Column Buckling Instability in a Discotic Liquid Crystal

When subjected to a compressive strain along the columns, a tubular discotic liquid crystal must present a buckling instability, where compressive elastic energy is transferred into bend energy of columns. We present the first observation of this column buckling instability in hexa-n-octyloxytriphenylene at $T=75$^∘{}C. From the instability threshold, the curvature elastic constant is found to be 6 orders of magnitude larger than in usual liquid crystals, i.e., the correlation length extends on a quasimacroscopic range of 10³ molecules.