Influence of Smectic Liquid Crystallinity on Lamellar Microdomain Structure in a Main‐Chain Liquid Crystal Block Copolymer Fiber

Koga, Maito; Satō, Kazunori; Kang, Sungmin; Sakajiri, Koichi; Watanabe, Junji; Tokita, Masatoshi

doi:10.1002/macp.201300353

Cited by 17 publications

(19 citation statements)

References 18 publications

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“…These LC BCPs, designated as B5‐ x ‐EMA‐ φ , comprise a main‐chain smectic LC BB‐5(3‐Me) polyester bonded at both ends to poly(ethyl methacrylate) (PEMA) segments ( Figure ). [ 15–21 ] x and φ are the number average molecular weight of the BB‐5(3‐Me) segment ( M n,LC ) in units of kDa and the PEMA segment volume percentage, respectively (see Table 1 for details). Characteristically, B5‐ x ‐EMA‐ φ forms lamellar microdomains at φ in a relatively wide range of 20–50%.…”

Section: Introductionmentioning

confidence: 99%

Stress Response and Deformation of Block Copolymer Lamellae on Stretching in Normal Direction: Effects of Lateral Size of Lamellae

Yagi

Oguro

Tokita

2022

Macro Chemistry & Physics

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Herein, it is determined that the stress response of stacked microlamellae to tensile deformation along the normal direction depends on the lateral size of the lamellae. Lamellae with different lengths are formed by B5‐29‐EMA‐φ block copolymers (BCPs) comprising poly(ethyl methacrylate) (PEMA) segments attached to a liquid crystal (LC) BB‐5(3‐Me) polyester having Mn = 29 kDa at both ends at PEMA volume fractions of φ%. The LC and PEMA blocks are segregated to form microlamellae; however, the lamellar length depends on the value of φ; B5‐29‐EMA‐22 forms long‐range lamellae, and B5‐29‐EMA‐44 comprises LC block lamellae separated by PEMA blocks. The stress response is similar between these copolymers in the elastic region but differs in the succeeding stage; B5‐29‐EMA‐22 films show a stress plateau, and B5‐29‐EMA‐44 films continuously increase the stress, displaying the strain hardening. Small‐angle X‐ray scattering measured simultaneously with the stress–elongation curves discloses that these different stress responses accompany individual lamellar deformations. B5‐29‐EMA‐22 undulates and folds the lamellae, whereas B5‐29‐EMA‐44 maintains parallel lamellar stacking, remarkably increasing the PEMA block lamellar thickness. These preferentially thickened lamellae are occupied by extended PEMA chains, which causes stress at the expense of the chain entropy, resulting in strain hardening.

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Section: Introductionmentioning

confidence: 99%

Stress Response and Deformation of Block Copolymer Lamellae on Stretching in Normal Direction: Effects of Lateral Size of Lamellae

Yagi

Oguro

Tokita

2022

Macro Chemistry & Physics

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“…Liquid crystals (LC) can be assembled from either small molecules [ 1 , 2 ] or polymers [ 3 – 6 ]. Compared with small molecular LC, liquid crystal polymers (LCP) offer both mesogen orientation and polymer mechanical merit [ 7 , 8 ]. The orientation of mesogens competing the penalty from the conformational entropy leads to abundant phase behaviors [ 9 – 11 ].…”

Section: Introductionmentioning

confidence: 99%

GPU-Accelerated Molecular Dynamics Simulation to Study Liquid Crystal Phase Transition Using Coarse-Grained Gay-Berne Anisotropic Potential

et al. 2016

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Gay-Berne (GB) potential is regarded as an accurate model in the simulation of anisotropic particles, especially for liquid crystal (LC) mesogens. However, its computational complexity leads to an extremely time-consuming process for large systems. Here, we developed a GPU-accelerated molecular dynamics (MD) simulation with coarse-grained GB potential implemented in GALAMOST package to investigate the LC phase transitions for mesogens in small molecules, main-chain or side-chain polymers. For identical mesogens in three different molecules, on cooling from fully isotropic melts, the small molecules form a single-domain smectic-B phase, while the main-chain LC polymers prefer a single-domain nematic phase as a result of connective restraints in neighboring mesogens. The phase transition of side-chain LC polymers undergoes a two-step process: nucleation of nematic islands and formation of multi-domain nematic texture. The particular behavior originates in the fact that the rotational orientation of the mesogenes is hindered by the polymer backbones. Both the global distribution and the local orientation of mesogens are critical for the phase transition of anisotropic particles. Furthermore, compared with the MD simulation in LAMMPS, our GPU-accelerated code is about 4 times faster than the GPU version of LAMMPS and at least 200 times faster than the CPU version of LAMMPS. This study clearly shows that GPU-accelerated MD simulation with GB potential in GALAMOST can efficiently handle systems with anisotropic particles and interactions, and accurately explore phase differences originated from molecular structures.

