Continuous isotropic-nematic liquid crystalline transition of F-actin solutions -: art. no. 040701

The phase transition from the isotropic (I) to nematic (N) liquid crystalline suspension of F-actin of average length lgreater than or equal to3 mum was studied by local measurements of optical birefringence and protein concentration. Both parameters were detected to be continuous in the transition region, suggesting that the I-N transition is higher than first order. Thus we report experimental evidence for a continuous I-N transition for a suspension of rodlike macromolecules. Our findings are consistent with a recent theory by Lammert, Rokhsar, and Toner [Phys. Rev. Lett. 70, 1650 (1993)], predicting that the I-N transition may become continuous due to suppression of disclinations.