Thermotropic Polypeptides. VII. Temperature Dependence of Cholesteric Pitches in Poly[(γ-benzyl L-glutamate)-co-(γ-dodecyl L-glutamate)s]

Watanabe, Junji; Nagase, Tatsuya; Ichizuka, Toshihiro

doi:10.1295/polymj.22.1029

Cited by 11 publications

(4 citation statements)

References 13 publications

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“…The cholesteric phase, hence, is concluded to result simply from the mainchain mesogens as has been observed in poly-(L-glutamates). [5][6][7][8][9][10][11][12] The biphasic appearance of the cholesteric and isotropic phases in the lower molecular weight PLG-BP-64(70) further reinforces this conjecture since it can be caused by the reduced axial ratio of the main-chain a-helix. 23 The cholesteric structure is schematically illustrated in Figure 8b.…”

Section: Resultsmentioning

confidence: 87%

Thermotropic liquid crystals in polypeptides with mesogenic side chains. 1

Watanabe¹,

Tominaga²

1993

Macromolecules

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We prepared a new type of thermotropic liquid crystalline polypeptide, denoted PLG- (see text), in which mesogenic biphenyl moieties are linked to a mesogenic a-helical main chain with a flexible spacer. This polymer exhibits transitions at 7\ = 143 °C and T2 = 222 °C and forms three distinct phases, the crystalline, the smectic A, and the cholesteric phases. In the crystalline phase below Ti, a-helical main chains form the layered structure and the biphenyl moieties in the side chains are crystallized in the space between the layers with their long axes perpendicular to the layer. In the temperature range from 7\ to T2, the layered structure remains unchanged but the biphenyl moieties are in a liquid crystalline state in which the molten biphenyl groups are located still having the orientational order between the main-chain layers as in the crystalline phase. The structure can be assigned to be the smectic A phase. At the final temperature stage above T2, the layered structure collapses and the biphenyl moieties are randomly dispersed around the main chain, which results in the well-known cholesteric phase based on the a-helical mesogenic groups. The thermotropic transition behavior and the mesophase structures are illustrated by considering a coupling effect of main-chain and side-chain mesogenic groups.

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Section: Resultsmentioning

confidence: 87%

Thermotropic liquid crystals in polypeptides with mesogenic side chains. 1

Watanabe¹,

Tominaga²

1993

Macromolecules

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“…It is also apparent that there is a relatively weak temperature dependence in accordance with results obtained for thermotropic cholesteric phases of polypeptides with the long alkyl side chains. 20 From the negative sign of optical rotation as measured in the wavelength region of 400-700 nm, it was found that the cholesteric phases of PG-18 observed for PG-18-220. Here, the negative value of pitch indicates that the specimen forms a left-handed cholesteric structure.…”

Section: Resultsmentioning

confidence: 99%

“…The liquid crystal is fluid and its cholesteric nature can be well identified by the presence of its fingerprint texture with the fine retardation lines in the microscopic observation. [18][19][20] The typical texture of a cholesteric phase is shown in Figure la. The pitch can be determined from the spacings between the lines19 and is plotted against temperature for PG-18-220 in Figure 2.…”

Section: Resultsmentioning

confidence: 99%

Columnar liquid crystals in polypeptides. 1. A columnar hexagonal liquid crystal observed in poly(.gamma.-octadecyl L-glutamate)

Watanabe¹,

Takashina²

1991

Macromolecules

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Poly(y-octadecyl L-glutamate) can form a new type of thermotropic phase in addition to a cholesteric phase. This new phase appears in a higher temperature region than the cholesteric phase, and the transition between them can be determined by microscopic observation of the mesophase texture. This new phase can be distinguished from the cholesteric phase as it exhibits a fan-shaped texture and extremely high viscosity. Furthermore, an X-ray examination indicates that in this phase the rigid a-helical molecules are packed into a regular two-dimensional hexagonal lattice. The new phase was thus assigned to a columnar hexagonal phase, which is first observed in a thermotropic polypeptide system.

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“…Thermotropic cholesteric mesophases of polyglutamates carrying long alkyl chains have been developed. [18][19][20][21][22] The polypeptide LC films show uniform Grandjean textures (the cholesteric axis being perpendicular to the film surface) that exhibit a bright reflective color when the optical pitch is within the visible region. Furthermore, the pitch can be controlled by annealing the film at appropriate temperatures and can be immobilized by quenching the film rapidly below its glass temperature.…”

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confidence: 99%