Thermic correlation length

In order to make these observations in the best conditions, it is necessary to proceed in the following manner. First, the experiment should be carried out on very long chains, because the asymptotic domain must be as large as possible. The temperatures of the solution should be such that the corresponding thermic correlation lengths satisfy the conditions... 

The thermic correlation lengths , derived from the interaction b are given in Table 15.6. Let us recall that the persistence length of atactic polystyrene is equal to 2 nm. Condition (15.3.29) is therefore satisfied. 

Considering these results, we can now see how the change from the expanded chains in dilute solutions to the ideal chains in a melt is accomplished With increasing concentration the screening length decreases continuously, and if it comes down to the thermic correlation length excluded volume effects disappear. Simultaneously the chain size shrinks, from the Flory radius Rp in the dilute solution down to the radius Rq of the Gaussian chains in the melt. 

Combining all the information collected so far, for the single chain pair distribution function in a semidilute solution we can predict an overall shape as indicated in Fig. 3.8. For the presentation we choose a plot of 4nr g r) versus r. The curve is a composite of different functions in four ranges, with cross-overs at the persistence length Ips, the thermic correlation length and the screening length Up to r we find the properties of the expanded chain, which... 

---