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“…The determined parameters are listed in Table S1 in the Supporting Information. [ 5–12 ] In Figure , the ratio of the lamellar thickness in a stretched sample to that of an unstretched sample was plotted against the λ for the LC block lamellae ( d LC / d LC,0 ) and the PEMA block lamellae ( d am / d am,0 ). The ratio of the lamellar spacing ( d / d 0 ) was also plotted in the same figure.…”

Section: Resultsmentioning

confidence: 99%

“…The B5‐26‐EMA‐41 was prepared according to the procedure reported previously. [ 5–9 ] The M n s of the BB‐5(3‐Me) ( M n,LC ) and PEMA ( M n,am ) segments were 26 000 and 16 000, respectively, as determined via 1 H NMR spectroscopy. The polydispersity indices (PDIs) the LC segment and block copolymer were 1.89 and 1.60, respectively, as determined via size exclusion chromatography (SEC) with PS standards.…”

Section: Methodsmentioning

confidence: 99%

“…The LC block copolymer, herein designated as B5‐ x ‐EMA‐φ, consists of a main‐chain smectic LC BB‐5(3‐Me) polyester bonded at both ends to poly(ethyl methacrylate) (PEMA) segments ( Scheme ). [ 5–9 ] x and φ are the number average molecular weight ( M n ) of the BB‐5(3‐Me) segment and the PEMA segment volume percentage, respectively. The B5‐ x ‐EMA‐φ copolymers at φ < 50 segregate these two types of segments from one another to form lamellar microdomains, within which the LC segment forms smectic layers lying parallel to the microdomain lamellae.…”

Section: Introductionmentioning

confidence: 99%

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Deformation of Hierarchical Lamellar Structure Formed by a Liquid Crystalline Block Copolymer

Kuribayashi

Ishige

Hayashi

et al. 2020

Macro Chemistry & Physics

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polystyrene-block-polybutadiene-block-polystyrene (SBS) copolymers form glassy/ rubbery type lamellae of the polystyrene (PS)/polybutadiene (PB) segments at ambient temperatures. The direction of the force with respect to the lamellar normal affects the deformation mechanism, as confirmed when using singlecrystal-like monodomain lamellar films prepared via the roll-casting method. [2,3] When force is applied perpendicular to the lamellae to increase the macroscopic strain, the lamellae tilt the normal away from the deformation direction and have sharp hinges to form chevron morphology. In contrast, when the temperature is raised to 100 °C to make the SBS form viscous/rubbery type lamellae of the PS/PB segments, the same deformation dilates the lamellae to increase the spacing without tilting them. Thus, the deformation mechanism of twophase lamellae can be affected by the state of each lamella.In this work, we investigate the deformation of viscous/ LC lamellae composed of an LC block copolymer upon being stretched in a direction parallel to the lamellar normal. The LC block copolymer, herein designated as B5-x-EMA-ϕ, consists of a main-chain smectic LC BB-5(3-Me) polyester bonded at both ends to poly(ethyl methacrylate) (PEMA) segments (Scheme 1). [5][6][7][8][9] x and ϕ are the number average molecular weight (M n ) of the BB-5(3-Me) segment and the PEMA segment volume percentage, respectively. The B5-x-EMA-ϕ copolymers at ϕ < 50 segregate these two types of segments from one another to form lamellar microdomains, within which the LC segment forms smectic layers lying parallel to the microdomain lamellae. A characteristic of B5-x-EMA-ϕ is the formation of fibers of a well-oriented "single-crystal-like" microstructure with the normal of both microdomain lamellae and smectic layers aligned along the fiber axis. Herein, we stretched the fibrous sample at a rate of 5% min −1 , and the sample stress and 2D X-ray scattering were simultaneously measured. The X-ray scattering analysis discloses the deformation mechanism of the lamellar microdomain and the smectic layers. With increasing the elongation ratio (λ) up to 1.6, the PEMA lamellae are preferentially dilated to cause the tilt of the lamellar normal with respect to the stretching direction, resulting in the lamellar undulation. The LC segment lamellae are dilated and comprise smectic layers that undulating along the lamellar boundary. With further increasing λ, the lamellae take chevron morphology that comprising straight parts connected with localized bends while recovering the spacing.The deformation of a structure of alternating liquid crystal (LC)/viscous layers upon being stretched along the normal layer is investigated using highly ordered, near-single-crystal lamellar fibers of an LC block copolymer. The block copolymer consists of poly(ethyl methacrylate) (PEMA) segments attached to a main-chain LC polyester at both ends. The LC block segregates from the PEMA block and forms a smectic LC, laying the layers parallel to the interface with PEMA block lamell...

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Influence of Smectic Liquid Crystallinity on Lamellar Microdomain Structure in a Main‐Chain Liquid Crystal Block Copolymer Fiber

Cited by 17 publications

References 18 publications

Stress Response and Deformation of Block Copolymer Lamellae on Stretching in Normal Direction: Effects of Lateral Size of Lamellae

Stress Response and Deformation of Block Copolymer Lamellae on Stretching in Normal Direction: Effects of Lateral Size of Lamellae

GPU-Accelerated Molecular Dynamics Simulation to Study Liquid Crystal Phase Transition Using Coarse-Grained Gay-Berne Anisotropic Potential

Deformation of Hierarchical Lamellar Structure Formed by a Liquid Crystalline Block Copolymer

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