THE MEAN STRAIGHT LENGTH OF A SHORT POLYELECTROLYTE - A MONTE-CARLO STUDY

The thermal and screening effects of polyelectrolytes are developed and analyzed in terms of the mean straight length [l(s)], which describes the chain persistence length. Universal values of [l(s)] are obtained for uncharged self-avoiding walk chains. For charged short chains the expansion of [l(s)] with increasing Bjerrum length lambda is observed and found to be dependent not only on lambda and salt concentration, but also on the chain length N. The [l(s)] expansion is found to be different from the expansion of the mean squared radius of gyration [S2], and the effective screening of [l(s)] is shown to be larger compared to the effective screening of [S2]. Among the results not predicted by any of the existing theories are that three regimes of salt concentration are found to have different influences on the screening of [l(s)], that the ratio [l(s)] / [S2]1/2 equals unity at the same value of lambda for N greater-than-or-equal-to 16, and that there exists a minimum value for [l(s)] / [S2]1/2 at a fixed lambda for N greater-than-or-equal-to 16. An attempt to identify the chromic transitions of the conjugated polymers and the polyelectrolyte thermal effect is made.