Thermotropic chiral nematic liquid crystalline copolymers

摘要

A thermotropic chiral nematic liquid crystalline copolymer composition comprises ##STR1## wherein --NEM-- and --NEM'-- are each independently nematogenic units of formula ##STR2## wherein R is H or CH. sub.3, --Q-- is an alkylene radical having 1 to about 8 carbon atoms, PP --X-- is --O--, --S--, or --CH.sub.2 --, --Y-- is ##STR3## --Z is --CN, -- NO.sub.2 or --N═C═S, q and r are each independently 0 or 1; PPwherein --CHI-- is a chiral unit of formula ##STR4## wherein R is H or CH.sub.3, --Q'-- is an alkylene radical having 1 to about 8 carbon atoms,PP--X'-- is --O-- , --S--, or --CH. sub.2 --,PP--Z' is an alkoxy, aralkoxy, alkylamino, or aralkylamino radical having 4 to about 12 carbon atoms and containing at least one asymmetric carbon atom,PPq' and r' are each independently 0 or 1;PPand wherein x is the mole fraction of chiral units and (y+y') is the total mole fraction of nematogenic units in said copolymer composition, and the ratio of x to (y+ y') is from about 1:50 to 1:1.PPThis compolymer composition is employed to form an optical device.