Equilibrium distribution of semiflexible polymer chains between a macroscopic dilute solution phase and small voids of cylindrical shape

The equilibrium partition coefficients (K) are calculated for self-avoiding, semiflexible chains with the same finite contour length (L) and a variety of persistence length (lp) values, partitioning between a macroscopic dilute solution phase and confined solution phases in cylindrical voids in the steric exclusion limit. It is found that, for the range of K -values most relevant to polymer separation in size exclusion chromatograph (0.1≲K≲0.9), the geometric mean of the radius of gyration (Rg) and the mean span (X) performs better than Rg or X alone in collapsing the partition curves of the various linear semiflexible chains onto a single curve. The dependence of the confinement free energy (ΔA) on the persistence length is also examined. For those chains having the same L, the pore diameter D<min(lp,2L/3) is found to be the necessary and sufficient condition for ΔA to decrease with the increase of lp. Two questions are answered: (i) which size parameter correlates best with the equilibrium partition coefficients of linear semiflexible chains in the range relevant to polymer separation in GPC? (ii) For two chains with the same contour length but different persistence length in equilibrium with a cylindrical pore, which chain spends less free energy to get in.