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Retarding Crystallization of Supercooled Nematic Liquid Crystals

IP.com Disclosure Number: IPCOM000079294D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 22K

Publishing Venue

IBM

Related People

Haller, I: AUTHOR [+2]

Abstract

A known phenomenon experienced by many nematic liquid crystals or mixtures thereof is their tendency to remain in a supercooled, metastable mesomorphic state for indefinite periods of time at temperatures below their thermodynamic melting points. Ultimately, crystallization of such metastable fluids results when nucleation occurs. The nucleation can be spontaneous at lower temperatures, or can be caused by the (either purposeful or inadvertent) introduction into the nematic fluid of "nucleating particles" such as crystal seeds, dust, small glass fragments, and the like.

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Retarding Crystallization of Supercooled Nematic Liquid Crystals

A known phenomenon experienced by many nematic liquid crystals or mixtures thereof is their tendency to remain in a supercooled, metastable mesomorphic state for indefinite periods of time at temperatures below their thermodynamic melting points. Ultimately, crystallization of such metastable fluids results when nucleation occurs. The nucleation can be spontaneous at lower temperatures, or can be caused by the (either purposeful or inadvertent) introduction into the nematic fluid of "nucleating particles" such as crystal seeds, dust, small glass fragments, and the like.

There are many situations where it is desirable to prevent such crystallization of supercooled nematic fluids. For example, a mesomorphic mixture with a true thermodynamic melting point of 35 degrees C may have a significantly practical application, when utilized in a device at temperatures in the range of 0 to 25 degrees C. Accordingly, it is desirable to provide additives which prevent mass crystallization of the nematic fluid around nucleating particles that tend to be present, or are introduced into or induced in the fluid.

In accordance with the method disclosed herein, there are added to the nematic fluid oils, or mixtures of oils which, in themselves, have little, if any tendency, to crystallize, and which are highly compatible with the liquid crystal. In this connection, the term "highly compatible" signifies that the additive oils contain the same or similar polarity, functional groups, and overall molecular shape. This type of oil is soluble in the liquid crystal, at least in small concentrations, and readily fits into the mesomorphic structure without excessive reduction of the nematic-isotropic transition temperature.

Several mixtures of diesters selected from the group having the following structure

(Image Omitted)

wherein R is a radical selected from the group consisting of alkyl radicals containing from 1 to 12 carbon atoms, alkoxy radicals containing from 1 to 8 carbon atoms, alkanoyloxy radicals containing from 1 to 8 carbon atoms, and alkoxycarbonyloxy radicals containing from 1 to 6 carbon atoms, S is a radical selected from the group consisting of alkyl radicals containing from 1 to 12 carbon atoms and alkoxy radicals containing from 1 to 8 carbon atoms, and A, X, Y an...