Excluded volume effects in dilute polymer solutions. XIII. Effects of chain stiffness

Abstract

The chain length dependence of mean-square radius of gyration ⟨S2⟩ for several polymers, stiff or flexible, in dilute solution is compared with that for the Kratky-Porod (KP) wormlike chain, using representative literature data. In the region of nK, the number of Kuhn’s statistical segments, below about 50, ⟨s2⟩ for all polymers examined is accurately described by Benoit-Doty’s expression for the KP chain. Upward deviations from this expression occur at nK of about 50, regardless of the chain stiffness. Thus, the critical chain length Lc for the onset of excluded-volume effect on the average dimensions of a polymer is approximately proportional to q, the persistence length of the polymer, with a proportionality factor of about 100. The value of Lc estimated from this relation is at least one order of magnitude larger than that predicted theoretically by Yamakawa and Stockmayer. © 1982, The Society of Polymer Science, Japan. All rights reserved.