Pretransitional Phenomena in the Isotropic Phase of a Lyotropic Liquid Crystal of Bacterial Virus fd

Measurements of transient magnetic birefringence are reported for isotropic solutions of a biological rodlike macromolecule, bacterial virus fd. A steep increase of the birefringence and a slowing down of the relaxation process are observed just below the concentration at which the liquid-crystalline phase appears. These pretransitional phenomena are considered to be due to the short-range order effects, and a Landau-de Gennestype approach based on the Onsager theory describes our results semiquantitatively.