NEMATIC PHASE-TRANSITION IN ENTANGLED DIRECTED POLYMERS

A Flory-type mean-field theory of a nematic phase transition in the sy stem of nonphantom, entangled, directed polymers has been elaborated. According to the conjectures expressed by Grosberg and Nechaev [Europh ys. Lett. 20, 613 (1992)], the ''link complexity'' of the chains is ch aracterized by the highest power of the Jones invariant for the corres ponding closed braid. The phase diagram is presented in the coordinate s the ''link complexity'' versus the ordering interaction constant. Th e order of the phase transition is shown to be different for ''weakly' ' and ''strongly'' entangled chains. (C) 1994 American Institute of Ph ysics.