EXPERIMENTAL-EVIDENCE OF A CONIC HELICAL LIQUID-CRYSTALLINE STRUCTUREIN CYLINDRICAL MICROCAVITIES

Optical activity has been measured for cholesteric (Ch), twisted nemat ic (N) and ferroelectric (S(C)*) substances confined in cylindrical c hannels of anodic oxidized aluminium (Anopore membranes). H-1 and C-13 NMR studies of the adsorbed N phase in combination with measurements of the rotary power suggest a conic helical director field in the por es, as in a common S(C) structure, with the helical axes oriented alo ng the cylindrical channels and the helicoidally ordered local directo rs on average being inclined at an angle theta < 90-degrees to the cyl inder axes. Supposing the validity of the de Vries formula, the sign a nd magnitude of the optical activity in Anopore indicate a change in b irefringence and pitch with respect to the bulk sample.