Kinetic Feature of Nematic Phase Polymerization of Diacetylenes

Izuoka, Akira; Okuno, Tsunehisa; Ito, Tomoyoshi; Sugawar, Tadashi; Sato, Naoki; Kamei, Sachiyo; Tohyama, Kohji

doi:10.1080/10587259308028799

Cited by 14 publications

(5 citation statements)

References 10 publications

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“…The topochemical polymerization of diacetylenes by irradiation or thermal annealing has been widely used for preparing ordered macromolecules. , Most topochemical polymerization of diacetylenes has been carried out in the solid state. Monomers with molecular arrangements suitable for polymerization are prepared as single crystals, Langmuir−Blodgett films, − self-assembling monolayers, , and vesicles. , Recently the liquid crystalline (LC) state polymerization of diacetylenes was also found to proceed by a 1,4-polymerization pathway as the solid-state polymerization. − In an LC state, molecules are self-organized into ordered arrays comparable to those in Langmuir−Blodgett or self-assembling processes. Several mesogenic linear diacetylenes have been polymerized in nematic or smetic phases. − …”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Mesogenic Disklike Benzenetricarboxylates Containing Diacetylenic Groups and Their Polymerization

et al. 2000

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Polymerizable disklike compounds that have a benzene ring core and three rigid diacetylenic units were prepared. The diacetylenic units were attached to the benzene ring via ester linkages. By varying number of alkoxy tail carbons and benzene rings of the disk, the morphological change of the compounds and their polymerization were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy, infrared spectroscopy (IR), and powder X-ray diffraction (XRD). Compound 7 with no alkoxy tail was glassy or small crystals at room temperature and showed crystal-to-crystal phase transition when heated. Compounds 8 with butyloxy tails, 9 with hexyloxy tails, and 10 with octyloxy tails showed monotropic transitions. When the compounds were cooled from the isotropic liquid states, birefringent phases with mosaic textures were observed. XRD study showed that compounds 9 and 10 had hexagonal columnar structures in their liquid crystalline (LC) states. The diacetylene compounds were polymerized by irradiation with UV in solid states or LC states. IR and UV−vis studies showed that the polymerization proceeded by 1,4-addition.

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Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Mesogenic Disklike Benzenetricarboxylates Containing Diacetylenic Groups and Their Polymerization

et al. 2000

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“…The importance of the relative orientation of the nematic phase polymerization is supported by the enhanced reactivity of polymerization in a thin film sample and the effect of applying an external electric field upon the rate of polymerization. 12…”

Section: Discussionmentioning

confidence: 99%

“…When an external electric field was applied, the sample showed dynamic scattering mode with a threshold value of 2500 V cm Ϫ1 . 12 Phase IV was, therefore, assigned to the nematic phase. The IR spectrum of DA-C8 in each phase was recorded to obtain information on the difference in the hydrogen-bonding scheme.…”

Section: Crystal Structure Of Da-c8 Of Phase Imentioning

confidence: 99%

Reactivity of mesogenic diacetylenes coupled with phase transitions between crystal and liquid crystal phases

Okuno¹,

Izuoka²,

Ito³

et al. 1998

J. Chem. Soc., Perkin Trans. 2

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“…The inherent order of monomers in the liquid crystalline phase may significantly alter the mechanisms of polymerization and affect the generated polymer networks. Increased polymerization rate [21][22][23][24][25] and reduced shrinkage [20,[26][27][28][29] have been observed in monomers polymerized in the nematic phase. In addition, tensile modulus is enhanced along the oriented polymer networks [30][31][32] and fracture toughness is improved if highly ordered smectic domains are formed during polymerization [33,34].These advantages of liquid crystal monomers are highly desirable in dental applications.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Thermal-Induced Changes in Molecular Order on Photopolymerization and Performance Properties of a Nematic Liquid-Crystal Diacrylate

2022

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Polymerization shrinkage and associated stresses are the main reasons for dental restorative failure. We developed a series of liquid crystal diacrylates and dimethacrylates which have markedly low polymerization shrinkage. In order to fully understand the effects of temperature-induced changes of molecular order on the photopolymerization process and performance properties of the generated polymers, the photopolymerization of a difunctional acrylate, 2-t-butyl-1,4-phenylene bis (4-(6-(acryloyloxy)hexyloxy)benzoate), which exists in the nematic liquid crystalline phase at room temperature, was investigated as a function of photopolymerization temperature over the nematic to isotropic range. Morphological studies suggested that a mesogenic phase was immediately formed in the polymer even if polymerization in thin films occurred above the nematic-to-isotropic (N→I) transition temperature of the monomer (Tn-i = 45.8 °C). Dynamic mechanical analysis of 2 × 2 mm cross-section bar samples polymerized at 60 °C showed reduced elastic moduli, increased glass transition temperature and formation of a more crosslinked network, in comparison to polymers formed at lower polymerization temperatures. Fractography analysis showed that polymers generated from the nematic liquid crystalline phase underwent a different fracture pattern in comparison to those generated from the isotropic phase. Volumetric shrinkage (2.2%) found in polymer polymerized from the nematic liquid crystalline phase at room temperature was substantially less than the 6.0% observed in polymer polymerized from an initial isotropic phase at 60 °C, indicating that an organized monomer can greatly contribute to reducing cure shrinkage.

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Kinetic Feature of Nematic Phase Polymerization of Diacetylenes

Cited by 14 publications

References 10 publications

Synthesis and Characterization of Mesogenic Disklike Benzenetricarboxylates Containing Diacetylenic Groups and Their Polymerization

Synthesis and Characterization of Mesogenic Disklike Benzenetricarboxylates Containing Diacetylenic Groups and Their Polymerization

Reactivity of mesogenic diacetylenes coupled with phase transitions between crystal and liquid crystal phases

Investigation of Thermal-Induced Changes in Molecular Order on Photopolymerization and Performance Properties of a Nematic Liquid-Crystal Diacrylate

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