Optical studies of supramolecular tubular structures generated by taper-shaped side groups in the columnar hexagonal phase Jian-Feng Li, James A. Heck, Virgil Percec, Charles Rosenblatt, Joseph S. Collura and Michael R. Fisch J. Phys. II France, 4 10 (1994) 1813-1822 DOI: 10.1051/jp2:1994234