Side-Chain Liquid Crystal Block Copolymers with Well-Defined Structures Prepared by Living Anionic Polymerization I. Thermotropic Phase Behavior and Structures of Liquid Crystal Segment in Lamellar Type of Microphase Domain

Yamada

Iguchi

Hirao

et al. 1998

Polym J

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“…Examples of liquid crystalline block copolymer are recently reported. 10 In this case, there is the possibility for the two components to micro-phase separate.…”

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Synthesis of Liquid Crystalline Oligomeric Polyoxetanes with Two Mesogenic Groups in the Repeating Unit

Kawakami

Kato

1997

Polym J

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“…Particularly, in the case of side chain LC block polymers, the interfaces between blocks are usually formed parallel to the oriented side-chain mesogens. 110 Therefore, the orientation of MPS structures in LC block copolymers strongly 118,119 independently demonstrated the in-plane photoalignment of MPS cylinder morphologies in azobenzenecontaining block copolymer films by irradiation with LPL. In the years since, considerable data have been accumulated, and several reviews on this topic are now available.…”

Section: Photoalignment Of Block Copolymer Thin Filmsmentioning

confidence: 97%

New strategies and implications for the photoalignment of liquid crystalline polymers

Seki

2014

Polym J

134

118

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The photoalignment of liquid crystalline materials has been studied extensively over the past two and a half decades and has recently become of technological importance in the liquid crystal display panel industry. This review introduces recent attempts at the photoalignment of liquid crystalline polymers and focuses on two aspects. First, strategies to ensure effective in-plane alignment of photoresponsive mesogens are highlighted. Despite the numerous investigations reported to date, film systems have not been well optimized in terms of realizing efficient photoreactions that consider the mesogen orientations. Second, new photoalignable systems composed of block copolymers with surface-grafted polymers and block copolymer films are introduced. The photoalignment processes in these mesoscopic systems involve strong cooperative motion of the different hierarchical size features. In the course of these approaches, a new strategic platform, photoalignment of liquid crystalline polymers via commanding from the free surface, is proposed. These approaches are expected to offer new concepts and possibilities for smart light-responsive materials and systems. Polymer Journal (2014) 46, 751-768; doi:10.1038/pj.2014.68; published online 13 August 2014 INTRODUCTIONPhotoreactions in ordered media have been the subject of numerous studies. In liquid crystal (LC) systems, molecules are packed with substantial motional freedom, and photoreactions trigger changes in the packing state or the collective molecular orientation. The effects can be amplified to the mesoscopic, microscopic and even macroscopic levels due to strong motional cooperativity. Photochromic reactions have frequently been incorporated in LC media because of their repeatability for controlling material properties. This approach has provided various types of smart, light-responsive materials 1 exhibiting surface-mediated photoalignment of LC materials, 2-6 photoinduced phase transitions, 7-12 photoorientation/addressing of polymer thin films, 13-18 photoinduced mass migrations, [19][20][21][22][23][24][25][26][27][28] phototactic sliding motions, 29-31 photo-driven motions and morphology of monolayers, 32-35 and macroscopic photomechanical deformations. [36][37][38][39][40][41][42][43][44][45][46] Photoalignment research and technology started in 1988 with the discovery of the reversible alignment control of nematic LCs by the photoisomerization of azobenzene on a substrate surface (Figure 1) by Ichimura et al. 47 It was demonstrated that the E/Z (trans/cis) photoisomerization of an azobenzene monolayer on a substrate can switch the alignment of nematic LC molecules between the homeotropic and planar modes. This active functional surface was dubbed a 'command surface' or 'command layer.' Shortly after this finding, Gibbons et al., 48 Dyadyusha et al. 49 and Schadt et al. 50 showed that angular selective excitation of an azo dye-doped polyimide or a photocrosslinkable polymer film with linearly

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Synthesis of Side-Chain Liquid Crystalline Homopolymers and Block Copolymers with Well-Defined Structures by Living Anionic Polymerization and Their Thermotropic Phase Behavior

Cited by 117 publications

References 8 publications

Side-Chain Liquid Crystal Block Copolymers with Well-Defined Structures Prepared by Living Anionic Polymerization I. Thermotropic Phase Behavior and Structures of Liquid Crystal Segment in Lamellar Type of Microphase Domain

Side-Chain Liquid Crystal Block Copolymers with Well-Defined Structures Prepared by Living Anionic Polymerization I. Thermotropic Phase Behavior and Structures of Liquid Crystal Segment in Lamellar Type of Microphase Domain

Synthesis of Liquid Crystalline Oligomeric Polyoxetanes with Two Mesogenic Groups in the Repeating Unit

New strategies and implications for the photoalignment of liquid crystalline polymers

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