Preparation and Properties of Polyurethanes Containing Mesogenic Units

Sugiyama, Kazuo; Shiraishi, Kohei; Kato, Koichi

doi:10.1295/polymj.25.103

Cited by 14 publications

(2 citation statements)

References 16 publications

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“…A number of papers concerning the preparation and physical properties of thermotropic polyurethanes have been reported, − since thermotropic polyurethanes were first reported by Iimura and co-workers − …”

Section: Introductionmentioning

confidence: 99%

“…A number of papers concerning the preparation and physical properties of thermotropic polyurethanes have been reported, [1][2][3][4][5][6][7][8][9][10] since thermotropic polyurethanes were first reported by Iimura and co-workers. 11 Although MacKnight and co-workers reported that a metatype polyurethane has enantiotropic liquid crystallinity, they later published that an almost similar polyurethane has monotropic liquid crystallinity.…”

Section: Introductionmentioning

confidence: 99%

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Liquid Crystallinity of Thermotropic Para-Type Homo- and Copolyurethanes Containing Biphenylene Mesogen and Their Blends

Lee

Koide

et al. 1998

Macromolecules

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High-molecular-weight para-type homopolyurethanes prepared by polyaddition of 2,5-tolylene diisocyanate with 4,4‘-bis(ω-hydroxyalkoxy)biphenyls showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane PU6T having [η] 0.82 which was obtained from 4,4‘-bis(6-hydroxyhexyloxy)biphenyl showed T I - LC of 201 °C and T LC - K of 181 °C. In addition, thermotropic liquid-crystalline para-type copolyurethanes PUmnT (m and n denoting carbon number in alkylene moiety: 2, 6, 8, and 11) were synthesized by polyaddition of the diisocyanate with two 4,4‘-bis(ω-hydroxyalkoxy)biphenyls having different alkylene lengths. For example, PU68T(75/25) had T I - LC of 188 °C and T LC - K of 173 °C. Blends of two para-type homopolyurethanes also exhibited monotropic liquid crystallinity. The liquid crystallinity was examined by differential scanning calorimetry measurement, polarized optical microscope observation, and X-ray diffractometry.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Liquid Crystallinity of Thermotropic Para-Type Homo- and Copolyurethanes Containing Biphenylene Mesogen and Their Blends

Lee

Koide

et al. 1998

Macromolecules

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Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 4. Poly(imide‐urethane‐carbonate)s based on pyromellitdiimide and 3,4:3′,4′‐biphenyldicarboximide

Hirata

Sato

Mukaida

1994

Macro Chemistry & Physics

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Main-chain types of thermotropic liquid-crystalline (LC) poly(imide-urethane-carbonate)s were synthesized by melt polycondensation of N,NP-bis(6-hydroxyhexyl)pyromellitdiimide or N,W-bis(6-hydroxyhexyl)-3,4 : 3',4'-biphenyldicarboximide with diphenyl hexamethylenedicarbamate and/or diphenyl hexamethylenedicarbonate. The poly(imide-urethane)s were also obtained from the dihydroxyalkylene diimide derivatives and hexamethylene diisocyanate by polyaddition. Yields and molecular weights of the resulting polymers tended to decrease with increasing urethane units. Differential scanning calorimetry (DSC) measurements, polarizing microscopic observations and powder X-ray analyses at various temperatures demonstrated that the carbonaterich copolymers comprising the 3,4 : 3',4'-biphenyldicarboximide derivative formed a nematic mesophase. Temperature-dependent Fourier-Transform infrared measurements suggest that hydrogen bonding of urethane linkages affects the formation of LC mesophases.

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The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethaneester)s

Laus

Angeloni

Francescangeli

et al. 1997

Macromolecular Symposia

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The peculiar liquid crystalline behavior of two poly(urethane-ester)s TDI-C6C4 and TDI-C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI-C6C8 and of one cybotactic nematic mesophase in TDLC6C4. IR spectroscopy indicates that different hydrogen bonded and non-bonded structum occur with varying temperature.The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic-mechanical behavior of these poly(urethane-ester)s which is similar to the one of slightly crosslinked thennoreversible networks.

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Preparation and Properties of Polyurethanes Containing Mesogenic Units

Cited by 14 publications

References 16 publications

Liquid Crystallinity of Thermotropic Para-Type Homo- and Copolyurethanes Containing Biphenylene Mesogen and Their Blends

Liquid Crystallinity of Thermotropic Para-Type Homo- and Copolyurethanes Containing Biphenylene Mesogen and Their Blends

Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 4. Poly(imide‐urethane‐carbonate)s based on pyromellitdiimide and 3,4:3′,4′‐biphenyldicarboximide

The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethaneester)s

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