Abstract
The diffusion of sodium polystyrene sulfonate through polycarbonate nanochanels was studied in saltβfree dilute aqueous solution. A stronger molecular weight dependence of diffusion was observed compared to free diffusion in dilute solution. Scaling exponentials relating polymer size to diffusivity were between Flory's theory (D~eff~ β N^β0.6^) and Rouse's model (D~eff~ β N^β1^), revealing a crossover regime from 3βD diffusion to 1βD diffusion. Diffusion was less hindered for the polyelectrolyte (D~eff~/D~0~), than for a rigid sphere, when the polymer/channel size ratio exceeded 0.2. This is attributed to elongated chains with reduced frictional hindrance. Simulation of the confined diffusion based on an elongated cigar model gave D β N^β1^
${R_{\rm t}^{2/3}}$
while the experimental results agree with D β N^β0.94^${R_{\rm t}^{ 2/3}}$. For charged polyelectrolytes, the transition to 1βD diffusion therefore begins before the polymer radius of gyration exceeds the channel size contrary to model assumptions. We attribute this to the charged nature of the polyelectrolytes causing extended chain conformations. Β© 2009 American Institute of Chemical Engineers AIChE J, 2010