Nematic liq. crystal compsn. contg. a tri:phenyl deriv. - to increase isotropic transition temp. and suppress first order nematic crystal transition

摘要

Liq. crystal compsn. contains =1 Schiff base (I), =1 non-Schiff base (II), both these being nematics, and 5-15 wt. % of a triphenyl cpd. (III) which increases the isotropic transition temp. The resulting compsn. has a suppressed first order nematic crystal transition. Pref. (I), used at 30-60 wt. % are of formula:- (where R and R1 are H, 1-8C alkyl, alkoxy or alkyl ester, CN or halo). (II) are azoxy cpds., phenyl benzoates or biphenyls (pref. at 25-65 wt. %) and (III) are of formula:- (where A and A' are each -CH=N-or-CO2-,R2 and R3 are each 1-8C alkyl, alkoxy or alkyl ester, Cn, Cl or Br. X1-X4 are each H, CN, Cl or Br but =2 must be H). Specified is bis (4'-n-octyloxybenzal)-2-chloro-1,4-phenylenediamine (IIIa). The compsn. have broad nematic temp. range, partly caused by redn. in the freezing point. (III) gives a relatively high isotropic transition without simultaneously increasing the nematic solid transition.