STRETCHING OF POLYELECTROLYTE COILS AND GLOBULES IN AN ELONGATIONAL FLOW

Scaling theory describing the stretching of a weakly charged polyelectrolyte molecule by elongational shear flow is developed. This stretching transition occurs as a first-order dynamic phase transition at a certain ''critical'' value of the flow-field gradient. The dependence of this critical gradient on the degree of chain ionization and on the solvent strength with respect to the interaction of uncharged monomers is analyzed. The stretching transition in neutral and polyelectrolyte globules is considered. It is shown that for a polyelectrolyte immersed in a salt-added solution two critical values of the flow-field gradient exist: the lower critical point corresponds to the stretching of the chain on the scale of superblobs of the size equal to Debye screening length, and the upper critical point corresponds to the complete stretching of the chain on the scale of monomer units.