Drug – bio-affecting and body treating compositions – Radionuclide or intended radionuclide containing; adjuvant... – Molecular bilayer structure
Patent
1989-10-04
1993-02-23
Waddell, Frederick E.
Drug, bio-affecting and body treating compositions
Radionuclide or intended radionuclide containing; adjuvant...
Molecular bilayer structure
424 63, 424 64, 424 69, 514785, 514788, 25229901, 25229961, 25229965, 25229967, 25229968, A61K 4900, A61K 7021, A61K 7035, C09K 1934
Patent
active
051888157
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The invention relates to thermochromic liquid crystalline phases with at least two components, characterized in that at least one component is an optically active compound of the formula I ##STR3## wherein R.sup.1 and R.sup.2 are each independently a chiral residue, imparting to the phase a tight helical twist, ##STR4## denotes a 1,4-phenylene group optionally substituted by fluorine, X.sup.1 and X.sup.2 are each independently O or NH, constitute an intermediate state which exists between the crystalline solid and the fully disordered liquid phase and within which certain long range ordering of the molecules takes place.
There are two broad types of liquid crystal phase; the smectic mesophase in which the long range ordering is of a substantially lamellar type and the nematic mesophase in which the ordering is substantially linear, i.e., the molecules tend to line up with the long axes of the molecules parallel. Included sometimes as a subclass of the nematic mesophase and sometimes classified as a separate mesophase is the cholesteric mesophase. This last has a helical long range order imposed upon the linear order of the nematic mesophase. Compounds displaying a cholesteric mesophase are optically active (chiral) and the pitch of the helical twist is determined by the nature and extent of the optical activity. The pitch of the helical twist may be such that thin films of the cholesteric phase reflect visible light, resulting in the observation of bright colors, and the pitch may also be sharply temperature dependent resulting in the reflection of particular colors over particular temperature ranges so that the cholesteric mesophase in question can act as a "thermometer". This behavior is known as thermochromism.
The chiral compounds of the formula I induce a cholesteric mesophase (hereinafter designated Ch) because of their molecular shape and optical activity and also a chiral smectic C mesophase (hereinafter designated S.sub.c) underlying the cholesteric mesophase to liquid crystalline phase which possess a nematic or a smectic C mesophase. They exhibit, either on their own or when mixed with one or more compounds capable of forming S.sub.c liquid crystal phases, a chiral S.sub.c liquid crystal phase in which the molecules lie tilted in the smectic layers which are themselves superimposed one upon the other to give a helical distribution of the tilt angles on passing through a stack of layers. A unique feature of the chiral S.sub.c mesophase of the phases of the present invention is that, in their planar S.sub.c textures, these mesophases have a helical pitch which gives a selective reflection of colored light of specific wavelengths which are dependent on temperature, i.e., the compounds are thermochromic.
The phases of the present invention exhibit, when mixed with one or more other liquid crystal compounds, a cholesteric liquid crystal phase in which the molecules are arranged in the helical formulation of that phase such that a film of the phase in the Grandjean plane texture rotates the plane of polarization of incident polarized light and reflects elliptically polarized light of specific wavelengths when illuminated by ordinary light, so that the mesophases are thermochromic.
The pitch of the cholesteric helix changes most abruptly in the temperature region close to a smectic phase, usually this is a smectic A or C phase. Hence thermochromic mixtures according to the invention are usually formulated such that they exhibit an underlying smectic phase so that the color change from blue (hot) to red (colder) occurs over a range of only few degrees (1-10.degree. C.). However in some applications a temperature in-sensitive color is required and the smectic phase is depressed.
The phases of the present invention have properties such that they may be used in a liquid crystal electro-optic device such as a "phase change" device in which the material is changed between a so-called "focal-conic" cholesteric state, which scatters light, and a transparent nematic state by an applied
REFERENCES:
patent: 4118370 (1978-10-01), Sannes et al.
patent: 4448727 (1984-05-01), Factor et al.
patent: 4880560 (1989-11-01), Yoshinaga et al.
patent: 5116527 (1992-05-01), Coates et al.
Patent Abstracts of Japan, vol. 7, No. 14, C146, abstract of JP57-170976, publ 1982.
Coates David
Jenner John A.
Sage Ian C.
Criares T. J.
Merck Patent Gesellschaft mit beschrankter Haftung
Waddell Frederick E.
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