Polymer reptation in semidilute solution

The self-diffusion constant and solution viscosity are calculated for polymers in semidilute solution using the reptation concept. A space-filling constraint (rather than binary contacts) is used to construct the tube in the reptation model. In good solvents, scaling predictions are recovered, but in marginal systems unexpected effective power-law exponents are predicted for the concentration dependence of the self-diffusion constant, relative viscosity, and reptation time.