Elastic moduli renormalization in self-interacting stretchable polyelectrolytes

We study the effect of intersegment interactions on the effective bending and stretching moduli of a semiflexible polymer chain with a finite stretching modulus. For an interaction potential of a screened Debye–Hückel type, renormalization of the stretching modulus is derived on the same level of approximation as the celebrated Odijk–Skolnick–Fixman result for the bending modulus. The presence of mesoscopic intersegment interaction potentials couples the bending and stretching moduli in a manner different from that predicted by the macroscopic elasticity theory. We thus advocate a fundamental change in the perspective regarding the dependence of elastic moduli of a flexible polyelectrolyte on the ionic conditions: stretchability. The theory presented here and its consequences compare favorably with recent experiments on DNA bending and stretching at not too low salt conditions.