The ground state of an $N$-monomer charged polymer, in the absence of screening, is stretched, with nonextensive energy growing as $N\ln N$. If the allowed bond angles are discrete, only discrete changes in conformation are possible, and the elementary excitations have energy growing as $\ln N$. Using analytical arguments, and Monte Carlo simulations, we show that such a polymer is rigid (flat) at low temperature $T$, and flexible (rough) at high $T$. The roughness exponent, for the scaling of transverse fluctuations with $N$, varies continuously with $T$, reaching the value for models which permit continuous changes in geometry only at very high $T$.

• Received 28 September 1998

DOI:https://doi.org/10.1103/PhysRevLett.83.745