Abstract: The present invention relates to compounds of the formula ##STR1## in which Z is a halogen atom, a cyano group or a hydroxyl group,n is 0, 1 or 2,R' is a radical of the formulaR"'--[Si(R*).sub.2 ].sub.x (CH.sub.2).sub.y R""-- (9),in whichx is the number 0 or 1,y is an integer from 1 to 18,R"'is a defined in the description,R* is identical or different, optionally substituted C.sub.1 - to C.sub.18 -hydrocarbon or hydrocarbonoxy radicals,R"" is a phenylene or biphenylene radical or a radical of the formula --E--, whereE is a divalent radical of the formula --O-- or --[Si(R*).sub.2 ].sub.z --, andz is the number 0 or 1,and the compounds contain at least one group of the formula --Si(R*).sub.2 -- per molecule, and the radicalR" is a cholesteryl radical, a radical as defined for R* or a radical of the formula --C.sub.6 H.sub.4 --R*,and the preparation and use thereof.