CONFIGURATIONAL PROPERTIES OF PARTIALLY IONIZED POLYELECTROLYTES FROM MONTE-CARLO SIMULATION

Monte Carlo simulations have been performed for a lattice model of an isolated, partially ionized polyelectrolyte whose charged groups interact through screened Coulombic potentials. Configurational properties are reported as a function of chain ionization and Debye screening length for chains containing 20–140 segments. At high screening between fixed charges, the chains exhibit power law scaling behavior for the dependence of the mean-square end-to-end distance, 〈r2〉, on chain length. At lower screenings the chains undergo a transformation from flexible to stiff conformations as ionization rises. Long-chain scaling behavior was not observed at low screenings due to the limits on the chain lengths studied here. Simulation results for polyion electrostatic energies and expansion factors are compared with predictions based on the theory of Katchalsky and Lifson and the uniform-expansion extension of this theory. Large discrepancies between theory and simulation are probably due to the assumed theoretical expressions used for describing distance probability distributions between charged groups. © 1990, American Chemical Society. All rights reserved.