X-ray investigation of 8CB and 8OCB under high pressure

Abstract

Octyloxycyanobiphenyl (8OCB) and octylcyanobiphenyl (8CB) were investigated by X-ray diffraction under atmospheric pressure and pressures up to 250 MPa. The layer spacing of 8OCB and 8CB versus temperature at atmospheric pressure as well as the layer spacing versus pressure up to 250 MPa for 8CB were determined. The suggestion that pressure induces a spacing expansion in 8CB were confirmed and the results are presented in this paper. At the pressure 170 MPa in 80CB we have observed neither a supercooled nematic phase nor a supercooled smectic phase, nor a reentrant nematic phase.

Key Words:

• X-ray diffraction
• high pressure
• layer spacings
• phase transition