Semi-dilute solutions crossover between good and poor solvent

Semi-dilute solutions crossover between good and poor solvent 

This has also been studied experimentally and theoretically by the Saclay group.Let us start from the good solvent side, at a fixed concentration c = and progressively reduce the excluded volume parameter i = a (1 - 2 )- When u a (athermal solvent), the scaling formulas of Chapter III hold. When v becomes much smaller than a , the single chain radius/ decreases and the overlap concentration c = N/R increases. To make this more precise, we use the Flory formula for / as a function of v [eq. (1.38)] 

Let us now repeat the arguments of Chapter ni to find the correlation length in the semi-dilute regime. We again write 

52) agrees rather well with the neutron data when the temperature T (controlling v(T)) is varied at constant d . Let us now see when the 

The nearly good solvent regimes described by eq. (IV.52) can be described more physically in terms of spatial correlations. The basic idea is that for small v, a short portion of a chain, with a number p of monomers must be nearly ideal. We see this from the perturbation expansion [eq. (1.42)] where we find no effect of v if n/a (p ) 1. There is a certain value of p[(p = gB beyond which excluded volume effects 

---

IV.3.4. Semi-dilute solutions crossover between good and poor solvent... 

---