We have synthesized new high Delta n 3-ring phenylacetylene(3PA) liquid cry
stals which have substituent groups with core center phenyl ring and invest
igated the effects of substitution on physical properties. Nematic range an
d viscosity were improved remarkably with keeping high Delta n by introduci
ng trifluoromrthoxy group. The Delta n of 3PAs were also descussed with rel
ationship of polarizability and order parameter.