Determination of the flexibility parameter of polymers

Abstract

This paper deals with the determination, in theta conditions, of the flexibility parameter λ defined by Kratky-Porod for random-coiled polymers, using three different methods: (a) from hydrodynamic data in θ conditions, (b) by using a new form of extrapolation to zero of the corresponding values for the average molecular weight, and (c) by extrapolation of λ tending to zero. From method (b), values of the interaction parameter, B, were in agreement with those from Stockmayer-Fixman theory. A linear relationship was obtained from (c) by plotting (R²/L)^½ versus λ. The slope, h*, of this plot was found to be related with λ^θ in the following way: where A₁ and A₂ are constants, and h is the monomeric unit projection length in terms of the wormlike theory.