Improved phase diagram of polyelectrolyte solutions

A previously reported phase diagram of polyelectrolyte solutions as functio ns of degree of polymerization and the concentration is improved. The new p hase diagram is also intended for salt-free solutions of polyelectrolytes w ith the constitutional repeating unit -C-CX-, X being a charged group. The main improved point is the crossover concentrations between the dilute and semidilute regimes in the low concentration range of less than 10(-2) mol/l , which is based on the recent most reliable experimental data on the persi stence length of flexible polyion chains. This phase diagram as well introd uces both the concentrated regime, which has been not only theoretically pr edicted but also experimentally confirmed, and the experimentally newly fou nd swollen regime. Furthermore, it is proposed that the dilute regime is se parated into four regions, gaslike, poor order, liquidlike order and crysta l. The degrees of orderliness in these regions have been assumed to depend on the ratio delta/xi (cent) of the amplitude of thermal fluctuations to th e mean intermolecular distance. Typically, delta/xi (cent)=1/5 as the criti cal Lindemann ratio of melting is assigned for the crossover between the li quidlike order and crystal regions. Interestingly, the most probable region for the formation of a 3-D lattice is located within the experimental appr oach. (C) 2001 American Institute of Physics.